UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA THE CODLING MOTH IN WALNUTS H. J. QUAYLE BULLETIN 402 April, 1926 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1926 Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://www.archive.org/details/codlingmothinwal402quay THE CODLING MOTH IN WALNUTS' H. J. QUAYLE2 INTRODUCTION The codling moth, Carpocapsa pomonella Linn., has been known to attack the English or Persian walnut (Juglans regia) in California since 1909.^ In 1913, Mr. C. W. Beers, Horticultural Commissioner of Santa Barbara County, sent the writer a quantity of walnuts infested with a larva which proved to be that of the codling moth. During the same season walnuts in the vicinity of Santa Ana were found to be infested with the same pest. These appear to be the first actual records of injury to walnuts by the codling moth in southern Cali- fornia, although walnut growers, including Roy K. Bishop, then Horticultural Commissioner of Orange County, recall having seen similarly infested nuts earlier than 1913. At that time, in Santa Barbara and Orange counties, less than one per cent of the crop was affected. An increase followed, with yearly fluctuations, and by 1918 the infestation had become serious. The Citrus Experiment Station at once undertook studies looking toward the control of the pest. At the instance of the California Walnut Growers' Association, a special appropriation was made by the Legislature. This appropriation was made payable to the State Commission of Horticulture and through its director, Mr. G. H. Hecke, one-half of the amount was turned over to the University for investi- gational work, while one-half was retained by Mr. Hecke 's office for quarantine and survey work. In 1908 C. P. Lounsbury, Chief of the Division of Entomology, Union of South Africa, first noted the occurrence of the codling moth in walnuts^ in Wellington and Worcester, Cape Province. In the 1 Paper No. 143, University of California, Graduate School of Tropical Agri- culture and Citrus Experiment Station, Eiverside, California. 2 During a portion of the years 1919, 1920, and 1921 Roy K. Bishop, and for a portion of the year 1920, George H. Vansell and Paul R. Kerrick, assisted in this investigation. 3 Foster, S. W., On the nut-feeding habits of the codling moth, U. S. Dept. Agr., Bur. Ent., Bull. 805; .... 1910. 4 Mally, C. W., Codling moth in Walnuts, South African Fruit Grower, 3:3. 1916. See also: Lounsbury, C. P., Worms in v^alnuts. South African Fruit Grower and Small Holder, 6:307. 1919. 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION following years the infestation increased rapidly and during the season of 1914-15 Mally reported an infestation amounting to 50 or 60 per cent of the crop in some parts of the Oudtshoorn district. In France the codling moth has been known to attack walnuts since 1859. It was originally considered to be a distinct species {Carpocapsa putaminana Stand.) but later was determined as a variety of pomo- nella L., the species which attacks the apple. Mr. Carl Heinrich, of the U. S. Bureau of Entomology, states in correspondence his opinion that the insect attacking the walnut in Europe is not a variety, but is the same form as that which occurs in the apple in the United States. IDENTITY OF THE SPECIES Several experiments were carried out in order to determine the behavior of the insect when transferred from the apple to the walnut, and vice versa. Eggs which had been deposited on apples were trans- ferred to walnuts; a normal number hatched, and the larvae bored into the walnut in the same manner as on the original host. Recently hatched larvae which had begun to feed on the apple were transferred to the walnuts and these also developed normally. The same was true with half-grown and nearly mature larvae. In whatever stage the codling moth larvae from the apple was transferred to the walnut, the change of food had no effect on their development. Similar transfers were made of larvae from the walnut to the apple, with similar results. The next step was to determine the behavior of the moth as to her choice between depositing eggs on the walnut and the apple. Moths which had been reared from the apple were liberated in cages where apples and walnuts were suspended. These moths deposited eggs with equal freedom on either apples or walnuts. In fact, eggs were laid on various other fruits, including the lemon, although fruits with a fuzzy surface, such as the peach, were generally avoided. Then moths that had been reared from the walnut were tested in the same way as those from the apple and these also showed no preference in egg laying. Since the above experiments were carried out in cages only two feet square, it was deemed advisable to work under more nearly natural conditions. Accordingly, tests were made on two walnut trees of fair size enclosed under cheesecloth. This furnished conditions as nearly normal as practicable while confining known moths to particular trees. For each walnut on these two trees there was suspended an apple, in most cases in direct contact with the nut. Under one tree pupae from Bull. 402] TPIE CODLING MOTH IN WALNUTS the apple were liberated, and under the other, pupae from the walnut. In both cases eggs were deposited indiscriminately on both apples and walnuts. The larvae, however, seemed to show some preference for the apple, since some larvae which hatched on the walnut moved over to and entered the apple. Three other walnut trees were enclosed in cheesecloth cages, 12 X 12 X 18 feet (see fig. 1). In one of these cages codling moth pupae from the walnut were liberated; in another, pupae obtained locally from the apple, and in the third, pupae obtained from the apple four Fig. 1. One of the walnut trees enclosed in cheesecloth cage in oviposition experiments. hundred miles away. Nuts on all of these trees were attacked, although more were infested on the tree where the pupae came from the walnut. This greater infestation was due, in part at least, to the better condition of the pupae obtained from the walnut. Approxi- mately the same number of pupae were liberated in each of the trees, but mold had developed, particularly in those obtained from the apple four hundred miles distant, because they had been kept in a cool basement to delay their emergence. There is nothing in the foregoing experiments to indicate that the codling moth which infests walnuts is a different species or variety from that which infests the apple, although some special adaptation to the walnut may be necessary. Critical examination of the morphology of the different stages also indicated no specific or varietal 6 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION differences. Under field conditions, however, the behavior of the insect seems to be somewhat different from that indicated in our control experiments. It has been noted that where the branches of walnut and apple trees were in close proximity (in some cases inter- woven) a heavy infestation occurred in the apple and only a slight or no infestation in the walnut. These facts have been noted within the area where it is well known that the codling moth attacks the walnut. Numerous cases might be cited outside of the areas where walnuts were infested, where apples were heavily infested while walnuts grow- ing in close proximity were entirely free from attack. Apples infested with codling moth occur throughout the walnut-growing area, but except in two or three limited areas, the codling moth is not at present a pest of economic importance on the walnut, and there are large walnut-growing areas where the codling moth has not yet been found on the walnut. Where the walnut is not known to be infested, occasional infested nuts are most likely to be found in close proximity to apple trees. For example, until 1921 the codling moth was unknown in walnuts in Ventura County, but the writer found a few infested nuts in two different localities in that county, and in both cases apple trees were growing in close proximity to the walnuts. Similar cases have been observed outside of the well known infested areas in Orange County. The insect undoubtedly has come to the walnut from the apple. For this reason many growers desire to remove apple trees from their dooryards; others have suggested the planting of apples among the walnut trees as a trap crop. We believe nothing practical can be gained by either removing the apple trees or extending their planting. LIFE HISTORY^ AT SANTA ANA Wintering Larvae The larvae hibernate in cocoons beneath the loose bark in old pruning cuts, under bands, in trays, and in other places in which they can find protection. Only very rarely do they remain in the nuts. They are inactive until early spring, when they remodel their cocoons so as to furnish exit tubes for the moths. Spring hrood of pupae. — In 1920, an average season, counts and estimates made in the field on April 6 indicated that about 10 per cent of the wintering larvae in the walnut and about 15 per cent of 5 Tables showing the life history of the codling moth in great detail can be found in various publications. Only a summary of our data is given here. Bull. 402] tj^^ codling MOTH IN WALNUTS 7 those in the apple had pupated. On April 19, about 20 per cent had pupated from the walnut and 30 per cent from the apple. The last pupation of this brood from the walnut occurred on June 19 and from the apple about 10 days earlier. The duration of this stage varies from 18 to 30 days. Spring hrood of moflis. — The first moths of the season were seen in the field on April 15 in 1919, and on April 24 in 1920. The maximum emergence was about June 1*^ and the last emergence record for the apple was June 20, and for the w^alnut June 30. The First Generation First hrood of eggs. — The first eggs observed on the walnut in the field in 1919 were seen on May 8. In 1920, eggs were first seen on pears, May 8, on apples. May 12, and on walnuts. May 14. The maximum number of eggs were present on the apple about June 1, and on the walnut about June 10. It has been noted that eggs are deposited earlier on the apple than on the walnut, and that eggs of this brood continue to be deposited until early in July. The incubation period varies from 10 to 20 days. First hrood of larvae. — Hatching of eggs was first observed on May 14. The greatest number of larvae appeared on walnuts during the second or third week of June. A large majority of the first-brood larvae enter or attempt to enter the calyx end of the nut. Before all of this brood enter, however, the nut becomes too hard at the calyx end (third week of June) and entrance is thereafter sought at other points, particularly where two nuts are in contact. The larvae remain in the nuts, on the average, about 35 days. Some of this brood were found in the nuts 69 days after entrance, and even then they showed no signs of spinning a cocoon until disturbed and induced to spin by cracking the nuts. Such cases were noted late in August. An occasional larva of this brood even passes the winter before transform- ing. Definite cases of wintering of this brood have been noted at Carpinteria as well as at Santa Ana. First hrood of pupae. — The first pupation of larvae hatched in the spring was observed on June 15. The majority of this brood pupated during the latter half of July. The period spent in the cocoon varied from 6 days to several weeks, but most of the specimens transformed in 10 to 12 days. 6 Where the year is not given, the data will be understood to be the average (or extreme) for the years 1919, 1920, and 1921. 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION First hrood of moths. — The appearance of moths from eggs laid in the spring began on June 25, reached a maximum by July 30, and continued until September 1 or later. Moths from the spring brood were still present on June 25, so there is an overlapping of broods that persists and becomes more pronounced as the season advances. In fact, the overlapping may continue into the following season, since larvae of two or three diffeernt broods may pass the winter together. The dates given for the first observed appearance of the eggs, larvae, pupae and adults do not necessarily refer to the same insect, nor do they represent the first actual appearance of the different stages, but only the '^ observed" appearance. For example, the moth that emerged on June 25 may have pupated earlier than June 20, the date of the first observed pupation. The maximum emergence of this brood occurred about July 30. The average length of life of the moth is about two weeks. The Second Generation Second hrood of eggs. — During the last week of June and the first two weeks of July, egg-laying is at a minimum, although occasional eggs are deposited during this period. The first eggs of the second brood were seen on July 3. By the third week of July, eggs become more numerous, and the peak of egg-laying by this brood is during the first or second week of August. Second hrood of larvae. — Second-brood larvae began to appear early in July and reached their maximum numbers the second and third weeks of August. One larva which hatched on July 30, pupated on August 18; this period (20 days) represented the shortest larval life observed. On the other hand, under the heading ''First Brood of Larvae," a record is given of 69 days in the larval stage. Many of the second-brood larvae pass the winter as such, and do not complete their development until the following year. Second hrood of pupae and moths.- — Some of the second-brood larvae transform to the pupa and adult, the first of which may appear the last week of August and continue to appear until October. The Third Generation Third hrood of eggs and larvae. — Eggs and young larvae of this partial brood appear in September and October. Recently hatched larvae have been observed to enter the nuts as late as the second week in October. When the nuts are harvested, though most of the larvae are fully developed, many are in earlier stages. Bull. 402] THE CODLING MOTH IN WALNUTS SEASONAL HISTORY AT SANTA ANA The wintering larvae in their cocoons begin to change to pupae late in March and continue to pupate until the middle of June. The first moths appear during the middle of April, the peak of emergence occurs about June 1 and the last of the brood has emerged by July 1. The peak of egg-laying by this spring brood of moths occurs the first or second week of June, while the first week of May and the first week of August respectively represent the beginning and the end of the brood. The peak of the appearance of the larvae occurs about June 15, while May 15 and July 15 represent, respectively, the beginning and Ap :i] M iy ^\ m« Ju] y>/ y "V. ,J ug . S ep1 ; , c ct Mn th ^ y / \ ^ En er ?;e Xl ?^" N Sj / \ s^ ^^ ,-^ ^ rii l^ 3ro od ^V y " ^ B :oo d ^ > bd B> >64 ^^ -H / -<^ N / / \ -E^ ;S3 —g/ /^ "^ N y / \ ^ ^ 1 Jt Br )0d ^ ^ ^ 2n i B ro( )d r^ >^ ^ r^ ^ / ^ N Lt irv ae / / \ aa- ch in^ s ora /) N s^ / \ u ^ ^ ij ; I ro Dd" ^ ^ y 2n( I i ro >d ^U iS twb Fig. 2. Diagram illustrating the seasonal history of the codling moth in walnuts at Santa Ana. the end of the brood. The peak of the appearance of the moths of the first brood occurs the first week of August. Second-brood eggs appear in maximum numbers about August 10. Second-brood larvae appear the second and third week of August, and second-brood moths about September 15. Eggs and larvae of the third generation appear in September and October (fig. 2). The wintering larvae include those of the first, second, and third broods. There is thus but one complete generation of the insect with a partial second and third generation. SEASONAL HISTORY AT CARPINTERIA While an occasional moth may appear at Carpinteria almost as early in the season as at Santa Ana, the great majority appear later, In 1919 the peak of appearance of the spring brood of larvae occurred during the first and second weeks of July. In 1920 the peak occurred about the third week in June. There is only a partial second brood 10 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION of larvae at Carpinteria, and so far as observed, no third brood. At Santa Ana the greatest amount of injury is done by the second-brood larvae in late July, in August, and in early September, while at Carpinteria the greatest injury is done by the first brood during the latter part of June and in July and August. Nuts containing the first -brood larvae were collected in July, and, while some of the larvae transformed to the adult, some remained in their cocoons throughout the following winter. There is thus only one complete generation of the insect at Carpinteria and a partial second generation. Differences in temperature between Carpinteria and Santa Ana (fig. 3) account for the difference in the seasonal history of the codling moth at the two places. 70'' AQ 68 fi7 fifi f.E 1 1 fi4 6.'^ A5> fil r fiO 59 1 5ff 1 t April May June July August Sept. Oct. Fig 3. Average monthly mean temperatures for years 1919, 1920, and 1921. Solid line represents Santa Ana and dotted line, Santa Barbara. Note the difference in mean temperature from May to September, inclusive, the active season for the codling moth. This accounts for the difference in life history of the insect at the two places. INSECTS LIKELY TO BE MISTAKEN FOR THE CODLING MOTH Two insects which attack the walnut may be mistaken for the codling moth. One of these, the fruit tree leaf-roller {Archips argyrospila Walt.), attacks the growing nut, and the other, the Indian- meal moth {Plodia inter punctella Hbn.), attacks the nut only in storage. The larva of the fruit-tree leaf-roller bores into the nut in Bull. 402] THE CODLING MOTH IN WALNUTS 11 much the same manner as the larva of the codling moth. The two larvae are of about the same size, but the larva of the leaf -roller when feeding in walnuts is cream colored while that of the codling moth is more frequently pink when full-grown. The fruit-tree leaf-roller occurs only occasionally on walnuts; hence its control is not thus far a problem, but in new localities its work may be mistaken and it may thus be reported for the more serious codling moth. In one case, for example, a few walnut trees growing in a dooryard showed a high percentage (20 per cent) of infestation by this moth. \^^ ^ Fig. 4. Development of walnut, showing the closing and shriveling of the stigma. The codling moth never breeds in storage, and, aside from rare hibernating specimens, it is not found in stored nuts except soon after harvesting. The worm that is most commonly found in the nuts in storage is the Indian-meal moth. This insect is frequently troublesome in storage, but it may be destroyed by heating the nuts to a tempera- ture of 130-140 degrees for one hour, or by fumigation with carbon disulphide. FEEDING HABITS IN WALNUTS Most of the larvae which appear in the early spring enter the nut at the calyx end when the nuts are small and the stigma is still fleshy and cleft, as shown in the smallest nut on the left of figure 4. Later, however, the cleft portion closes and becomes brown and shriveled. The stigma furnishes suitable protection for the larva while it is entering the nut, and hence entrance is sought at this point. Tables 1 to 4 on page 17 give definite data on the proportion of larvae entering at the calyx. The calyx end is the point where the shell of the nut first 12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION hardens. Hence, after about the third week in June, entrance cannot be effected at this point, although attempts may be made throughout the season. As the nuts become larger, they often come in contact with one another, since two or more generally occur together, and the point of contact furnishes a favorite place for the larvae to enter throughout the rest of the season (fig. 5). The young larvae frequently make several shallow burrows at this point of contact and sometimes they eat over the surface generally without making a distinct burrow. Fig. 5. The commonest place of entrance of the codling moth in walnuts is where two nuts are in contact as shown. If the shell of the nut has not hardened, the larvae penetrate directly through the husk and shell to the interior. After about the middle of July, the entire shell of the nut becomes so hard that the larvae cannot burrow their way through, in which case feeding con- tinues on the husk adjacent to the shell. A more or less wandering burrow may be made until the fibrous suture at the base or stem end is found, where entrance may be effected regardless of the hardness of the shell. Sometimes the burrow leads directly to the suture, but in other cases there is no definite direction taken. Occasionally the suture is not found, and the larvae completes its development by feed- ing entirely on the husk. Larvae have sometimes been found to burrow for a considerable distance down into the stem of the nut. Larvae emerge from the nut generally through the suture at the base. The earliest first-brood larvae may emerge through the shell of the nut (fig. 7). Bull. 402] THE CODLING MOTH IN WALNUTS 13 Fig. C. Walnuts infested with the codling moth. Fig. 7. The four nuts to the left show exit holes of codling-moth larva; the upper center nut shows an exit hole made by an early first-brood larva in June, before the shell had hardened. After the shell hardens the only exit is through the basal suture. The two nuts on the right show that the larva has entered at the suture, but has not emerged. Such nuts show no entrance burrow, but they may be distinguished by the presence at the suture of small brown pellets. 14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION VARIETIES OF WALNUTS ATTACKED While all varieties of the English walnut are attacked by the codling moth, there is some evidence that ''hard-shells" and such budded varieties as the Placentia may be somewhat more susceptible than the average soft-shell type. The Eureka seems to be the least invested. Some nuts are much more tightly sealed than others and hence it is more difficult for the larvae to enter them. "Hard-shells" have a flattened base and a wide suture. Placentias are characterized as loosely sealed nuts. Eurekas, on the other hand, are firmly sealed and, while there is individual variation, some Eurekas are so closely sealed at the base that codling moth larvae cannot effect an entrance. In addition to its common food plants, the codling moth has been found in the field in apricots and in one case a considerable infestation in oranges that were growing close by a walnut drying house. Since it is the larvae entering the nuts in July and later that do the most conspicuous injury, nuts which are tightly sealed at the base are least often infested. Such nuts will not necessarily be free from attack, since the larva will feed on the husk in any case, but fewer worms will actually enter the nut, and so long as the feeding is con- fined to the husk the nut is not materially affected. Most of the larvae of the second brood, and all those of the later broods, as well as some of the first brood w^hich attack the nut in the cooler sections after about the middle of July, cannot gain entrance to the nut except through the fibrous suture at the base. AMOUNT OF INFESTATION When the attention of the Station was first called to the infestation of walnuts by the codling moth in 1913, counts made in the most heavily infested orchards at Carpinteria showed an infestation of less than 1 per cent. Between 1913 and 1918 there was marked yearly fluctuation, but, aside from a few individual orchards, the degree of infestation had not become serious before 1918. In 1918, however, there was a marked increase, and growers placed the infestation as high as 50 per cent in particular orchards. From 1919 we have authentic records of the amount of infestation, and the highest average record for a single season in any orchard is 37 per cent. In this particular orchard in the same season 45 per cent of the first picking was infested. In 1918 some orchards may have exceeded even this Bull. 402] THE CODLING MOTH IN WALNUTS 15 figure for the first picking, which, if true, would account for the high percentage recorded by certain growers. During the year 1919, however, the infestation reached its highest point in the Santa Ana district as a whole. A marked decrease occurred in 1920, and in 1921 the infestation was scarcely severe enough to justify the expense of control measures. The three-year records for the orchards in this district treated under my supervision follow : Percentage of Infestation in Check Plots (Without Control Measures), Santa Ana Year Orchard A Orchard B Orchard C Orchard D 1919 ... 16.1 6.3 1.5 9.8 6.3 3.1 12.0 6.1 1.1 12.1 1920 22.0 1921 3.6 In 1924 the infestation at Carpinteria was as high as in any season since the codling moth appeared in walnuts. In Orange County in the same year the infestation had become so reduced as to make control work unnecessary except on one property. At Rivera in Los Angeles County the infestation in 1924 was as high as 22 per cent in some orchards. The infestation here had increased rapidly between 1922 and 1924. A general campaign of control was then inaugurated under the supervision of the Los Angeles County Horticultural Commissioner. In 1925 there was a marked decrease in the infestation. Thus, it will be seen that there is considerable seasonal fluctuation and local variation in the amount of codling moth infestation in walnuts. As is well known, there are seasonal fluctuations of the codling moth in apples, but there has been no general decrease in infestation of the apple to a point where treatment has been unnecessary. The section of Orange County where the codling moth was first abundant was where control work first became unnecessary. Another section where the peak of infestation appeared a few years later was the last to require treatment. Carpinteria is the chief section where the codling moth has maintained about a uniform infestation through- out the period of observation, that is from 1918 to 1925. Prediction cannot be made that the codling moth may not increase again in Orange County or that it may not decrease in Carpinteria. It seems safe to assume, however, that the walnut is not the favorite host for 16 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION the codling moth and for that reason greater fluctuations in infestation may be expected than with the apple. It is sometimes maintained that measures should be applied regu- larly and continuously throughout a district from the time the first worms are found in order to prevent any development of infestation, rather than reduce the infestation after it has started. The writer does not recommend such a program, however. Control measures according to the best practice at present will allow three or four per cent of worms to escape if conditions in the particular area are at all favorable for the development of the moth. When the infestation does not exceed two or three per cent, control measures will not decrease materially this amount of infestation. There are thousands of acres of walnuts where the codling moth has been known to occur for the past eight or ten years, but where without the use of control measures there has been practically no increase in the amount of infestation. The application of control measures during this period in such areas would have involved an unprofitable expenditure. With certain newly introduced insects that are sure to become serious pests, control work cannot be started too soon. In the case of the codling moth in walnuts the increase of the insect has been erratic, since it has reached the status of an economic pest (that is three or four per cent or greater infestation) in only a limited part of the total walnut area known to be infested. In Contra Costa County, where this insect was first found on walnuts, it is only rarely that a nut has been found infested. Clearly, it would have been false economy to have treated all the trees in that section every year since 1909. Pest control work must be considered solely on an economic basis, although, of course, more than an immediate crop must be taken into consideration, since the health of the tree or the possible effect on subsequent crops may justify treatment at once. DROPPING OF NUTS Most of the nuts that are attacked by May or early June, drop from the tree while still immature. Those attacked later are also more likely to drop than sound nuts, and the first harvest therefore always shows a heavier percentage of infestation than later pickings. The percentage of nuts dropped during the seasons of 1920 and 1921 was much less than in 1919 because the first brood of worms was smaller in 1920 and 1921 than in 1919. A systematic effort was made in 1920 to record all nuts that dropped under certain trees (tables 1 to 4). These data follow: Bull. 402] THE CODLING MOTH IN WALNUTS 17 TABLE 1 Maybury Orchard — Lot 7, 50 trees Date picked June 14 June 22 July 3 July 16 July 22 July 28 Totals Number of fallen nuts . . 44 6 14 6 5 99 12 12 11 10 391 28 7 26 14 194 22 11 9 7 178 15 8 5 7 102 5 5 2 1 1008 Number infested 88 Per cent infested 9 Worms in nuts 59 Blossom-end entrance 44 TABLE 2 Brown Orchard — 30 trees Date picked June 16 June 24 July 2 July 9 July 15 July 21 Totals Nnmher of fallen nuts 157 35 22 29 30 270 58 21 50 41 535 126 23 94 92 448 57 12 21 16 468 48 13 18 17 301 19 6 5 5 2179 Number infested 344 Per cent infested 15 Worms in nuts Blossom-end entrance 217 201 TABLE 3 Stevens Orchard — 50 trees Date picked June 4 and 7 June 17 June 25 July land 2 July 15 July 21 July 26 Totals Number of fallen nuts 385 16 41 12 15 646 98 15 77 79 874 222 25 176 135 1331 228 17 168 126 983 115 12 52 53 454 37 8 6 10 475 9 2 1 4 5148 Number infested . . . 725 Per cent infested 14 Worms in nuts 492 Blossom-end entrance 422 TABLE 4 Crookshank Orchard — 40 trees Date picked June 25 July 6 July 13 Totals Number of fallen nuts 322 60 18 43 45 327 79 24 57 46 234 40 17 7 14 903 Number infested 179 Per cent infested 19 Worms in nuts . . 107 Blossom-end entrance 105 18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION It will be noted that the heaviest drop due to the codling moth occurred late in June and early in July. It is important to remember in this connection that various factors may cause walnuts to drop prematurely, and that only where the nuts are found to be infested, but otherwise sound, can the drop be attributed to the codling moth. Where both blight and codling moth occur, the dropping of the nuts may be due to either or both. Of these tAVO causes, the blight is very much more serious than the codling moth. It will also be noted from the figures given that a larger percentage of the larvae entered at the calyx in the earlier than in the later pickings. On some of the trees for which records were kept the infestation was reduced by treatment for the codling moth. DISTRIBUTION IN CALIFORNIA The codling moth has been found in all of the walnut districts of Orange County, with the heaviest infestation occurring about Santa Ana and Tustin. It also occurs in Los Angeles County in the Whittier- Puente-Covina districts, with the heaviest infestation in certain orchards near Los Nietos and Rivera. It occurs occasionally in the Chino district in San Bernardino County. In Santa Barbara County it occurs most abundantly in the vicinity of Carpinteria. An occa- sional nut has been found to be infested in the Goleta district in the same county. A few infested nuts have been seen in Casetas Pass, Ventura County, where walnuts and apples are growing in close proximity. A light infestation occurs near Saticoy in Ventura County. Here also the first walnuts found infested in 1921 were growing close to apple trees. A few codling-moth infested nuts have been found at Arlington in Riverside County. PARASITES AND PREDATORS There are a number of parasites and predators that attack the codling moth in its different stages. The commonest egg parasite is Trichogamum minutum Riley. Eggs harboring this parasite (there are commonly three in each egg) may be distinguished by their darker color. From the time the codling moth larva hatches until it has bored into the nut it is exposed to the attacks of a number of predatory enemies including insects, spiders, and birds. After it has emerged from the nut and while it is in the cocoon the larva, and later the pupae, are attacked by several parasites such as Aenoplex carpocapsa Cush- Bull. 402] the codling moth in walnuts 19 man and a number of predatory insects such as carabid and clerid beetle larvae (fig. 8). Any factor that helps to reduce the number of worms which attempt to enter the nuts is an aid in control in con- junction with the arsenical applied; but seldom, if ever, are the parasitic and predatory enemies of the codling moth important enough in themselves to effect a satisfactory control. Mr. Stanley E. Flanders, entomologist for the Saticoy Walnut Growers' Association, is making a special study of the parasites of the codling moth and the details of this subject will be left for treatment by Mr. Flanders. Fig. 8. A predaceous larva, Cermatydera sp. (Family Cleridae) that attacks the codling moth in its cocoon. CONTROL Banding the trees and picking up the infested nuts are two possible methods of control which have been given attention. Picking up the infested nuts, in our experience, did not reduce the amount of subse- quent infestation enough to justify the expense of the work. The figures given in tables 1 to 4 show that less than 10 per cent of the nuts on the ground harbored larvae. During seasons and in sections where walnut blight is more prevalent, the per cent of worms in the nuts on the ground would be much less. Banding the trees is recom- joaended as an auxiliary to spraying and also as a means of partial 20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION control where the infestation is not severe enough to warrant spraying. Burlap cut a foot wide and doubled when placed around the tree makes a satisfactory band. It may be held in place by two finishing nails driven into the tree trunk. If the bark is particularly rough it is best to smooth it in order to make a more suitable place for the larvae to make their cocoons. The bands should be in place by June 15, and removed every ten days or two weeks until October 15 to kill the larvae and pupae when they may be taken off for the winter. Most of the codling moth larvae or pupae may be detected at the points where the bands stick to the tree. Crushing is the simplest method of killing them. There is but one thoroughly satisfactory method for controlling the codling moth, viz., to coat the nuts with some poison which will destroy the larvae before entrance is effected. The poison may be applied as a dust or as a spray. Our further discussion of the control of the codling moth will have to do with these two methods. Results of Dusting in 1919 In 1919 a survey was made of the infested areas at Santa Ana and Carpinteria in which extensive applications of arsenate of lead applied as a dust had been made. More than 200,000 nuts, representing some 5000 pounds, were examined. Counts were made with each picking in most cases, and data representing the percentage of infestation were obtained from over 100 orchards, about one-half of which had been dusted. A general summary of the results is given in table 5. TABLE Percentage of nuts infested Santa Ana Carpinteria General average of all orchards dusted 4.73 6.33 10.00 21.9 .8 .33 4.2 General average of orchards not dusted 9.7 Highest percentage in any orchard dusted 6.6 Highest percentage in any orchard not dusted 15.8 Lowest percentage in any orchard dusted .7 Lowest percentage in any orchard not dusted .8 In considering the data given in table 5, it seems fair to assume that most of the heavily infested orchards had been dusted. This wa$ Bulk 402> THE CODLING MOTH IN WALNUTS 21 certainly the case, at least at Carpinteria. One orchard well toward the center of the infested area in that section, however, was left untreated, and another was not treated until very late in the season. These two orchards alone Avere used in arriving at the percentage of infestation (9.7) in the undusted groves of Carpinteria. Counts made just outside the infested district at Carpinteria showed practically no infestation, whether the trees had been dusted or not. Fig. 9. Dusting walnuts for the codling moth. At Santa Ana, however, many orchards that were not dusted occurred among the dusted orchards in the general area of infestation. Approximately an equal number of determinations were made also between dusted and undusted orchards, so that the figures should be fairly reliable. 22 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION ' The experience with dusting in 1919 indicated that when there was a considerable infestation the treatment paid, but that where the infestation was light, that is, under three or four per cent, the cost of the treatment was not returned in the extra amount of sound nuts secured. In order to determine the relative merits of spraying and dusting, certain orchards were divided into plots and treated under my super- vision. The results for 1919 are given in table 6 ; the results for 1920 are given in diagrams 1 to 4, and in tabular form in table 7. TABLE 6 Percentage of Infestation in Sprayed and Dusted Plots in 1919 Spra Orchard A Sprayed July 3 1 D usted July 3 1 Check 6.0 12.1 16.1 Orchard B Sprayed May 21 ^ed May 21 and July 17 Sprayed July 17 Check 3.4 2.1 4.5 9.8 Orchard D Sprayed July 23 Dusted June 13 Check 7.1 9.5 12.1 As is shown by the above results, as well as by other data, the best time to give the treatment for the codling moth in walnuts is from the last week of May to the third week of June. Allowance should be made in the above results for the variations in time of treatment, but, in spite of the unfavorable dates of application, the figures are in favor of the spray. Bull. 402] THE CODLING MOTH IN WALNUTS 23 TABLE 7 Tabular Summary — Spraying and Dusting/ 1920 Orchard A Orchard B Orchard c 1.1 1.3 1.1 3.0 3.5 5.2 6.10 6.30 6.10 157 70 60 7.85 3.50 3.00 4.86 1.96 0.54 0.74 0.56 0.40 0.75 0.37 0.38 10 4.9 5 33 23 18 1.96 0.87 0.75 1.21 0.49 0.13 1.22 0.31 0.35 0.46 0.12 0.25 18.30 6.90 11.40 6.20 2.40 3.80 7.00 5.00 12.00 Orchard D Infestation with one spraying (per cent) Infestation with one dusting (per cent) Infestation of check plots (per cent) Average production per tree (pounds) Increase in sound nuts per tree by one spraying, (pounds) Increase in sound nuts per tree by one dusting (pounds) Cost of spraying per tree Cost of dusting per tree Amount of dust per tree (pounds) Amount of spray per tree (gallons) Increased value of nuts per tree, at 25 cents per pound, due to spraying Increased value of nuts per tree, at 25 cents per pound, due to dusting Net returns per tree from one spraying Net returns per tree from one dusting Net returns per acre from one spraying Net returns per acre from one dusting Net difference per acre in favor of spray.. 3.7 10.5 22.00 60 11.00 6.90 0.45 0.44 6 20 2.75 1.72 2.30 1.28 46.00 25.60 20.40 7 The cost figures represent what was actually paid for the materials 'used and for the work done in 1920 on the following basis: arsenate of lead dust, 6 cents per pound; arsenate of lead used in spray, 25 cents per pound; charge for apply- ing dust, 8 cents to 15 cents per trees; charge for applying spray, 1^2 cents per gallon. 24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION COMPAKISON OF SPRAYING AND DUSTING, 1920 Diagram 1 Orchard A — 15 acres Location of Plots, and Treatments and Percentages of Infested Nuts Dusted Dusted Sprayed Dusted June 1 June 1 June 1 July 8 July 8 E,8% 3.2^ 1.3^ 4/a \ Sprayed Check >s^^ June 1 ^ July 9 6.355 Sprayed July 9 3'^ Bull. 402J THE CODLING INLOTII IN WALNUTS 25 Diagram 2 Orchard B — 15 acres Location of Plots, and Treatments and Percentages of Infested Nuts Sprayed Dusted June 15 June 18 1.3^J 3.5^ Check 6.3fo Dusted June 18 5% arsenate of lead Sprayed June 15 July 9 Dusted June 18 July 9 3.3^ Ifo 2.4^ Diagram 3 Orchard C — 10 acres Location of Plots, and Treatments and Percentages of Infested Nuts Dusted Sprayed Dusted Sprayed June June 2 June 11 June 10 5.2^ 1.1^ Che ok 6. If, z.rfo 1.1^ Dusted Sprayed Dusted Sprayed June 2 June 2 June 11 June 10 July 17 July 10 July 17 July 10 5.6fo .6% 4.9^ *9fo 26 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Diagram 4 Orchard D — 10 acres Location of Plots, and Treatments and Percentages of Infested Nuts Sprayed June 10 Dusted June 9 3.75S Check ZZfo 10,5?J Sprayed June 10 July 12 ■ Dusted June 9 July 10 3.9fo 8.9^ Results in 1921 The four orchards indicated in the diagrams and in the tabular statement for 1920 received the same treatments in 1921, except that the sprayed and dusted plots were interchanged. The infestation was so light in 1921, however, that the variation in the figures was too small to be reliable ; hence the data for that year are omitted. Discussion of Dusting versus Spraying The data presented consistently indicate that spraying is more effective than dusting for the codling moth in walnuts. The cost of spraying is not much greater, and sometimes is less than that of dusting. The proper basis on which to judge any method of control is that afforded by the ' ' net returns, ' ' and it is here that the advantage of spraying is most pronounced, as is shown by the data presented. Bull. 402] THE CODLING MOTH IN WALNUTS 27 There is another consideration of importance, the rapidity with which a given acreage can be treated. As regards the actual time employed, this point is very much to the advantage of dusting. Dust- ing is, however, greatly restricted by weather conditions, so that the difference in acreage covered by the two methods in one season is not so great as might at first appear. Wind, even if very light, interferes with dusting, and this is, of course, a variable factor. Dusting opera- tions are restricted to a few hours in the early morning, while spraying may usually be continued throughout the day. On account of their large size, walnut trees have been considered unsuitable for spraying, not only because of the difficulty of covering the highest trees, but because of the large quantity of spray required. The first of these objections has been overcome by the recent develop- ments in high-power spray outfits. Through the courtesy of the Bean Spray Pump Company we secured the loan of the first super-giant machines manufactured by that concern. In fact, this machine was designed to meet the particular demands of walnut spraying. Such a machine (figs. 10 and 11) can maintain a pressure of 300 pounds with two spray guns that will throw the spray to the top of the highest walnut tree. The same type of machine is now (1925) very generally manufactured and used for all kinds of spraying work. The ordinary larger power spray outfits are also fairly satisfactory but only one gun can be used when large trees are sprayed. Another objection to spraying, namely the quantity of spray required, seems important when the amount required per tree is con- sidered. It is true that large trees will require 40 gallons, while for trees of average size the amount will be about 25 gallons. But the proper standard of comj^arison for spraying, as well as for returns on the crop, etc., is cost per acre or amount of land involved. Most authorities are agreed that mature walnut trees should stand not less than 60 feet apart, which would make about 12 trees to the acre. Fifty feet apart is the minimum, and at this distance there would be only 17 trees to the acre. Twelve walnut trees requiring 35 gallons of spray each would require 420 gallons of spray. An acre with 60 apple trees requiring 8 gallons of spray each would require 480 gallons of spray. An acre with 90 citrus trees requiring 10 gallons of spray each would require 900 gallons of spray. Thus, the quantity of spray required on an acre basis presents no more serious a problem with walnuts than with fruit trees such as the apple or orange ; furthermore while apples may require as many as five applications, one application or two will suffice for the same pest in the walnut. 28 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Fig. 10. Spraying walnut trees. Nozzle adjusted for spraying upper part of tree. Bull. 402J THE CODIJNG MOTPI IN WAT.NUTS 29 Fig. 11. Spraying walnut trees for codling moth. Nozzle adjusted for spraying lower part of tree. 30 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Material and Amount to Use A large acreage was dusted in 1919 in both Santa Ana and the Carpinteria district, with the standard, or acid, arsenate of lead. After a few weeks the walnut foliage began to show characteristic arsenical burning and this burning continued to increase as the season advanced. In my own tests during the same year only basic or neutral arsenate of lead was used, since previous experience in walnut spray- ing indicated that walnut foliage is very susceptible to spray injury. No injury resulted from the basic lead arsenate ; consequently, for the second dusting that year, basic arsenate of lead only was recommended and the acid arsenate of lead was withdrawn from the market so far as walnut dusting or spraying was concerned. In 1920 a single orchard was sprayed with acid arsenate of lead, and the same severe burning occurred as during the previous year. In 1925 a brand of basic arsenate of lead not previously used was applied in the Rivera section. Arsenical burning appeared in several of the orchards. This particular arsenate of lead showed 0.45 per cent water soluble arsenic, but yielded a considerable amount of soluble arsenic when treated with strong ammonia. During and after the time of the application there was foggy weather and a few showers of rain. Such conditions are favorable for arsenical injury. Other brands of arsenate of lead used in the same section, and in a few cases in the same orchard, produced no signs of injury. The writer's conclusion is that any brand of basic arsenate of lead that does not meet the ammonia test^ is unsafe on walnut trees in the coastal districts of California. Basic arsenate of lead is not so poisonous as the acid form and this is a disadvantage to the walnut grower. However, the injury due to ''stings" or small burrows made by the larvae before the weaker poison becomes effective is not very important in the case of the walnut because it occurs in the husk and does not affect the nut. A suitable amount to use is 5 pounds to 100 gallons of water. The dust as usually received by the grower is ready to apply. Self -mixing dust machines are in use, however, and a considerable saving in cost is effected by the use of such machines. In the case of nicotine greater efficiency is obtained if the dust is made immediately before applying, as is the case with the self -mixing machines. With arsenate of lead however long standing of the arsenical and carrier produces no deterioration. 8 Gray, Geo. P. and Firman Thompson, Economic poisons, California State Dept. Agr., Sp. Publ. 58:12. 1924. Bull. 402] tjj^ CODLING MOTH IN WALNUTS 31 Experiments were made Avith dust containing 2, 5, 10, and 15 per cent of arsenate of lead, but 15 per cent seems to be the most satis- factory proportion. For a filler or carrier, kaolin, hydrated lime, and the refuse lime from beet-sugar factories have been used. The amount of dust required to the tree is about 10 pounds for the largest trees and 6 pounds for trees of average size. Fifteen per cent of the weight of the dust is arsenate of lead, hence when 10 pounds is applied to a tree there will be IV2 pounds of arsenate of lead. If 6 pounds is applied there w^ill be %o of a pound of the arsenate. When the spray contains 5 pounds of arsenate of lead to 100 gallons of water, the tree receiving 35 gallons of spray will receive 1% pounds of arsenate of lead. A tree receiving 25 gallons of spray (the same sized tree should receive at least 6 pounds of dust or %o pound of arsenate of lead) will receive l\i pounds of arsenate of lead. Whether spraying or dusting is employed, the object is to get the necessary amount of arsenate of lead on the tree. Eighty-five per cent of the weight of the dust in the 85-15 combination, and all of the water in the spray, are merely carriers and have no insecticidal value. It is important to cover, so far as is practicable, every nut on the tree with the arsenical. Other parts of the tree should also be covered if aphis is being sprayed for at the same time. Our data show that there is less infestation of the codling moth in the upper than in the lower part of the walnut tree ; nevertheless, the upper part of the tree should be covered. At the present time spraying has been the com- mercial practice employed in all of the codling moth infested groves in the Carpinteria district excepting one where dust is applied with a self -mixing dust machine. At Rivera the next most important district from the standpoint of codling moth infestation, spraying has been used exclusively. At Saticoy where there is a light infestation dusting has been used exclusively. Codling-Moth and Aphis Control Combined Where it is necessary to control the walnut aphis {Chromaphis juglandicola Kalt), it so happens, according to the writer's conclusion, that the time practically coincides with the time for the treatment of the codling moth, namely, during the last week of May and the first two or three weeks of June. Hence, for the control of the aphis and codling moth, it is only necessary to combine 40 per cent nicotine sulfate with the arsenate of lead. For spraying use 10 pounds of basic arsenate of lead and from % to % of a pint of 40 per cent nicotine 32 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION sulfate to 200 gallons of water. For dusting, the amounts are 15 pounds of arsenate of lead, 1 to 2 pounds of 40 per cent nicotine sulfate, and a carrier to make 100 pounds. In some years, particularly in Santa Barbara County, aphis control may be necessary before the proper time for the codling-moth treatment. The walnut aphis is one of the easiest of the aphids to kill with nicotine. Since a liberal amount of dust is necessary for the codling moth, the amount of nicotine, whether in spray or dust, may be less than that necessary for aphis control work alone. Aphis Control Alone Two per cent nicotine dust^ is the most satisfactory material for the walnut aphis. The amount of dust per tree may be much less than that used for the codling moth; ordinarily, 2 to 5 pounds per tree is sufficient. During the latter part of May and the first part of June is the best time to make the application. If the treatment be postponed as long as possible, but given before any important injury is done, the trees will be protected against infestation later in the season. A spray may be used giving satisfactory results also against the walnut aphis. For this purpose a mixture of 1 2 to % pint of 40 per cent nicotine sulfate and 4 or 5 pounds of soap to 200 gallons of water is recommended. Number of Applications The results given for 1919 and 1920 indicated no advantage in making more than one application of spray or dust. However, when the infestation is severe or the broods of larvae are irregular a second application is desirable. The time for making a second application is the latter part of July or early in August. Time of Application The time of treatment is based on the appearance of the first brood of larvae in the nuts. They commence to enter the nuts early in May, but at this time the nuts are so small that a spray applied then would become so thinly distributed as the nut grows as to be ineffective. Something may be gained by an early application in getting the spray more effectively into the stigma, which is open or parted at this time 9 A material originated by R. E. Smith, consisting simply of 40 per cent nicotine sulphate incorporated into a carrier. Bull. 402] tjjj. codling MOTH IN WALNUTS 33 (see fig. 4), but this advantage is more han offset by the small size of the nuts. The peak of appearance of the first-brood larvae in the Santa Ana district occurs during the second or third week of June. Hence, the period of treatment there should begin during the last week in May and end about the third week in June. The development of the codling moth varies in different seasons. For example, my own control work at Santa Ana in 1919 was started on May 25, in 1920 on June 1, and in 1921 on June 8. There is thus seasonal variation, but this is not so great as to make the control ineffective if the work is carried on during the period indicated. In the case of the apple, the time for the calyx spraying is governed, not by the calendar, but by the development of the blossoms. With the walnut, the nuts should be as large as possible at the time of spraying, but the proper size of the nut is not so important as is the proper condition of the calyx in the apple. At Carpinteria the time for the applications should be from about the first or second week of June to the first of July. SUMMARY The codling moth is an important pest of walnuts in certain limited sections of the walnut-growing area of California. It is found spar- ingly, however, over a large area. In France and South Africa, also, walnuts are sometimes infested. The highest infestation noted in any particular orchard during the years 1919 to 1925 was 37 per cent. The codling moth which attacks the walnut is the same insect that is universally known to attack the apple. The life history of the insect is similar in all important respects to that of the same insect when living in the apple in the same locality. The larvae begin to enter the nuts as early as the middle of May, but do not enter in maximum numbers until the second or third week in June in the Santa Ana district and from the third week of June to the first week of July at Carpinteria ; hence, the time of application in seasons of average temperatures is during the last week of May and the first two weeks of June at Santa Ana, and a little later in the Carpinteria district. Spraying with basic arsenate of lead is the most satisfactory method of control. Dusts containing 15 per cent of basic arsenate of lead may also be employed, but the data obtained in this investigation show that the poison applied as a dust is not so effective as when applied as a spray. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION Xo. 253. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. 261. Melaxuma of the Walnut, "Juglans regia." 262. Citrus Diseases of Florida and Cuba Compared with Those of California. 263. Size Grades for Ripe Olives. 268. Growing and Grafting Olive Seedlings. 273. Preliminary Report on Kearney Vine- yard Experimental Drain. 275. The Cultivation of Belladonna in California. 276. The Pomegranate. 277. Sudan Grass. 278. Grain Sorghums. 279. Irrigation of Rice in California. 280. Irrigation of Alfalfa in the Sacra- mento Valley. 283. The Olive Insects of California. 285. The Milk Goat in California. 294. Bean Culture in California. 304. A Study of the Effects of Freezes on Citrus in California. 310. Plum Pollination. 312. Mariout Barley. 313. Pruning Young Deciduous Fruit Trees. 319. Caprifigs and Caprification. 324. Storage of Perishable Fruit at Freez- ing Temperatures. 325. Rice Irrigation Measurements and Experiments in Sacramento Valley, 1914-1919. 328. Prune Growing in California. 331. Phylloxera-Resistant Stocks. 334. Preliminary Volume Tables for Sec- ond-Gro-w^h Redwood. 335. Cocoanut Meal as a Feed for Dairy Cows and Other Livestock. 339. The Relative Cost of Making Logs from Small and Large Timber. 340. Control of the Pocket Gopher in California. 343. Cheese Pests and Their Control. 344. Cold Storage as an Aid to the Mar- keting of Plums. 346. Almond Pollination. 347. The Control of Red Spiders in Decid- uous Orchards. 348. Pruning Young Olive Trees. 349. A Study of Sidedraft and Tractor Hitches. 350. Agriculture in Cut-over Redwood Lands. 352. Further Experiments in Plum Pollina- tion. 353. Bovine Infectious Abortion. 354. Results of Rice Experiments in 1922. 357. A Self-mixing Dusting Machine for Applying Dry Insecticides and Fungicides. 358. Black Measles, Water Berries, and Related Vine Troubles. 359. Fruit Beverage Investigations. 361. Preliminary Yield Tables for Second Growth Redwood. 362. Dust and the Tractor Engine, BULLETINS No. 363. 364, 365. 366. 367. 368. 369. 370. 371. 372. 373, 374. 375. 376. 377. 379. 380. 381. 382. 383. 384. 385. 386. 387. 388. 389. 390. 391. 392. 394. 395. 396. 397. 398. 399. 400. The Pruning of Citrus Trees in Cali- fornia. Fungicidal Dusts for the Control of Bunt. Avocado Culture in California, Turkish Tobacco Culture, Curing and Marketing. Methods of Harvesting and Irrigation in Relation of Mouldy Walnuts. Bacterial Decomposition of Olives dur- ing Pickling. Comparison of Woods for Butter Boxes. Browning of Yellow Newtown Apples. The Relative Cost of Yarding Small and Large Timber. The Cost of Producing Market Milk and Butterfat on 246 California Dairies. Pear Pollination. A Survey of Orchard Practices in the Citrus Industry of Southern Cali- fornia. Results of Rice Experiments at Cor- tena, 1923. Sun-Drying and Dehydration of Wal- nuts. The Cold Storage of Pears. Walnut Culture in California. Growth of Eucalyptus in California Plantations. Growing and Handling Asparagus Crowns. Pumping for Drainage in the San Joaquin Valley, California. Monilia Blossom Blight (Brown Rot) of Apricot. A Study of the Relative Values of Cer- tain Succulent Feeds and Alfalfa Meal as Sources of Vitamin A for Poultry. Pollination of the Sweet Cherry. Pruning Bearing Deciduous Fruit Trees. Fig Smut. The Principles and Practice of Sun- drying Fruit. Berseem or Egyptian Clover. Harvesting and Packing Grapes in California. Machines for Coating Seed Wheat with Copper Carbonate Dust. Fruit Juice Concentrates. Cereal Hay Production in California. Feeding Trials with Cereal Hay. Bark Diseases of Citrus Trees. The Mat Bean (Phaseolus aconilifo- lius). Manufacture of Roquefort Type Cheese from Goat's Milk, Orchard Heating in California. The Blackberry Mite, the Cause of Redberry Disease of the Himalaya Blackberry, and its Control. The Utilization of Surplus Plums. No. 87. Alfalfa. 113. Correspondence Courses in Agriculture. 117. The Selection and Cost of a Small Pumping Plant. 127. House Fumigation. 129. The Control of Citrus Insects. 136. Melilotus indica as a Green-Manure Crop for California. CIRCULARS No. 144. Oidium or Powdery Mildew of the Vine. 151. Feeding and Management of Hogs. 152. Some Observations on the Bulk Hand- ling of Grain in California. 154. Irrigation Practice in Growing Small Fruit in California. 155. Bovine Tuberculosis. CIRCULARS — (Continued) No. 157. 160. 164. 166. 167. 170. 173. 178. 179. 184. 190. 199. 202. 20?,. 209. 210. 212. 214. 215. 217. 220. 228. 2.30. 231. 232. 233. 234. 235. 236. 238. 239. 240. 241. 242. 243. 244. 245. 247. 248. 249. 250. 251. 252. 253. 254. 255. Control of the Pear Scab. Lettuce Growing in California. Small Fruit Culture in California. The County Farm Bureau. Feeding Stuffs of Minor Importance. Fertilizing California Soils for the 1918 Crop. The Construction of the Wood-Hoop Silo. The Packing of Apples in California. Factors of Importance in Producing Mi]k of Low Bacterial Count. A Flock of Sheep on the Farm. Agriculture Clubs in California. Onion Growing in California. County Organizations for Rural Fire Control. Peat as a Manure Substitute. The Function of the Farm Bureau. Suggestions to the Settler in California. Salvaging Rain-Damaged Prunes. Seed Treatment for the Prevention of Cereal Smuts. Feeding Dairy Cows in California. Methods for Marketing Vegetables in California. Unfermented Fruit Juices. Vineyard Irrigation in Arid Climates. Testing Milk, Cream, and Skim Milk for Butterfat. The Home Vineyard. Harvesting and Handling California Cherries for Eastern Shipment. Artificial Incubation. Winter Injury to Young Walnut Trees during 1921-22. Soil Analysis and Soil and Plant Inter-relations. The Common Hawks and Owls of California from the Standpoint of the Rancher. Directions for the Tanning and Dress- ing of Furs. The Apricot in California. Harvesting and Handling Apricots and Plums for Eastern Shipment. Harvesting and Handling Pears for Eastern Shipment. Harvesting and Handling Peaches for Eastern Shipment. Poultry Feeding. Marmalade Juice and Jelly Juice from Citrus Fruits. Central Wire Bracing for Fruit Trees. Vine Pruning Systems. Colonization and Rural Development. Some Common Errors in Vine Prun- ing and Their Remedies. Replacing Missing Vines. Measurement of Irrigation Water on the Farm. Recommendations Concerning the Com- mon Diseases and Parasites of Poultry in California. Supports for Vines. Vineyard Plans. The Use of Artificial Light to Increase Winter Egg Production. Leguminous Plants as Organic Fertil- izer in California Agriculture. No. 256. The Control of Wild Morning Glory. 257. The Small-Seeded Horse Bean. 258. Thinning Deciduous Fruits. 259. Pear By-products. 260. A Selected List of References Relating to Irrigation in California. 261. Sewing Grain Sacks. 262. Cabbage Growing in California. 263. Tomato Production in California. 264. Preliminary Essentials to Bovine Tuberculosis Control. 265. Plant Disease and Pest Control. 266. Analyzing the Citrus Orchard by Means of Simple Tree Records. 267. The Tendency of Tractors to Rise in Front; Causes and Remedies. 268. Inexpensive Labor-saving Poultry Ap- pliances. 269. An Orchard Brush Burner. 270. A Farm Septic Tank. 271. Brooding Chicks Artificially. 272. California Farm Tenancy and Methods of Leasing. 273. Saving the Gophered Citrus Tree. 274. Fusarium Wilt of Tomato and its Con- trol by Means of Resistant Varieties. 275. Marketable California Decorative Greens. 276. Home Canning. 277. Head, Cane, and Cordon Pruning of Vines. 278. Olive Pickling in Mediterranean Coun- tries. 279. The Preparation and Refining of Olive Oil in Southern Europe. 281. The Results of a Survey to Determine the Cost of Producing Beef in Cali- fornia. 282. Prevention of Insect Attack on Stored Grain. 283. Fertilizing Citrus Trees in California. 284. The Almond in California. 285. Sweet Potato Production in California. 286. Milk Houses for California Dairies. 287. Potato Production in California. 288. Phylloxera Resistant Vineyards. 289. Oak Fungus in Orchard Trees. 290. The Tangier Pea. 291. Blackhead and Other Causes of Loss of Turkeys in California. 292. Alkali Soils. 293. The Basis of Grape Standardization. 294. Propagation of Deciduous Fruits. 295. The Growing and Handling of Head Lettuce in California. 296. Control of the California Ground Squirrel. 297. A Survey of Beekeeping in California; The Honeybee as a Pollinizer. 298. The Possibilities and Limitations of Cooperative Marketing. 299. Poultry Breeding Records. 300. Coccidiosis of Chickens. 301. Buckeye Poisoning of the Honey Bee. 302. The Sugar Beet in California. 303. A Promising Remedy for Black Measles of the Vine. The publications listed above may be had by addressing College of Agriculture, University of California, Berkeley, California. 10m-4,'20