CALIFORNIA AGRICULTURAL EXPERIMENT STATION CATERPILLARS DESTRUCTIVE TOMATO A. E. MICHELBACHER W. W. MIDDLEKAUFF N. B. AKESSON May, 1948 Bulletin 707 ■^H^^BBMHB THE COLLEGE OF AGRICULTURE UNIVERSITY OF CALIFORNIA • BERKELEY ) Corn earworm, sometimes called tomato fruit worm, is the most important of the caterpillars which attack tomato in California. This pest is abundant and widely distributed throughout tomato-growing districts. It normally completes its larval growth inside the tomato fruit, making detection difficult. THIS BULLETIN is a research report on the value of the new insecticides— DDT, DDD, and others— as substitutes for calcium arsenate in the control of tomato pests. After years of use as a dust, calcium arsenate has come into disfavor because of its drift into adjacent fields with resultant injury to susceptible plants, bees, and livestock. Certain questions arose quite naturally from this situation: • Could dusting equipment be improved to help control drift? • Might calcium arsenate applied as a concentrated spray be as effective as the dust, and less apt to drift? • Would the new insecticides give more or less satisfactory con- trol of caterpillars than had been given by calcium arsenate? • If used, what would be the after-effects of such compounds as DDT: to the soil, as residues on canning tomatoes, to forage crops and bee pastures? These questions were the basis for the investigations conducted in 1946 and 1947 by the authors. The findings reported in this bulletin are the result of two years of extensive experimentation on small replicated plots and on commercial plantings. EARLIER TOMATO investigations, begun in 1935, had already deter- mined the life histories and habits of the insects as well as the best control measures based upon the insecticides available before the advent of the many new organic compounds. Descriptions and habits of the insect pests, pre- viously reported in Agricultural Experiment Station Bulletin 644, are re- peated and substantially expanded herein, inasmuch as Bulletin 644 is now out of print. THE AUTHORS A. E. Michelbacher is Assistant Professor of Entomology and Assistant Entomologist in the Experiment Station. W. W. Middlekauff is Assistant Professor of Entomology and Assistant Entomologist in the Experiment Station. N. B. Akesson is Instructor in Agricultural Engineering and Junior Agricultural Engineer in the Experiment Station. TABLE OF CONTENTS THE CATERPILLARS AND THE DAMAGE THEY DO . . 3 Corn earworm 4 Yellow-striped armyworm 8 Night-feeding cutworms 9 Beet armyworm 10 Alfalfa looper 11 Tomato pinworm 11 Potato tuber moth , 12 Tomato and tobacco hornworms 15 TOMATO MITE ! ... 18 EXPERIMENTAL METHODS 19 Plot arrangement; equipment 19 Sampling methods; materials used in tests 21 CONTROL GIVEN BY VARIOUS INSECTICIDES 22 Advantages of a generalized control program 22 Investigations during 1946 toward eliminating drift 23 Investigations during 1947 tested new insecticides 25 Small plot replicated experiments 25 Experimental commercial tests 27 Hornworm control 32 Tomato mite control 33 Cultural methods can aid control 34 Natural enemies help control 35 Possibility of injury to plants from DDT 35 STUDIES OF INSECTICIDAL RESIDUES 36 Experimental procedure 36 Methods of analysis 37 Residues of DDT, DDD 37 Calcium arsenate residues 41 CONCLUSIONS TO BE DRAWN 42 ACKNOWLEDGMENTS 45 LITERATURE CITED . . 47 CATERPILLARS DESTRUCTIVE TO TOMATO A. E. Michelbacher, W. W. Middlekauff, and N. B. Akesson Calcium arsenate has long been one of the most important insecticides used to control caterpillars attacking tomato. It has been primarily used as a dust and al- though it has resulted in satisfactory con- trol of most caterpillars, its drift to fields other than the ones being treated has given rise to complaints. Crops suscep- tible to arsenical burn have been injured, and forage crops and bee pastures have been contaminated. The seriousness of the problem has increased due to faulty ap- plication, to the application of the in- secticide when not needed, and to an increase in recent years in the acreage devoted to tomato production. In 1946 investigations were undertaken to determine means of eliminating the hazard associated with the application of calcium arsenate. The tests were con- tinued in 1947. The problem was attacked from the standpoint of developing better methods of application, and by investigat- ing promising new insecticides to find out whether some of them might not serve as satisfactory substitutes for calcium ar- senate in the tomato insect control pro- gram. The results of these investigations are presented in this bulletin. The investigation has been limited to the northern tomato-growing sections of the state and results and conclusions given are based upon these findings. THE CATERPILLARS AND THE DAMAGE THEY DO Knowledge of the pests, their habits, and the damage they inflict to tomato is the key to an effective control program. Cutworms of several species are the most important of the caterpillars attack- ing tomato. The most destructive species is the corn earworm, Heliothis armigera (Hbn.), although the yellow-striped armyworm, Prodenia praefica Grote, and the beet armyworm, Laphygma exigua (Hbn.), do much damage, and under some conditions are more important than the corn earworm. The alfalfa looper, Autographa californica (Speyer), some- times occurs in abundance but is of little importance because its feeding is con- fined almost entirely to the foliage. All of the above cutworms spend their entire larval life upon the plants, which distin- guishes them from a second group which feed only at night, and during the day hide in the soil or the debris covering it. Occasionally caterpillars belonging to this group are troublesome. The tomato pinworm, Keiferia lycoper- sicella (Busck), and the potato tuber moth, Gnorimo schema operculella (Zel- ler), are insects of similar habits, and in certain areas or under favorable condi- tions are likely to be very destructive to tomato. The tomato hornworm, Protoparce sexta (Johan.), and the tobacco horn- worm, P. quinquemaculata (Haw.), are important pests and are particularly de- structive in the warmer interior valleys. All the above pests pass through four distinct stages of development : egg, larva (caterpillar), pupa (chrysalis) and adult (moth). Damage is only inflicted during the larval stage. Any discussion of pests of tomato must include, in addition to the caterpillars, mention of the tomato mite. Where not controlled, this pests causes serious dam- [3] Fig. 1. Stages in the life cycle of the corn earworm: A, mature larvae; B, pupa removed from earthen cell; C, pupa within earthen cell; D, adult in a position of rest; E, adult with wings spread. (All natural size.) age through defoliation. Therefore, al- though this bulletin is intended to treat primarily with caterpillar control, there is included on page 18 a description of the mite and its destructiveness. Control of the mites can be accomplished in con- junction with the control of caterpillars. Suggestions for such control are given as part of the integrated program discussed on pages 22 and 33. Corn Earworm Corn earworm is one of the most serious and most prevalent of the cater- pillars attacking tomato. When found on tomato this insect is frequently referred to as the tomato fruit worm. The stages in the life history of the corn earworm with the exception of the egg stage are shown in figure 1. The length of time spent in any one stage is influenced by the type of food and weather condi- tions. In the northern tomato-growing re- gions of California, there are at least three complete generations a year. The winter is passed in the pupal stage in earthen cells 2 to 10 inches beneath the soil surface. Emergence of the moths from the over- wintering pupae occurs principally dur- ing the months of May and June. The adults (fig. 1, D and E) have a wing expanse of about 1% inches, and their basic color is tan to brownish tan, over which a rather inconspicuous but definite darker pattern is superimposed. Egg laying begins several days after emergence and continues until death; a single female may lay 500 to 3,000 eggs throughout the fields. Quaintance and Brues (1905) 1 reported a single female depositing 780 eggs in one day. Usually at dusk on warm days in heavily infested tomato fields, female moths may be seen flitting here and there, seldom flying higher than the tops of the plants, and laying eggs at random over the vines. Only an instant is required for the deposi- tion of an egg. Although egg laying usu- ally begins just before dusk, on occasions 1 See "Literature Cited" for citations, referred to in the text by author and date. [4] moths may be observed laying eggs earlier in the day, especially if the day is over- cast. The eggs are dome-shaped and longi- tudinally ridged. At first the color is waxy white, but as the incubation period advances they become darker in color due to the development of the larva. During warm weather they hatch in from 3 to 5 days. In growing the larvae cast their skins about five times, and under favorable con- ditions reach maturity in approximately 2 to 3 weeks. When full-grown (fig. 1,A), they measure about 1% inches in length and exhibit a marked variation in color from green to almost black, and may be marked with longitudinal stripes of vari- ous colors. In the later stages they are very cannibalistic and, where two meet in competition or combat, the larger one is usually victorious. On completing development, they bur- row into the soil and construct pupal cells a few inches below the surface, from which they build tunnels upward to within a half inch of the surface for the subse- quent emergence of the adults. Larvae of the overwintering individuals generally pupate deeper in the soil than those of the summer brood. The pupae (fig. 1, B and C) vary from dark amber to chestnut brown and are about % of an inch in length. The duration of the pupal period is only 2 to 3 weeks during the summer; those formed in the fall remain as pupae all winter or longer. Corn earworm prefers other crops The corn earworm has a very extensive host range and feeds on many different species of wild and cultivated plants. It is an important pest of corn, cotton, toma- toes, tobacco, beans, and several other crops. Sweet corn is the preferred host, although in northern California caterpil- lars are present in large numbers on beans and other legumes. Tomatoes are not a preferred host, but are subject to serious damage because they mature later in the season than most crops and are therefore in an attractive state of growth at a time when other crops are reaching maturity and drying up. Host plants that are de- veloping their fruiting bodies and making a rapid growth are most attractive to egg- laying moths. Although tomato plants are set out in the field early in the season, they are sel- dom subjected to serious attack until the latter part of July or later, and there are areas in central and northern California where they may go through the entire season without being seriously infested. The reason for this in part appears to be linked with host sequence or types of crops grown in the various sections. The overwintering moths start emerging as Fig. 2. Corn earworm damage to tomatoes; A, advanced injury of the stem end with caterpillar in burrow; B, tomato cut in half to show the internal de- struction caused by the caterpillar. [5] Sample Tomatoes Show Infestation JULY AUGUST SEPTEMBER OCTOBER NOVEMBER JULY AUGUST SEPTEMBER OCTOBER A/OVEMBER Fig. 3. Infestation trends of the corn earworm are shown in the charts above from samples taken in 1936 and 1937 in several northern tomato-growing locations. It will be seen that serious infestations of this pest do not occur before the first of August. The charts are in terms of the per cent of infested tomatoes found in the samples taken. [6] early as May, and by the end of June sweet corn may be severely infested. By July nearly all ears of sweet corn may be at- tacked, while tomatoes growing only a short distance away may show a very low infestation. Beans also appear to attract egg-laying moths to a greater extent than tomato and in some sections there is a considerable increase in the population on this crop. The moth populations that arise from the preferred hosts then mi- grate to tomato when these earlier crops are no longer available. Similar observa- tions have been made by other investiga- tors. Isely (1935) reported that a com- bination of corn and leguminous crops may lead to a serious outbreak on cotton. If an infestation once becomes established in a locality, it is likely to continue for the remainder of the season. If established in August, there is apparently sufficient time for two broods of larvae to appear in the field before tomato harvest is completed. Infestation may be high Where an infestation is severe, more than 50 per cent of the tomatoes may be destroyed or rendered unfit for human consumption. The moths lay their eggs singly and at random over the periphery of the vine. The newly hatched larvae start feeding on the foliage. If a fruit is not en- countered, they may complete their devel- opment on the foliage, in which case they are green in color and the tubercles from which the hairs arise do not appear to be as conspicuous as those present on larvae that develop within the fruit. The larvae apparently experience little difficulty in finding the fruit as is evidenced by the fact that many of them enter the fruit at a very early stage of development. Entry is usually made at the calyx or stem end, and some of the larvae are so small that one must look very carefully to detect the point of penetration. Development may be completed within a single fruit, although a larva may dam- age or destroy more than one tomato. A nearly mature caterpillar often leaves the fruit in which it has developed and feeds externally on other fruits in the same clus- ter. Sometimes it even drops to the ground and feeds externally on a fruit that is resting on the soil surface. This and other types of external feeding are usually char- acterized by irregular feeding holes. Typi- cal advanced calyx-end injury is shown in figure 2. Examine small fruit There is a strong tendency for the small corn earworm larvae to enter developing tomatoes % to 2 inches in diameter. The beginning of an infestation can therefore be determined by picking and thoroughly examining fruit in this size range. As far as the corn earworm is concerned, a con- trol program need not be started until 2 to 3 per cent of the fruit in this stage of development shows signs of infestation. Usually no less than 300 fruits should be picked at random throughout the field in determining the degree of infestation. Late in the harvest season small larvae may enter the ripe tomatoes as well as the small developing green fruit. Where this occurs the canner is caused much annoy- ance because these infested fruits are nearly impossible to detect on the sorting belts. Begin in August Serious infestations by the corn ear- worm do not usually make their appear- ance before the first of August. This is well illustrated in figure 3 where charts show the trend of the infestation for sev- eral regions, based on the amount of in- fested fruit observed in the check plots associated with experiments conducted in 1936 and 1937. The reason for desig- nating the corn earworm as the most im- portant caterpillar attacking tomato is due to its abundance, wide distribution, and to the fact that it normally completes its larval development within the tomato fruit. The degree of injury varies greatly from year to year, and from field to field in any given year. [7] Confusion with Heliothis phloxiphaga Heliothis phloxiphaga (Grote and Rob- inson) is likely to be confused with the corn earworm, to which it is closely re- lated. Early in the growing season, moths of the former insect (fig. 4) may be present in large numbers in tomato fields. The females lay their eggs, which are similar to those of the corn earworm, at random over the tomato vines in the same manner as does the corn earworm. How- ever, this fact need cause no concern, be- cause the larva of this insect is unable to develop on either the foliage or the fruit of the tomato. The larvae feed on culti- vated crops such as lettuce and alfalfa. There are a number of native hosts and in late summer and early fall they may be found breeding in large numbers on tarweed and gum plant. Yellow-Striped Army worm The adult of the yellow-striped army- worm (fig. 5) has a wing expanse of about 1% inches. It is grayish in color. The forewings have an intricate color pattern of slate and buff markings, while the hind wings are silver and gray. Eggs laid in masses Eggs are laid in masses upon the plants, which results in a concentrated attack by the larvae, although as they develop the larvae tend to disperse. The larvae are rather colorful, being almost black in color with two prominent and many fine, bright yellow stripes on the side. When full-grown they may attain a length of slightly more than 2 inches. Mature larvae leave their host plants, burrow into the soil, and construct earthen pupal cells, one to several inches below the surface. Here they transform into adults and after several weeks the moths emerge. There are several generations a year and the winter is spent in the pupal stage. Moths emerge from the overwintering pupae in late April or May, mate, and lay eggs on host plants available at that time. Fig. 4. Adult moths of Helio- this phloxiphaga (G. and R.). This pest is frequently con- fused with corn earworm be- cause of resemblance, however this one damages neither foli- age nor fruit of tomato. [8] May migrate from other fields The yellow-striped armyworm attacks 'many kinds of cultivated and native plants. Among the important crops are alfalfa, beans, cotton, tomato, and melons. The pest, although present, does not cause serious damage every year. On occasions it is very destructive and causes wide- spread damage. It probably occurs in greatest numbers on alfalfa, and under severe conditions this crop may be defoli- ated. Infestations on other crops arise either from eggs deposited in the field or from migrations of caterpillars that occur when nearby infested alfalfa fields are cut. Migrating larvae may cause severe dam- age to the outer rows of plants in adjacent fields. The depth of penetration is usually not great, but in the case of tomatoes many caterpillars, by following the fur- rows, may wander rather far into the field if the rows run in the same direction as the migration. During 1947 an out- break of considerable proportions oc- curred and had it not been for control measures directed against the pest, the tomato crop in many fields would have been destroyed or very seriously injured. The yellow-striped armyworm feeds both on the foliage and the fruit of to- mato. Unlike the corn earworm, it does not enter the fruit, but eats small to large irregular holes in its surface. Its most serious attacks on tomato occur from July through the middle of September. Night-Feeding Cutworms There are several species of cutworms which attack tomato only at night. Under some conditions they are likely to be rather destructive. The adults of these caterpillars are somber in color and are active only after dark. The caterpillars exhibit a dull color pattern and are usu- ally dark brown or grayish. When mature, the caterpillars burrow into the soil to pupate. All feeding is done at night, the caterpillars hiding in the soil or surface debris during the day. These pests injure Fig. 5. The yellow-striped armyworm, Prodenia praefica Grote. Above, as a moth this species is grayish in color; the forewings have an intricate pattern of slate and buff markings while the hind wings are silver and gray. Below, typical injury to tomato by the caterpillar. [9] Fig. 6. Above, adult of al- falfa looper, frequently seen flying over the tomato fields; below, A, full-grown larvae of the beet armyworm, Lap- hygma exigua (Hbn.); B, full- grown larvae of the alfalfa looper, Autographa califor- nica (Speyer). tomatoes by eating irregular holes in the surface, and those tomatoes which rest on the ground are in general the most seri- ously injured. Early in the season this group of cut- worms sometimes causes serious damage by cutting off recently transplanted to- mato plants. Beef Armyworm The adults of the beet armyworm are a mottled gray with distinct paler markings on the forewings, and have a wing ex- panse of about one inch. The eggs are laid in groups over the host plants. The larvae (fig. 6, A) when mature measure a little more than an inch in length and ap- pear in several color phases which range from pale green to nearly black. In all cases, however, the basic pattern is the same. They are darker above than below and down each side there is a lighter stripe. Also, on the dorsal side a close examination will reveal a number of closely set very fine longitudinal lines. There are several broods each year and in the winter they remain in pupal stage. The beet armyworm feeds upon a wide variety of native and cultivated plants. It is one of the most common and wide- spread pests to be found in California. It feeds on most truck, field, and forage crops, and sometimes occurs in sufficient numbers to do serious damage. It is pres- ent in tomato fields every year, and at times in certain fields it may be the most important caterpillar attacking tomato. It is primarily a foliage feeder, but it will also seriously attack the fruit. It will occasionally enter the fruit but like the yellow-striped armyworm it usually feeds externally, eating single or closely grouped circular or irregular holes in the fruit. In many cases the feeding is of a very superficial nature, and little loss would be occasioned if it were not for rot and decaying organisms entering the wounds. The pest occurs in tomato fields from early summer to the end of harvest. It is usually most abundant from late July un- til early November. Although found in L 10] most fields it is probably most common and destructive in the warmer interior valleys. Under severe conditions of infes- tation it is not uncommon to find 25 to 50 or even more caterpillars on a single to- mato plant. Alfalfa Looper The larvae of this insect are very com- mon in tomato fields. The caterpillars (fig. 6, B) are pale green and longitu- dinally striped with fine whitish lines. They are easily distinguished from other caterpillars found on tomato by the fact that in crawling they arch their backs. This characteristic has given rise to the common name "looper." Pupation does not occur in the soil, but towards the crown of the plants or in the debris cover- ing the soil under the plants. They spin a light silken cocoon, and in so doing may fold a leaf or tie together some of the debris. It is not uncommon to find these cocoons in tomato fields, and the amber or chestnut-brown pupae are revealed when the cocoons are torn open. This insect is a foliage feeder and only on very rare occasions will it feed on a fruit. Although it may be found in fair abundance, no situation has been en- countered where enough damage was being done to justify control measures. In California the most complete study of this insect has been conducted by El- more and Howland (1943) and much of the following has been summarized from their report. The larva of this insect is a leaf miner and a leaf folder but will also frequently bore into the fruit during the latter half of its larval existence. Under favorable temperature conditions devel- opment is very rapid, and under some California conditions there may be as many as seven or eight generations in a year. The winter is passed in the pupal stage at or near the soil surface. The pest is active from early spring and until frosts kill its host plants in the fall. Size makes detection difficult The preferred hosts of the tomato pin- worm are tomato and potato. It has also been reported on eggplant, horse nettle, and blue witch nightshade. In California the insect occurs through- out the southern portion of the state, most of the San Joaquin Valley, and in very limited numbers in Alameda, Santa Clara, and San Benito counties. In the San Joa- quin Valley it has never been taken by the writers north of the Tracy area, and seldom has it been found to be destruc- tive in tomato fields north of Merced County. Most of the northern producing Tomato Pinworm The adults are small gray moths about % inch from head to tips of folded wings. The eggs are very small. When first laid, the eggs are whitish but become darker as the incubation progresses. When newly hatched, the tiny larvae are light pinkish in color. When full-grown they are % inch in length and to the naked eye ap- pear grayish purple. This color serves to distinguish them from the larger, lighter- colored larvae of the potato tuber moth. A mature larva is shown in figure 7, to- gether with a mature larva of the potato tuber moth to show the relative differ- ence in size. ■■f"""™"- Fig. 7. A, Full-grown larva of the potato tuber moth, Gnorimoschema oUerculella (Zel- ler); B, full-grown larva of the tomato pin- worm, Keiferia lycopersicella (Busck). (x3.) [ii] section of the state is entirely free of the pest, or at most, subject only to light in- festation in certain fields in the southern portion. Where abundant the tomato pinworm may cause serious damage to the foliage, and nearly 100 per cent of the fruit may be infested. The larvae commonly attack the fruit at the stem or calyx end (fig. 8) although they may enter the fruit at any point. The larvae that enter beneath the calyx generally confine their feeding to the core, while those that enter at other points usually feed on the fleshy portion of the tomato just beneath the skin. This latter type of injury is similar to that of the potato tuber moth larva shown in figure 10, B. One characteristic feature concerning injury by both of these insects is that their burrows are dry, and this is the case whether they enter at the calyx or through the side of the tomato. Because of their small size they do not penetrate very far into the core, and coring of the fruit usually removes the pinworms be- neath the calyx. More than one larva may attack a single fruit. After infested fruits are picked, the larvae quickly spin webs over the entrances to their burrows, which sometimes make their presence and in- jury difficult to detect. Because the pinworm passes through a number of generations in a season, it gen- erally becomes more serious as the season advances. Greatest damage is likely to oc- cur where tomatoes are produced from early in the growing season to late in the fall. Late summer- and fall-grown toma- toes in the central and southern San Joa- quin Valley are very likely to be seriously infested. Potato Tuber Moth The potato tuber moth has a life cycle very similar to that of the tomato pin- worm. It passes through a number of gen- erations each year, and in storage, if food is present and the temperature does not fall too low, breeding continues through- out the year. The length of a single gen- eration varies from about one month in the summer to three or more months in the winter. In areas where it is able to survive, the winter, it probably passes through periods of low temperatures as a full-grown larva or pupa. The adults are small and gray with sil- very bodies and minute dark specks on Fig. 8. Tomatoes seriously infested with the tomato pinworm, showing the several types of injury. [12] dtiPK Fig. 9. Injury of the potato tuber moth on tomato. Calyx removed to show entrance to burrows. the forewings. They are nocturnal and each female may lay from 150 to 200 eggs, which are small, oval, pearly white, and are deposited indiscriminately over the plant. The larvae (fig. 7, A) molt four times. When full-grown they are slightly more than % inch in length, and are either white, yellow, pinkish, or greenish, with the head and prothoracic shield dark brown. Pupation occurs in a white silken cocoon in any secluded place, on the host, in the surface soil, sacks, or storage bins. In tomato fields, most larvae probably pupate just beneath or on the surface of the soil. Potato culture increases this pest The hosts of the potato tuber moth are apparently limited to solanaceous plants, including potato, tomato, tobacco, Jim- son weed, pepper, horse nettle, eggplant, and nightshade. Tomatoes are subject to attack by the larvae of the potato tuber moth over a large portion of the tomato-growing area of California. In some areas such as Sacramento, Yolo, and Solano counties, it has never been a pest, and only on rare occasions are any individuals found. It appears to be most prevalent in the coastal regions, although serious outbreaks in localized areas have occurred in the San Joaquin Valley. Although the tuber moth larva feeds on other parts of the plant, damage is serious only on the fruit. Infestations as high as 57 per cent have been encountered, although in most fields where it does occur usually less than 5 per cent of the tomatoes are infested. The potato tuber moth population normally increases as the season advances and gen- erally is not a problem until late in the season. Early in the season very few in- fested tomatoes are encountered, but from late September to the end of the growing season, at least a few infested fruits will be found in most of the tomato fields in the coastal area. Serious infestations are almost always associated with potato culture. Where to- matoes follow potatoes and where there are volunteer potato plants, there is al- ways the danger of a serious infestation developing. Wherever destructive popu- [13] - Fig. 10. Work of the potato tuber moth larvae on tomatoes: A, enlarged view of the calyx end showing the webbing over the burrow entrances; B, larval mines just below the skin. lations have occurred in the San Joaquin Valley the above-mentioned conditions have usually prevailed. Make webbed burrows Because the injured fruit is rather dif- ficult to detect, infestations, even though low, are of considerable annoyance. The larvae prefer to enter the fruit at the calyx end, and seem to be more numerous in those varieties of tomatoes which have firm, solid flesh. When entry is made at the calyx end, the burrows follow the core and the fleshy portions that radiate from it. In the early stages the burrows do not extend far into the fruit, but as the larvae increase in size, they may penetrate deep into the interior. When the calyx is re- moved, the entrances to the burrows are usually exposed (fig. 9). After the fruit has been picked for some little time, the larvae, if still present, close the entrance to the burrows with a webbing and the calyx end of the fruit appears as shown in figure 10, A. As this webbing tends to obscure the injury, the fruit must be care- fully observed or the damage will pass un- noticed. The potato tuber moth larvae will at- tack the fruit at any point. Where en- trance is made at some spot other than the calyx, the larvae may act as miners and work just below the epidermis as illustrated in figure 10, B. They may pene- trate deeper into the fruit if they en- counter a fleshy part that radiates from the core. A large number of larvae may enter a single fruit, although from one to three are the numbers most commonly found. Their mode of working and the type of damage done is very similar to that caused by the tomato pinworm. However, be- cause of their larger size, the injury may be slightly more noticeable. A survey made in 1944 in the Bakers- field area, where many potatoes are grown, well illustrates the above. Six to- mato fields were examined. In some of these there were volunteer potato plants, and despite extensive control measures, rather heavy infestations of the potato tuber moth were found. The average infestation of tomatoes by potato tuber moth larvae, per 100 fruits, ranged from 2 to 25 per cent. The fields had been dusted three to four times with insecticides containing cryolite or arse- nate of lead. Had there been no control, it is likely the infestation by potato tuber moth larvae in some of these fields would have exceeded 50 per cent. [14] Tomato and Tobacco Hornworms The tomato and tobacco hornworms are very similar in all stages. The adults are large moths with a wing spread of 4 to 5 inches and are commonly called "sphinx" or "humming bird moths." They are swift fliers and are crepuscular and nocturnal in habit. They are fre- quently seen at dusk hovering over flow- ers in a manner similar to humming birds, hence one of their common names. The adult of the tomato hornworm is shown in figure 12. It has six orange- colored spots on each side of the abdomen which distinguishes it from the tobacco hornworm which has but five. They lay their large, round, greenish eggs at ran- dom on the undersides of the leaves of their host plants. The larvae, which are called "hornworms" after the character- istic horn on the tip of the abdomen, often attain a length of 4 inches. A mature to- mato hornworm larva is illustrated in figure 11. It is green in color, has 7 diagonal white stripes on its sides and a red horn. The tobacco hornworm looks much like the tomato hornworm, but can be distin- guished from the former in that along the sides eight "_\" markings replace the white diagonal lines and in the larger specimens the horn is black instead of red. The tobacco hornworm also has a melanistic color phase. When mature, the larvae burrow into the soil and pupate. The pupae which are chestnut brown in color are shown in figure 12. They can be distinguished from one another by the sheathed proboscis which is longer in the tobacco hornworm. The winter is passed in the pupal stage. The moths emerge dur- ing April-May, and there are probably no less than three generations in a season. Cause serious defoliation The host range of the tomato horn- worm and tobacco hornworm is rather extensive. Both native and cultivated crops are attacked. Important among the latter are tomato, tobacco, and potato. Of the native hosts Jimson weed is probably by far the most important. The larvae strip the leaves from tomato vines as shown in figure 13. When they are abun- dant serious damage may also be done to the developing fruit (fig. 14). Although they may occur in any tomato-growing area, they are most serious in the warmer interior valleys, and if severe infestations are allowed to go unchecked, an entire field may be defoliated. Fig. 11. These drawings show clearly the similarity of the two hornworms which attack tomato. Above, tomato hornworm, Protoparce sexta, and be- low, tobacco hornworm, P. quinquemaculata. [15] Hornworms at Three Stages of Life Fig. 12. The caterpillar of the tomato hornworm, above, has hatched from the egg and has grown to full size. At left, B, is the pupa of the caterpillar, in its cell. The pupa of the tobacco hornworm is shown in A, at left, where its longer sheathed probos- cis may be seen. Below, the adult moth of the tomato hornworm has emerged from its pupa. [16] Typical Hornworm Damage Fig. 13. Tomato stems pictured above have been seriously defoliated by horn worms. Fig. 14. Tomato fruits show injury by caterpillars of the tomato hornworm. [17] Fig. 15. The tomato mite, Phyllocoptes destructor, showing adults, immature, and eggs. (x40.) Tomato Mite Another Pest Needing Control The tomato mite, Phyllocoptes destruc- tor Keifer (fig. 15), also known as the tomato russet mite, is a free-living, micro- scopic eriophyid mite, which appears slightly humped and tannish white under high magnification. It crawls about slowly on the surface of the leaves, stems, and fruit of the tomato plant and sucks out the cell contents. The stems and leaves some- times, but not always, become greasy bronze or russet in color, but later they die. The infestation usually starts near the ground and as it progresses up the plant the lower leaves dry which gives the plants an open and unhealthy appear- ance. Mite damage should be suspected if the leaves on the basal portion of a plant are dead, and particularly if there is a zone where the leaves and stems show a greasy bronze discoloration, while the outer growth of the plant still appears normal. The tomato mite reproduces from eggs and passes through many generations in a season. In the field, continuous repro- duction has been reported by Bailey and Keifer (1943) from early May until frost. Defoliates vines The tomato mite feeds and reproduces on a number of solanaceous plants. Among the more favorable cultivated hosts are tomato, potato, and petunia. Un- cultivated hosts which are less favored than the above include nightshades and Jimson weed (Bailey and Keifer, 1943). Where not controlled, the tomato mite causes serious damage in California. It was not known to occur in this state until 1940, when it was found injuring toma- toes in a greenhouse at Modesto. Since then it has spread throughout the major tomato-producing regions. In the north- ern tomato-producing section, injury may appear during the month of June, but sel- dom becomes serious enough to be noted until late July and August. Damage in the southern San Joaquin Valley may occur at an earlier date and Michelbacher (1944) reported serious mite injury to a small planting of tomatoes near Edison, Kern County, on the first of June, 1944. If not controlled, the tomato mite causes serious defoliation, which is par- ticularly rapid during periods of hot weather, resulting in sunburned fruit and the loss of the crop. If damage by the tomato mite does not become apparent until after the first of September, there is little likelihood of its becoming destruc- tive, and control measures rarely are justi- fied after that date. [18 EXPERIMENTAL METHODS Investigations were made on small plots and on commercial plantings, testing various equipment and new insecticides. Plot Arrangement Two types of plot arrangement were used in the investigation. In one, mate- rials and methods of application were tested on small plots that were 10 rows wide and from 50 to 60 feet in length. Applications were made by hand equip- ment and the treatments replicated four times in a randomized experiment. In the other, treatments and methods of applica- tion were investigated on a commercial experimental scale. The treatments were applied with power equipment, were not replicated in a given field, and the plots ranged from 5 to 8 acres in extent, except for a single experimental series in 1946. In this, the individual plots averaged 0.85 of an acre, applications were made with power equipment, and each treatment replicated four times in a randomized experiment. Equipment In the case of the small plot replicated experiments, Root rotary hand dust guns (Model C-3) were used for the applica- tion of dusts and Hudson hand sprayers (Dumore No. 247) for the application of concentrated sprays. Power dusters and sprayers were used for the application of insecticides to the commercial blocks. Most of the ground dusting was done with a 5-row standard tomato duster equipped with three nozzles to the row, and ar- ranged so that the dust was directed to the sides and the top of the plants. (The theory and operation of spraying ma- chines: high pressure, compressed air, and mist sprayers, were presented by 0. C. French in 1942.) The ground machine used for applying concentrated sprays in 1946 was a com- pressed-air atomizing type (fig. 16). It was designed to supply compressed air at about 15 pounds per square inch and 7 cubic feet per minute to each nozzle, mix- ing with and atomizing the liquid at the nozzle. The spray material was carried in Fig. 16. Three-row, compressed-air power sprayer in operation. [19] Fig. 17. A two-row commercially built vapor sprayer and duster used during the 1947 season. a 75-gallon tank provided with mechani- cal agitation. The mixture was drawn from the tank by a small gear pump and forced to the nozzles at about 5 to 10 pounds per square inch and discharged at a rate controlled to give about 0.16 gal- lons per minute from each nozzle when spraying at the rate of 10 gallons per acre. The machine covered three rows at a time with three nozzles to a row; one on each side and one on top. The machine was of a design to give satisfactory coverage. It produced a spray with droplet size large enough to eliminate serious drift but not so large as to impair distribution or burn plants with materials of potential danger when unevenly applied. Vapor spray machine used The machine used in 1947 for ground spraying was a commercially built vapor spray type, known as a Naconizer (fig. 17) and variously called a vapor or mist sprayer, or duster. It could be converted to a straight duster by making a few me- chanical changes. Both this machine and the one used in 1946 were designed to re- duce the amount of liquid carrier re- quired, by replacing a portion of the carrier of the suspended toxic ingredient with air. The obvious benefit of these ma- chines is that the amount of liquid carrier required is greatly reduced. It is believed that the machine used in 1947 was su- perior to the one used in 1946 in that it gave better coverage to all parts of the vine due to deeper foliage penetration of the spray-laden air. Improved equipment The machine used in 1947 was equipped with a 15-gallon tank, and the spray mix- ture was agitated hydraulically with by- passed flow from the pump. The small centrifugal pump handled 20-30 gallons per minute at 7-10 pounds per square inch. When spraying at the rate of 10 gallons per acre, each nozzle discharged about 0.25 gallons per minute. A blower coupled directly to the driving motor fur- nished the high-volume air which picked up and atomized the liquid as it was dis- charged from a special nozzle. Air volume at each nozzle was about 500 cubic feet per minute at a velocity of approximately 150 miles per hour. [20] The capacity of the machine was two rows at a time. There were two nozzles per row and they were adjusted to the height of about 18 inches above the plants and directed into the sides of the row at an angle of 35 degrees. The nozzles were tilted backward at about 10 degrees to reduce laying the plants forward by the force of the high-volume air and the for- ward motion of the machine. Unless this condition was corrected, the plants were thoroughly sprayed only on one side. This equipment gave satisfactory me- chanical performance with a minimum of breakdown. It was designed to be tractor -mounted and power -take- off - driven requiring about 15 hp. Because of its light weight and compactness, it was easy to handle. Airplanes test dusts and sprays Regularly equipped airplane dusters with gravity-flow hoppers were used for the application of dusts by air. 0. C. French reported on the airplane dusters and sprayers in 1947. The airplane used for spraying in 1946 produced droplets too large to give most satisfactory results. Not only was the atomizing device inadequate, but the plane also lacked precision shutoff valves at the nozzles which made it impossible to confine the spray to the field being treated. These difficulties, although still present, were largely overcome in the airplanes used in the 1947 investigations. Stearman biplanes equipped with wing-length boom applicators were used. One plane had the cluster nozzle system where several noz- zles are controlled by one valve, while a second had a single nozzle per valve. The spray tank capacity of the planes was ap- proximately 120 gallons. Both used hy- draulic agitation obtained by forcing the excess of by-pass flow of liquid from the pump back into the storage tank. One of the machines used a power-take-off-driven pump mounted inside the fuselage and operating with pressure up to 90 pounds per square inch while the second was mounted in the main slipstream driven by a small propeller and operated on a rela- tively low pressure of 25 pounds per square inch. Sampling Methods Trends of infestation in the experi- mental fields were determined by follow- ing the infestation in the developing green fruit as well as that occurring in the ripe fruit. In making surveys the fruits were picked and carefully examined. During the harvest season the degree of infesta- tion was determined for each picking that occurred in the experimental fields. From 200 to 600 fruits were examined, depend- ing upon the size of the plots. For the small plot replicated experiments usually 200 fruits were examined per plot, while in the large commercial blocks 400 or more fruits were inspected. Infested fruit was divided into two categories, super- ficial and severe. The superficial category comprised those fruits which showed only a slight amount of injury, while the se- vere included those fruits that had been severely injured or were infested with a caterpillar. Materials Used in Tests A brief description of the primary ma- terials used in the tomato investigations may be listed as follows : Calcium Arsenate This was a commercial grade prepara- tion which contained 70 per cent of cal- cium arsenate. Reference to the use of calcium arsenate either in dusts or con- centrated sprays in the text and tables applies to this grade. DDT Dichlorodiphenyl-trichloroethane was used as 3 and 5 per cent commercially pre- pared dusts. Where used as a concentrated spray a commercial preparation contain- ing 50 per cent DDT was used. [21] DDD An analog of DDT known as DDD or TDE, Dichlorodiphenyl-dichloroethane, was used in 5 per cent commercially pre- pared dusts, and a commercially prepared 50 per cent wettable powder for concen- trated sprays. Toxaphene Toxaphene is a chlorinated camphene having the approximate empirical for- mula C 10 H 10 C1 8 , with the technical grade containing 67 to 69 per cent chlorine. Two dust formulations were used. One con- tained 10 per cent by weight of the tech- nical material and the second contained a like amount plus 5 per cent DDT. In both cases the dusts contained 25 per cent sulfur. Cryolite A 50 per cent natural cryolite dust was used which contained 45 per cent of so- dium fluoaluminate to which was added 25 per cent dusting sulfur. CONTROL GIVEN BY VARIOUS INSECTICIDES Integrated control program for entire season is advocated. New insecticides show promise as good substitutes for arsenic. Experimental results from 1944 to 1947 have indicated that some of the recently developed insecticides offer exceptional promise as superior substitutes for cal- cium arsenate in the tomato insect control program. Experiments with these recently introduced insecticides were begun dur- ing 1944 when DDT first became avail- able for agricultural testing, and have continued with increasing vigor to the present season. Studies have also been conducted on the improvement of application of cal- cium arsenate. If calcium arsenate dust is used at the recommended rate of 15 to 25 pounds to the acre, satisfactory to excellent control of the corn earworm, armyworms, and hornworms can be ex- pected. Against the tomato pinworm and the potato tuber moth, however, only in- different control has been obtained. With the recent increase of tomato acreage in northern California came the concomitant demand for a more effective and less haz- ardous material to be used against all insects attacking tomato. Advantages of Planning a Generalized Control Program The problem of controlling tomato pests is probably best approached from the wider viewpoint of the progressional seasonal picture, rather than by giving a discussion of the control of individual in- sects. Repetition is thus avoided and the insect problems are seen in broad per- spective. A well-integrated control pro- gram should consider all the important pests and provide protection to the crop throughout the summer and fall. In general it has been found that the tomato mite is the first pest against which control measures must be directed. Be- tween July 1 and 15, tomato fields should be dusted with sulfur. During this period hornworms, yellow-striped armyworms, and beet armyworms may be making their appearance, and where this occurs an ef- fective insecticide should be used in con- junction with sulfur to control them. During early August the important in- sects to control are the beet armyworm, yellow-striped armyworm, and horn- worms. A suitable insecticide should be applied to check their damage. A material applied at this time will also control the few corn earworms which may be making their appearance. The insecticide should contain sulfur to further aid in the con- trol of the tomato mite. Early in September a third treatment is usually needed and is primarily di- [22 rected against the attack of the corn ear- worm, but it should also be effective against other armyworms and hornworms which are almost certain to be present. If damage by the tomato mite is not ap- parent, sulfur may be excluded from the third treatment. The above timing schedule is one well suited to most of the northern area de- voted to canning tomatoes, but the timing is not applicable to the early producing tomato sections of the San Joaquin Val- ley. Investigations in the latter regions have been rather limited but indicate that the control program should be put into operation in late May or June and con- tinued as long as protection is considered necessary. However, application of insec- ticides at all times and in all areas should be based upon a knowledge of the insect pests present. Investigations During 1946 Toward Eliminating Drift The 1946 investigations have been re- ported by Michelbacher, et al. (1947) , so only a brief summary will be presented here. The work was done with the follow- ing objectives in view. 1. To determine whether ground dust- ers could be equipped with hoods that would restrict drift. 2. To determine whether the incorpora- tion of 2 and 4 per cent highly refined oil in calcium arsenate dust would settle it sufficiently to eliminate a serious drift problem. 3. To determine the feasibility of ap- plication and the effectiveness of calcium arsenate applied as a concentrated spray. 4. To determine the effectiveness of such new insecticides as DDT and DDD in controlling the important pests of to- mato. Hood ineffective In order to study the efficiency of a hood in restricting drift, a five-row, trac- tor-mounted tomato duster was equipped with a seven-foot adjustable rigid hood supplied with end and side drapes. This equipment was used on several occasions, but even under favorable weather condi- tions the hood proved to be ineffective. No drift control from oil Where 2 and 4 per cent highly refined oil was incorporated in calcium arsenate dusts, little or no control of drift was ob- served. The oil had a tendency to keep the drift from boiling high into the air but not to settle it. Although the drift cloud failed to rise to any extent above the ground, it did drift from the field be- ing treated. Spray lessens drift problem Investigations were conducted wherein calcium arsenate was used in a concen- trated liquid spray the composition of which was as follows : Oil emulsion 1 gallon Water 3 gallons Calcium arsenate 12 pounds Where the above mixture was applied with a three-row compressed-air atomiz- ing power sprayer (fig. 16), drift was eliminated and good control resulted. Where applied by airplane, no serious drift occurred, but the lack of precision shutoff valves at the nozzles made it im- possible to confine the application to the field being treated. Further, the atomizing device was not adequate in that it could not be regulated accurately as to rate of delivery or to the most desirable particle size. Despite these disadvantages, fair control of caterpillars attacking tomatoes was obtained when an airplane was used. New insecticides prove effective In order to determine the effectiveness of some of the newer insecticides and sev- eral calcium arsenate mixtures against caterpillars attacking tomato, a series of experimental plots was laid out in a field near Woodland. There were seven treat- ments, and each was replicated 4 times in a randomized experiment. The individ- ual plots averaged approximately 0.85 of [23 rl • 3 o CO CO CO IO 00 00 CO CN i> c>: to r-J 00 CO tf H O CO CN O CD CO to 00 .S CO C4M M.2 2* v eel s lOO(D CO tO to CN 3 ■O 2*3 to* 1 CO 00 ID in cn d "* ^ 00 IO CO to to CO Eh fc t^ 00 CN rH iH CO rH fc CD rH CN OO CN tH rH w 4) 02 tH a 3 o CO CO IO IO 00 CO © CN CN 00 CO IO CO rH X I H O CO cn r-i d "* »o CN w s« •"• t; o IOO 00 CO IO CO P M ■?£ S.| IO t> © oq th t> l-\ 4> 2 eS a o Eh 5* CO CO CO H ri 6 CO* CO* O IO O O IO r-i o O s M * i-J tO CN O to l> p £3 •a CN odd rA tA tA Ph 1 C9 to tH W a «* W$ tM 3 o CN t- CN "^ O -■ "^ l> © © t- O to p to co p cn t-I d «-i cn t! o Ph a* 4) CS CO 00 00 IO o 9 w,5 V IO t> CN t- O t- CN H O CO S3 c- CO H M IO CO CO od odd d d d 09 3 tN IO IO t- t~ to to S Eh hfl o C^ CN 00 00 t> H ri 6 rH i-i tA §3 t-fl IS .2 2'S s «a 00 T-H O to t- o o p l> CO p p tA O G t-I r-I to d *l CO (*4 C0 tO to o o t- to o h 4) ► CN CN t> IO to 00 t> g g d d d p rH k S CO CO &S a*! O 00 o to to ^ w Ph 2 i I Ml Qj f 3 S.2 CO CN CO CN CN CN P - 1 fc < lei tO o o o to to ^ H B (A S « 4> U O O O >h M M M S o e a O, CN C co © a P. o. o. io to -3 r^ « d> rH 2 Eh 1 CO O o o oo t- lO IO TJ1 ^ ^ H H p" "§ g l> o t8 rt Eh 1-. 4 PPP § s g s O * Q P P 2 fc.g IS 2 g 00 r* § § S g »« S co S O S § CN g CN «« .2 (H CO * CJ fl> CO 0) ^J S o S O. 0, Q, c«] < * H 73 *« •5 S 73 * o co to to O o o c8 a * u ■n & X) q D. 3 4 o xn d (N * 1-i A o JG 0> * eB u >> A a M CO ♦* o C C CO • 5 u "3 I a g 2 I * .2 « 3 I ! d 3 e t- a is ■0.2 o'-S a, X CO •15 o S3 — 3 A O oj 05 3 ^CO 1^ 4) is O a. ^ ««fl o ^s 4) > 'US •o 4> (0 ■4= a a 5s cS n*3 ;3 >»« C9 Ss < m'Oco an acre. The treatments, rate of applica- tion, and the control obtained of caterpil- lars infesting tomatoes are summarized in table 1. All the treatments resulted in good control. Slightly better control was obtained with DDD and DDT than with calcium arsenate. The calcium arsenate- oil-water concentrated spray proved to be as effective as the calcium arsenate dust treatments. Special attention to Hornworms The effect of the various treatments in controlling hornworms was observed. The per cent of damaged plants (that is, those on which feeding had occurred) as de- termined on September 12 was as follows : Check 5 per cent DDD 3 per cent DDT 5 per cent DDT Calcium arsenate plus sulfur Calcium arsenate plus sulfur plus 2 per cent oil Calcium arsenate-oil- water, concentrated spray 15.50 per cent 0.00 per cent 6.50 per cent 1.75 per cent 0.25 per cent 0.37 per cent 0.37 per cent The above information was obtained by examining 200 plants from each plot for a total of 800 for each treatment. Ob- servations made throughout the season indicated that the tomato hornworm made up the bulk of the hornworm population. The results show that DDD was more ef- fective in controlling hornworms than was DDT. Investigations During 1947 Tested New Insecticides In 1947 testing of newer insecticides was continued, and considerable time was devoted to determining the effectiveness of several insecticides in controlling to- mato insects when applied as liquid con- centrated sprays. The concentrated sprays were applied by hand, ground machine, and by airplane. Dust mixtures were also applied by the above-mentioned methods. Extensive experiments were conducted at Woodland, Davis, Tracy, Westley, Patter- son, and Merced. Some of the investiga- tions were conducted on an experimental commercial scale, while others involved small plot replicated experiments. Small plot replicated experiments The small plot treatments were repli- cated four times in each experiment in a randomized plot arrangement. The small plot experiments were established not only to test the relative effectiveness of several insecticides but also to compare the merits of applying them as dusts ver- sus concentrated sprays. In two such experimental series, 10 dif- ferent treatments were compared. One of these was located at Woodland and the other at Patterson. The information con- cerning treatments, rate and time of appli- cations, and the control obtained of all species of caterpillars infesting tomatoes are given in table 2 for the Woodland ex- periment, and in table 3 for the Patterson experiment. The results indicate that DDT and DDD were more effective in controlling caterpillars infesting tomatoes than was calcium arsenate. Cryolite, 10 per cent Toxaphene, and calcium arsenate were in the same range of effectiveness. Variations noted As might have been expected, the dust mixture that contained 10 per cent Toxa- phene and 5 per cent DDT resulted in excellent control. Calcium arsenate ap- plied as a spray was about as effective as where applied as a dust. DDT and DDD applied as concentrated sprays or as dusts resulted in very satisfactory con- trol, and there was little to choose be- tween the two methods of application. In the case of DDT it appeared as if the sprays were slightly more effective than the dust, although the reverse occurred in the case of DDD. The differences, how- ever, are not great, and probably are too small to be of any significance. [25 w H O s o Eh w 5 w P fa o O O Eh Eh* 11 55 & 5 p Ph X H P W H to Tl< -tf Oi © O c4 th i-i cs CS ir: (N o w CN CN ft o o *> £ fl M £ M CD > CC CD CO O) (C -<* CC lO CC 00 49 o oc th d o* o r4 CD ► c rldri W H t- d 3m - 05 o s ^ M "O vi 0) ^ s Pi o> J: lO °i 03 co d Eh P H Ifurd derf. Ifurd derf 0) O P d CD ! 3 £ 3 ? w 5 w o •S e d in g cs o c d © IH per cent ettable p< per cent ettable d It 1 ■ i« a> d 0) tN F (N J* T3 03 03 _ c .d U Pi - Eh - O ■*■ -»J H e€ cS DDT tDD 1 DDD tDD P 03 Sh C 03 xr. 1 S 1- o Eh tS •g d -t* C e< a >2- c d T3 d © d a «•» « ^ tH D O O U ® o ° d ^ O M « K ^3 ** 0) "^ CJ >-. O) >-. 03 ■5 •^ 43 c a k 03 '1 o CD P. s° « aw a S a o o o = | to o to to wTJ .13C0-CCN £<*H «« •o°S° »2S2 s S m 2 cd ^ 55 ^ J3 £> O, 3 s| I fl ft+S ft CD w p co is d a c S °T3 ° "cS ©c« ««% 'H c8 p e3 J CD 3 CD 5 ft3 ft 0t>io t>csii> S-Sg O CN OOP O O C 3 bo H i-iO ri H id rHCsJlO ia* coco co* co" id n co e CN N N C i 3 O.S CO Jtf o a 0.0.& ^.2 gi'S 010 0100 lOOO^I O CM O t> lO N O IO o o a. "• < ■S? £ j= 3 « CO rA i-i d csi rA c4 co < 1 O O C > §1 Ch > 010 ipoo >o 10 IOCS] t>00 IOCS1CN do d rH co" d O* CN* ^ CO 0) cu 0- 0, aa ft ft c H 1 4> CO o O a>o> a> h3 ft ° 1 ft 'S COCO N O ^ COOCO O 5* CO 1 "Si* Soft coco" co* co" id co'oic CM CM tH O 0) Ot> COOCO -^t-CN pio oqpoq t-jiotjj 4 "3 o o. Pi e3 -91 I >• CO O O* O" ri CO ri O C0* ^ hh" T3 | I i>»o t>iqp Eh a L o o e CO c9 co co cococo 00 00 a tub c*i> tub tub tj> bi) bi & S.I H cn* 10" iri id ^ cn* ^a* d rl tH § Q S d 322 P P r. < CN CN | t tf « co w ri CO* CN* CM* CO O* CN rji 1 Ph XI w Pk »l V 100 m m m 01010 -1 CM IO CM CM CM_ O CM t^ c8 „ «> > ri CM* C0* CO* 00* CM* CM* IO* fc g?s P P ppc 1 CO V i-i x S «* CO co 06 00* c 1 CO | m o 2 AAq. 1 "3 IOIO 000 IOIOIO cm t- 10 10 10 cm cm cm i o «S "Si - f Eh Q 3 ? H ri O* IO "^* 00 C0* CM t> CM t- t- l> O O ri O CO* CM* CO* ri ri -^" o CO M 0) tH rl iH rl CO CO Cs 5-5 a) cd 3 X! CO ^ (8 j*, >> >» >» > •> at- P P "3 3 B1p £E CO CM O CM t> t> IO CM CM i Eh CO > do* CM* ri ^ tA tA CO* CO V fc hH - fo o H < • fc „ W fi a 4 o S I M PC! 1 0) * # * * •)(■ * * V Ph J3 s © s © h >- ^ 5 T5 a C3 P" 5 P c 73 "O T3 "O » S •X) 'V -rj "C3 jti a a a * S •• * £ a ^ fc 6 - fc B p 2 CO w < o N ft Pi © ft ft « 1 a) a> 2 KJ ft ft « ft ft g g Eh 1 •a o © iJ S © © 3 .a if 3 .q '2 -^ ^3 +^» aj

> P O QP'43QP © P P P ooftooq2»a>a>e ftM^ftMMg^ooSi I a> CO o CO CO CO CO CO p CO bo Eh IO 6 d c-" d d t-* ^ 2 CO ^3 fa © efl © CO CO CO CM CO CO CO CO 6 o o CO o to © d co Q CO © CO CO CO d 8 o o d 8 8 CO CO CO ► i-i d d "** d d ■«** 00 •^ 3 o IO IO O IO IO o o t> CN IO CM t- IO m bo M.5 Eh lO rH* O "tf d CN* ^' CO rH w i as 3 o o 8 IO O CN O IO CN IO CN o IO © o 2t3 CO tH* O CN* d iH CO "5 s OS Eh a IO IO IO IO o IO o o N c- CM CN CN IO CN o TJ ► I>* © d cn* d rH CO © 4) tH W CO a> a «w 3 o 8 O CO o CO CO o o IO CO p o CO CO fl V si H a* CN* CN "tf* CN IO* l> t> CN f-3 M © ft ®.2 ©IS 3-r- W* 1 8 oi CO CO tH* CO CO p co rH C4 CO CO T-I 8 <* 8 " 5 2*1 CO iH «5 © o CO CO CO co CO CO h IO CO CO CO CO CO CO fc © © O CN d tH CO © •«* rH 3 IO tH CN IO co l> t- © t> rH O CN CN CO c- Eh •** c4 CO* "<*" co* ^' oo rHt* "# !s-2 It ■ n*3 o t> t~ o CO b- IO © oj D.-3 o rH tH io p IO oo 3 « CO rH T-I rH CN tA CN* ■"^ wiC © IO "tf IO IO CO o CN © l> © °°. "*■; p 1-i p & CO d rH* tH* rH* CN* CO* 9 02 tN roximate rate ere in pounds d method of pplication August 28 second application by airplane o d CO o o d io CO CN p CO* o co" o Tj* CN July 30 first application by Naconizer ++ o o o p p o Pi d CO d co CO CN CO* CO* CN i TJ CO *3 3 ea a> o CO CO o CO 88 3 3 o ■a 3 ^co 2 3 o (H CO P< CO » O Pi Q. § CO a3 CO 1 a © 1 M H O IO IO 00 o to H— a> * t* 5^= CO o Pi Q Q Q p Q H p P CO 1 p s CO H Eh Q Q ■♦J uy Q Q Q 9 -»J U7 cd CO CO ) t-l IO CN H «5 CO o ce CO 00 CO T3 O >- c£ *> C! 9 CTJ co CN c a P "O • c P "- 1 ft IO b g -3 c8 O 1 s IO t* .2 U Q CO I It S 3 I! O o S3 "OS "3 » a w 2S S bo H O fe S s ° |*s||a M - U ** CO ,>, j-M ^ n in * 3 © 9 • £*«%% .t3 ct) g o o C » S ° © b m «s * H M oJ «3 >>'g St3T3 gag©© «Ii*a"S o ,3 aa OQo«jJ< M s IO o lO IO IO U3 5 t- 00 t- # t- cs >, M o T-1 cs T-i T-i cs CO* "3 *H n.S < w NJd d 3 Eh n 2 ll to o o o »o IO ^s, w © 00 IO CS cs T3 CO 1 '1 In T-l lO CS 10 d o T-i cs" IO o cs o d a CS t> q CS IO q S H d d T-i d d T-i M 0.3 J3 Pi II 3cd co** © 10 to o o IO "o o ©TJ tH T-i T-i d d d ri 5 H M o in o IO o lO o o o io s 43 • to 3 09 CM* d cs" T-i d cs o 3 IO CS s 10 IO o CS lO 8 5s 3 ft Eh 525 o "3 u P4 «d o EH .5* CO s CS CO T-i CS* tH o o CO cs* o io o cs cs* d CO* IO cs T-i to w Is •M O 2« EXPERIME lane) 2-1 ° CO > CO 10 © s IO t> 00 lO lO cs cs i-i cs IO tH d-g 1 10 lO CS 10 CS O IO q cs o Ifl M -a Z% o H T-l CS cs' CO cs* cs* ©•O TOES ns by ®3 e-2 •-■a S.-S JO* 3 o T-i 10 CS T- lO CS T-i io o t» IO T-i d IO cs T-i ss 1! !1 TOMA plicatio 0.3 10 o o lO IO lO ► CS d q T-i q T-i CS t«; T-i T-i cs T-i CO a © P * o'-S O q q o 2 NFESTE (All a d ** H KS o CO o CO <* CS CO* CO* cs Am Si 03 5- en tH 8 CO CS IO IO IO «3 .a -s i-i o. -*j -»j ■*» -*j ■** -*j S • O . u fc c9 Q Pi Pi Pi Pi O, p CO c CO CO CO CO O CO CO CO CO CO CO Eh CO . « H 1 " 3 CO CS q q CO* CO* q ■** cs OS B io tH tH CS cs cs tH t-I cs tH fill • SI 6? S "OH cS ts bb at be bi> bit b. p Q CS s p 3 fl C fc < < < • e8 (9 *d 4* +» •3 o ■a 0) d'Ettsts co G ■*» ■** « S co d P •3 g ©£« H 8 = a |l CO s si Si v a, CS si ■jj CO CO 2 ° ° p CO CO CO Pi Pi CO-- P cc i "s d «o CO w Otd&& P ^ 10 to ^ •5 P S Table 7: TREATMENT, RATE OF APPLICATION, AND PER CENT OF INFESTED TOMATOES IN EXPERIMENTAL COMMERCIAL BLOCKS AT PATTERSON (All applications by airplane) Per cent of infested tomatoes Treatment* in pounds September 25 First picking October 15 Second picking First ap- plication August 12 Second ap- plication Sept. 5 Se ™ e ficLT Totel Se ™ e fiSaT Total 50% DDT wettable powderf 50% DDD wettable powderf . . . Commercial calcium arsenate. | 3.0 3.0 24.0 3.0 3.0 24.0 1.00 3.50 4.50 1.50 1.75 3.25 2.00 2.75 4.75 1.00 0.50 1.50 0.00 0.50 0.50 1.50 0.50 2.00 * On July 15 entire field treated with a dust mixture containing 50 per cent calcium arsenate and 50 per cent dusting sulfur. t Used at the rate of 3 pounds to 10 gallons of water. | Used at the rate of 24 pounds to 10 gallons of water. the Naconizer was greater than the amount of dust applied by the duster. Likewise, the treated plants in the Nacon- izer plots received a greater amount of actual insecticide than did the treated plants in the airplane plots. However, the amount of insecticide applied in both cases during the most critical period was nearly the same. Here the difference in the effectiveness could be due to the Na- conizer giving better coverage, more de- sirable particle size, and also a higher deposit due to the fact that the nozzles directed the spray to the vines. An air- plane, on the other hand, applies a spray over the entire field, and cannot con- centrate it on the growing plants. Abundance of caterpillars present In 1947 the infestation of caterpillars attacking tomatoes was one of the most severe encountered during any recent year. In spite of the destructive popula- tion, most of the treatments resulted in very satisfactory control. The severity of the infestation is clearly indicated by the fact that in the Davis experiment nearly 80 per cent of the fruit from the check plot (table 5) on the second picking was infested. The vellow-striped armyworm was par- ticularly destructive in this field as it was over much of the rest of the tomato- producing region. One particular source of annoyance was migrations of this pest from newly cut alfalfa to tomato fields. These migrations were frequently exten- sive but tomato fields could be protected by a barrier of 5 per cent DDT or DDD dust a foot to 18 inches wide, placed be- tween them and the source of the mi- gration. The corn earworm population reached a destructive level and, at least in the San Joaquin Valley, was more abundant than usual. Large flights of moths from mature or harvested bean fields to tomato fields during the latter part of August and Sep- tember resulted in serious infestations in tomatoes. In the experimental field at Patterson infestation of small developing fruit by the corn earworm rose from one half of one per cent on August 22 to 30 per cent on September 16. Yet despite this heavy influx, excellent control was ob- tained in the treated portion of the field (table 7). The beet armyworm, which is usually very destructive, was less abundant than usual during the 1947 season. One of the prime reasons for establish- ing an experimental series at Merced was to determine the effectiveness of DDT and DDD against the tomato pinworm. A serious infestation of this pest failed to develop in the experimental field. How- [31] ever, what information was obtained in- dicated that these two insecticides were effective against this pest. Neiswander ( 1945) has reported DDT as giving satis- factory control of the tomato pinworm. In none of the fields surveyed was the potato tuber moth observed doing dam- age and as a result no experiments were conducted on the control of this insect with the newer insecticides. Hornworm control The tomato hornworm and the tobacco hornworm were present throughout the important tomato-producing regions of northern California. In the absence of control measures, serious damage to to- matoes would have occurred, particularly in many of the fields in the warmer in- terior valleys. The relative effectiveness of several insecticides in controlling these pests was obtained in two small-plot repli- cated experiments. One of these was lo- cated at Davis and the other at Patterson. The treatments and the results obtained are given in table 8. The insecticides involved in the experi- ment at Davis were DDT, DDD, and cal- cium arsenate. DDD both as a dust and concentrated spray resulted in excellent control. Where DDT was applied as a concentrated spray, satisfactory control Table 8: COMPARATIVE EFFECTIVENESS OF SEVERAL TREATMENTS IN CON- TROLLING HORNWORMS IN EXPERIMENTAL PLOTS AT DAVIS AND PATTERSON • First application Second application Per cent of Treatment Date Approx. pounds per acre Date Approx. pounds per acre injured plants on Sept. 10 Davis experimental plots : Check 36.0 2.9 29.0 3.0 36.3 34.5 3.5 26.0 3.5 32.0 22.0 32.0 30.5 25.5 August 9 August 9 August 9 August 9 August 9 34.0 3.0 29.0 3.0 21.2 30.0 3.5 37.0 3.2 22.0 30.5 37.5 33.5 34.5 65.0 5% DDT, 25% sulfur July 16 July 16 July 16 July 16 July 16 28.0 50% DDT wettable powder* 2.3 5% DDD, 48% sulfur 0.0 50% DDD wettable powder* 0.0 75% calcium arsenate, 25% sulfur dust 2.0 Patterson experimental plots : Check 23.0 5% DDT, 25% sulfur dust July 28 July 28 July 28 July 28 July 28 July 28 July 28 July 28 July 28 September 2 September 2 September 2 September 2 September 2 September 2 September 2 September 2 September 2 15.0 50% DDT wettable powder* 1.9 5% DDD, 25% sulfur dust 0.8 50% DDD wettable powder* 0.5 Calcium arsenate dust J 0.9 Calcium arsenate! 0.9 Cryolite (sodium fluoaluminate 45%), 25% sulfur dust 20.0 10% Toxaphene, 25% sulfur dust 10% Toxaphene, 5% DDT, 25% sulfur dust 2.6 1.4 water * Applied as a concentrated spray at the rate of 3 pounds to 10 gallons of water. t Applied as a concentrated spray at the rate of 22 pounds of commercial calcium arsenate to 10 gallons of t Material applied July 28 contained 25 per cent dusting sulfur. [32] was obtained, but the results were unsatis- factory where it was applied as a dust. Where the dust was used, 28 per cent of the plants were injured as compared to 2.3 per cent for the concentrated spray and 65 per cent for the check. In the experiment at Patterson, DDT, DDD, calcium arsenate, Cryolite, and Toxaphene were used. All of these pro- duced satisfactory control, except for the Cryolite and the DDT dusts. In this ex- periment 23 per cent of the plants in the check plots were injured, 20 per cent in the Cryolite treatment, 15 per cent in the DDT dust treatment, and 0.0 per cent in the DDD dust treatment. Where DDT was applied as a concentrated spray, only 1.9 per cent of the plants were injured. Other observations were made that clearly indi- cated that a 5 per cent DDT dust was somewhat ineffective against hornworms, but where DDT was applied as a concen- trated spray, satisfactory control resulted. In the course of these investigations it has been observed that the tobacco horn- worm is more susceptible to DDT than is the tomato hornworm. However, if the coverage is sufficient, the tomato horn- worm is killed. White (1945) reported that in field experiments at Florence, S.C., and Oxford, N.C., the application of a 5 or 10 per cent DDT dust did not give a satisfactory reduction of Protoparce sexta. In laboratory tests the fifth instar of P. sexta was not affected by a 10 per cent dust but the same instar of P. quin- quemaculata succumbed readily. White (1946) reported that P. sexta in Tennes- see, South Carolina, and North Carolina was not satisfactorily controlled with up to 30 pounds per acre of a 10 per cent dust, but in southern California it was successfully controlled by a 10 per cent DDT, 25 per cent sulfur dust in pyrophyl- lite. Wilcox and Howland (1946), in southern California reported undiluted calcium arsenate to be superior to 10 per cent DDT dust in the control of horn- worms. Apparently the reason for the effective- ness of the concentrated DDT spray over the dust is due to the relatively higher de- posit of material built up on the periphery of the vines by the spray, the region where hornworms feed the most. Miscellaneous experiments A series of experiments were conducted to determine whether the addition of 1 or 2 per cent of a highly refined mineral oil would increase the insecticidal effec- tiveness of DDT dusts. The results of this investigation indicated that the addition of the oil had little or no beneficial effect. In conjunction with the above experi- ment, a concentrated DDT emulsion spray was tested. The control obtained was su- perior to that obtained with a dust, but the experiment was too limited to be con- clusive. Tomato mite control The control of the tomato mite is not difficult where dust formulations are used. If necessary, sulfur can be added to the mixtures. However, with the concentrated sprays, mite control presents a problem. It is possible to add a wettable sulfur to the concentrated spray mixture as was done in the Woodland experiment (table 4) where the applications were made with a Naconizer. Although satisfactory results were obtained, it was difficult to prepare the concentrated spray material in a suit- able manner to insure proper application. It would appear that where concentrated sprays are used, the mite control program might be undertaken as a separate opera- tion. It is possible that a thorough appli- cation of a sulfur dust early in July would in many cases adequately control the pest for the entire season. Observations have shown that DDT has no controlling action upon the tomato mite. In fact some evi- dence was obtained that applications of a concentrated DDT spray may encourage an increase in the mite population. In the Woodland experiment, light and spotty infestations of the tomato mite de- veloped in late August and September in [33] some of the plots that received concen- trated spray applications of DDT and DDD. However, in none of these did the mite become destructive, and no evidence of their reducing the yield could be de- tected. Cultural Methods Can Aid Control of Caterpillars The destruction of crop refuse is a sani- tary measure that should be practiced. It is particularly important that this be done in regions where the tomato pinworm or usually been encountered in those fields where volunteer potato plants have been growing. Infestations by the corn earworm on tomatoes are likely to be most severe in areas where more preferred hosts such as sweet corn and beans are grown in fair abundance. While these preferred crops are in an attractive state of growth for the adult moths to oviposit upon, there may be but a light infestation of corn ear- worms in tomatoes. However, the moths that emerge from these fields after the jlll!!!!! rm*\i f 1 * J C B Fig. 18. Hyposoter exiguae (Vier.), an important hymenopterous larval parasite of the corn earworm: A, adult enlarged three times; B, adult corn earworm attached (natural size). the potato tuber moth is likely to be a problem. Where the pinworm is a pest, growing of an early and late season crop should be avoided if this is at all possible. There is danger of the pest developing a pupulation on the early crop that will serve as a focus of infestation for the later one. If two crops are grown, the first should be destroyed by burning or plow- ing under just as soon as harvest is com- pleted. Elmore and Howland (1943) re- ported on the importance of cultural methods in the control of this pest. The practice of following potatoes with tomatoes should be avoided. As previ- ously indicated, serious infestations of the potato tuber moth in tomatoes is usually associated with potato culture. Most extensive damage by this pest has crops are mature may migrate to toma- toes and give rise to destructive popula- tions. Infestations in tomatoes from such sources do not usually arise until late August or September. Although there is not much a grower can do to avoid these migrations, he can encourage the destruc- tion of crop refuse as soon as the pre- ferred hosts are harvested. This is of particular importance in the case of sweet corn. Early maturity Because the corn earworm infestation becomes more acute as the season ad- vances, a grower should adopt those cul- tural practices that will enable him to bring his crop to maturity at the earliest possible date. [34] Natural Enemies of Pests Are of Help in Control Caterpillars infesting tomato are sub- ject to the attack of a number of parasites. The full value of these parasites in reduc- ing the damage done by the several species of caterpillars is difficult to determine. There is little question but that they are extremely important and may be respon- sible in a large measure for some species of caterpillars not reaching a destructive level every year. In this regard Elmore striped armyworm, and may be one of the important natural factors that deter- mine the abundance of this annoying pest. The action of the many parasites upon their host, and the influence they exert in regulating populations is a subject that is in need of thorough investigation. It is important that insecticidal control pro- grams be developed that will have the least adverse effect upon these important natural enemies. Control programs that will supplement the work of the natural parasites and predators are the goal. Fig. 19. Injury to tomato leaflets caused by spraying with DDT, 1 pound per 100 gallons: A, normal leaflet; B, C, sprayed leaflets snowing interveinal and marginal yellowing; D, sprayed leaflet in final stages of injury, showing tan-colored, papery drying-out of the marginal tissues. andHowland (1943) reported "Parasites have undoubtedly been an important fac- tor [in southern California] in the grad- ual decrease in pinworm abundance since 1936, the period of maximum abundance, until 1941, when a low point in degree of pinworm injury was reached." The most important parasite attacking the corn earworm is Hyposoter exiguae (Vier.) (fig. 18). It attacks the small larvae, and frequently a large proportion of the population is parasitized. When abundant, the adults of this parasite may be seen flying about the tomato vines. Ob- servations have indicated that this para- site plays an important role in limiting the damage done by the corn earworm. This parasite also attacks the yellow- Possibility of Injury to Tomato Plants from DDT Under certain conditions DDT has been known to cause injury to tomato plants. Gardner, et al. (1945), reported serious injury to greenhouse tomatoes that were treated with DDT. The nature of the in- jury to the leaflets is illustrated in figure 19. The following year Gardner and Michelbacher (1946) again reported in- jury to tomatoes grown under glass when treated with DDT. Tanada, et al. (1947) , reported DDT injurious to tomato in Hawaii, and plant injury has been re- ported from New Jersey by the United States Department of Agriculture (1945) . Baker and Porter (1945) stated that 25 [35] pounds of actual DDT per acre applied to the soil resulted in injury to tomatoes planted on the treated land. Lange and Carlson (unpublished) conducted inves- tigations at Davis which showed that to- matoes were injured when planted on land treated with either 20 or 40 pounds of DDT to the acre. The authors have observed no injury to tomato under field conditions where DDT has been applied at the rates used in these investigations. Wilcox and How- land (1946) reported no injury from three applications of 10 per cent DDT at 30 pounds per acre in southern Califor- nia. It appears that there is not a great deal of danger of serious plant injury from the direct application of DDT. How- ever, very little information is available as to the rate of decomposition of DDT in the soil, and if this process should be extremely slow there may be some dan- ger of the insecticide accumulating in the soil to a dangerous level. In this connec- tion Fleming and Maines (1947), who used 25 pounds of actual DDT per acre, showed that the effectiveness of DDT against the third instar larvae of the Japa- nese beetle did not change significantly in various types of soils during 128 weeks. STUDIES OF INSECTICIDAL RESIDUES 2 Tests made to determine effectiveness of usual washing meth- ods in removing residues from tomatoes used for canning. Since the Federal Food and Drug Ad- ministration has announced no tolerance for the presence of DDT and related com- pounds in canned foods, it is imperative that residual amounts of these compounds be effectively removed before the raw product is canned. The purpose of this phase of the investigation was to deter- mine the effectiveness of removal of DDT and DDD from tomatoes by washing methods similar to those used in commer- cial canneries. Further, since there is a likelihood of calcium arsenate being widely used as a concentrated spray for the control of caterpillars attacking tomato, it was deemed desirable to investigate the effec- tiveness of removal of calcium arsenate residue from tomatoes where fields had been treated by this method. For previous studies on the residue of calcium arsenate dusts, see Michelbacher and Essig (1935) and Michelbacher, et al (1940) . Tomato samples for analysis were ob- tained from treatments in the experi- mental fields. The fruit samples were picked the same day that the final appli- 2 This section was prepared by F. C. Lamb of the National Canners' Association Laboratories. cation of insecticides was made and there- fore would probably have the maximum deposit of residue. Samples were taken from fields that had been treated with DDT and DDD dusts or concentrated sprays, and from fields where calcium arsenate had been applied as a concen- trated spray. Residue determinations were made where the above insecticides had been applied with hand dusters, hand sprayers, ground power dusters, with a Naconizer, airplane dusters, and airplane sprayers. This was done in order to study residue removal under all the different methods of application. The treatments, method and dates of application, pounds of insecticides used, and the date samples were picked for the residue analysis are given in table 9 for DDT and DDD pro- grams, and in table 10 for the calcium arsenate programs. Experimental Procedure One box containing approximately 45 pounds of tomatoes, representing each of the insecticide field treatments, was used in this study. Duplicate samples of the unwashed tomatoes representing from 15 [36 to 20 tomatoes (about 2 kilograms) for each separate determination were set aside for the analysis of DDT, DDD, or arsenic. The remaining tomatoes were then given the following washing treat- ment: 1. Immersed in a tank of clean water and agitated gently for 1 minute. 2. Spread out in a single layer on a screen and sprayed for 30 seconds, using the full pressure of the city water supply. The tomatoes were then turned over and sprayed for an additional 30 seconds. Duplicate samples of the washed toma- toes were then prepared for analysis, as before. The remaining tomatoes were put through a "Victorio" home juicer and samples of the juice and of the residue preserved with formaldehyde. The re- remainder of the juice was canned in pic- nic cans by the following procedure : The juice was heated to 210° F. in enamel buckets and held at this tempera- ture for several minutes. It was then filled into picnic cans and the cans quickly sealed. They were then allowed to stand for about 3 minutes, following which they were cooled to room temperature in a tank of water. Methods of Analysis The raw samples treated with DDT or DDD were extracted with chemically pure benzene (thiophene free) according to the method described by Wichmann, et at. (1946) . An aliquot of the benzene extract was set aside in the refrigerator for determination of DDT and DDD by the Schechter-Haller method and the re- mainder was used for determination by the total chlorine method. Both methods were performed as outlined by Wich- mann, et al., with minor modifications. Tn the Schechter-Haller method both DDT and DDD were calculated from the same calibration curve plotted from chemically pure DDT (Eimer and Amend) using the Evelyn colorimeter equipped with a 580 mu filter. Schechter and Haller (1944) have reported specific extinction coefficients (g./cm.) for p p' DDT at 600 mu and for p p' DDD at 593 mu of 48.0 and 38.7 respectively. Toxicity studies have shown that the p p' isomer of DDT is considerably more toxic than the o p' isomer. These data indicate that DDD produces approximately 80 per cent as much color as DDT. This correction factor was not applied to the present re- sults since it was not known how closely the extinction coefficients of Schechter and Haller would apply to the experi- mental conditions obtained in these stud- ies. No pure DDD was available for plotting an absorption curve. No effort was made to determine the o p' and p p' isomers of DDT individually since it was felt that the calibration curve plotted with chemically pure DDT was reasonably close to the curve that would be obtained with technical DDT, and that the additional refinement of the method was not justified. Readings taken with the 515 mu and 440 mu filters showed the above assumption to be valid. The samples of juice and of the residue from juice extraction were analyzed for DDT and DDD by the Schechter-Haller method only. The samples were extracted with benzene according to the directions ofTressler (1947). Arsenic was determined by the Cassil and Wichmann method (1939). On all the raw samples except for those from the Davis plot the whole tomatoes were ground in a Waring Blendor until homo- geneous, and arsenic was determined on the ground mixture. On the raw samples from the Davis plot the tomatoes were peeled and cored by hand and the peel- ings and cores ground in the Waring Blendor and analyzed for arsenic. The results were calculated on the basis of the original tomatoes. Residues of DDT, DDD In table 9 are shown the results ob- tained on the DDT and DDD treated sam- ples. The samples were analyzed both by [37 fl 1 CO CM 5 CO CD i ••* ! ^" P§ CD • o • io • • , " d : d S3 E-.0 CJ 1 Qh ++ Q 8. n i eo o o o o O o o o o o o A «•« ttO o CM rH CM t-J r- ^J t> ; CO IO CM CO ° M o o" © d d O <6 41 a a a a a a a fa r. P S3 P P CU CD CD +> eo co M >-• P p © © -rt -rt © N © N 3 > 5 1 5 -g 5 •§ * 1 to T) to TJ w T3 co T3 rHCMrHCMrHCMrHCM jh c9 m c9 O O '3 S3 '3 fc bo bo g g|i • q • cm q q O a '. co" ! CO* CM* CO i-3 O ?>>>>>> tub >> ti >» >v >. Eh Q p p "p 1 "p sssldl P _ 1-, ■_, I-, H S-r •H (H M »H V CD (D © © © © — •d •« ■o-o-o-o ec3 £ eel * £ - et} s ► ^ ► Eh 3 CD o O CO ea P o o p. p. _ g © © «§ M e8 e8 co to CD O •a" 1 o O o o o ft Pi A 0, Jh |h ,2 iJ ^ 5 •« a 3 3 3 3 p p cd et3 cd cd co co f +J -U +J -M ^ o, +» 4» +> +> kO bP © © © © 6^ o N © 1 " 5 g § S § k- a ° « § § ^\ ^ vO ^O O O o^ ©^ io m m io O "el +3 o £ £ £ £ o © r r w w Eh Eh P P - - a | (=1 1 QQflQ^O s H © •c © CO pq a CD CD & CO M ppppgg © o © © s - S^ IO IO IO IO IO to fa C fa CJ « 9 a 5 fc- OJ • *° Q e CM (N ; «m* Q% M p§ 4) O O • • CO * "3 e o o • • o h'S s 6 © : d Q* ' Qg, ■^ o o o o o o o o io io ih cs »- CO IP O CO d dodo d d d 33 •O P. 4) 1 g-Sip to o o o o o ° 2 o O t- q i -^ co T- CO o tf pq* O i-i th d d d d i-i J CN (N CM CM CN o o q »x3 T-l rH iH p S-S -«j ■+» -♦* ■+* -»J -** -»* p. a a a a a. a ft co CD CO 0) cc CO CO CO I GO tn xn m m 02 02 03 U* tH M co a> «- (- >H CO iod of nation & & 2 * 2 2 « « P. P. » - d p. rg-s « ifl "d T3 T3 W »2 a "O "d 13 X T3 T3 « R" PJ e n cQ ce ec § § \ A A A A .c! ^3 \ M M £ 8 "3*3 g &§* o '8 "3. o. e co Q oOO ^ co • IP Sis IO WOO O CO a II* co* co" d t> OJ tH "1 ala CO CO CN o g tN CO CM CM o o eS iH »H •o d 4* -M 4^ •* -M 4« tN s Pi Pi Pi C i Pi Pi *7 CO CO CO 91 CO CO xn xn xn xn 03 03 : to v c©0 O sis io o io o CO CO ^ cc O CO oo* rA '43 Soft CO CN CM o -JjO-g, A S 1 00 CO CO oc CO CO 01 V CM CN CN CN 1 Q •-9 «-8 1-9 H- > bib bio P" P M (H CO CO . . -a TJ fc d ► * T3 1 ii A 1 =3 8 i a o CO 13 CD o Ph o o • . ft ft £ fc ctl es w v 'c P C s r- 3 C Treatment Pi ® P Ph S P. 1 Ph § CM » Q Q £N i>^ kO ^c O O s O" . JH P, ^ s - IP S W i » IO w m s w i IP CM 03 rj 1 oo C Q Q Ph' O *g a<« •3° O o |I §s §2 II aw CO +» CQ g E_. ® ■dg >Q >.- ml 111 I "£Q"S"S PflQ< the total chlorine method and by the Schechter-Haller method, except for the 5 per cent DDD dust treatment in the commercial blocks at Woodland, in which case only the total chlorine method was used. Only the results obtained by the Schechter-Haller method are shown with the above exception for the reason that these results are thought to be more re- liable. Although agreement between the two methods was satisfactory in many of the samples, occasional samples gave definitely higher results by the total chlor- ine method. Since these high results could not be explained by any logical means, it was concluded that they probably were caused by the chance presence in the sam- ple of other chlorine-containing com- pounds. Carter (1947) suggests that the Schechter-Haller method, by reason of its greater specificity, should be used in all cases where it is suspected that the total chlorine determinations may not be valid. The maximum amount of DDT and DDD residue found by the Schechter- Haller method before washing was 1.7 ppm and the minimum was 0.2 ppm in the samples treated with these materials. Except in one instance the amount of DDT and DDD present after washing was not in excess of 0.5 ppm and in this in- stance the residue amounted to only 0.7 ppm. DDT and DDD were determined in the samples of juice and residue preserved with formaldehyde which contained 0.5 ppm or more residue on the washed tomatoes. These results were so low, par- ticularly on the juice, that it was not con- sidered necessary to test the remainder of the samples nor of the samples of processed juice. The amount of DDT or DDD in the juice prepared from the washed tomatoes was negligible in every instance, but there was a considerable concentration of the DDT or DDD in the residue from juicing operations. This concentration is un- doubtedly the result of the extreme in- solubility of DDT and to its affinity for certain portions of the residue material. This concentration of DDT and DDD in the residue, or pumice, indicates that a potential hazard may exist if this material is dried for use as a cattle feed. Tomato pulp made by re-extraction of the residue from partial extraction of tomato juice may also contain higher amounts of DDT and DDD residues than would be present in juice extracted from whole tomatoes. Similarly, it may be reasoned that puree made from cores and peelings might con- tain increased amounts of DDT and DDD residues. Conclusions Examination of the data in respect to the treatment variables employed in these studies leads to the following conclusions : 1. The concentrations of DDT and DDD on the unwashed tomatoes varied from 0.2 to 1.7 parts per million (ppm) and on the same fruit after washing, from 0.1 to 0.7 ppm, when determinations were made by the Schechter-Haller method. Juice prepared from these washed toma- tose contained 0.1 ppm or less of DDT or DDD. The juice residue contained from 2.7 to 4.3 ppm DDT or DDD. 2. DDT and DDD residues were higher when the material was applied as a spray than when it was applied as a dust, and higher when the insecticide was applied by ground dusting or spraying than when applied by airplane. 3. The amount of residue obtained as a result of airplane dusting was less than that obtained by ground dusting. 4. DDT residues appeared to be slightly higher than DDD residues in most in- stances. These differences might have been due in part to the method of calcula- tion of the results by the Schechter-Haller method; however, results obtained by the total chlorine method, in which calcula- tion was based on the total number of chlorine atoms of DDT and DDD, gave the same indication in all samples which were not completely out of line with the Schechter-Haller results. [40 § i-t t- CN 2 CO CM © to © d d d * c ti Sw <-= < O Pi V o iH CO Oh o *H ^H CO CO S3 '3 •-9 d d d Q .§1 bo ++ 00 CO to < OS O t-I Tj< CO » S E M "5 'S o o a aS — < e8 S ft CO y-i CM •a J o .: w © (j SlS © o io X o T* id d Eh "5 CM CM CO l-H E § Q w e8 •3 00 ^ CM a 0) CM Eh o » bio >> o "3 »-9 ^ "3 CO W i 5D CO TJ Q •— 1 CO > Q O 1 w +»* tf j>> o o o £ M 75 3 3 •S3 55 o o Is •a CD CO 73 CD PS < S V V CD d © o o 43 iH o o 3 a J2 In