CALIFORNIA AGRICULTURAL EXPERIMENT STATION 
 
 THE 
 
 PEACH TWIG 
 
 BORER 
 
 Stanley F. Bailey 
 
 September, 1948 
 
 Bulletin 708 
 
 THE COLLEGE OF AGRICULTURE 
 UNIVERSITY OF CALIFORNIA • BERKELEY 
 
TtllS BUll&tllti written for the grower, pest-control op- 
 erator, and entomologist, describes the life history and 
 annual cycle of the peach twig borer from the view- 
 point of recently discovered biological facts. It discusses 
 the injurious, seasonal habits of the pest on peaches, 
 apricots, nectarines, plums, and almonds, and presents 
 the difficulties in attempting to predict the annual de- 
 gree of crop damage. 
 
 • The recommended control program is based on ac- 
 cumulated experimental data concerning the two chief 
 sources of control: 
 
 CHEMICALS — the principal means of controlling infes- 
 tations in areas where annual loss occurs. Experimental 
 data are given on dormant sprays and on early spring 
 and summer applications. The effectiveness of DDT 
 sprays is compared with that of standard sprays. 
 
 PARASITES — also an important means of control. New 
 data are given on the reduction of the pest by native 
 parasites. Control by introduced parasites is also given, 
 as well as its present limitations. 
 
CONTENTS 
 
 Page 
 
 Distribution 3 
 
 Hosts 3 
 
 Economic importance 3 
 
 Injury 4 
 
 Description 11 
 
 Adult 11 
 
 Egg 11 
 
 Larva 11 
 
 Pupa 13 
 
 Life history and habits 13 
 
 Length of stages 13 
 
 Habits of moth 13 
 
 Egg stage 15 
 
 Habits of larva 16 
 
 Habits of pupa 22 
 
 Seasonal cycle 22 
 
 Parasites 24 
 
 Control 34 
 
 Cultural methods 34 
 
 Biological methods 34 
 
 Chemical methods— by banding 34 
 
 Insecticidal methods 35 
 
 Control experiments, 1937-1946 36 
 
 Control of feeding larva . 36 
 
 Control of dormant larva 41 
 
 Control with DDT 47 
 
 Discussion 50 
 
 Summary 52 
 
 Recommended control program 53 
 
 Acknowledgments 54 
 
 Selected references 55 
 
In order that the information in our publications may be more intelligible, it is 
 sometimes necessary to use trade names of products or equipment rather than 
 complicated descriptive or chemical identifications. In so doing, it is unavoid- 
 able in some cases that similar products which are on the market under other 
 trade names may not be cited. No endorsement of named products is intended 
 nor is criticism implied of similar products which are not mentioned. 
 
THE PEACH TWIG BORER 
 
 Stanley F. Bailey 
 
 The peach twig borer, Anarsia lineatella 
 Zell., is a pest of major importance in 
 peach growing. Considerable loss is also 
 suffered every year to almonds, apricots, 
 and plums, but not always in the same dis- 
 trict nor on the same property. An annual 
 spray program is necessary, therefore, es- 
 pecially on peaches, to prevent a serious 
 increase of the insect. 
 
 The price of fruit and the size of 
 the crop have considerable influence on 
 the spray schedule and the subsequent 
 amount of injury by the pest. For in- 
 stance, as methods of grading and stand- 
 ards of almonds were modified, the 
 relative importance of the peach twig 
 borer increased on soft-shelled varieties 
 of this crop. 
 
 The use of many new chemicals in the 
 field of insect control has challenged the 
 relative value and efficiency of the exist- 
 ing methods of control of this and of other 
 insect pests. Because of the rapid change 
 in methods of control, any recommenda- 
 tions set forth will be only temporary. For 
 an established industry a middle course 
 should be followed— for instance, a grad- 
 ual change from established practice to 
 more efficient and more economical meth- 
 ods as they are proven. 
 
 Although the biology of insects changes 
 but little, new facts are discovered from 
 time to time, which enable us to under- 
 stand the problem better and to apply 
 newer methods of control. 
 
 DISTRIBUTION 
 
 The peach twig borer occurs in many 
 peach-growing states of this country. It is 
 also known in Europe and the Old World. 
 In California it is found in all peach- and 
 almond-growing districts. The heaviest 
 concentration of the pest is to be found in 
 the upper San Joaquin and Sacramento 
 
 [3 
 
 valleys. South and west of this area, in- 
 festations are generally of less impor- 
 tance. 
 
 The peach twig borer has been recorded 
 by the Insect Pest Survey Section of the 
 United States Department of Agriculture, 
 Bureau of Entomology and Plant Quaran- 
 tine, from the following states : Alabama, 
 Arizona, Arkansas, California, Colorado, 
 Connecticut, Delaware, Georgia, Idaho, 
 Illinois, Iowa, Kansas, Kentucky, Mary- 
 land, Massachusetts, Michigan, Missis- 
 sippi, Missouri, Nebraska, New Jersey, 
 New Mexico, New York, North Carolina, 
 Ohio, Oklahoma, Oregon, Pennsylvania, 
 South Carolina, South Dakota, Tennessee, 
 Texas, Utah, Virginia, Washington, and 
 West Virginia. 
 
 In hibernacula (a hibernaculum, ac- 
 cording to Webster's International Dic- 
 tionary, is "a hibernating-case constructed 
 of foreign materials by certain insects") 
 the peach twig borer is readily trans- 
 ported on nursery stock, cuttings, and 
 buds. It doubtless occurs in all areas 
 where its deciduous host crops are culti- 
 vated. «*%«- 
 
 HOSTS 
 
 The principal host plants of the peach 
 twig borer are the peach and almond. In 
 addition to these crop hosts are the apri- 
 cot, cherry, nectarine, plum, and prune. 
 In California, to our knowledge, this in- 
 sect has never attacked any other crop or 
 native plant. 
 
 ECONOMIC IMPORTANCE 
 
 Since the peach twig borer was first dis- 
 covered in California about sixty years 
 ago, it has annually been a pest of eco- 
 nomic importance. As early as 1887, a 50 
 per cent loss of peaches was experienced 
 
 1 Received for publication October 7, 1947. 
 
 2 Associate Professor of Entomology and As- 
 sociate Entomologist in the Experiment Station. 
 
in some districts. Clarke (1902) wrote 
 that "In some seasons this loss has aggre- 
 gated as high as 30 per cent of the entire 
 crop." During the years 1898 to 1901 the 
 total loss was estimated at $1,373,000. 
 
 Essig (1926) reported that as much as 
 80 per cent of the late peaches was de- 
 stroyed when control measures were not 
 practiced. 
 
 The heaviest known loss from this pest 
 occurred in 1931. In a study of the infes- 
 tation in the Sacramento Valley, Mackie 
 and Jones (1931) reported an average of 
 10.78 per cent infested fruits in the peach 
 belt. Many individual properties in the 
 Yuba City area suffered as much as 50 to 
 70 per cent damage. Since 1931, the in- 
 jury has been spotty and irregular. 
 
 Economic factors in the soft-shelled al- 
 mond industry have worked to focus at- 
 tention on the losses caused by the twig 
 borer. After a federal tolerance of 5 per 
 cent on "bad meats" was established, 
 shelling operations indicated that 90 per 
 cent or more of the annual supply of bad 
 meats was caused by the twig borer. From 
 time to time "Almond Facts," the official 
 publication of the California Almond 
 Growers' Exchange, has referred to the 
 seriousness of this pest. For example, the 
 October, 1940, issue stated, "In consider- 
 ing the problem of the peach twig borer 
 this year, it is interesting to note that the 
 most heavily affected areas were in the 
 Sacramento and San Joaquin valleys. The 
 Paso Robles district remained virtually 
 untouched, as is disclosed by the figures 
 in the next column, which represent an 
 average of deliveries containing over the 
 5 per cent tolerance. Not all districts are 
 shown, the tabulation being merely a 
 cross section of the state. 
 
 From 1937 to 1942, in our experimen- 
 tal unsprayed plots (of Nonpareil) at Ar- 
 buckle, the percentage of injured meats 
 varied from 1.5 to 35.0 with a six-year 
 average of 12.5. The economic loss to the 
 Nonpareil variety of almonds from the 
 peach twig borer for the years 1933 to 
 1945 inclusive has been compiled for this 
 
 publication by the Almond Growers' Ex- 
 change. This is presented in table 1. The 
 injury to the IXL and to other varieties 
 of almonds should be added to the total 
 loss of $537,162 for the period shown in 
 table 1. 
 
 Nonpareil IXL NePlus Drake 
 per per per per 
 cent cent cent cent 
 
 Arbuckle 41.5 23.4 6.0 35.5 
 
 Chico-Durham 31.5 33.7 5.6 11.5 
 
 Orland 47.8 52.8 23.0 32.8 
 
 Esparto 35.2 22.2 5.7 31.0 
 
 Contra Costa .... 7.9 1.8 1.2 
 
 Oakdale 23.7 22.6 .... 1.8 
 
 Salida 16.8 17.8 1.8 1.4 
 
 Merced 4.4 1.7 0.6 2.2 
 
 Live Oak 71.2 53.0 11.1 59.2 
 
 Paso Robles 
 
 State-wide 
 
 Average 27.3 29.2 9.9 17.1 
 
 The damage to plums occurs chiefly in 
 the Vacaville, Penryn, Lodi, and Visalia 
 districts. The so-called stem worms or 
 small larvae which attack plums at har- 
 vest usually appear at the time the early 
 varieties ripen, but in delayed seasons the 
 damage occurs on later maturing vari- 
 eties, such as Kelsey, Grand Duke, and 
 President. Even in the seasons of heaviest 
 infestation affected fruit on plums is 
 rarely greater than 20 per cent. Here 
 again, the local degree of injury varies 
 greatly and is difficult to predict. 
 
 Conditions affecting injury to apricots 
 are closely parallel to those on early 
 plums. The damage to apricots is usually 
 more severe in years of light crops, is 
 spotty and unpredictable, but is not wide- 
 spread. 
 
 As is true of the result of most injurious 
 fruit insects, the presence of damaged 
 fruits and nuts immediately increases 
 picking and sorting costs. This expense is 
 in addition to the loss through reduction 
 in salable tonnage. 
 
 INJURY 
 
 The damage caused by the peach twig 
 borer is twofold : killing the twigs and di- 
 rectly injuring the fruit. The former is of 
 
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Fig. 1. — Severe twig borer injury to young almond causes deformation by killing of terminals. 
 
It.: 
 
 ■■■-i'-v-- 1 - 
 
 
 Fig. 2.— Wilted shoots of almond as seen on early spring growth. Twig borer larvae enter 
 near the tip and burrow downward. Before reaching maturity, a single larva may attack sev- 
 eral shoots. The damage is the same on all fruit trees attacked. 
 
 7] 
 
minor importance, but the latter— the eco- 
 nomic loss to the fruit itself— is of major 
 concern. 
 
 No damage is caused to the trees by the 
 feeding of the minute larva under the 
 bark, while forming the hibernaculum, 
 nor its tunneling in the crotches for the 
 short period in the spring before bloom. 
 On two-year-old trees as many as 80 hi- 
 bernacula have been found on one tree, 
 where they had caused no apparent in- 
 jury. However, the deformation and stunt- 
 ing of nursery stock, young orchard trees 
 (fig. 1) and replants by such heavy infes- 
 tations often become serious, especially 
 on unsprayed trees. 
 
 Upon emerging from hibernation, the 
 larvae migrate to the tips of the twigs 
 where they burrow and often kill several 
 before reaching maturity. This type of in- 
 jury is seen on all the crop hosts— apricot, 
 prune, plum, nectarine, peach, and al- 
 mond. The more vigorous and rapidly 
 growing varieties and individual trees es- 
 cape serious stunting. The May brood at- 
 tacks the lateral shoots which have been 
 stimulated by the killing of the terminal 
 bud earlier in the season. From this time 
 on, the succulent and vigorous varieties 
 exhibit more wilted shoots (fig. 2), and 
 the slower-growing and nonirrigated trees 
 begin to harden off and become less at- 
 tractive to the worms. 
 
 On bearing trees, the damage to the 
 fruit of all the host crops, with the excep- 
 tion of almonds, is essentially the same. 
 The feeding injury to the fruit begins 
 with the May brood and is usually evi- 
 denced by "bleeding" or sap droplets on 
 the green fruit of almonds (fig. 3) , plums, 
 prunes, nectarines, peaches, and, to a 
 lesser extent, of apricots. The larvae often 
 make several attempts to penetrate the 
 fruit, but rarely make entry at this stage 
 of growth except in double fruit or in 
 fruit with split pits (fig. 4) . The relative 
 amount of culls resulting from this injury 
 in May is very small in comparison with 
 the damage from the midsummer broods. 
 On apricots, however, if the May brood is 
 
 large, and has hatched later than normal, 
 the infestation coincides with the ripen- 
 ing of early fruit. Then, considerable local 
 injury results. The feeding of the twig 
 borer on green almond hulls is of no con- 
 cern. It occurs more often in dry-farmed 
 orchards, as the tip growth hardens, than 
 in irrigated sections. 
 
 Growers commonly speak of twig borer 
 injury to ripe stone fruits as being caused 
 by "stem worms" and "skin worms." 
 Early varieties of plums and peaches, 
 when attacked, usually show a high per- 
 centage of large larvae present at harvest. 
 These larvae attack the majority of fruits 
 near the stem end, where two fruits touch, 
 or where leaves are stuck to the surface 
 of fruit (figs. 3 and 4) . When the larvae 
 crawl about over the trees seeking early- 
 ripening fruit, they migrate down the 
 stems and usually enter the fruit at that 
 point. Large larvae sometimes penetrate 
 to the pit. An increasingly greater propor- 
 tion of the small and newly hatched larvae 
 called skin worms seek later-ripening 
 varieties. They penetrate the skin of the 
 fruit only a short distance, feed over an 
 area of about % to % inch in diameter 
 ( fig. 5 ) , and are seldom more than a third 
 to half grown by harvest. As varieties of 
 fruit ripen and are harvested, the moths 
 migrate to adjacent orchards seeking un- 
 picked fruit and, if successful, lay their 
 
 eggs- 
 Many of the eggs are laid directly on 
 the fruit, particularly if it has begun to 
 ripen, rather than on the leaves, as earlier 
 in the season. It can then be seen that, as 
 the picking season advances, there is a 
 progressively greater concentration of the 
 twig borer on late varieties. Distinct 
 broods or peaks of larvae hatching are no 
 longer evident. Also, each day that pick- 
 ing is delayed, additional eggs are laid, 
 more larvae hatch, and the feeding larvae 
 extend their visible injury. This vicious 
 circle results in a rapidly mounting loss 
 at a time when it is practically impossible 
 to use any control measures. The in- 
 creased amount of worm-infested fruit 
 
 8] 
 
Fig. 3. — Twig borer injury by larvae to green Texas almonds early in June. Although the 
 later midsummer brood feeds under the cracking hulls, it injures the meats of soft-shelled varie- 
 ties only. 
 
 [9 
 
Fig. 4.— Sugar prunes injured by midsummer brood of twig borer larvae. 
 
 dropped by the pickers becomes evident 
 as the picking progresses, especially in 
 years of above-average infestation. In 
 large fruit-growing districts the outside 
 rows of an orchard nearly always show 
 more damaged fruit than the inside rows. 
 This happens because the moths, in their 
 migration, alight at the margins first and 
 deposit their eggs nearby. 
 
 The injury to almonds is different from 
 that to stone fruits. Early in July the hulls 
 begin to crack ; then the moist interior of 
 the hull and the surface of the nut are ex- 
 posed to migrating larvae. Larval feeding 
 is of no concern on hard-shelled varieties 
 and, as the hulls dry up, the larvae mature 
 
 rapidly. On the other hand, soft-shelled 
 varieties are readily damaged by the mid- 
 summer brood as the larvae can easily 
 penetrate the paper-shell covering and 
 feed directly on the meat. This damage is 
 done chiefly' in July by one prolonged 
 brood. At harvest time in August, a few 
 larvae are found still feeding, but the 
 great majority of those hatching after the 
 nuts begin to mature go directly into the 
 hibernacula and remain there. The twig 
 borer larvae, rarely consume the meat; 
 instead, they feed on the margins, end, or 
 sides, which disfigures or blemishes the 
 skin covering the meat (fig. 6) . There is 
 no known direct reduction in tonnage of 
 
 10 
 
Fig. 5.— Simms peaches injured by peach twig borer larvae in early August. At this season, larvae 
 of all sizes are often found with very small "skin" and "stem" worms predominating. 
 
 almonds brought about by the twig borer. 
 The injury to the meats is of economic 
 importance when it exceeds 5 per cent 
 (under present government regulations) , 
 and, as has been discussed above, this 
 condition does occur nearly every year in 
 some districts. 
 
 DESCRIPTION 
 
 Adult. The adult moth (fig. 7) is dark 
 gray with irregular spots and streaks of 
 light and dark gray. It is about 8 milli- 
 meters, or %e inch, long with a wing ex- 
 panse of twice its length. The head is 
 bluntly rounded, as are the wings which, 
 when not in use, are held roof-like over 
 
 the body. The palpi curve back over the 
 head and resemble horns. The male is 
 slightly smaller than the female. 
 
 Egg. The egg is bluntly oval, and its 
 surface is covered with reticulations. 
 When first laid, it is yellowish white ; later 
 it turns orange. It measures about 0.4 
 millimeter in length and 0.2 millimeter 
 in width. 
 
 Larva. The newly hatched larva is light 
 yellowish brown with a black head. It is 
 about 0.5 millimeters in length. The ma- 
 ture larva (figs. 8 and 9) is, on the aver- 
 age, 10 millimeters, or % inch, long. It is 
 reddish brown with black head and black 
 cervical and anal plate. The yellowish- 
 
 11 
 
Fig. 6. — Wilted shoots of almond, and worm-cut almond meats injured by twig borer larvae. 
 Hard-shelled varieties of almond are rarely injured. Note pupa at extreme lower right in hull. 
 
 [12 
 
white intersegmental membranes offer 
 sharp contrast with the segments. 
 
 Pupa. The pupa or chrysalis is naked, 
 smooth, about 6 millimeters, or % inch, 
 long and dark brown (figs. 10 and 11) . 
 
 LIFE HISTORY AND HABITS 
 
 Various authors have contributed to 
 the life history and habits of Anarsia li- 
 neatella in California. Ehrhorn (reported 
 by Marlatt, 1898), Clarke (1902), and 
 Duruz (1923) made various observations 
 of the insect, which included the funda- 
 
 velop faster than those which first tunnel 
 under bark and later complete their 
 growth on fruit and twigs. As would be 
 expected during the cooler weather of 
 spring and fall, the stages are somewhat 
 prolonged. 
 
 The overwintering larval stage is, of 
 course, not to be compared with the sum- 
 mer generations. The minimum longevity 
 of larvae in the overwintering stage 
 would be from mid-September, the time 
 of hatching of the last eggs of the sea- 
 son, until earliest pupation the following 
 
 Fig. 7.— Adult twig borer moth. Natural size about 
 
 mentals of the seasonal cycle and the out- 
 standing biological characteristics. Jones 
 (1935) , however, published the most de- 
 tailed and comprehensive study yet made. 
 It is upon his study that we draw freely in 
 the following discussion, and supplement 
 it with our own studies carried on from 
 1937 to 1942 and again in 1946 and 1947. 
 Jones studied the insect on peaches almost 
 exclusively, and our work has been con- 
 centrated largely on almonds. 
 
 Length of Stages. The life history 
 stages and their approximate length dur- 
 ing the summer season are shown here: 
 
 Days 
 
 Egg 5-7 
 
 Larva 10-20 
 
 Pupa 6-7 
 
 Adult (longevity) (in laboratory) 10 
 
 The great variation in the number of days 
 for the larva occurs because larvae which 
 feed entirely on green shoots or fruit de- 
 
 spring— about April 15, or 7 months. 
 Some individual larvae of this group live 
 longer— perhaps 9 months— especially if 
 they enter the hibernacula in midsummer 
 and do not mature until late April, as hap- 
 pens in a delayed spring. 
 
 Habits of Moth. The adult Anarsia 
 lineatella is the most difficult stage to col- 
 lect and study. The number of moths seen 
 and collected under natural conditions in 
 the orchards is very small. There appear 
 to be several reasons for the paucity of in- 
 formation concerning this stage, namely, 
 the natural protective coloration of the 
 moths, their nocturnal habits, small size, 
 and short, irregular flight. In heavily in- 
 fested peach orchards at picking time the 
 moths become fairly numerous. They may 
 be observed resting on all parts of the 
 trees, in lug boxes, and even on the 
 ground on clods and on fallen fruit. Dur- 
 ing the day, they rest quietly in the shade 
 with the anterior portion of the body 
 
 13 
 
slightly raised. When disturbed, they fly 
 rapidly in a zig-zag course and alight only 
 a few feet away. In addition to flying, they 
 often run about jerkily over bark and 
 leaves. Mating and egg laying have been 
 observed only in cages. 
 
 Attempts to trap the moths by means of 
 bait pens or by lights (Jones, 1935) have 
 been unsuccessful. It does not appear 
 
 at Arbuckle in June, 1941, from which 
 emerged 97 females and 112 males. 
 
 The amount of feeding done by the 
 moths is very limited and irregular. In 
 a number of instances in the field, moths 
 have been observed feeding on nectaries 
 at the base of leaves and on the moist 
 flesh of injured fruits. In cages they feed 
 readily on sugar and water solutions. 
 
 Fig. 9.— Side view of mature twig borer larva. 
 Natural size about Y% inch. 
 
 Fig. 8.— Dorsal or top view of mature twig 
 borer larva. Natural color is reddish brown 
 with a black head. Natural size about Ys inch. 
 
 practical to try to obtain data on the 
 flights of moths to aid in timing the spray 
 applications. 
 
 The proportion of sexes appears to be 
 about equally divided. G. L. Smith (un- 
 published notes) raised 126 moths from 
 peaches at Yuba City in May, 1933; of 
 these, 52 were females and 74 males. The 
 writer collected 209 pupae in tree bands 
 
 The longevity of moths under natural 
 conditions is unknown. In cages they sur- 
 vive from 3 to 20 days (G. L. Smith, un- 
 published notes) with an average of 10.3 
 days. Even under laboratory conditions 
 with live plant material and with sugar 
 and water available, we were unable to 
 keep moths alive longer than 18 days. 
 Without water, 100 per cent mortality oc- 
 curred within 5 days. 
 
 Various workers have studied the moth 
 under laboratory conditions and report 
 the following facts: 
 
 The preoviposition period is from 1 to 
 4 days. More than half of the eggs depos- 
 
 [14] 
 
ited in the life of a female are laid in the 
 first half of its adult life. The largest num- 
 ber of eggs laid by one individual was 
 115. 
 
 Among other habits of the moth, the 
 manner and place of egg laying are 
 worthy of mention. In the spring the ma- 
 jority of the eggs are deposited on the 
 twigs and leaves of the new growth. They 
 are laid singly and are lightly cemented 
 
 in May, 1933. Of 412 eggs located and 
 marked, 98 per cent were laid on the fruit. 
 On young trees, the writer has observed 
 that the majority of the eggs are depos- 
 ited on the bark, near the base of leaf 
 clusters, or next to the midrib on the 
 lower side of leaves. Oviposition has been 
 observed in the daytime, but the greater 
 number of eggs are laid at night because 
 the moths are most active at dusk. 
 
 Fig. 10. — Twig borer pupa in place on section of bark removed from pruning scar. Left, rough, 
 silken web and bark fragments covering pupa; right, underside of same bark section showing 
 pupa (center) under web. 
 
 to the surface. On young trees, many eggs 
 are laid on the bark in the crotches of new 
 wood. As the fruit ripens, a majority of 
 the eggs are deposited on the fruit. On 
 peaches, particularly, eggs may readily 
 be found in the fuzz. Here, a single moth 
 may deposit 1 to 10 eggs in a square inch 
 of fruit surface. 
 
 Nothing is known concerning parasites 
 or enemies of the moth itself. 
 
 Egg Stage. As mentioned above, the 
 eggs are deposited by the moth, more or 
 less at random, on the surface of bark, 
 twigs, leaves, and fruit. In cages, eggs are 
 laid on paper, glass, or wood, but, if 
 available, living plant material is pre- 
 ferred by the moths. Smith recorded care- 
 ful observations on egg laying on peaches 
 
 When the eggs are first laid, they are a 
 pale cream color and gradually darken 
 until, before hatching, they become a 
 pinkish orange. 
 
 At the time of hatching, there does not 
 appear to be a distinct line of cleavage of 
 the shell. The larva breaks out the shell at 
 one end, leaving an irregular opening in 
 the area of its head. 
 
 There appears to be some natural mor- 
 tality of the eggs but it is not high. Some 
 fail to hatch from lack of fertilization or 
 other causes. The predaceous thrips, Lep- 
 tothrips mali (Fitch), in both the larval 
 and adult stages in some orchards attacks 
 a large number of twig borer eggs. If red 
 spider eggs are also present, however, the 
 thrips do not concentrate on the twig 
 
 [15 
 
borer eggs, and the mortality from this 
 cause is therefore lower. The length of 
 the egg stage varies considerably. It was 
 as short as 4 days in very warm weather 
 in late June, 1940. During this period, 
 
 From the data obtained by Smith and 
 Jones, and that cited above, it can be seen 
 that the time spent in the egg stage short- 
 ens from early spring to summer, with 
 the extreme range from 4 to 18 days. 
 
 lm 4* 
 
 
 
 ■ 
 
 - 
 
 Fig. 11.— Pupae of the twig borer found clustered under tree protectors 
 on young almond trees in late May. 
 
 172 eggs were laid on peach terminals. 
 Of this number, 74 hatched and the re- 
 mainder were attacked by thrips or were 
 sterile. Of those that hatched, the length 
 of incubation was as follows : 
 
 Days 
 
 46 4 
 
 13 5 
 
 2 6 
 
 3 7 
 
 10 9 
 
 Average 5.00 
 
 Habits of Larva. There are two prin- 
 cipal and distinct types of peach twig 
 borer larvae: the overwintering larvae 
 and their characteristics, and the feeding 
 larvae of the midsummer broods. This 
 latter group in turn is made up of two 
 types of larvae : one that feeds on the bark 
 and forms temporary hibernacula, then 
 later migrates to fruit and completes its 
 growth; and another that feeds entirely 
 on green shoots and fruits. The habit of 
 
 16 
 
tunneling into the young twigs has given 
 the insect its accepted common name of 
 twig borer. To distinguish it from the 
 beetle, Polycaon confertus Lee. (the 
 branch and twig borer ) the prefix "peach" 
 
 mer broods which have been under the 
 bark for several weeks (table 3). Some 
 feeding continues in tunnels under the 
 bark until cold weather, but the larvae 
 increase in size very slowly. Counts made 
 
 Fig. 12. — Peach twig borer larva in its hibernaculum under bark of two-year-old twig. 
 
 should be used. In this report, the term 
 twig borer refers only to Anarsia linea- 
 tella. 
 
 At the beginning of the hibernating 
 season in October, there are two sizes of 
 larvae in the hibernacula: very small 
 newly hatched individuals, and the sec- 
 ond-instar larvae hatched from midsum- 
 
 of the larvae during the late fall show the 
 proportion of the first and second instars 
 (table 3). By mid-November all feeding 
 stops. Then the larvae enclose themselves 
 in the silken-lined hibernating tubes (fig. 
 12) and remain dormant for 2 to 3 
 months. 
 
 The majority of these tubes or cells are 
 
 [17] 
 
constructed in the corky, rough bark or 
 cracks in the crotches or on lateral limbs 
 of one- to four-year-old wood (fig. 12). 
 Occasional chimneys may be found at the 
 base of buds, at the margins of old scars, 
 and even on the stems of fruit. The depth 
 (or diameter) of the tunnel is rarely more 
 than 1 millimeter and the length of the 
 hibernaculum is usually from 2 to 5 milli- 
 meters. The depth to which the larvae 
 penetrate beneath the bark is rarely more 
 than 2 millimeters or about y iQ inch. Not 
 all hibernacula have chimneys and some 
 show no external evidence of their pres- 
 ence. 
 
 During the dormant period, the exter- 
 nal parts of the hibernacula become 
 weathered and are difficult to see. In late 
 January and February, the beginning of 
 feeding activity is evidenced by bright- 
 yellow or cinnamon-colored particles of 
 bark in the crotches of the young wood. 
 The larvae break out of their silken tubes 
 and begin to extend their burrows, throw- 
 ing up tiny piles of frass loosely joined by 
 strands of silk. Another molt usually oc- 
 curs at this time. The majority of the 
 larvae which migrate to the buds appear 
 to be the third instar, and nearly all are 
 the same size. Emergence from dormancy 
 extends over a period of about a month. 
 Thus, the earliest emerged larvae are ma- 
 ture by the time all the hibernacula are 
 empty. 
 
 Parasite larval activity continues dur- 
 ing the winter season. This is discussed 
 elsewhere in the bulletin (p. 31). Al- 
 though there is some mortality of the 
 newly hatched twig borer larvae before 
 entrance is made into twigs, bark, or fruit, 
 the amount is difficult to determine. 
 
 There is usually only one larva in each 
 hibernaculum but, now and then, when 
 the infestation is heavy, several larvae 
 may be found in interconnecting tunnels 
 in a small bark section. Only the chimneys 
 and the dorsal portion of the tubes are 
 covered with silk. This silk is not tough— 
 for instance, not nearly so tough as that 
 of the codling moth. 
 
 Large numbers of hibernating larvae 
 are often found on young almond and 
 peach trees which have not yet come into 
 bearing and therefore are not yet sprayed 
 annually. We have found as many as 80 
 hibernacula on a single three-year-old al- 
 mond tree at Arbuckle, but the average 
 number is many fewer. In 1942, young 
 trees were sampled to determine the de- 
 gree of variation in the infestation and 
 parasitism. The results are presented in 
 table 8. The variation from orchard to 
 orchard and district to district is even 
 greater. 
 
 The larvae often construct several tun- 
 nels before settling down to their perma- 
 nent overwintering quarters. If removed, 
 a larva quickly forms another chamber. 
 It may be readily transplanted from peach 
 to almond, to plum, etc. Also, both in sum- 
 mer and winter, we have removed larvae 
 from the bark, and have placed them on 
 green shoots upon which they immedi- 
 ately began to feed. Larvae hatched from 
 the same group of eggs have been sepa- 
 rated, and some have been caged on bark 
 and the remainder on growing terminals. 
 Those confined to the bark developed very 
 slowly, while those feeding entirely on 
 new growth developed to maturity in 
 about 10 days. Larvae that have fed upon 
 fruit and green shoots will not feed upon 
 bark unless forced to do so— for example, 
 under laboratory conditions. As the bark 
 dries out, the larvae abandon it. 
 
 The number of instars varies from 4 to 
 5, apparently depending on the rate of 
 growth of the larvae. 
 
 A method sometimes used for deter- 
 mining larval instars is the measurement 
 of the head capsule which, according to 
 Dyar's Law, follows a regular geometri- 
 cal progression in successive instars. In 
 his studies of Anarsia lineatella in 1933, 
 G. L. Smith made such measurements of 
 hibernating larvae on peach during Janu- 
 ary, February, and March. His unpub- 
 lished tabular data are given on page 19. 
 
 In our studies, 1,189 larvae were 
 mounted and the head widths measured. 
 
 [18] 
 
The tabulation in table 2 (p. 20) sum- 
 marizes the results and shows that the 
 larvae found feeding (or hibernating) on 
 the bark range from 0.1 to 0.5 millimeter 
 in the width of head. Those larvae recov- 
 ered from fruits and wilted twigs are 
 larger, the measurements varying from 
 0.2 to 1.0 millimeter in the width of head. 
 The width of the head of newly hatched 
 larvae averages about 0.1 millimeter and 
 that of the full-grown larvae about 0.9. 
 
 Width of head Number of 
 
 capsule larvae 
 
 in mm measured 
 
 0.15-0.19 5 
 
 0.20-0.24 18 
 
 0.25-0.29 36 
 
 0.30-0.34 52 
 
 0.35-0.39 11 
 
 0.40-0.0 3 
 
 0.85-0.0 1 
 
 126 
 
 Field observations and rearing experi- 
 ments lead us to believe that there are 4 
 to 5 instars in the feeding larvae during 
 the summer, and that the hibernating lar- 
 vae pass through an additional instar. 
 However, a large number of larvae should 
 be carefully reared in order to verify com- 
 pletely this observation and to determine 
 the validity of Dyar's law as it may, or may 
 not pertain to Anarsia lineatella. Some 
 individual larvae, in the summer months, 
 first feed on bark— and actually form a 
 hibernaculum— and later migrate to green 
 shoots or fruit. This condition makes it 
 additionally difficult to accurately evalu- 
 ate the number and length of instars by 
 measurements of only those feeding lar- 
 vae collected in the field (table 3) . Peter- 
 son and Haeussler (1928) have pointed 
 out these features when employing similar 
 measurements of the oriental fruit moth 
 larva. Imms (1934, p. 195) , in discussing 
 Dyar's work, states, "The factors deter- 
 mining the number of ecdyses need inves- 
 tigation and it is at present impossible to 
 judge how far they are phylogenetic in 
 significance, and how far they are an ex- 
 
 pression of internal physiological proc- 
 esses in the species concerned." 
 
 In the spring, the emerging larvae 
 crawl upward along the limbs and twigs 
 seeking new growth on which to feed. The 
 first blossoms or leaf buds encountered 
 show a small amount of feeding injury, 
 seldom severe. This wandering and feed- 
 ing period extends from the time the buds 
 begin to swell until the new growth is 
 about 3 to 4 inches long. By the time 
 wilted tips are readily found, many of the 
 larvae have matured. This is evidenced by 
 the empty tunnels in the dead tips. An in- 
 dividual larva will attack several buds or 
 shoots before reaching maturity. The lat- 
 eral buds or slower-growing shoots usu- 
 ally have the terminal bud eaten out by 
 the larva. The succulent shoots are nearly 
 always attacked from the tip downward 
 for a distance of about % to 2 inches. 
 
 When emerging from the tip, the larva 
 either backs out or chews a hole to the 
 outside at a point where the new growth 
 has begun to harden. The flow of sap 
 induced by feeding sometimes causes the 
 larva to abandon its attempt to burrow in. 
 When feeding in the blossoms, the larva 
 commonly chews through the calyx and 
 consumes the ovary. Only the most succu- 
 lent growth is attacked, and the larval ac- 
 tivity progresses upward and outward 
 with the growth of the host. The variation 
 in the number of wilted twigs— as well as 
 the injured meats— among varieties of al- 
 monds (table 4) is apparently caused by 
 the rate of growth and relative number of 
 succulent shoots present. 
 
 After reaching full growth, the larva 
 migrates downward to the larger limbs 
 and trunk as it seeks a suitable place in 
 which to pupate. This prepupal period or 
 wandering stage lasts 2 or 3 days. After 
 finding a suitable crack, pruning scar, 
 section of curled bark, or similar spot, the 
 larva spins a loose, grayish-white web, 
 and transforms into the pupal stage be- 
 neath it. 
 
 The feeding larvae of the summer gen- 
 erations appear to prefer the fruit to the 
 
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twigs, particularly if given a choice. On 
 young, nonbearing trees the feeding hab- 
 its of the larvae are the same as those of 
 the overwintering brood in the spring. 
 Terminal buds are eaten out and the tips 
 mined. The rate of growth is more rapid, 
 
 seek more suitable food. In large peach 
 orchards in which the ground is well 
 shaded, larvae will mature and pupate in 
 and on fallen fruit. 
 
 Jones (1935) wrote that "the fruit feed- 
 ing larvae rarely attack more than one 
 
 Table 3: SEASONAL DEVELOPMENT OF LARVAE IN HIBERNACULA ON ALMOND 
 
 Arbuckle, California 
 
 Date 
 
 Number of 
 hibernacula 
 
 Number of 
 
 first instar 
 
 larvae 
 
 Number of 
 
 second instar 
 
 larvae 
 
 Total 
 
 1940: 
 
 May 28* 
 
 June 19 .... . 
 
 July 8 
 
 August 13 . . . 
 September 13 
 
 1941: 
 
 April 10 
 
 May 20 
 
 May 29 
 
 June 10 
 
 July 2 
 
 August 4 
 
 September 3 . 
 October 3. . . 
 November 4 . 
 December 1 . . 
 
 1942: 
 January 2 . . . 
 February 4 . . 
 February 17 . . 
 
 March 2 
 
 March 16... . 
 
 50 
 39 
 76 
 75 
 
 48 
 22 
 104 
 91 
 113 
 108 
 122 
 115 
 106 
 103 
 
 71 
 84 
 92 
 72 
 
 94 
 
 25 
 
 2 
 
 52 
 
 21 
 
 
 
 13 
 
 54 
 
 50 
 
 35 
 
 20 
 
 34 
 
 7 
 
 1 
 
 
 
 25 
 20 
 10 
 37 
 
 
 
 12 
 9 
 62 
 45 
 23 
 23 
 24 
 14 
 
 50 
 22 
 62 
 58 
 
 
 13 
 66 
 59 
 97 
 65 
 57 
 30 
 25 
 14 
 
 * Many new hibernacula — all first instar larvae. 
 
 and all sizes of larvae are commonly seen 
 on the same tree. 
 
 Twig borer larvae rarely attack over- 
 ripe fruit, and they do not feed in rotten, 
 watery, or mushy portions of fruit be- 
 cause they readily become trapped and 
 drowned in such media. Infested fruit 
 often drops to the ground with feeding 
 larvae inside. If such fruit lies in the sun 
 or becomes hot, the larvae die or quickly 
 leave and attempt to crawl up the trees or 
 
 fruit or feed in more than one spot upon 
 a single peach. Several larvae may attack 
 one fruit; in 1931 as many as 15 were 
 counted in one peach." The larvae in fruit 
 typically mine cavities just beneath the 
 skin; occasionally they tunnel into the 
 flesh. Jones found that on 350 infested 
 peaches there were 378 points of entry. 
 Of these, 41 per cent were near the stem, 
 34.4 per cent on the side, 19 per cent in 
 the seam, and 5.6 per cent in split pits. 
 
 [21] 
 
In comparison with the hibernating 
 larvae, there is very little evident para- 
 sitism of the feeding larvae. Various pred- 
 atory insects and birds consume a few 
 larvae, but their effect on the population 
 appears insignificant. 
 
 Habits of Pupa. On young trees, the 
 pupae are concentrated on the trunk from 
 
 Additional data on abundance were se- 
 cured by placing untreated corrugated 
 cardboard bands on 24 trees from May 
 28 to June 10, 1940. These attracted 98 
 larvae for pupation, or an average of 4.0 
 per tree. The per cent of natural mortality 
 of this collection was 20.5. No parasites 
 were present. 
 
 Table 4: WILTED TWIG COUNTS OF PEACH TWIG BORER ON ADJACENT ROWS 
 OF THREE-YEAR-OLD ALMOND, ARBUCKLE, CALIFORNIA, 1940 
 
 Variety 
 
 Total 
 
 number 
 
 trees 
 
 Number trees infested 
 
 Number newly 
 wilted twigs 
 
 Average number 
 
 wilted twigs 
 
 per tree 
 
 
 May 13 
 
 June 10 
 
 July 16 
 
 May 13 
 
 June 10 
 
 July 16 
 
 May 13 
 
 June 10 
 
 July 16 
 
 Texas 
 
 52 
 52 
 52 
 52 
 
 35 
 37 
 51 
 48 
 
 47 
 48 
 18 
 30 
 
 35 
 
 23 
 
 8 
 
 10 
 
 197 
 192 
 546 
 568 
 
 186 
 
 137 
 
 23 
 
 49 
 
 72 
 35 
 13 
 12 
 
 3.78 
 
 3.69 
 
 10.50 
 
 10.92 
 
 3.58 
 
 2.65 
 
 .45 
 
 .95 
 
 1.38 
 
 Ne Plus 
 
 .67 
 
 Nonpareil 
 
 .25 
 
 Peerless 
 
 .23 
 
 
 
 Table 5: PEACH TWIG BORER PUPAE FOUND UNDER TREE PROTECTORS ON 
 
 THREE-YEAR-OLD ALMOND, ARBUCKLE, CALIFORNIA 
 
 May 7, 1940 
 
 Variety 
 
 Number 
 trees 
 
 Number 
 
 trees 
 infested 
 
 Total 
 
 number 
 
 pupae 
 
 Number 
 pupae 
 alive 
 
 Per cent 
 mortality 
 
 Average 
 
 number pupae 
 
 per tree 
 
 Peerless 
 
 Nonpareil 
 
 NePlus 
 
 Texas 
 
 52 
 52 
 52 
 52 
 
 32 
 40 
 26 
 20 
 
 187 
 
 174 
 
 96 
 
 68 
 
 56 
 89 
 30 
 26 
 
 31.0 
 51.1 
 31.2 
 38.2 
 
 3.58 
 3.34 
 1.85 
 1.30 
 
 
 
 the ground up to the crotch and under the 
 rougher bark of the main forks (fig. 11) . 
 The description, time of pupation, and 
 the length of this stage have been dis- 
 cussed elsewhere. Pupae are readily dis- 
 tributed in the corners and cracks of lug 
 boxes where many mature larvae have 
 pupated after crawling out of picked fruit. 
 Observing that pupae often collect under 
 tree protectors in young orchards (fig. 
 11 ) , we obtained data on their abundance 
 by removing the tree protectors on four 
 adjacent rows and recording the num- 
 bers. These trees were the same unsprayed 
 ones used in table 4. The results are 
 shown in table 5 (see also table 16) . 
 
 Seasonal Cycle. The seasonal cycle 
 of this insect (table 6) is the same, no 
 matter what the host is, but the number of 
 annual generations varies. The period of 
 seasonal activity is longer on peaches than 
 on apricots, plums, and almonds and, 
 consequently, there are one or two more 
 annual generations in peach-growing dis- 
 tricts. This difference is more clear-cut in 
 areas where only peaches, apricots, or al- 
 monds are grown. In districts where many 
 types of orchards are within close prox- 
 imity, the number and peaks of broods 
 are less distinct. 
 
 The annual cycle of the twig borer can 
 be illustrated by using the two extreme 
 
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cases— on apricots and on late cling 
 peaches, such as Levi or Phillips. On apri- 
 cots the overwintering larvae begin feed- 
 ing under the bark in late February or as 
 soon as the trees break dormancy. These 
 larvae complete their maturity at a rather 
 slow rate during the cool weather or early 
 spring, and may be found tunneling into 
 the twigs during March and early April. 
 Pupation lasts 10 to 15 days. The mating 
 and egg-laying period of the moth is 
 about 2 weeks. The egg stage at this sea- 
 son lasts 7 or 8 days. In early May the 
 larvae of the first brood appear in small 
 numbers. Stragglers of this brood may be 
 found even a month later. By the time the 
 second generation of the season hatches 
 (early July), the apricots are harvested, 3 
 and the larvae distribute themselves over 
 the trees as they feed on the new growth. 
 Some of the larvae feed under the bark, 
 and do not seem to develop beyond the 
 second instar. In August it is difficult to 
 find any larvae feeding on the new growth 
 except occasionally in young orchards. 
 Thus, since a very small third generation 
 occurs on apricots, wilted shoots are very 
 rarely seen at this time of year. However, 
 more than 90 per cent of the larvae are to 
 be found in the crotches feeding under 
 the bark. From the above discussion, it 
 can be seen that a large seasonal build-up 
 does not occur on apricots. Hibernacula 
 are found readily only on young apricot 
 plantings. 
 
 In contrasting the annual cycle of the 
 pest on peaches with that on apricots we 
 note some differences. Spring activity of 
 the twig borer begins somewhat later on 
 peaches than on almonds and apricots, 
 but is fundamentally the same. The May 
 brood also appears a little later. In years 
 when cool weather causes very slow devel- 
 opment, the May brood does not reach a 
 peak of activity until the first of June. In 
 most peach-growing districts in the upper 
 San Joaquin and Sacramento valleys, the 
 period May 15 to 20 will find this brood 
 
 3 The peak of the apricot harvest (at Winters, 
 California) is May 25 to 28 in an average year. 
 
 active. The first summer brood, or second 
 generation, appears in early July at the 
 time the Tuscan variety is being har- 
 vested. From this time on, it is difficult to 
 distinguish clear-cut broods. All stages can 
 be found up to the first of September. The 
 movement of moths to later-maturing va- 
 rieties of peaches, as discussed elsewhere, 
 contributes to a build-up in the total pop- 
 ulation by the harvest peak of midsummer 
 varieties in August. In districts of large 
 acreages of the Phillips variety, the sea- 
 sonal peak of these overlapping summer 
 broods is not reached until early Septem- 
 ber. It may be said, therefore, that there 
 are three definite broods— in May, July, 
 and late August— with a partial fourth 
 brood in early September in some dis- 
 tricts. 
 
 It appears that the relative proportion 
 of each brood tunneling under the bark 
 increases throughout the season until late 
 summer when, after the last varieties of 
 fruit are harvested, all larvae form hiber- 
 nacula. The annual cycle of the hiber- 
 nacula is illustrated in table 7. 
 
 The seasonal cycle on nectarines, 
 plums, and almonds is very similar to that 
 on peaches— two definite broods, May and 
 July, with a partial third. On almonds, 
 the third brood extends over a period of 
 4 or 5 weeks or until the last hard-shelled 
 varieties are harvested. On these hosts, a 
 much larger percentage of the newly 
 hatched larvae of the July brood— the sec- 
 ond generation— and nearly all of the Au- 
 gust brood feed entirely under the bark 
 (table 3). These larvae do not mature 
 until the following spring. Occasional 
 mature larvae may be found during warm 
 days in September on any of the host 
 crops. These individuals constitute, tech- 
 nically, a fourth generation. 
 
 PARASITES 
 
 Ever since the peach twig borer was 
 first studied by Marlatt and his associates, 
 by Clarke, and later workers in Cali- 
 fornia, parasites have been known to play 
 
 24 
 
an important part in its abundance. In this parasite is given under the section on 
 
 1931, Paralitomastix pyralidis (Ashm.) control. Whether or not the remainder of 
 
 was introduced into this state and liber- the parasites listed are all native enemies 
 
 ated in both southern and northern Cali- is not known. The parasites and predators 
 
 fornia. Although now established in Cali- include wasp and fly parasites of the 
 
 fornia, it is rarely seen. It attacks the twig larva. In the hibernaculum, the larva is 
 
 borer egg, but eventually kills the host in attacked by 2 species of wasps, a thrips, 
 
 the larval stage. P. pyralidis is poly- 2 species of beetles, and the grain or itch 
 
 embryonic. Additional information on mite, as listed in the following tabulation. 
 
 KNOWN PARASITES AND PREDATORS 
 OF THE PEACH TWIG BORER, Anarsia lineatella Zell. 
 Hymenoptera 
 
 Ichneumonidae 
 
 Ephialtes sanguinipes (Cress.)— most common in 1932-1933 from pupa of host. 
 
 Itoplectis obesus Cush.— from pupa. 
 
 Aenoplex phryganidiae Ashm.— from pupa (may be secondary) . 
 
 Dicaelotus pacificus Ashm.— from pupa. 
 
 Eulophidae 
 
 Secodella cushmani Crawf .— on larva in hibernacula. 
 
 Pteromalidae 
 
 Dibrachys boucheanus (Rata.)— stage of host reared from unknown. 
 Pseudomicromelus deplanatus (Nees)— from pupa. 
 
 Eupelmidae 
 
 Tineobius californicus Ashm.— from pupa supposedly. 
 Eupelmus sp. (near brevicauda Crawf.) —from pupa. 
 
 Chalcididae 
 
 Spilochalis torvina (Cress.)— from pupa (quite common) . 
 
 Braconidae 
 
 Microbracon mellitor (Say)— stage of host attacked unknown. 
 Microbracon gelechiae (Ashm.)— attacks twig borer larva. 
 
 Encyrtidae 
 
 Paralitomastix pyralidis (Ashm.)— host egg parasitized and adult parasites hatch 
 
 from host larva. Introduced from France in 1931. 
 Copidosoma variegatum Howard occurs in New York but not in California. 
 
 Elasmidae 
 
 Elamus setosiscutellatus (Crawford)— from host larva. 
 
 Tetrastichidae 
 
 Hyperteles lividus (Ashm.)— on larva in hibernacula. 
 
 Diptera 
 
 Tachinidae 
 
 Anachaetopsis tortricis Coq.— from host pupa. 
 
 Thysanoptera 
 
 Phlaeothripidae 
 
 Leptothrips mali (Fitch)— on eggs and small larvae chiefly in hibernacula. 
 
 [25] 
 
Coleopoptera 
 
 Anthicidae 
 
 Notoxus constrictus Casey-adult beetle predacious on pupae and larvae in 
 hibernacula on almonds. Observed at Chico only. 
 
 Hydnocera scabia LeConte-Larva predacious on hibernacula observed at Chico 
 only. 
 Arachnid a 
 
 Tarsonemidae 
 
 Pediculoides ventricosus (Newport)-predacious on larva in hibernacula. Espe- 
 cially abundant in the Vacaville district and westward. 
 
 Our attention has recently been called to the parasite host catalogue prepared by 
 W. R. Thompson (1944). This author lists the following additional parasites of 
 Anarsia lineatella: 
 
 Apanteles anarsiae Faure and Alabouvette (Hym. Braconid) 
 
 Apanteles emarginatus Nees (Hym. Braconid) 
 
 Apanteles xanthostigmus Hal (Hym. Braconid) 
 
 Dibrachys cavus Walk. (Hym. Pteromalid) 
 
 Elasmus flabellatus Fonsc. (Hym. Elasmid) 
 
 Euderus sp. (Hym. Eulophid) 
 
 Hemiteles incisus Bridgm. (Hym. Ichenumonid) 
 
 Paralitomastix varicornis Nees (Hym. Encyrtid) 
 
 Perisierola gallicola Kieff (Hym. Bethylid) 
 
 Phygadeuon rusticatus Wesm. (Hym. Ichenumonid) 
 
 Spilochalcis side Walk. (Hym. Chalcid) 
 
 In the period of years that the writer of pupae in sufficient numbers to be. 
 has studied this pest, many observations, indicative is made most difficult by the 
 counts, and miscellaneous data have been insect's habit of secreting the pupa in the 
 gathered on parasitism, particularly on rough bark. On young trees, however, 
 the hibernaculum stage. It has been hoped strips of cardboard, cloth, or tree pro- 
 that some basis could be established for tectors wrapped around the trunk will re- 
 predicting the relative numbers of over- suit in a concentration of pupae. The eggs 
 wintering larvae and the subsequent in- of the twig borer are most difficult to find 
 festation the following spring. This study, in the field. In addition to the parasite 
 however, has brought out a number of P. pyralidis, adult and larval thrips (Lep- 
 facts not previously known, and shows tothrips mali) have been seen feeding on 
 that, as yet, we do not understand the en- the eggs. There are no known parasites of 
 tire picture of natural parasitism. the adult moth. 
 
 During the period of active feeding in On the other hand, during the greater 
 
 the spring and summer, it is very difficult part of the year, hibernacula can be found 
 
 to obtain data on the degree of parasitism on the young wood (table 7) . It is in this 
 
 on the eggs, feeding larvae, and pupae, stage exclusively that overwintering takes 
 
 Larvae may be collected from wilted place. Therefore, it has been possible to 
 
 shoots and infested fruit. This process is make a detailed study of the parasites at- 
 
 slow and yields very little data of value, tacking this stage, and their effect on the 
 
 Many of the parasites thus collected seasonal abundance of the host insect, 
 
 hatch from the pupae. The collecting The degree of mortality of the inactive 
 
 [26] 
 
Table 7: ANNUAL CYCLE OF HIBERNACULA ON ALMOND 
 Arbuckle, California 
 
 Date 
 
 Number 
 
 
 samples 
 
 
 50 
 
 50 
 
 39 
 
 22 
 
 76 
 
 62 
 
 75 
 
 58 
 
 133 
 
 75 
 
 133 
 
 40 
 
 106 
 
 10 
 
 106 
 
 15 
 
 104 
 
 4 
 
 116 
 
 4 
 
 97 
 
 6 
 
 105 
 
 
 
 48 
 
 
 
 22 
 
 13 
 
 104 
 
 66 
 
 91 
 
 59 
 
 113 
 
 97 
 
 108 
 
 65 
 
 122 
 
 57 
 
 115 
 
 30 
 
 106 
 
 25 
 
 103 
 
 14 
 
 71 
 
 6 
 
 84 
 
 7 
 
 92 
 
 7 
 
 72 
 
 2 
 
 94 
 
 
 
 42 
 
 
 
 None 
 
 
 present 
 
 
 49 
 
 26 
 
 39 
 
 14 
 
 73 
 
 49 
 
 93 
 
 52 
 
 99 
 
 49 
 
 104 
 
 66 
 
 65 
 
 4 
 
 23 
 
 
 
 42 
 
 37 
 
 121 
 
 77 
 
 108 
 
 46 
 
 87 
 
 41 
 
 84 
 
 55 
 
 95 
 
 66 
 
 104 
 
 69 
 
 166 
 
 84 
 
 Dead 
 
 Empty 
 
 Parasitized 
 
 
 
 
 
 17 
 
 
 
 14 
 
 
 
 15 
 
 1 
 
 20 
 
 21 
 
 44 
 
 23 
 
 51 
 
 15 
 
 50 
 
 25 
 
 90 
 
 8 
 
 102 
 
 10 
 
 75 
 
 8 
 
 99 
 
 4 
 
 43 
 
 2 
 
 9 
 
 
 
 25 
 
 
 
 28 
 
 1 
 
 11 
 
 2 
 
 33 
 
 6 
 
 44 
 
 10 
 
 48 
 
 25 
 
 49 
 
 22 
 
 63 
 
 17 
 
 48 
 
 12 
 
 48 
 
 24 
 
 62 
 
 22 
 
 64 
 
 6 
 
 89 
 
 5 
 
 42 
 
 
 
 23 
 
 
 
 23 
 
 
 
 23 
 
 
 
 33 
 
 3 
 
 43 
 
 2 
 
 30 
 
 2 
 
 57 
 
 3 
 
 23 
 
 
 
 6 
 
 
 
 31 
 
 4 
 
 45 
 
 12 
 
 41 
 
 1 
 
 29 
 
 
 
 23 
 
 1 
 
 30 
 
 2 
 
 54 
 
 20 
 
 Per cent 
 mortality* 
 
 1940: 
 
 June 19 
 
 July 8 
 
 August 13 . . . 
 September 13 
 October 16 . . 
 November 14 
 December 14 
 
 1941: 
 January 9 . . . 
 February 12 . 
 February 24 . 
 
 March 7 
 
 March 17 
 
 April 10 
 
 May 20 
 
 May 29 
 
 June 10 
 
 July 2 
 
 August 4 . . . . 
 September 3. 
 October 3 . . . 
 November 4 . 
 December 1 . . 
 
 1942: 
 January 2 . . . 
 February 4 . . 
 February 17 . . 
 
 March 2 
 
 March 16... 
 
 April 16 
 
 May 22 
 
 June 5 
 
 June 11 
 
 June 24 
 
 July 7 
 
 August 3 . 
 
 September 19 
 
 1946: 
 
 March 15 
 
 April 24 
 
 May 27 
 
 June 29 
 
 July 29 
 
 August 27 . . . 
 September 30 
 October 28 . . 
 November 29 . 
 December 27 . 
 
 
 
 
 
 
 
 
 
 17 
 
 26 
 
 30 
 
 16 
 
 Z 
 
 
 
 8 
 
 2 
 
 3 
 
 
 
 8 
 
 3 
 
 3 
 
 4 
 
 11 
 
 12 
 
 10 
 
 9 
 
 
 
 
 
 
 
 1.6 
 
 33.0 
 
 55.0 
 
 81.0 
 
 73.0 
 
 71.0 
 
 71.0 
 
 72.0 
 
 100.0 
 
 100.0 
 
 0.0 
 
 0.0 
 
 1.5 
 
 4.8 
 
 13.3 
 
 26.9 
 
 55.2 
 
 56.1 
 
 65.0 
 
 73.3 
 80.5 
 76.6 
 75.0 
 100.0 
 0.0 
 
 0.0 
 
 6.6 
 
 2.0 
 
 13.3 
 
 12.5 
 
 10.8 
 
 50.0 
 
 0.0 
 
 0.0 
 
 14.4 
 
 28.5 
 
 10.8 
 
 0.0 
 
 8.3 
 
 6.7 
 
 25.0 
 
 * The per cent mortality was determined by subtracting the number of empty hibernacula from the number of 
 samples ; the number of dead and parasitized were added and this figure was divided by the number of hibernacula 
 containing live larvae plus those dead and parasitized. For example, on December 27, 1946, of the 166 samples 
 collected, 54 were empty. 166-54=112. There were 28 dead and parasitized — 28/112=25.0 per cent mortality. 
 
 [27] 
 
larvae is negligible during May, June, and 
 July, but in the fall it rises sharply and 
 by February usually reaches the seasonal 
 maximum. If bark samples are taken in 
 late January and February to determine 
 the degree of parasitism, a general indi- 
 cation is had of the potential infestation 
 for the season, at least in the orchard 
 sampled. 
 
 Neither Clarke nor Duruz found this par- 
 asite, probably because the major portion 
 of their work was conducted in a different 
 area from that of Ehrhorn. The writer has 
 noted a marked increase in the abundance 
 of this mite progressively from Winters 
 to Vacaville to Fairfield. Also, there ap- 
 pears to be some correlation between the 
 type and amount of covercrop and subse- 
 
 Table 8: PARASITISM OF HIBERNACULA* ON ALMOND, ARBUCKLE, CALIFORNIA 
 
 February 4, 1942 
 
 Row 
 
 Num- 
 ber 
 hiber- 
 nacula 
 
 Alive 
 
 Dead 
 
 Empty 
 
 Wasps t 
 
 Parasites 
 
 Per cent 
 
 num- 
 ber 
 
 Larva 
 
 Pupa 
 
 Adult 
 
 Thrips 
 
 Mites 
 
 Beetles 
 
 Total 
 
 tality 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 8 
 
 48 
 42 
 57 
 50 
 47 
 52 
 44 
 40 
 
 380 
 
 1 
 1 
 2 
 6 
 2 
 1 
 2 
 6 
 
 21 
 
 5 
 3 
 
 1 
 2 
 2 
 4 
 2 
 
 37 
 34 
 44 
 36 
 31 
 39 
 31 
 26 
 
 2 
 6 
 1 
 3 
 
 4 
 1 
 1 
 
 2 
 1 
 3 
 5 
 5 
 2 
 6 
 1 
 
 25 
 
 2 
 
 1 
 2 
 4 
 
 
 3 
 
 1 
 
 1 
 1 
 
 3 
 
 1 
 
 1 
 
 1 
 3 
 
 5 
 
 4 
 
 10 
 
 7 
 
 12 
 
 10 
 
 7 
 
 6 
 
 61 
 
 90.9 
 87.4 
 84.6 
 57.1 
 87.5 
 92.3 
 84.6 
 57.1 
 
 Total 
 
 19 
 
 278 
 
 18 
 
 9 
 
 3 
 
 80.1 
 
 * Variation of population of hibernacula and parasites in one orchard of four-year-old unsprayed almond trees, 
 adjacent rows. All visible hibernacula removed from 5 trees in each row. 
 t Hyperteles lividus (Ashm.). 
 
 In conducting this study it was ex- 
 tremely difficult to find sufficient hiber- 
 nacula on apricots, prunes, and plums to 
 compile any data, chiefly because of the 
 light infestations on the young trees and 
 the unusually rough bark on the older 
 trees. Therefore, the majority of the hi- 
 bernacula was obtained from peach and 
 almond. A continuous record of parasit- 
 ism in an unsprayed almond orchard at 
 Arbuckle was obtained from June, 1940, 
 to January, 1947. 4 These data are given 
 in table 7. 
 
 The grain or itch mite, Pediculoides 
 ventricosus (Newport), was recognized 
 by Marlatt (1898) as destroying as high 
 as 95 per cent of the overwintering larvae. 
 
 4 Exclusive of November, 1942, to February, 
 3946, when the writer was with the Armed 
 Forces of World War II. 
 
 quent mulch in the orchard, and the 
 abundance of the mite. Herms (1939) has 
 reviewed the life history of this predator. 
 
 The predacious thrips, Leptothrips 
 mali (Fitch), frequently becomes suffi- 
 ciently abundant to aid somewhat in re- 
 ducing the peach twig borer but holds 
 only a poor third place in abundance in 
 the hibernacula. The details of its habits 
 have been published by the writer (Bai- 
 ley, 1940). 
 
 The data in table 7 show very clearly 
 the seasonal trend which reoccurs in the 
 same order each year, at least for the prin- 
 cipal hymenopterous parasite here in- 
 volved, namely, Hyperteles lividus. The 
 seasonal peak of mortality is reached in 
 the late winter. In March and April, or 
 at the time all of the surviving host larvae 
 have emerged and have migrated to the 
 
 [28] 
 
Table 9: PARASITISM OF HIBERNACULA* ON ALMOND, ARBUCKLE, CALIFORNIA 
 
 January, 1942 
 
 Number 
 
 Alive 
 
 Dead 
 
 Empty 
 
 Waspsf 
 
 Parasites 
 
 Per cent 
 
 samples 
 
 Larva 
 
 Pupa 
 
 Adult 
 
 Thrips 
 
 Mites 
 
 Beetles 
 
 Total 
 
 tality 
 
 88 
 
 24 
 
 11 
 
 41 
 
 3 
 
 4 
 
 
 2 
 
 3 
 
 
 12 
 
 49 
 
 88 
 
 26 
 
 10 
 
 32 
 
 14 
 
 
 
 2 
 
 4 
 
 
 20 
 
 53 
 
 116 
 
 * 53 
 
 14 
 
 35 
 
 5 
 
 7 
 
 
 
 2 
 
 
 14 
 
 34 
 
 106 
 
 53 
 
 8 
 
 38 
 
 4 
 
 
 
 
 3 
 
 
 7 
 
 22 
 
 91 
 
 21 
 
 15 
 
 45 
 
 2 
 
 2 
 
 
 
 3 
 
 1 
 
 10 
 
 54 
 
 104 
 
 21 
 
 17 
 
 44 
 
 11 
 
 
 
 4 
 
 2 
 
 
 17 
 
 56 
 
 76 
 
 26 
 
 6 
 
 27 
 
 6 
 
 
 
 8 
 
 3 
 
 
 17 
 
 46 
 
 126 
 
 16 
 
 30 
 
 57 
 
 8 
 
 
 2 
 
 9 
 
 3 
 
 1 
 
 23 
 
 76 
 
 59 
 
 14 
 
 15 
 
 23 
 
 3 
 
 
 
 4 
 
 
 
 7 
 
 65 
 
 129 
 
 58 
 
 9 
 
 47 
 
 2 
 
 
 
 1 
 
 12 
 
 
 15 
 
 29 
 
 68 
 
 21 
 
 13 
 
 21 
 
 4 
 
 
 
 1 
 
 8 
 
 
 13 
 
 55 
 
 80 
 
 22 
 
 17 
 
 28 
 
 9 
 
 
 
 3 
 
 1 
 
 
 . 13 
 
 38 
 
 Ill 
 
 35 
 
 16 
 
 52 
 
 3 
 
 
 
 2 
 
 2 
 
 1 
 
 8 
 
 41 
 
 Total 
 
 390 
 
 181 
 
 490 
 
 74 
 
 13 
 
 2 
 
 36 
 
 46 
 
 3 
 
 176 
 
 47 
 
 * Variation of parasite population of hibernacula in unsprayed portions of the spray plots. All visible hibernacula 
 removed. 
 
 t Hyperteles lividus (Ashm.). 
 
 Table 10: PARASITISM OF HIBERNACULA* ON ALMOND, ARBUCKLE, CALIFORNIA 
 
 1940-1942 
 
 Date 
 
 Num- 
 ber 
 samples 
 
 un- 
 sprayed 
 
 Alive 
 
 Dead 
 
 Empty 
 
 Waspsf 
 
 Parasites 
 
 Per cent 
 mor- 
 
 
 Larva 
 
 Pupa 
 
 Adult 
 
 Thrips 
 
 Mites 
 
 Beetles 
 
 Total 
 
 tality 
 
 1940: 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Jan. 
 
 100 
 
 70 
 
 4 
 
 
 
 
 
 
 
 
 26 
 
 30 
 
 Dec. 
 
 81 
 
 46 
 
 10 
 
 23 
 
 2 
 
 
 
 
 
 
 2 
 
 20 
 
 1941: 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Jan. 
 
 500 
 
 257 
 
 18 
 
 219 
 
 4 
 
 1 
 
 
 
 
 
 7 
 
 8 
 
 Feb. 
 
 331 
 
 147 
 
 39 
 
 129 
 
 8 
 
 
 
 
 1 
 
 7 
 
 16 
 
 27 
 
 Dec. 
 
 328 
 
 120 
 
 31 
 
 94 
 
 49 
 
 1 
 
 2 
 
 7 
 
 12 
 
 2 
 
 73 
 
 43 
 
 1942: 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Jan. 
 
 1,242 
 
 390 
 
 181 
 
 490 
 
 74 
 
 13 
 
 2 
 
 36 
 
 46 
 
 3 
 
 176 
 
 47 
 
 Feb. 
 
 304 
 
 76 
 
 26 
 
 147 
 
 19 
 
 18 
 
 
 
 18 
 
 
 55 
 
 51 
 
 * In checks of the spray plots. All visible hibernacula removed. 
 t Hyperteles lividus (Ashm.). 
 
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new terminals, all of the remaining hiber- 
 nacula are occupied by dead larvae or 
 parasites. Usually in May some new hi- 
 bernacula begin to appear, and from this 
 time on the parasites find enough small 
 host larvae to maintain themselves. The 
 increase in the number of first instar 
 larva forming hibernacula in August and 
 September temporarily reduces the pro- 
 portionate number of parasites. During 
 the fall, parasite activity increases as the 
 host's population becomes stabilized. 
 
 The normal variation in the number, 
 type, and per cent of parasitism in a 
 young unsprayed almond orchard on ad- 
 j acent rows is shown in table 8. The aver- 
 age per cent mortality of the overwinter- 
 ing larvae on February 4, 1942, was 80.1, 
 but the extreme range of the 8 samples 
 was from 57.1 to 92.3 per cent on adj acent 
 rows. 
 
 During the period 1940-1942, 7 widely 
 scattered orchards were sampled in Jan- 
 uary to obtain comparative data on para- 
 sitism. The data are given in table 15, 
 with an indication of the relative degree 
 of injury the same season. Here again 
 there is exhibited great variation. These 
 data were based on one sample only— 
 about 100 hibernacula— from a selected 
 orchard of almond or peach in each dis- 
 trict. When compared with the relative 
 degree of injury during the following 
 summer, little correlation can be seen. 
 
 In order to determine a possible varia- 
 tion in the type of seasonal cycle or in the 
 other habits of the parasites of the hiber- 
 naculum on hosts other than almond, 
 monthly records likewise were kept on a 
 young peach orchard. This orchard, lo- 
 cated at Tudor in Sutter County, received 
 a normal spray schedule. The data are 
 presented in table 12. The seasonal trend 
 shown is the same as that on almonds, and 
 the same parasites are involved. 
 
 During the course of the dormant con- 
 trol studies, complete records were kept 
 on the number and type of parasites (ta- 
 bles 9 and 10), and these present addi- 
 
 tional facts of value in this phase of the 
 study. Tables 9, 13, and 14 illustrate the 
 nature of the parasitism on plums, nec- 
 tarines, and almonds in January, 1942. 
 These data show that the per cent of nat- 
 ural parasitism varies greatly, not only on 
 almonds but also on plums and nectar- 
 ines. Here again, the hymenopterous par- 
 asite, Hyper teles lividus, is the most 
 important, a fact also true in 1921-1922 
 when Duruz reported 70 to 90 per cent 
 parasitism. 
 
 Hyperteles lividus (illustrated by Du- 
 ruz, fig. 10, page 436, 1923) has defi- 
 nitely been the most effective parasite in 
 recent years in the Sacramento and upper 
 San Joaquin valleys. It is generally more 
 effective in the southern portion of the 
 Sacramento Valley (compare tables 7 and 
 11), the San Joaquin Valley, and toward 
 the coast than in the upper Sacramento 
 Valley. This condition may be the result 
 of higher minimum winter temperatures 
 in these areas. The eggs are deposited on 
 the body of the twig borer larva in the 
 hibernacula. The host larva appears to be 
 stung and paralyzed at this time since, 
 when removed from the bark chamber, it 
 lacks the ability to crawl. The parasite 
 larva feeds externally and, during the 
 summer, matures in about 3 weeks. Its 
 pupal stage lasts from 7 to 10 days. Dur- 
 ing the fall and winter there is one pro- 
 longed generation of the parasite. The 
 larva and pupa of this parasite are, in 
 turn, attacked by the predators mentioned 
 above. As shown in tables 8 to 14, inclu- 
 sive a few pupae and adults are found 
 during the winter, but the majority of the 
 parasites passes the winter in the larval 
 stage and emerges in the early spring. The 
 parasite larva is legless, attacks only one 
 host larva, and does not migrate to adjoin- 
 ing hibernacula. As previously mentioned, 
 nearly 100 per cent of the wasp larvae 
 found in the hibernacula during this 
 period have been H. lividus. Secodellu 
 cushmani Crawf. has been recorded as 
 common by Keifer and Jones (1933) and 
 
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Table 13: PARASITISM OF HIBERNACULA ON TRAGEDY PLUMS 
 
 Marysville, California 
 
 January, 1942 
 
 Number 
 
 samples* 
 
 (unsprayed) 
 
 Alive 
 
 Dead 
 
 Empty 
 
 Waspsf 
 
 Parasites 
 
 Per cent 
 
 Larva 
 
 Pupa 
 
 Adult 
 
 Thrips 
 
 Mites 
 
 Beetles 
 
 Total 
 
 tality 
 
 92 
 
 87 
 
 97 
 
 Total : 
 
 276 
 
 74 
 53 
 69 
 
 196 
 
 3 
 
 4 
 6 
 
 13 
 
 15 
 27 
 22 
 
 64 
 
 1 
 1 
 
 
 
 1 
 1 
 
 1 
 1 
 
 
 3 
 3 
 
 3 
 
 11 
 8 
 
 7 
 
 Santa Rosa 
 
 plums 
 101 
 
 50 
 
 18 
 
 22 
 
 3 
 
 
 
 5 
 
 2 
 
 
 10 
 
 35 
 
 * 100 bark samples removed from each plot. 
 t Hyperteles lividus (Ashm.). 
 
 Table 14: PARASITISM OF HIBERNACULA ON NECTARINES 
 
 Marysville, California 
 
 January, 1942 
 
 Number 
 
 samples* 
 
 (unsprayed) 
 
 Alive 
 
 Dead 
 
 Empty 
 
 Wasps t 
 
 Parasites 
 
 Per cent 
 
 Larva 
 
 Pupa 
 
 Adult 
 
 Thrips 
 
 Mites 
 
 Beetles 
 
 Total 
 
 tality 
 
 95 '.. 
 
 76 
 
 Total 
 
 171 
 
 23 
 32 
 
 55 
 
 14 
 10 
 
 29 
 21 
 
 50 
 
 23 
 
 11 
 
 34 
 
 2 
 2 
 
 1 
 
 1 
 1 
 
 2 
 2 
 
 4 
 
 
 
 29 
 13 
 
 65 
 
 41 
 
 24 
 
 1 
 
 42 
 
 54 
 
 * Samples obtained as in Table 13. 
 t Hyperteles lividus (Ashm.). 
 
 Table 15: PER CENT OF PEACH TWIG BORER PARASITISM FOR THE MONTH OF 
 
 JANUARY IN VARIOUS FRUIT-GROWING DISTRICTS 
 
 1940-1942 
 
 District 
 
 1940 
 Moderate 
 infestation 
 
 1941 
 
 Bad infestation 
 
 on almonds 
 
 1942 
 Moderate to 
 light injury 
 
 Average 
 
 Chico 
 
 Per cent 
 
 94 
 
 33 
 
 90* 
 
 93 
 
 98 
 
 Per cent 
 43 
 97 
 41 
 73 
 97 
 61 
 55 
 
 Per cent 
 61 
 83 
 30 
 73 
 82 
 69 
 65 
 
 Per cent 
 52 
 
 Gridley 
 
 Tudor 
 
 90 
 55 
 
 Ar buckle 
 
 59 
 
 Winters 
 
 Vacaville 
 
 89 
 76 
 
 Manteca 
 
 72 
 
 
 
 Average 
 
 81.6 
 
 66.7 
 
 66 
 
 
 
 
 * Not the same orchard as reported in 1941 and 1942. All samples (100 from adjacent trees) were taken from the 
 same orchard each year. 
 
 [33] 
 
Basinger (1935), and it is possible that 
 some of the larvae recorded may be this 
 species, but all the adults captured or 
 reared proved to be H. lividus. 
 
 CONTROL 
 
 Control methods against the peach twig 
 borer may be classified as cultural, bio- 
 logical, and chemical. 
 
 Cultural Methods. Destroying fallen 
 fruit, sterilizing lug bpxes, and burning 
 the prunings are orchard practices which 
 aid in reducing this pest. In seasons of 
 heavy infestation in peach districts, it is 
 very desirable to destroy the infested 
 fallen or dropped fruit of midsummer 
 varieties to reduce the moth popula- 
 tion which moves on to later-maturing 
 orchards. Mackie and Jones (1931) have 
 discussed this phase of control. 
 
 In the vicinity of loading platforms, re- 
 distribution points, and canneries, the 
 population builds up greatly during pick- 
 ing season. General sanitation around 
 these areas, as well as sterilization of lug 
 boxes, reduces local population. 
 
 An additional method of cultural con- 
 trol of the overwintering larvae is the 
 burning of prunings. In the San Joaquin 
 Valley, in orchards on sandy soil it is a 
 common practice to disk under the prun- 
 ings. In other areas the prunings are piled 
 and burned. In 1938 the writer collected 
 hibernacula from peach prunings at 
 Davis and caged them for observation. 
 During January, February, and early 
 March the larvae thus confined remained 
 in their cells, but as the bark dried out 
 they crawled away or died. To secure the 
 best results, the prunings should be 
 gathered up and burned as soon as pos- 
 sible after being cut. The proportion of 
 the hibernacula removed by the normal 
 pruning operation, however, is so small 
 that it has little effect on the infestation. 
 
 Biological Methods. Biological con- 
 trol methods have not been very success- 
 ful against the twig borer. Aside from the 
 established, natural parasites— discussed 
 in the section on parasites— either intro- 
 
 duced with the twig borer into California, 
 or occurring on other hosts that have 
 adapted themselves to Anarsia lineatella, 
 there is one parasite which deserves spe- 
 cial mention. This is the parasite, Para- 
 litomastix pyralidis (Ashm.). Basinger 
 (1935) has reported on this introduced 
 parasite. 
 
 In the summer of 1932, A. J. Basinger 
 and F. H. Wymore made liberations of 
 this parasite in Yuba City. Keifer and 
 Jones (1933) reported on the parasites 
 collected in this area in 1932 and the first 
 half of 1933 and did not find P. pyralidis. 
 However, it has been established, and has 
 actually spread to the north and west 
 since its liberation in northern California. 
 The writer has found twig borer larvae 
 attacked by this parasite on three oc- 
 casions: May 3, 1940, at Chico; May 7, 
 1940, at Arbuckle; and June 10, 1941, at 
 Arbuckle. In each instance the host plant 
 was almond. 
 
 It can be concluded that if in fourteen 
 years this parasite has not become more 
 abundant than is indicated above, it will 
 not play an important part in the control 
 of its host insect. 
 
 The two most important enemies are 
 the predacious mite, Pediculoides ventri- 
 cosus and the parasite Hyperteles lividus, 
 both feeding on the small larvae in the 
 hibernacula. No attempts have been made 
 to encourage, increase, or liberate these 
 parasites. Additional data on the occur- 
 rence, biology, and seasonal cycle of these 
 parasites, as well as others, are given in 
 another section. 
 
 Chemical Method — by Banding. 
 To our knowledge, no previous attempts 
 to explore the possibilities of control of 
 the twig borer by banding have been 
 made. In 1940 a heavily infested three- 
 year-old almond orchard at Arbuckle was 
 selected for a test with corrugated paper 
 bands treated with beta naphthol, such as 
 are used for the' codling moth. Untreated 
 bands were used as a check. Since the 
 most concentrated and uniform time of 
 pupation is early in June, the bands were 
 
 [34 
 
placed on the trunk, just below the fork 
 on May 28, or as the larvae began to 
 mature. The bands were removed June 10 
 when the first moths began to emerge. The 
 moths were reared in the laboratory, and 
 the data were compiled as indicated in 
 table 16. 
 
 Since less than half as many larvae 
 pupated in the treated than in the un- 
 treated bands, we infer that the beta naph- 
 thol has a repellent action on the mature 
 
 Smith has kindly made his unpublished 
 notes available to us, and we cite below 
 various data from this source. The oils, 
 60 neutral, 100 filtered pale, 70 filtered 
 pale, one of 140 viscosity, and kerosene, 
 were applied at full strength and then with 
 5 per cent pyridine, 5 per cent creosote, 5 
 per cent toluidine, and 5 per cent "selo- 
 cide." Kerosene and 70 filtered pale were 
 used also as a carrier of 5 per cent hexa- 
 chlorobenzine, 5 per cent alpha-naphtho- 
 
 Table 16: RESULTS OF EXPERIMENTAL CONTROL OF PUPAE BY BETA NAPHTHOL 
 
 TREE BANDS 
 Arbuckle, California, 1940 
 
 Number trees banded 
 
 Average 
 
 number 
 
 pupae 
 
 caught 
 
 per band 
 
 Total 
 number 
 of pupae 
 
 Dead in bands 
 
 Live 
 
 moths 
 
 emerged 
 
 Per cent 
 
 natural 
 
 mortality 
 
 Per cent 
 
 control by 
 
 treated 
 
 bands 
 
 22 treated 
 
 1.8 
 4.0 
 
 40 
 98 
 
 38 pupae 
 
 9 moths 
 
 14 larvae 
 
 12 pupae 
 8 moths 
 larvae 
 
 2 
 78 
 
 20.5 
 
 93.7 
 
 24 untreated 
 
 
 
 
 larvae. The actual kill was surprisingly 
 high by this method which is frequently 
 used on apples as a supplementary means 
 of controlling the codling moth. The 
 method, however, would not be effective 
 on large almond trees which have in- 
 numerable roughened areas on the trunks 
 and larger limbs where the larvae pupate. 
 
 Insecticidal Methods. Periodically, 
 as outbreaks of the pest have occurred, 
 the newer insecticides have been tested in 
 order to find more effective and cheaper 
 methods. For those readers who wish to 
 review early experimental work and con- 
 trol suggestions on this pest, we point out 
 the reports of Craw (1894), Marlatt 
 (1898), Clarke (1902), Duruz (1923), 
 and Plank (1936). 
 
 G. L. Smith conducted some tests dur- 
 ing February and March, 1933, at Yuba 
 City, California, on sucker shoots of 
 peach heavily infested with hibernacula. 
 
 lamine, beta naphthol and PDB, as well 
 as 0.5 per cent pyrethrum and "Nicolite" 
 which were used in kerosene and the 60 
 neutral pale. In studying the data on the 
 45 combinations which Smith applied, we 
 note that of the formulas giving more 
 than 85 per cent kill, nearly all, as might 
 be expected, showed injury to buds and 
 bark. Those combinations that did not 
 result in injury to the shoots were as 
 follows : 
 
 Date Per cent 
 
 applied F °™» 1 »* »<£«* 
 
 2/20 60 neutral pale 5 per cent 
 
 creosote 100.0 
 
 2/27 60 neutral pale, 0.5 per 
 
 cent "selocide" 90.1 
 
 3/10 Water, 9 parts, "Petrotine" 
 1 part, 2}i per cent 
 
 ^Nicolite" 100.0 
 
 * Materials within quotes not in general use at present 
 time. 
 
 [35 
 
Smith states that the oils 100 and 70 
 filtered pale, and the 140 vis. oil gave the 
 greatest penetration into the hibernacula 
 and concludes that "so few hibernacula 
 have been examined that no definite state- 
 ments can be made on the toxic effects and 
 of the effects on the peach." Smith also 
 added that conditions varied so greatly in 
 the district, it was not surprising that 
 lime-sulfur was generally believed to give 
 a good control. Under controlled condi- 
 tions where accurate observations could 
 be made, lime-sulfur gave a very poor 
 kill. Based on observations made in many 
 orchards in a test conducted by himself, 
 Lawrence Jones, and Plank, G. L. Smith 
 concluded that, in early spring, the best 
 control from sprays was obtained when 
 applied on trees in full bloom. Smith 
 stated that when this early spray is 
 omitted, the brood is so uneven by late 
 May that, unless an ovicide is used with 
 the basic lead arsenate, control is poor. 
 
 Control measures employed in other 
 states have been given by Edmundson 
 (1916) in Idaho, Lovett (1923) in Ore- 
 gon, List and Newton (1936) in Colo- 
 rado, and Newcomer (1941) in the 
 Pacific Northwest. 
 
 In Michigan, Anarsia lineatella is 
 found in peach orchards but has never re- 
 quired control measures. It also occurs 
 throughout the southern states but is 
 rarely injurious. The usual spray of lime- 
 sulfur— 1 gallon to 10 gallons of water— 
 and lead arsenate— 3 pounds to 100 gal- 
 lons of water— is used if necessary. Neither 
 do fruit growers in New York State have 
 to spray for this insect. R. C. Smith, et al. 
 (1943) recorded this orchard pest in 
 Kansas as being unimportant. Recent 
 literature from the Georgia Experiment 
 Station indicates that the peach twig 
 borer is of so little concern in Georgia 
 
 that 
 
 spraying is unnecessary. 
 
 CONTROL EXPERIMENTS, 
 1937-1946 
 
 Following the yearly increasing losses 
 to almonds from 1933 to 1936 (table 1), 
 
 the California Almond Growers' Ex- 
 change requested advice from the Uni- 
 versity of California. Dr. J. F. Lamiman 
 of the Division of Entomology at Davis 
 in 1937 and 1938 carried on control ex- 
 periments at Arbuckle, which the writer 
 took over in 1939. 
 
 Control of Feeding Larva. In col- 
 lecting the data cited in table 17, a ran- 
 dom 5 pound sample of unhulled nuts was 
 collected from the canvas at the end of 
 each row after knocking. This totaled 
 about 30 pounds per plot. These nuts 
 were hulled, cracked, and the number of 
 wormy meats tallied. The total number of 
 meats counted per plot of 6 rows of trees 
 each averaged about 2,000. This method 
 was used on all plots for the six-year 
 period, 1937-1942 and for 1947. After 
 two years of work the Ne Plus variety 
 was found to be uniformly lightly infested 
 as compared with Nonpareil. The latter 
 variety only therefore was used in the 
 later plots. 
 
 All applications were made with the 
 same power sprayer and standard or- 
 chard spray equipment. The dormant 
 sprays using dinitro compounds in a 
 power sprayer in 1940 and 1942 were dis- 
 appointing when compared with the re- 
 sults obtained with a knapsack sprayer in 
 small plots of young trees in the same 
 district. The poor control on the large 
 trees may be partially accounted for by 
 the fact that the rough bark absorbs a 
 greater proportion of the oil than does 
 the thin, smooth bark of the young trees. 
 Too, less oil was used in comparison with 
 the other tests listed in table 17. 
 
 A summary of the lead arsenate sprays 
 shown in table 17 is listed in table 18. 
 
 It will be noted in table 18 that the 
 jacket spray plus the May spray reduced 
 the infestation only slightly below the 
 effectiveness of the May spray alone. 
 Therefore, the value received from the 
 two sprays did not justify the additional 
 expense ; and the two sprays were discon- 
 tinued after three years. Since the chief 
 objective of these experiments was to pre- 
 
 36 
 
Table 17: RESULTS OF SPRAY PLOTS ON SOFT-SHELLED ALMONDS 
 
 Arbuckle, California 
 1937-1940 
 
 Date 
 
 Stage of growth 
 
 Material 
 
 Dosage 
 
 Per cent injury 
 to nuts 
 
 sprayed 
 
 Non- 
 pareil 
 
 Ne 
 Plus 
 
 1937 
 
 Mar. 2 
 
 Bud opening 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 5.1 
 
 1.1 
 
 Mar. 2 
 May 14 
 
 Bud opening 
 
 Basic lead arsenate 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 4 lbs. per 100 gals, of water 
 
 \ 3.8 
 
 1.3 
 
 Mar. 30 
 
 Petal fall 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 5.3 
 
 0.5 
 
 Mar. 30 
 May 14 
 
 Petal fall 
 
 Basic lead arsenate 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 4 lbs. per 100 gals, of water 
 
 | 3.0 
 
 1.2 
 
 Mar. 30 
 
 Petal fall 
 
 Basic lead arsenate 
 Lime-sulfur 
 
 4 lbs. per 100 gals, of water 
 13^ gallons 
 
 7.0 
 
 0.9 
 
 Mar. 30 
 
 
 Basic lead arsenate 
 Lime-sulfur 
 
 4 lbs. per 100 gals, of water 
 l l A gallons 
 
 !,. 
 
 2.4 
 
 May 14 
 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 , 
 
 
 May 14 
 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 » 
 
 3.7 
 
 2.2 
 
 
 Check 
 
 
 
 7.3 
 
 1.2 
 
 1938 
 
 Mar. 31 
 
 Petal fall 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 20.5 
 
 0.6 
 
 Mar. 31 
 May 24 
 
 Petal fall 
 
 Basic lead arsenate 
 Basic lead arsenate* 
 
 4 lbs. per 100 gals, of water 
 4 lbs. per 100 gals, of water 
 
 .,, 
 
 0.3 
 
 Mar. 31 
 
 Petal fall 
 
 Basic lead arsenate 
 Lime-sulfur 
 
 4 lbs. per 100 gals, of water 
 13^2 gallons 
 
 23.1 
 
 0.5 
 
 Mar. 31 
 
 Petal fall 
 
 Basic lead arsenate 
 Lime -sulfur 
 
 4 lbs. per 100 gals, of water 
 V/<i gallons 
 
 ) 
 
 { 9.8 
 
 0.5 
 
 May 24 
 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 I 
 
 
 May 24 
 
 
 Basic lead arsenate* 
 
 4 lbs. per 100 gals, of water 
 
 11.4 
 
 0.3 
 
 
 Check 
 
 
 
 35.0 
 
 1.5 
 
 * Lime-sulfur added to late spray as entire orchard was being sprayed for red spider. 
 
 t "Vaporol" and "zinc-coposil" are proprietary concentrates, applied with a spray duster. 
 
 t 4.1 oz. dinitro-ortho-cyclo-hexyl-phenol (hereafter referred to as DNOCHP) per gallon of oil (100-110 vis. 
 
 § Tri-ethanolamine salt of DNOCHP. 
 
 [37] 
 

 
 Table 17— Continued 
 
 
 
 
 Date 
 
 Stage of growth 
 
 Material 
 
 Dosage 
 
 Per cent injury 
 to nuts 
 
 sprayed 
 
 Non- 
 pareil 
 
 Ne 
 Plus 
 
 1939 
 
 1940 
 
 Mar. 15 
 
 Petal fall 
 
 Basic lead arsenate 
 Casein spreader 
 
 4 lbs. per 100 gals, of water 
 
 1.9 
 
 
 Mar. 15 
 May 9 
 
 Petal fall 
 
 Basic lead arsenate 
 Casein spreader 
 Basic lead arsenate 
 Casein spreader 
 
 4 lbs. per 100 gals, of water 
 
 Hlb. 
 
 4 lbs. per 100 gals, of water 
 
 Mlb. 
 
 :» 
 
 3 
 1 
 
 CO 
 
 Mar. 15 
 
 Petal fall 
 
 Basic lead arsenate 
 Casein spreader 
 
 4 lbs. per 100 gals, of water 
 Mlb. 
 
 1.8 
 
 o 
 
 CO 
 
 Mar. 15 
 May 9 
 
 Petal f all 
 
 Basic lead arsenate 
 Casein spreader 
 Basic lead arsenate 
 Casein spreader 
 
 4 lbs. per 100 gals, of water 
 
 Mlb. 
 
 4 lbs. per 100 gals, of water 
 
 Mlb. 
 
 \u 
 
 3 
 
 CO 
 
 1 
 
 
 
 | 
 
 May 9 
 
 Check 
 
 Basic lead arsenate 
 Casein spreader 
 
 4 lbs. per 100 gals, of water 
 X lb. 
 
 1.6 
 1.5 
 
 O 
 
 8 
 
 o 
 
 Feb. 2 
 
 Delayed 
 dormant 
 
 Sodium dinitro 
 cresylate (30 per 
 cent) 
 
 1 per cent 
 
 4.5 
 
 CD 
 
 1 
 
 to 
 o 
 
 Feb. 2 
 
 Delayed 
 dormant 
 
 DN and oilf 
 
 2 per cent 
 
 3.2 
 
 CO 
 
 Mar. 7 
 May 16 
 
 Jacket stage 
 
 Basic lead arsenate 
 Spreader 
 
 Basic lead arsenate 
 Spreader 
 
 ^4 lbs. per 100 gals, of water 
 }A lb. 
 
 4 lbs. per 100 gals, of water 
 Mlb. 
 
 2.7 
 2.3 
 
 o 
 
 CO 
 
 
 
 a 
 
 CO 
 
 s 
 
 0> 
 
 May 16 
 
 Check 
 
 Xanthone 
 Spreader 
 
 2 lbs. to 100 gals, of water 
 
 1.5 
 2.1 
 
 1 
 
 O 
 
 [38 
 
Table 17 — Continued 
 
 Stage of growth 
 
 Material 
 
 Dosage 
 
 Per cent injury 
 to nuts 
 
 Non- 
 pareil 
 
 Ne 
 Plus 
 
 1941 
 
 Feb. 26 
 
 Late jacket 
 
 Basic lead arsenate 
 Liquid adhesive 
 
 3 lbs. to 100 gals, of water 
 Kgal. 
 
 18.0 
 
 
 May 9 
 
 
 Basic lead arsenate 
 
 4 lbs. to 100 gals, of water 
 
 17.9 
 
 
 
 
 Powdered spreader 
 
 3^ lb. 
 
 
 .2 
 
 July 7 
 
 Hulls cracking 
 
 Basic lead arsenate 
 
 4 lbs. to 100 gals, of water 
 
 19.3 
 
 s 
 
 
 
 Powdered spreader 
 
 Klb. 
 
 
 ho 
 
 o 
 
 July 7 
 
 Hulls cracking 
 
 Rotenone powder 
 (0.58 per cent rote- 
 none from Cube', 
 other ether extrac- 
 tions 1.16 per cent, 
 plus 0.06 per cent 
 pyrethrins) 
 
 5 lbs. to 100 gals, of water 
 
 21.4 
 
 a 
 
 o 
 
 ■i 
 
 +» 
 
 to 
 
 o 
 
 CM 
 
 a 
 
 to 
 c3 
 
 T3 
 
 
 Check 
 
 
 
 20.8 
 
 O 
 
 o 
 o 
 
 Feb. 7 
 
 Bud swelling 
 
 Basic lead arsenate 
 
 10 lbs. 
 
 12.7 
 
 
 
 Oil concentrate J 
 
 10 gals. 
 
 
 o 
 5 
 
 
 
 Zinc-copper concen- 
 
 
 
 
 
 
 trate 
 
 15 lbs. 
 
 
 
 
 
 Water 
 
 10 gals. 
 
 
 
 
 
 (35 gals, per acre) 
 
 
 
 
 
 Check 
 
 
 
 12.3 
 
 
 1942 
 
 Jan. 31 
 
 Dormant 
 
 Sodium dinitro cresy- 
 late (30 per cent) 
 
 1:200 
 
 
 £ 
 3 
 
 
 
 Dormant oil emulsion 
 
 3 per cent 
 
 10.0 
 
 i 
 
 Jan. 31 
 
 Dormant 
 
 DN(T.E.A. salt)§ 
 
 1:400 
 
 
 Pi 
 
 
 
 Dormant oil emulsion 
 
 3 per cent 
 
 5.9 
 
 c9 
 
 May 26 
 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 4.2 
 
 o 
 
 
 
 Spreader 
 
 Mlb. 
 
 
 ■fa 
 
 to 
 9 
 
 July 17 
 
 Hulls cracking 
 
 Basic lead arsenate 
 
 4 lbs. to 100 gals, of water 
 
 4.5 
 
 CO 
 
 
 
 Liquid spreader 
 
 lqt. 
 
 
 oS 
 
 July 17 
 
 Hulls cracking 
 
 Fixed nicotine 
 (14 per cent nico- 
 tine sulfate) 
 
 4 lbs. to 100 gals, of water 
 
 4.9 
 
 ■*-» 
 O 
 
 o 
 
 4a 
 O 
 
 
 Check 
 
 
 
 8.4 
 
 £ 
 
 [39] 
 
Table 18: SIX- YEAR SUMMARY OF PER CENT OF INFESTED NONPAREIL ALMOND 
 
 MEATS IN BASIC LEAD ARSENATE SPRAY PLOTS 
 
 Arbuckle, California 
 
 
 1937 
 
 1938 
 
 1939 
 
 1940 
 
 1941 
 
 1942 
 
 Average 
 
 Check 
 
 7.3 
 5.3 
 3.7 
 3.0 
 
 35.0 
 
 20.5 
 
 11.4 
 
 9.1 
 
 1.5 
 
 1.8 
 1.6 
 1.4 
 
 2.1 
 2.7 
 2.2 
 
 20.8 
 18.0 
 17.9 
 
 19.3 
 
 8.4 
 4.2 
 4.5 
 
 12.5 
 
 Jacket spray only 
 
 May spray only 
 
 9.6 
 6.8 
 
 Jacket plus May spray . . . 
 July spray 
 
 
 
 
 vent the midsummer brood of larvae from All of the rotenone compounds listed 
 
 attacking the meats of the soft-shelled killed the larvae by contact. The general 
 
 varieties, a July spray was added to the observation was made that the period of 
 
 tests in 1941. As can be seen from the effectiveness was largely dependent on the 
 
 above figures, the results were somewhat rate of growth of the terminal leaves to 
 
 disappointing. which the larvae migrate. These new 
 
 In the summer of 1942 an experiment leaves were without spray residue. This 
 was conducted at Davis on young peach accounts for the variation in the effective- 
 trees to determine the maximum period of ness of duplicated treatments. Also, from 
 effectiveness of sprays against the twig the standpoint of practical field control, 
 borer larvae. it accounts readily for the lack of control 
 
 During May, June, and July the sprays by the May spray often reported in years 
 
 listed below were used; fresh larvae were of heavy infestation. If there is a marked 
 
 caged each successive day over the grow- overlapping of stages at this time, a single 
 
 ing terminals after the spray had dried. May spray is not too effective. 
 
 Maximum period 
 Material f effectiveness 
 
 (days) 
 Rotenone powder (about .60 per cent rotenone plus 0.06 per cent pyrethrins and 
 
 17.00 per cent petroleum oils) 5 lbs. to 100 gals 5 
 
 Rotenone powder (about .60 per cent rotenone plus 0.06 per cent pyrethrins and 
 
 17.00 per cent petroleum oils) 5 lbs. to 100 gals 9 
 
 Rotenone powder (about .60 per cent rotenone plus 0.06 per cent pyrethrins and 
 
 17.00 per cent petroleum oils) 5 lbs. to 100 gals 4 
 
 Rotenone powder (about .60 per cent rotenone plus 0.06 per cent pyrethrins and 
 
 17.00 per cent petroleum oils) 2% lbs. to 100 gals 4 
 
 Rotenone powder (about .60 per cent rotenone plus 0.06 per cent pyrethrins and 
 
 17.00 per cent petroleum oils) 2% lbs. to 100 gals 2 
 
 Rotenone powder, 4 per cent, 2 lbs. to 100 gals q 
 
 Rotenone powder, 4 per cent, 2 lbs. to 100 gals ' 5 
 
 Rotenone powder, 4 per cent, 1 lb. to 100 gals 2 
 
 Rotenone powder, 4 per cent, 1 lb. to 100 gals 6 
 
 Rotenone liquid concentrate (5 per cent rotenone and 1 per cent dispersing oil) 2 
 
 Rotenone liquid concentrate (2.8 per cent rotenone) 1/400 
 
 Sodium fluoaluminate, 3 lbs. to 100 gals., % lb. spreader 5 
 
 Sodium fluoaluminate, 3 lbs. to 100 gals., % spreader, with 1 lb. sugar ...... . ....... 8 
 
 Sodium fluoaluminate, 3 lbs. to 100 gals., % spreader, with 1 lb. sugar 4 
 
 Xanthone, 3 lbs. to 100 gals. V 2 lb. spreader 
 
 Tartar emetic, 3 lbs. to 100 gals., sugar 3 lbs 
 
 Liquid basic lead arsenate, 2 qts. to 100 gals 13 
 
 Liquid basic lead arsenate, 2 qts. to 100 gals., with 4 lbs. sugar 8 
 
 Basic lead arsenate, 4 lbs. to 100 gals., V 2 lb. spreader 4 
 
 [40] 
 
In 1940, reports indicated that in the 
 Sacramento Valley heavy worm infesta- 
 tions were building up on midsummer 
 peaches. Various orchards having dif- 
 ferent treatments were checked at picking 
 time (table 19) to determine the actual 
 degree of injury and the relative effective- 
 ness of the control measures locally em- 
 ployed. No check trees were left by 
 growers. 
 
 None of the trees at Gridley received a 
 spring spray. The newly hatched larvae 
 of the midsummer brood first appeared 
 about July 30 and reached a peak August 
 13 to 15. The above counts were made 
 from the boxes immediately after picking. 
 The total per cent of infested fruit was 
 not ascertained since many badly injured 
 fruits with split pits, thrips scars, and 
 other defects— were not placed in boxes by 
 the pickers. 
 
 All applications, which were unsuper- 
 vised, were made by the growers. The sul- 
 fur was used for disease control, and the 
 DN for red spiders. 
 
 From these data and from observations 
 in many peach orchards over a period of 
 years it can be concluded that, where a 
 heavy infestation of larvae appears at 
 picking time, about 50 pounds of 70-30 
 dust (70 per cent sulfur and 30 per cent 
 basic lead arsenate) per acre, applied 
 under ideal conditions, are necessary to 
 give adequate protection. The majority 
 of the commercial applications is made 
 carelessly, with inadequate dusters, and 
 with too small an amount of dust applied 
 per acre to obtain satisfactory coverage 
 of all fruit. In addition, as has been 
 pointed out several times in this report, 
 the infestations vary so greatly from or- 
 chard to orchard that growers often be- 
 lieve a good control has been obtained 
 from what was actually a poor applica- 
 tion. When serious outbreaks of the pest 
 do occur, such control measures quickly 
 show their shortcomings. 
 
 Data on Santa Rosa plums were ob- 
 tained in 1942, and the results are sum- 
 marized in table 20. From the dates in- 
 
 dicated, it can be seen that the larvae were 
 very late in hatching that particular sea- 
 son. While this experiment was not very 
 conclusive in some respects, it indicates 
 that nicotine spray powder has value in 
 the program, especially if a poisonous 
 residue is to be avoided. Also, it is to be 
 noted that the 70-30 dust which is of value 
 at this time of year likewise reduces the 
 residue problem. 
 
 Control of Dormant Larva. After 
 studying the results of the experimental 
 dormant control of the twig borer, re- 
 ported by other workers, it seemed 
 desirable to test many of the newer in- 
 secticides and especially the new wetting 
 agents, to determine their value. Also, a 
 review was made of published reports of 
 attempts to control other fruit insects hav- 
 ing similar hibernating habits, particu- 
 larly the codling moth, oriental fruit 
 moth, pecan nut casebearer, and pecan 
 leaf casebearer. 
 
 Various workers, especially Garman 
 (1930) , have tested many emulsions and 
 toxicants in attempts to control the hiber- 
 nating oriental fruit moth. The materials 
 showing the greatest promise have been 
 too expensive or have resulted in too 
 much injury to the trees to be practical. 
 Similar experiments with the hibernating 
 codling moth have been conducted as 
 newer chemicals became available. 
 
 Among the latest reports is that on the 
 work of Gnadinger et al. (1940) in which 
 the best results were obtained, on apples, 
 with a spray containing 60 milligrams 
 of pyrethrins per 100 cc of kerosene. 
 Aqueous sprays did not give adequate 
 penetration, even at 700 pounds pres- 
 sure. The above-mentioned kerosene- 
 pyrethrum spray would obviously cause 
 injury to the trees; therefore, the upper 
 two thirds of the tree was scraped, and 
 only the lower portion sprayed. This 
 method is, of course, impractical for the 
 twig borer. 
 
 Bilsing (1926) has experimented with 
 the possibility of dormant control of the 
 pecan nut casebearer with poor results. 
 
 41 
 
Table 19: PEACH TWIG BORER CONTROL ON PEACHES, 1940 
 
 Variety 
 and location 
 
 Haus 
 (Gridley) 
 
 Haus 
 (Gridley) 
 
 Peak 
 (Gridley) 
 
 Simms 
 (Gridley) 
 
 Halford 
 (Tudor) 
 
 Halford 
 (Tudor) 
 
 Simms 
 (Gridley) 
 
 Phillips 
 (Gridley) 
 
 Treatment* 
 
 Basic arsenate of lead and sulfur 30-70, 
 July 14. DN 1.5 per cent. Sodium fluo- 
 aluminate 49 per cent and sulfur 49.5 
 per cent, July 29 
 
 Basic arsenate of lead and sulfur 30-70. 
 July 14 
 
 Basic arsenate of lead and sulfur 30-70. 
 July 14 and 23 
 
 30-70 dust. August 6 
 
 Xanthone, 2 lbs. to 100 gals, (with y z lb. 
 spreader). May 22 
 
 Basic arsenate of lead, 4 lbs. to 100 gals. 
 May 22 
 
 DN 1 per cent, sodium fluoaluminate 60 
 per cent and sulfur 39 per cent. August 
 6 
 
 28 per cent basic arsenate of lead, 60 per 
 cent sulfur, remainder inert. August 14 
 
 Number 
 peaches counted 
 
 734 (6 boxes) 
 July 30 
 
 768 (6 boxes) 
 July 30 
 
 882 (8 boxes) 
 August 8 
 
 872 (8 boxes) 
 August 13 
 
 784 (8 boxes) 
 August 14 
 
 804 (8 boxes 
 August 14 
 
 395 (4 boxes) 
 August 15 
 
 857 (6 boxes 
 August 23 
 
 Number 
 peaches 
 infested 
 
 46 
 
 73 
 
 53 
 
 262 
 
 58 
 
 34 
 
 97 
 
 89 
 
 Per cent 
 infested 
 
 6.2 
 
 9.5 
 
 6.0 
 
 30.0 
 
 7.3 
 
 4.2 
 
 24.5 
 
 10.3 
 
 * Dusts applied with power machine; amount per acre varied from 30 to 50 pounds. 
 
 Table 20: PEACH TWIG BORER CONTROL EXPERIMENT ON SANTA ROSA PLUMS 
 
 Marysville, California, 1942 
 
 Date treated 
 
 Material 
 
 Dosage 
 
 Average number 
 
 of wilted shoots 
 
 per tree* 
 
 May 23 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 2.2 
 
 June 5 
 
 Basic lead arsenate 
 
 4 lbs. per 100 gals, of water 
 
 0.1 
 
 June 10 
 
 Basic lead arsenate 
 
 30 lbs. 
 
 0.9 
 
 
 Sulfur 
 
 70 lbs. 
 
 40 lbs. dust per acre 
 
 
 June 10 
 
 DND8f dust 
 
 40 lbs. dust per acre 
 
 4.7 
 
 June 12 
 
 Fixed nicotine J 
 
 6 lbs. per 100 gals, of water 
 
 0.2 
 
 
 Check 
 
 
 3.6 
 
 * 40 trees per plot; count made on June 19. 
 
 t Dicyclohexylamine salt of DNOCHP— 1.5 per cent. Petroleum oil (70 U.R., 100 vis.)— 2 per cent. 
 
 \ Proprietary compound of about 14 per cent nicotine sulfate. 
 
 [42] 
 
This worker, in correspondence, cites 
 some of his recent unpublished data as 
 follows : "I have obtained the best control 
 by the use of an oil with a viscosity of 200 
 to 220. I am inclined to believe that a 
 
 with this material but have not been able 
 to get as good control on the nut case- 
 bearer which spins a tougher cocoon." 
 Bilsing further states that the twig burn- 
 ing, which resulted from this mixture, is 
 
 Table 21: SUMMARY OF DORMANT SPRAY EXPERIMENTS ON 
 THE PEACH TWIG BORER 
 
 . Season 
 
 Number of different 
 formulas applied 
 
 Number of 
 hibernacula examined 
 
 Average mortality 
 of all sprays 
 
 Average mortality 
 of all checks 
 
 1939-40 
 
 33 
 
 48 
 86 
 
 167 
 
 2,108 
 
 6,491 
 
 10,655 
 
 per cent 
 
 49.4 
 41.5 
 68.7 
 
 per cent 
 68.0 
 
 1940-41 
 
 1941-42 
 
 19.4 
 47.1 
 
 
 19,254 
 
 
 Table 22: PER CENT MORTALITY OF DORMANT LARVA TREATED WITH DN AND 
 OIL* COMPARED WITH UNTREATED LARVA 
 
 Dates of sampling 
 hibernacula 
 
 Sprayed 
 Dec. 6. 1941 
 
 Check 
 
 Sprayed 
 Jan. 5, 1942 
 
 Check 
 
 Sprayed 
 Jan. 31, 1942 
 
 Check 
 
 1941: 
 December 12 
 December 19 
 December 26 
 
 1942: 
 
 January 2 
 
 January 9 
 
 January 16. . 
 January 23 f. 
 January 30. . 
 February 6. . 
 February 14. 
 
 Average 
 
 per cent 
 
 77.0 
 93.4 
 64.3 
 
 77.4 
 88.7 
 73.8 
 
 88.3 
 80.8 
 86.0 
 
 81.0 
 
 per cent 
 
 44.0 
 53.4 
 47.2 
 
 44.0 
 41.3 
 54.3 
 
 34.5 
 40.3 
 45.5 
 
 44.7 
 
 per cent 
 
 66.6 
 85.4 
 
 95.5 
 96.4 
 97.6 
 
 88.6 
 
 per cent 
 
 53.5 
 56.6 
 
 55.3 
 51.6 
 
 47.4 
 
 52.4 
 
 per cent 
 
 98.2 
 90.0 
 
 94.1 
 
 per cent 
 
 68.4 
 66.1 
 
 67.7 
 
 * The formula used was the tri-ethanolamine salt of DNOCHP at 1:200 (30 per cent) oil emulsion (80 vis., 70 
 U.R.) at 2 per cent, and a 10 per cent solution of wetting agent at 1:500. 
 t Heavy rain; no sample taken. 
 
 peach tree would not withstand an oil of 
 that viscosity, however. I have also ob- 
 tained very good control with an oil hav- 
 ing a sulphonation of 70 and a viscosity of 
 108. To this oil (at 2 per cent) I have 
 added about 2 pounds of dinitro-ortho- 
 cyclo-hexyl-phenol to each 100 gallons of 
 water. We have obtained practically 100 
 per cent control on the leaf casebearer 
 
 a serious disadvantage, and that water- 
 soluble dinitro compounds show greater 
 promise. 
 
 The dormant work reported below was 
 begun in December, 1939, and continued 
 for three winters. The experiments were 
 conducted in Colusa, Yuba, and Solano 
 counties with peaches, nectarines, plums, 
 and almonds. The majority of the work 
 
 43 
 
Table 23: MOST EFFECTIVE DORMANT SPRAYS FOR THE CONTROL OF PEACH 
 TWIG BORER LARVA ON PEACHES (1939-40) AND ON ALMONDS (1941-42) 
 
 Material and dosage 
 
 Date sprayed (1) 
 and examined (2) 
 
 Number 
 hibernacula 
 
 Per cent 
 mortality 
 
 1. DNOCHP, 1:600. 
 
 Dormant oil (100 vis., 72 U.R.) emulsion 2 per 
 cent 
 
 (1) Dec. 15, 1939 
 
 (2) Dec. 29, 1939 
 
 137 
 
 93 
 
 2. DNOCHP, 1:200 
 
 (1) Jan. 29, 1940 
 
 (2) Feb. 3, 1940 
 
 160 
 
 90 
 
 3. DNOCHP, 1:600 
 
 (1) Jan. 29, 1940 
 
 (2) Feb. 3, 1940 
 
 143 
 
 100 
 
 Check 
 
 (2) Dec. 29, 1939 
 
 46 
 
 90 
 
 4. DNOCHP (Tri-ethanolamine salt), 1:400 
 
 (1) March 5, 1940 
 
 (2) March 8, 1940 
 
 31 
 
 100 
 
 5. As above with pine oil 1 per cent, 1 :800 
 
 (1) March 1, 1940 
 
 (2) March 4, 1940 
 
 12 
 
 100 
 
 6. Pyrethrum extract (about 0.5 per cent pyreth- 
 rum), 10 per cent wetting agent, 1:400. 
 Pine oil, 1 per cent 
 
 (1) March 5, 1940 
 
 (2) March 8, 1940 
 
 28 
 
 100 
 
 Check: 
 
 (2) March 4, 1940 
 
 32 
 
 53 
 
 7. Rotenone (0.25 per cent by wt.) in oil emulsion 
 (82 vis., 76 U.R.), 4 gals. Wetting agent, 4 oz., 
 blood albumen, 4 oz. to 100 gals, water 
 
 (1) Jan. 9, 1941 
 
 (2) Jan. 20, 1941 
 
 118 
 
 93 
 
 8. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion, 82 vis., 76 U.R., 2 per cent. Wet- 
 ting agent, 4 oz. 
 
 (1) Jan. 10, 1941 
 
 (2) Jan. 24, 1941 
 
 120 
 
 90 
 
 9. Sodium dinitro cresylate (30 per cent) 1 :200. 
 Oil emulsion, 82 vis., 76 U.R., 2 per cent. 
 Wetting agent, 4 oz. 
 
 (1) Jan. 10, 1941 
 
 (2) Jan. 27, 1941 
 
 109 
 
 91 
 
 Check 
 
 (2) Jan. 24, 1941 
 
 121 
 
 19 
 
 10. Sodium dinitro cresylate 30 per cent, 1 :200. 
 Oil emulsion, 80 vis., 73-79 U.R., 4 per cent 
 
 (1) Jan. 16, 1942 
 
 (2) Jan. 27, 1942 
 
 134 
 
 91 
 
 11. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion 80 vis., 73-79 U.R., 4 per cent 
 
 (1) Dec. 22, 1941 
 
 (2) Jan. 5, 1942 
 
 71 
 
 100 
 
 Check 
 
 (2) Jan. 5, 1942 
 
 126 
 
 77 
 
 12. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion, 105 vis., 70 U.R., 4 per cent 
 
 (1) Jan. 16, 1942 
 
 (2) Jan. 28, 1942 
 
 98 
 
 100 
 
 Check 
 
 (2) Jan. 20, 1942 
 
 129 
 
 29.1 
 
Table 23— Continued 
 
 Material and dosage 
 
 Date sprayed (1) 
 and examined (2) 
 
 Number 
 hibernacula 
 
 Per cent 
 mortality 
 
 13. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion, 80 vis., 73-79 U.R., 4 per cent 
 
 (1) Jan. 16, 1942 
 
 (2) Jan. 27, 1942 
 
 91 
 
 90.9 
 
 14. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion, 80 vis., 80 U.R., 4 per cent 
 
 (1) Jan. 6, 1942 
 
 (2) Jan. 13, 1942 
 
 67 
 
 95.5 
 
 15. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion 105 vis., 70 U.R. (cut 25 per cent 
 with kerosene), 4 per cent 
 
 (1) Jan. 9, 1942 
 
 (2) Jan. 29, 1942 
 
 102 
 
 93.2 
 
 16. DNOCHP (T.E.A. salt) 1:200. 
 
 Oil emulsion 80 vis., 73-79 U.R. (cut 25 per 
 cent with kerosene), 4 per cent 
 
 (1) Jan. 16, 1942 
 
 (2) Jan. 28, 1942 
 
 110 
 
 90.6 
 
 17. As above with 10 per cent wetting agent, 1 :1500 
 
 (1) Jan. 16, 1942 
 
 (2) Jan. 28, 1942 
 
 78 
 
 95.8 
 
 Check 
 
 (2) Jan. 28, 1942 
 
 68 
 
 55.3 
 
 18. As above but oil emulsion at 2 per cent 
 
 (1) Jan. 9, 1942 
 
 (2) Jan. 27, 1942 
 
 115 
 
 98.4 
 
 19. As above with oil emulsion 105 vis., 70 U.R. 
 (cut 25 per cent with kerosene), 2 per cent 
 
 (1) Dec. 18, 1941 
 
 (2) Jan. 5, 1942 
 
 87 
 
 92.1 
 
 Check 
 
 (2) Jan. 5, 1942 
 
 76 
 
 46.9 
 
 20. DNOCHP (T.E.A. salt) 1:200. 
 Kerosene, 1:200. 
 10 per cent wetting agent, 1 .1500 
 
 (1) Jan. 9, 1942 
 
 (2) Jan. 27, 1942 
 
 123 
 
 98.4 
 
 was concentrated at Arbuckle on almonds. 
 Two progress reports were made on this 
 work by the writer in "Almond Facts" 
 (Bailey, 1941, and 1942). 
 
 Unless otherwise indicated, the applica- 
 tions were made with a knapsack sprayer 
 to young trees three to five years old. 
 From 5 to 15 trees were sprayed with each 
 material or mixture, the number depend- 
 ing on the visible number of hibernacula 
 present, in order that about 100 larvae be 
 subjected to each treatment. The entire 
 tree was sprayed with a uniform cover- 
 age. After sufficient time had elapsed to 
 make it possible to determine definitely 
 the dead larvae, the hibernacula were cut 
 from the test trees and from adjacent un- 
 
 sprayed trees, taken to the laboratory, and 
 examined under a microscope. 
 
 The following types of insecticides used 
 in these tests were found to have little or 
 no value in dormant control: thiocya- 
 nates, alkyl phenol, several proprietary 
 mixtures of dinitro phenols and cresols 
 (both dry and liquid), three proprietary 
 pyrethrum extracts, two types of rotenone 
 concentrates in solvents, nicotine sulfate, 
 dichloropentane, ortho-dichloro-benzene 
 (saturated solution in kerosene) , pine oil, 
 liquid lime-sulfur (at 2, 6, 8, and 10 per 
 cent), liquid lime-sulfur at 2 per cent 
 with 4 per cent oil emulsion (80 vis. and 
 79 U.R.) ; and heavy oil emulsions listed 
 at the top of the next page. 
 
 45 
 
100-110 vis 60-70 U.R. 
 
 130 vis 73 U.R. 
 
 144 vis 78U.R. 
 
 150 vis 60-70 U.R. 
 
 160 vis 73U.R. 
 
 175 vis 60-70 U.R. 
 
 200 vis 60-70 U.R. 
 
 Several oil emulsions in common use in 
 the range of 80-105 vis. and 70-80 U.R. 
 
 Following the first two winters of work, 
 one of the most satisfactory formulas was 
 used on almonds in a test to determine the 
 best time to apply such dormant sprays. 
 Three applications were made about one 
 month apart. At weekly intervals there- 
 after, approximately 100 hibernacula 
 were cut out of the bark of the sprayed 
 and unsprayed trees and examined under 
 
 Table 24: DORMANT SPRAY EXPERIMENTS FOR THE CONTROL OF PEACH TWIG 
 BORER LARVA WITH DN AND OIL 
 
 Material and dosage 
 
 Date sprayed (1) 
 and examined (2) 
 
 Number 
 hibernacula 
 
 Per cent 
 mortality 
 
 1. DNOCHP powder,* 2 lbs. 
 Diesel fuel oil, 6 per cent 
 Dried blood, 8 oz. to 100 gals, water 
 
 (1) Jan. 15, 1942 
 
 (2) Feb. 9, 1942 
 
 111 
 
 95.3 
 
 Check 
 
 (2) Jan. 21, 1942 
 
 87 
 
 11.6 
 
 2. DNOCHP powder,* lib. 
 
 Oil emulsion, 80 vis., 80 U.R., 4 per cent 
 Oxalic acid crystals, 2 oz. to 100 gals, water 
 
 (1) Jan. 15, 1942 
 
 (2) Feb. 9, 1942 
 
 115 
 
 97.5 
 
 Check 
 
 (2) Jan. 21, 1942 
 
 92 
 
 3.8 
 
 3. DNOCHP (T.E.A. salt),f 1:300. 
 
 Oil emulsion, 80 vis., 80 U.R., 4 per cent 
 Oxalic acid crystals, 2 oz. to 100 gals, water 
 
 (1) Jan. 15, 1942 
 
 (2) Feb. 9, 1942 
 
 107 
 
 91.4 
 
 Check 
 
 (2) Feb. 9, 1942 
 
 97 
 
 8.0 
 
 * 12.5 per cent active ingredient. t 30 per cent active ingredient. 
 
 were used at 4 per cent alone with poor 
 results. 
 
 Many of the materials were experi- 
 mental or were special preparations, and 
 certain others, offered for sale at the time, 
 are not on the market at present. The con- 
 tact toxicants were used in various stand- 
 ard dilutions— for instance, 1 :200, 1 :400, 
 1:800, with and without spreaders and 
 wetting agents, as well as with and with- 
 out oil emulsions. The heavy oil emul- 
 sions, used at 2 to 6 per cent, did not give 
 satisfactory penetration. They are danger- 
 ous to use in the delayed dormant period. 
 Kerosene alone evaporates too quickly to 
 give adequate penetration of the bark. A 
 summary of this work is given in table 21. 
 
 the microscope to determine the per cent 
 of mortality. The results are presented in 
 table 22. It can be seen from these data 
 that when the spray was applied at the 
 latest possible date, the control was better. 
 
 The most effective formulas used in 
 these experiments are listed in table 23 
 with the per cent control (or mortality) 
 obtained. No injury to the trees with any 
 of these mixtures was observed. The mor- 
 tality in the checks was from parasites. 
 
 A preliminary trial was made with 
 dry-mix dinitro powder which showed 
 promise. Following this trial, 16 combi- 
 nations of the material with various oil 
 emulsions, kerosene, and diesel fuel oil, 
 with and without a spreader and/or 
 
 46 
 
wetting agent, were applied to plums with 
 a power sprayer. The three combinations 
 giving better than 90 per cent control are 
 listed in table 24. 
 
 This plot was studied throughout the 
 spring. A wilted twig count made on April 
 2 is shown in table 25. 
 
 These data would seem to indicate that 
 the DN powder did not give quite such 
 good results as the liquid concentrate by 
 the time the overwintering larvae had all 
 emerged. The individual applications 
 
 The DDT wettable powder was tested 
 on a small scale in 1946 and 1947 against 
 the spring broods in the field on young 
 almonds. The data, presented in tables 26 
 and 27 were based on the shoot damage 
 caused by a rather light infestation. It in- 
 dicates, nevertheless, that DDT gives con- 
 siderable promise in the control of the 
 twig borer, in every instance being 
 slightly better than the basic lead arsenate. 
 
 Furthermore, the widely used wettable 
 DDT powder was compared with the basic 
 
 Table 25: WILTED TWIG COUNT ON PLUMS 
 
 Marysville, California, April 2, 1942 
 
 (Sprayed as indicated in table 24) 
 
 Plot 
 
 Total trees 
 counted 
 
 Total injured 
 twigs 
 
 Average 
 per tree 
 
 Per cent 
 control 
 
 1 
 
 Check 
 
 24 
 19 
 23 
 24 
 24 
 24 
 
 87 
 216 
 
 40 
 391 
 
 28 
 376 
 
 3.6 
 
 11.3 
 1.7 
 
 16.2 
 1.1 
 
 15.6 
 
 68 
 
 2 
 
 88 
 
 Check 
 
 
 3 
 
 93 
 
 Check 
 
 
 
 
 were not replicated. A practical control 
 was obtained, however. 
 
 Control with DDT. In the early 
 spring of 1946 a small-scale test of wetta- 
 ble DDT powder on the larvae was made 
 in the laboratory. Newly leafed out ter- 
 minal twigs of prune which had been 
 sprayed with wettable DDT powder (1 
 pound of DDT per 100 gallons of water) 
 were brought into the laboratory. Twig 
 borer larvae, about one half to two thirds 
 grown were caged on these shoots. All 
 larvae, whether crawling on the bark or 
 on the leaves, became excited and very 
 active within 20 minutes after contacting 
 the residue. Many individuals dropped 
 from the shoots and made no attempt to 
 return. No actual feeding was observed, 
 and all larvae were dead in 24 to 36 hours. 
 The same results were obtained when this 
 test was repeated. Furthermore, it was ob- 
 served that many of the larvae exuded 
 salivary fluid from the mouth a few 
 minutes after contacting the DDT. 
 
 lead arsenate in the almond orchard in 
 which we have records for several years 
 (table 17) . It can readily be seen that the 
 infestation was too light for us to have 
 arrived at any conclusion (table 28) . No 
 difference in the red spider infestation 
 was noted in any of the plots. In parts of 
 Stanislaus County in 1946 and 1947, how- 
 ever, twig borer infestations were rather 
 severe on cling peaches. In this area, DDT 
 is being more generally used each season, 
 since basic lead arsenate apparently fails 
 to give control, even when four applica- 
 tions are made. The reason is unknown 
 unless an arsenic-resistant strain of twig 
 borer is being developed here. In no case 
 known to us has DDT given poor results 
 when used against the peach twig borer. 
 Growers feel that if such obstinate twig 
 borer infestations can be controlled by 
 DDT, red spider injury can be reduced 
 if necessary by spraying after harvest. 
 
 For many years it has been a standard 
 practice not to apply basic arsenate of 
 
 47 
 
lead spray to peaches within 60 days of 
 harvest because of the potential residue 
 of lead and arsenic. Studies made by 
 Plank (1933), however, proved that 
 "peaches sprayed from one to four times 
 with basic arsenate of lead up to within 
 five days before harvest never contain 
 
 Division of Entomology and Parasitology 
 samples of peaches were analyzed from 
 orchards sprayed with DDT for adult 
 mosquito control before picking opera- 
 tions. The residue on the fruit was found 
 to be 2 to 6 p.p.m. (parts per million). 
 During the summer of 1946 further DDT 
 
 Table 26: PEACH TWIG BORER CONTROL* WITH DDT ON ALMOND 
 Dixon. California. 1946 
 
 Treatment 
 
 Variety 
 
 Row 
 
 Count 
 
 before 
 
 spraying 
 
 (May2)f 
 
 Count as 
 
 worms 
 
 begin 
 
 feeding 
 
 (May 27) 
 
 Count at 
 end of 
 larval 
 
 activity 
 (June 18) 
 
 Per cent 
 control 
 
 Check 
 
 Peerless 
 
 1,2 
 
 2.6 
 
 0.8 
 
 2.5 
 
 
 DDT (50 per cent) 
 
 Wettable— 2 lbs. 
 
 Yz lb. spreader 
 
 1 pt. kerosene to 100 gals. 
 
 Texas 
 
 3,4 
 
 5.1 
 
 0.0 
 
 0.15 
 
 94.0 
 
 Check 
 
 Nonpareil 
 
 5,6 
 
 1.8 
 
 0.05 
 
 1.3 
 
 
 DDT (10 per cent) and 
 Wettable sulfur (83 per cent) 
 10 lbs. to 100 gals. 
 
 Peerless 
 
 7,8 
 
 4.3 
 
 0.0 
 
 0.05 
 
 96.1 
 
 Check 
 
 Jordanola 
 
 9,10 
 
 3.2 
 
 0.8 
 
 3.8 
 
 
 Check 
 
 Texas 
 
 11,12 
 
 2.0 
 
 0.6 
 
 3.1 
 
 
 Basic lead arsenate 4 lbs., 3^ 
 lb. spreader to 100 gals. 
 
 Nonpareil 
 
 13,14 
 
 2.9 
 
 0.15 
 
 0.5 
 
 83.8 
 
 * Counts based on number of wilted shoots per tree (20 trees per plot) and average only given. Trees were 
 sprayed May 14 as eggs were hatching. 
 
 t This damage was caused by the spring brood and is an index of the infestation. No red spiders were present 
 before or after spraying. Following spraying, very cool, rainy weather delayed larval activity and washed off con- 
 siderable deposit. 
 
 more than negligible minute traces of 
 arsenic when subjected to the accepted 
 peeling and washing process now com- 
 mercially used." 
 
 On plums, the poisonous and objection- 
 able visible residue problem has been cir- 
 cumvented by the use of rotenone and 
 nicotine sprays. The sulfur and basic lead 
 arsenate dust (70-30) has been com- 
 monly used in canning peach districts 
 during early summer with no objection- 
 able residue left. 
 
 In 1945, through the facilities of the 
 
 residue studies were made in cooperation 
 with the Division of Chemistry (at Da- 
 vis), the Agricultural Extension Service 
 office at Modesto, and the Research De- 
 partment of the California Packing Cor- 
 poration. The data, listed in table 27, are 
 from peaches. 
 
 From these preliminary data it can be 
 seen that the present forms of DDT, ap- 
 plied at the strengths employed, leaves 
 a very small amount of residue. No resi- 
 due was found on the lye-peeled sprayed 
 fruit, and determinations were not run 
 
 [48] 
 
Table 27: PEACH TWIG BORER CONTROL WITH DDT ON ALMOND 
 
 Arbuckle, California, 1947 
 
 Spray material 
 
 Date 
 
 sprayed 
 
 Average 
 
 wilted shoots 
 
 per tree * 
 
 Per cent 
 control 
 
 Remarks 
 
 Wettable DDT (50 per cent) : 
 2 lbs. to 100 gallons 
 
 Mar. 13 
 
 2.3 
 (20 trees) 
 
 73 
 
 The March 13 spray for the 
 emerging larvae should have 
 been applied about 5 days 
 earlier for the best results, 
 but the weather did not per- 
 mit. 
 
 Basic lead arsenate: 4 lbs. 
 plus 1 qt. liquid spreader 
 to 100 gallons 
 
 Mar. 13 
 
 3.9 
 (20 trees) 
 
 55 
 
 No red spider infestations de- 
 veloped in this plot. 
 
 Wilted shoot count made Mar. 
 25 
 
 Check 
 
 
 8.7 
 (20 trees) 
 
 
 
 Wettable DDT (50 per cent) : 
 2 lbs. to 100 gallons 
 
 Apr. 30 
 
 0.08 
 (58 trees) 
 
 84 
 
 The April 30 spray was applied 
 after all moths had emerged 
 in this area and before any 
 wilted shoots were seen (the 
 first larva was found May 5). 
 
 Basic lead arsenate: 4 lbs. 
 plus 1 qt. liquid spreader to 
 100 gallons 
 
 Apr. 30 
 
 0.11 
 
 (54 trees) 
 
 78 
 
 No red spider build-up in this 
 
 orchard. 
 Wilted shoot count made May 
 
 22. 
 
 Check 
 
 
 0.51 
 (56 trees) 
 
 
 Five- to seven-year-old almond trees. 
 
 Table 28: PEACH TWIG BORER SPRAY PLOT ON NONPAREIL ALMONDS* 
 
 Arbuckle, California, 1947 
 
 Date 
 sprayed 
 
 Stage of growth 
 
 Material 
 
 Dosage 
 
 Per cent 
 
 of injury 
 
 tojiuts 
 
 March 13 
 
 Late jacket 
 Check 
 
 Wettable DDT (50percent) 
 
 2 lbs. to 100 gals, of water 
 
 0.3 
 0.3 
 
 March 13 
 
 Late jacket 
 Check 
 
 Basic lead arsenate 
 Liquid spreader 
 
 4 lbs. to 100 gals, of water 
 1 qt. 
 
 0.3 
 0.2 
 
 April 30 
 
 Check 
 
 Wettable DDT (50percent) 
 
 2 lbs. to 100 gals, of water 
 
 0.3 
 0.5 
 
 April 30 
 
 Check 
 
 Basic lead arsenate 
 
 4 lbs. to 100 gals, of water 
 
 0.7 
 0.3 
 
 In this test, 26,222 nuts were hulled, cracked, and counted. 
 
 [49 1 
 
Table 29: DDT RESIDUE ANALYSIS ON PEACHES 
 
 Sample 
 
 Variety 
 
 1 
 
 Palora 
 
 2 
 
 Phillips 
 
 3 
 
 Palora 
 
 A 
 
 Phillips 
 
 A 
 
 Phillips 
 
 B 
 
 Phillips 
 
 B 
 
 Phillips 
 
 C 
 
 Phillips 
 
 D 
 
 Phillips 
 
 4 
 
 Phillips 
 
 Treatment 
 
 May 15, wettable spray (1 
 lb. actual DDT to 100 
 gallons of water) 
 
 June 26, as above 
 
 July 19, dusted. DDT, 5 
 per cent and sulfur 50 per 
 cent, about 30 lbs. per acre 
 
 August 15, wettable spray 
 (1 lb. actual DDT to 100 
 gallons water, 300 gallons 
 per acre) 
 
 As above 
 
 As above 
 As above 
 
 As above 
 
 As above 
 
 July 30 and August 15 DDT 
 5 per cent, sulfur 50 per 
 cent, 33 lbs. per acre 
 
 Date 
 picked 
 
 July 30 
 
 July 30 
 July 30 
 
 Aug. 30 
 
 Aug. 30 
 
 Aug. 30 
 Aug. 30 
 
 Sept. 6 
 
 Sept. 6 
 
 Sept. 11 
 
 Condition 
 of fruit 
 
 Ripe 
 
 Green 
 Ripe 
 
 Ripe 
 
 Ripe 
 
 Ripe 
 Ripe 
 
 Ripe 
 
 Ripe 
 
 Ripe 
 
 . DDT residue in 
 parts per million 
 
 2.0 
 
 1.8 
 
 1.5 
 
 5.45 (Average of dupli- 
 cates) as received 
 
 0.0 (Average of dupli- 
 cates) lye-peeled 
 
 2.45 (Average of dupli- 
 cates) as received 
 
 0.0 (Average of dupli- 
 cates) lye-peeled 
 
 2.3 (Average of dupli- 
 cates) 
 
 2.9 (Average of dupli- 
 cates) 
 
 2.1 
 
 on the canned peaches. It is unknown 
 whether or not, under average cannery 
 conditions, the DDT residue in the lye- 
 peeler, when handling a large volume of 
 DDT-sprayed fruit, would accumulate 
 sufficiently to contaminate the commer- 
 cial pack. 
 
 DISCUSSION 
 
 The most outstanding fact observed in 
 this entire study is the great variation in 
 the twig borer population. This fact is 
 very evident in studying the work of 
 Clarke, Duruz, and others, as well as in 
 our own studies of parasitism and degree 
 of injury, in both the test and the control 
 
 plots. Even during the most severe epi- 
 demic of the twig borer on record, Mackie 
 and Jones (1931) showed that the de- 
 gree of injury varied from 0.1 per cent 
 to 20.7 per cent on 110 properties in Sut- 
 ter and Yuba counties. Since 1932 no ex- 
 tensive survey of this type has been made, 
 but the irregularities of outbreaks of this 
 pest in the principal peach-growing dis- 
 tricts are well known. The injury is not 
 only unpredictable from year to year but 
 also from district to district. 
 
 Our studies have been more closely 
 concentrated on almonds, and the facts 
 gathered on this crop and reported in the 
 tables of this study well bear out this 
 
 [50 
 
habit of great variation. Wide variation 
 occurs not only in the density of hiber- 
 nacula and parasitism, but in the number 
 of wilted twigs and number of pupae as 
 well as in the degree of infested fruit, 
 even in adjacent plantings. The percent- 
 age of injured soft-shelled nuts varies 
 widely every year in different districts, as 
 is pointed out by the Exchange records. 
 Our winter studies show that a consis- 
 tently high population is maintained in 
 Colusa and Butte counties and that, in 
 general, to the south and west progres- 
 sively the infestations become somewhat 
 lighter. The Paso Robles district suffers 
 no loss from this pest and the Santa Clara 
 Valley, lower San Joaquin Valley, and 
 southern California areas rarely report 
 any economic damage. 
 
 Following a comparative study of the 
 data gathered from the 1937, 1938, and 
 1939 spray plots at Arbuckle, consider- 
 able variation was noted in the degree of 
 injury occurring even from row to row. 
 In 1940 and 1941 records were carefully 
 kept to determine the degree of variation 
 in the infestation in the experiments re- 
 ported in table 17. 
 
 An analysis of these data— based on a 
 count of over 19,100 almond meats— indi- 
 cated a great range of injury from row to 
 row and plot to plot in the same orchard, 
 in two successive seasons, one of low and 
 one of medium injury. This variation 
 tends to throw doubt on the reliability of 
 the data obtained in the spray plots since 
 replications (or the Latin square method) 
 were not used. The great amount of work 
 involved in collecting and dissecting the 
 hibernacula, as well as in the harvesting, 
 made it impossible to replicate the various 
 sprays. 
 
 We feel, however, and it has been dem- 
 onstrated, that a practical reduction in the 
 number of overwintering larvae can be 
 accomplished by delayed dormant appli- 
 cations of an oil emulsion of about 80 vis. 
 and 80 U.R. with a toxicant, such as dini- 
 tro, on almonds and plums. At least many 
 materials have been eliminated, even 
 
 though DDT and other newer chemicals 
 are yet to be thoroughly tried. The mat- 
 ter of cost of such an application is still a 
 limiting factor as compared with basic 
 lead arsenate. The advent of new spray 
 materials for disease control also raises 
 many unanswerable questions of compati- 
 bility of the new chemicals and the possi- 
 bility of more efficient combinations of 
 insecticides and fungicides. 
 
 It was hoped that a determination of 
 the degree of parasitism of the hiber- 
 nacula in January would furnish a good 
 basis for predicting the severity of the 
 infestation the following summer. How- 
 ever, as pointed out above, the variation 
 is so great that such data are not too re- 
 liable. Furthermore, if conditions are 
 very favorable during the growing sea- 
 son, a moderate number of overwintering 
 larvae may build up to a sizable infesta- 
 tion by midsummer. There is no obvious 
 or regular cycle of epidemics of this pest. 
 
 The year-to-year variation in the de- 
 gree of injury to varieties of plums and 
 peaches depends on the time of ripening 
 in relation to the appearance of the mid- 
 summer brood. This is also true of apri- 
 cots. For instance, in some years the fruit 
 ripens at the peak of hatching of a brood ; 
 the considerable amount of damage which 
 results could not have been predicted in 
 February solely on the basis of the degree 
 of parasitism. Also, if the crop is heavy, 
 or light, the total injury is proportion- 
 ately small or great with a given number 
 of larvae. One of the principal factors in- 
 fluencing the severity of outbreaks is eco- 
 nomic—the price of fruit which, if good, 
 is usually reflected in a conscientious local 
 spray program which keeps the worm 
 population down to a minimum. 
 
 At present, biological control by para- 
 sites—as has been accomplished with cer- 
 tain scales and other insects— does not 
 seem practical, although there is room 
 for additional work on this phase of con- 
 trol. The native parasites operating so 
 effectively in the coastal areas and in the 
 lower San Joaquin Valley have their limi- 
 
 51 
 
tations. The relative importance of the 
 twig borer will determine the desirability 
 of searching abroad for additional and 
 more effective parasites. 
 
 Preliminary tests with wettable DDT 
 sprays indicate that it is somewhat better 
 than the widely used basic lead arsenate. 
 If DDT comes into general use, it is al- 
 most sure to throw certain local insect 
 and red spider populations out of balance, 
 particularly if applied after early May. 
 Experience only can indicate whether the 
 advantages of DDT will overcome the dis- 
 advantages in the control of the peach 
 twig borer. 
 
 SUMMARY 
 
 The peach twig borer, Anarsia linea- 
 tella Zell., is an introduced insect. It has 
 been an important insect pest in Cali- 
 fornia for over sixty years. Its two most 
 important host plants are the peach and 
 the almond. 
 
 Irregular epidemics have occurred in 
 the principal peach-growing areas of the 
 great valleys of California during this 
 period. Local infestations of major pro- 
 portions often arise in plum and almond 
 orchards in the upper San Joaquin and 
 Sacramento valleys. It is found in all 
 peach- and almond-growing areas of this 
 state as well as in nearly all deciduous 
 fruit sections of the United States. 
 
 In epidemic years, a 50 per cent loss of 
 peaches is common, and 20 to 30 per cent 
 damaged meats of soft-shelled almonds is 
 frequently encountered in the Sacramento 
 Valley. The damage to plums and nectar- 
 ines is usually less and more localized. 
 
 Great irregularity is observed in the 
 infestations. This makes the prediction of 
 outbreaks impossible with present meth- 
 ods of control. 
 
 The injury to the trees themselves is 
 unimportant as compared with the direct 
 damage by midsummer broods to the 
 ripening fruit. 
 
 The dark-gray moth is about % 6 inch 
 long. The minute yellowish-white, oval 
 eggs are laid on bark, leaves, and fruit, 
 
 singly or in small groups. The larva is 
 chocolate brown in color, with a black 
 head, and is about % inch long when full 
 grown. The naked pupa, usually found 
 under the bark, is dark brown and about 
 % inch in length. 
 
 During the summer season the approxi- 
 mate length of the life history stages is as 
 follows: egg, 5 to 7 days; larva, 10 to 20 
 days; pupa, 6 to 7 days; adult longevity, 
 about 10 days. The winter is passed in a 
 cell— the hibernaculum— hollowed out in 
 crotches of two-year-old wood and lightly 
 covered with frass and silk. Emergence of 
 these immature larvae takes place at blos- 
 soming time. There is a brood in May, 
 additional broods with a wide spread in 
 July and August, and a partial brood in 
 September. Some larvae from each brood 
 form hibernacula. 
 
 There are many known parasites and 
 predators of various stages of the peach 
 twig borer. The two most important at- 
 tack the dormant larva, namely the hy- 
 menopteran, Hyperteles lividus (Ashm.) , 
 and the grain or itch mite, Pediculoides 
 ventricosus (Newport). 
 
 The principal control measure is by 
 direct chemical control with insecticides 
 applied against the feeding larva during 
 early spring and in May. Spraying with 
 basic arsenate of lead, 3 to 4 pounds per 
 100 gallons of water, is the most widely 
 used program. Wettable 50 per cent DDT 
 spray powder has been used on a small 
 experimental scale only and may, in the 
 future, with limitations, partly replace 
 the lead arsenate. The potential poisonous 
 residue problem on market fruit must be 
 remembered; therefore, summer sprays 
 should be applied with caution. Prehar- 
 vest control may be obtained on canning 
 peaches with the generally used 70-30 
 dust (70 per cent sulfur and 30 per cent 
 basic lead arsenate) if a modern power 
 duster is employed, and about 50 pounds 
 of dust applied per acre in mature or- 
 chards. DDT dust of 5 per cent strength 
 likewise has shown great promise, but 
 should be used on a small scale only until 
 
 52 
 
more data are available on its relative 
 value and limitations. In general, the use 
 of DDT in orchards after late May tends 
 to increase the red spider hazard. Experi- 
 mental work with delayed dormant sprays 
 has demonstrated that a practical reduc- 
 tion in the number of overwintering lar- 
 vae can be accomplished by the use of an 
 oil emulsion of about 80 vis. and 80 U.R., 
 with a toxicant such as dinitro on al- 
 monds and plums. 
 
 RECOMMENDED CONTROL 
 PROGRAM 
 
 Little change can be made in the con- 
 trol recommendations for the peach twig 
 borer at this time. Many new chemicals 
 have been introduced into the field of 
 insecticides in recent years, but the ma- 
 jority is not adapted to this insect. Pre- 
 liminary experimental work with DDT 
 has been conducted, but not enough is 
 known concerning its value against the 
 twig borer to recommend its general use 
 in place of basic lead arsenate. 
 
 1. Dormant application. Until the 
 advent of DDT, the newest method of at- 
 tack was delayed dormant applications 
 of dinitro compounds with medium spray 
 oil emulsion. Growers have made little use 
 of this method of control. This type of 
 treatment must not be used on peaches. 
 On prunes and plums it has a place, espe- 
 cially where aphid eggs and scale also are 
 being treated during the dormant season. 
 Heavy infestations on almonds may also 
 be markedly reduced by such a spray. To 
 obtain the best results, apply the follow- 
 ing formula after about January 15 and 
 up to the early green bud stage : 
 
 Sodium dinitro-o-cresylate (30 per cent) 
 
 l]/ 2 to 2 qts. (1:200 or 1:300) 
 or wettable dinitro powder (DNOCHP, 
 20 to 30 per cent) .... 1 pound to 100 gallons 
 
 Medium oil emulsion (about 80 vis., and 
 80 U.R.) approximately 85 per cent 
 actual oil 2 to 3 gallons 
 
 Water 100 gallons 
 
 2. Prebloom spray. Where light in- 
 festations occur, annual early basic lead 
 
 arsenate sprays apparently hold down the 
 pest. This application is widely used on 
 apricots. In wet seasons such early treat- 
 ment is not physically possible and rains 
 reduce its effectiveness. Heavy infesta- 
 tions cannot be controlled by one early 
 application. The spray should be applied 
 from the bud-swelling stage to the pop- 
 corn stage. 
 
 Basic lead arsenate 3 to 4 pounds 
 
 Spreader or sticker ... 1/3 pound or 1 quart 
 
 Water 100 gallons 
 
 NOTE: If the basic lead arsenate is used 
 with bordeaux, no spreader is necessary. Also, 
 when there is a shortage of help and a large 
 acreage must be covered between rains, the 
 "Vapo" type of application — employing oil 
 concentrate, 10 to 12 gallons and 10 to 12 
 pounds of basic lead arsenate per acre — may 
 be used with considerable success for the first 
 brood. Our experiments, as well as those of 
 others, have indicated actually a very poor kill 
 of the larvae with lime-sulfur. In the central 
 and lower portions of the San Joaquin Valley, 
 the worms become active somewhat earlier 
 and prebloom sprays are very effective. 
 
 3. Jacket spray. This spray is par- 
 ticularly desirable on apricots, plums, and 
 peaches after petal fall. Use basic lead 
 arsenate as above. 
 
 4. May spray. The time of applica- 
 tion (May 5 to 25) varies from year to 
 year and is best correlated with the first 
 wilted shoots seen on young trees and 
 replants. Use powdered spreader (or wet- 
 table sulfur) and avoid "deposit build- 
 ers" or oils. Where mixed varieties occur, 
 all trees must be sprayed. Both the jacket 
 spray and May spray (basic lead arsenate 
 as above) are necessary in many peach- 
 growing districts. 
 
 5. Midsummer treatment. Substi- 
 tutes for the basic lead arsenate spray 
 must be used (except on almonds) to 
 avoid poisonous residue. The 70-30 dust 
 is widely used on peaches. On mature 
 trees, 50 pounds per acre are necessary 
 for adequate protection. On plums, spray- 
 ing with rotenone powder (3 to 5 pounds, 
 depending on strength of rotenone per 
 100 gallons of water) or with about 6 
 
 53 
 
pounds of fixed nicotine spray powder 
 (14 per cent strength) about a week be- 
 fore picking has given excellent results; 
 each variety must be sprayed as it ripens. 
 Such crops should be treated as soon as 
 any small stem worms are observed on 
 the first fruits to turn color. 
 
 6. DDT. This compound has been 
 tested against nearly all our important 
 pests, including the twig borer. To date, 
 we have used the wettable DDT powder 
 in controlled tests on almonds only. Some 
 growers have used 2 to 4 pounds of the 
 wettable powder (or 1 pound of actual 
 DDT) to 100 gallons of water, as well as 
 a 5 per cent dust, on canning peaches in 
 July and August, and report excellent 
 control during 1946 and 1947. The 5 per 
 cent DDT dust (particularly with 50 per 
 cent sulfur) appears to give excellent 
 promise of stopping the small larvae at 
 harvest time on late cling peaches. 
 
 As is true with any new material or 
 method, refinements and modifications 
 are necessary, partly by trial and error, 
 over a period of years before the best 
 standard of mixture and strength can be 
 established. Therefore, the above sugges- 
 tions for DDT are only preliminary. 
 Growers should keep this in mind, to- 
 gether with the fact that red spiders and 
 aphids are a serious potential problem 
 where DDT is employed. We do not have 
 sufficient data to recommend the whole- 
 sale use of DDT for the peach twig borer 
 at present, and before using it on fruit 
 trees, growers should obtain a clearance 
 from the canner or shipper. 
 
 ACKNOWLEDGMENTS 
 
 Modern research is rarely the product 
 of one individual's efforts, thoughts, and 
 observations. Such is true of this report. 
 The first bulletin on the twig borer (144) 
 prepared at the Experiment Station was 
 by W. T. Clarke in 1902. In 1923, W. P. 
 
 Duruz published bulletin 355 which pre- 
 sented more recent information on newer 
 spray materials. 
 
 Over a period of years various other 
 staff members of the Division of Entomol- 
 ogy and Parasitology have studied the 
 peach twig borer. Some of these workers 
 are no longer connected with the Univer- 
 sity and others have taken up different 
 types of research. I wish to acknowledge 
 at this time the contributions of A. D. 
 Borden, E. 0. Essig, J. F. Lamiman, G. L. 
 Smith, and F. H. Wymore. 
 
 From time to time, various students 
 have helped with the field control work 
 and have since become professional en- 
 tomologists. I am happy to recall the en- 
 thusiastic aid rendered by B. J. Konk- 
 right, I. R. Burden, Ray Barron, R. L. 
 Suggett, and Warren Stoner. 
 
 The field work has been conducted in 
 various fruit-growing counties, the offi- 
 cials of which have been most cooperative 
 and helpful. I wish to acknowledge par- 
 ticularly the aid of and pleasant associa- 
 tions with H. E. Catlin, V. W. DeTar, J. N. 
 Fiske, H. I. Graser, A. A. Jungerman, 
 R. H. Klamt, W. D. Norton, A. D. Rizzi, 
 J. E. Spurlock, C. H. Swanson, T. D. 
 Urbahns, A. G. Volz, and S. V. Walton. 
 
 Various fruit growers have been very 
 cooperative in the control experiments, 
 furnishing labor and equipment. I wish 
 to thank A. K. Andross, Harold Angier, 
 William Bethel, B. T. Mathews and son, 
 Ralph Newcomb, and Howard Rogers for 
 this type of aid. Insecticides and various 
 adjuncts, as well as field aid and helpful 
 suggestions have been supplied by Dr. 
 K. E. Maxwell, William B. Parker of the 
 California Spray-Chemical Corporation, 
 R. W. Underhill of the Dow Chemical 
 Company, various members of the Stauf- 
 fer Chemical Company, and Warren 
 Westgate of the Standard Agricultural 
 Chemicals, Inc. 
 
 54] 
 
SELECTED REFERENCES 
 
 We cite here only the principal references to the peach twig borer and especially 
 those reporting studies made since Duruz who cited thirty-seven references to earlier 
 work. Certain other references cited in the text are also listed. 
 
 Bailey, S. F. 
 
 1940. The black hunter, Leptothrips mali (Fitch) . Jour. Econ. Ent. 33(3) :539-44. June. 
 
 1941. Summary of twig borer studies for the season 1940. Almond Facts 7(1) :1, 6. January. Sac- 
 ramento, California. 
 
 1942. A progress report on the twig borer. Almond Facts 6(2) :1, 6, 7. February. 
 
 Basinger, A. J. 
 
 1935. Notes on the parasites of the peach twig borer in Southern California. California State Dept. 
 Agr. Mo. Bui. 24(4-6) :245-46. April-June. 
 
 BlLSING, S. W. 
 
 1926. The life history and control of the pecan nut case-bearer. Texas Agr. Exp. Sta. Bui. 328:51, 
 76. April. 
 
 Clarke, W. T. 
 
 1902. The peach worm. California Agr. Exp. Sta. Bui. 144:1-44. 
 
 Craw, A. 
 
 1894. Insect pests and remedies. California State Bd. Hort. Bui. 67:9. 
 
 Duruz, Willis P. 
 
 1923. The peach twig-borer (Anarsia lineatella Zeller) . California Agr. Exp. Sta. Bui. 355:1-57. 
 March. 
 
 Edmundson, W. C. 
 
 1916. Insect pests of the orchards and gardens of Idaho and their control. Idaho Agr. Exp. Sta. 
 Dept. Hort. Bui. 87:19-20. February. 
 
 Garman, P. 
 
 1930. The oriental peach moth in Connecticut. Connecticut Agr. Exp. Sta. Bui. 313:423. March. 
 
 Gnadinger, C. B., J. B. Moore, and R. W. Coulter. 
 
 1940. Experiments with pyrethrum for the control of codling moth (Carpocapsa pomonella Linn) . 
 Jour. Econ. Ent. 33(1) :144, 147. April. 
 
 Herms, W. B. 
 
 1939. Medical entomology. 582 pp. (See specifically pages 459-90.) The Macmillan Company, 
 New York. 
 
 Imms, A. D. 
 
 1934. A general textbook of entomology. 727 pp., 3d ed. (See specificially page 195.) E. P. Dutton 
 and Company, Inc., New York. 
 
 Jones, L. S. 
 
 1935. Observations of the habits and seasonal life history of Anarsia lineatella in California. 
 Jour. Econ. Ent. 28(6) :1002-11. 
 
 Keifer, H. H., and L. S. Jones. 
 
 1933. Some parasites of Anarsia lineatella Zell. in California. California State Dept. Agr. Mo. Bui. 
 22(7-11) :387-88. July-November. 
 
 List, G. M., and J. H. Newton. 
 
 1936. Insect and mite pests of the peach in Colorado. Colorado Exp. Sta. Bui. 427 : 18-20. May. 
 
 Lovett, A. L. 
 
 1923. The peach and prune twig-miner. Oregon Agr. Exp. Sta. Cir. 38:1-4. April. 
 
 Mackie, D. B., and M. L. Jones. 
 
 1931. Some biological aspects of the 1931 peach situation. California State Dept. Agr. Mo. Bui. 29 
 (10-11) :661-65. October-November. 
 
 f 55 1 
 
Marlatt, C. L. 
 
 1898. The peach twig-borer. U. S. Dept. Agr. Farmers' Bui. 80:1-15. 
 
 Newcomer, E. J. 
 
 1941. Orchard insects of the Pacific Northwest and their control. U. S. Dept. Agr. Cir. 270:64-65. 
 June. 
 
 Peterson, A., and G. J. Haeussler. 
 
 1928. Some observations on the number of larval instars of the oriental peach moth, Laspeyresia 
 molesta Busck. Jour. Econ. Ent. 21 (6) :843-52. December. 
 
 Plank, H. K. 
 
 1933. Removal of spray residue from canning peaches sprayed for twig borer control. California 
 
 State Dept. Agr. Mo. Bui. 22(2-3) :113-30. February-March. 
 1936. Results of miscellaneous insecticides used on larvae of the peach twig borer in hibernation. 
 
 California State Dept. Agr. Mo. Bui. 25(2) :216-25. April-June. 
 
 Smith, R. C, et al. 
 
 1943. Common insects of Kansas. (See specifically page 221.) Kansas State Bd. Agr. LVII, No. 
 255. June. Topeka. 
 
 Thompson, W. R. 
 
 1944. A catalogue of the parasites and predators of insect pests. Section I, Part 5 (A-Ch) . (See 
 specifically pages 43 and 44.) Imperial Agricultural Bureaux, Institute of Entomology, 
 Parasite Service, Belleville, Ontario, Canada. 
 
 10m-9,'48(A8248) 
 
 [56]