Division of Agricultural Sciences II uv €> UNIVERSITY OF CALIFORNIA Controlling MELON INSECTS and Spider Mites A. E. Michelbacher W. W. Middlekauff O. G. Bacon J. E. Swift CALIFORNIA AGRICULTURAL EXPERIMENT STATION BULLETIN 749 THIS BUUBTIH. . . . . . tells how to recognize and control the principal insects and other pests that attack California melons. . . . recommends insecticides, amounts, and methods of application. . . . describes recent experiments show- ing the relative effectiveness of melon pest controls. The Authors: A. E. Michelbacher and W. W. Middlekauff are Associate Professors of Entomology and Para- sitology and Associate Entomologists in the Experiment Station (Berkeley); O. G. Bacon is Assistant Professor of Entomology and Assistant Entomologist, Experiment Station (Davis); J. E. Swift is Associate Agriculturist, Extension Service. Submitted for publication April, 1954. APRIL, 1955 Briefly Speaking . . . Successful control of melon pests depends on: Recognition of the pests involved Selection of a suitable insecticide Thorough application of the insecticide Good timing in each application To produce good melons year in and year out, growers in most parts of Cali- fornia must protect the crop from serious attacks by insects and related pests. Melons can be injured at any time dur- ing growth. Many insects are involved, and often they inflict severe damage in a short time if not controlled. All parts of the melon plant are subject to attack, and some pests are harder to cope with than others. Up to now no publication has dealt completely with the several melon pests and their control. Such information is widely scattered and not easily available to melon producers. This bulletin at- tempts to consolidate the information and present an integrated control pro- gram that will ensure satisfactory pro- tection of melon crops. Good results can be obtained, of course, only if the pests to be controlled are correctly identified and effective in- secticides are applied with equipment that gives thorough coverage. First you must determine whether a definite need exists for a pest control program. It can't be justified simply as insurance, if only because of the expense and the danger of increasing other pests. When pests appear in a melon field, give their natural enemies a chance to control them. Then, if you see that they cannot cope with the pests, apply treatments be- fore the pest population reaches an eco- nomic level. Remember, however, that insecticides are often harmful to bene- ficial insects. This bulletin tells how to achieve maximum control with the few- est treatments, thus reducing the chances of harming beneficial insects. Seldom will all the pests mentioned in this bulletin present a problem in a single field. Usually, however, more than one pest will be present, and wherever pos- sible a treatment should be used that will control several of them. Parathion, thoroughly applied, has almost always given excellent control of all the important melon pests. Continued use of parathion may of course result in selecting out strains of certain pests that will become resistant to it. Therefore other materials should be used alter- nately, at least in part of the control program. When insecticides are properly ap- plied, economic control of the several pests, even under conditions of heavy infestation, should be obtained for the entire growth of the crop with from two to four applications. Dieldrin, aldrin, and heptachlor are effective against most melon pests but not against the melon leaf hopper and spider mites. In fact, spider mites usually FOR A QUICK SUMMARY of this bulletin, read pages 3 to 6 inclusive. THE REST of the bulletin covers the same material in greater detail, with illustrations, scientific nomenclature, and tabulated results of tests. [3] CAUTION Always bear in mind that DDT, dieldrin, aldrin, heptachlor, and the other chlori- nated hydrocarbons are apt to stimulate an increase in spider mites. Where a serious spider mite infestation is indi- cated, an acaricide such as aramite or ovotran should be included in one treat- ment when these insecticides are applied repeatedly. multiply drastically when these insecti- cides are used. Therefore it is advisable that an acaricide be included in one of the early applications if one of these in- secticides is used. DDT is also effective against many melon pests, but because it too is likely to cause, indirectly, an increase in spider mites and melon aphids, it should be used at a rate of not more than one pound of actual material per acre. If several appli- cations are needed, an acaricide — such as aramite or ovotran — should be in- cluded in one application before the spider mite population has reached a destructive level. Another possibility is to substitute one or more parathion treat- ments before a serious mite population occurs. On honeydew melons, the spider mite problem can be reduced by using DDT combined with 50 per cent sulfur. COMMON AND CHEMICAL NAMES OF PESTICIDES USED DDT PERTHANE PARATHION MALATHION HEPTACHLOR DIELDRIN ALDRIN BHC OVOTRAN ARAMITE l,l,l-trichloro-2,2-bis(/?-chlorophenyl)ethane (= Q-137), l,l-dichloro-2,2-bis(p-ethylphenyl)ethane 0,0-diethyl 0-/?-nitrophenyl thiophosphate 0,0-dimethyl-S-(l / 2-dicarboxyethyl)dithiophosphate 1 (or 3a), 4,5,6,7,8,8-heptachloro-3a, 4,7,7a-tetrahydro-4, 7-methano indane 85% of l,2,3,4,10,10-hexachloro-6,7,-epoxy-l,4,4a,5,6,7,8,8a- octahydro-l,4,5,8-dimethano-naphthalene, and not more than 15% of insecticidally-active related compounds 95% of 1, 2,3,4, 10,10-hexachloro-l,4,4a,5,8,8a-hexahydro- 1,4, 5,8-dimethano naphthalene and 5% of insecticidally-active related hydrocarbons 1,2,3,4,5,6-hexachlorocyclohexane, consisting of several isomers and containing 12-14 per cent of the gamma isomer p-chlorophenyl p-chlorobenzenesulfonate product containing 2-(p-tert-butylphenoxy) isopropyl- 1 -methylethyl 2-chloroethyl-sulfite [4] The Principal "Enemies" of Melons In California, the principal pests at- tacking melons are two species of cucum- ber beetles, the melon leaf hopper, the melon aphid, an agromyzid leaf miner, and several species of spider mites. CUCUMBER BEETLES Cucumber beetles are among the most important of the melon pests. The two principal species — western spotted and western striped cu- cumber beetles — prefer smooth-skinned melons such as honeydews, Crenshaws, and casabas to netted varieties such as cantaloupes and Persian melons. Cucumber beetles ravage melons from the time they are planted until the crop is harvested. They injure melons in any or all of four ways: (1) adults feed on foliage or (2) scar fruit stems and crowns; (3) larvae feed on roots or (4) scar melons by feeding on the part of the fruit in contact with the soil. Destruc- tive populations may breed in a melon field or migrate from near-by crops being harvested or from harvested fields that are drying up or being disked under. In early stages of growth and melon formation — especially with preferred melon varieties — control measures must be applied as soon as cucumber beetles are detected. Several insecticides give such control: cryolite, DDT, dieldrin, aldrin, heptachlor, parathion, and mala- thion, among others. Since DDT, dieldrin, and related in- secticides tend to increase the spider-mite problem, they should be used in the low- est concentrations that will give adequate control; and when several treatments are necessary, one application should contain an acaricide. MELON LEAF HOPPER The melon leaf hopper is particu- larly destructive in California's Central Valley. Individuals suck cell contents from leaves, causing a characteristic stippling of the upper leaf surface. They pump out an enormous amount of plant sap and excrete large quantities of liquid, which drops on lower plant foliage and fruit. These tiny spots give the contaminated area a speckled appearance. Destructive popula- tions kill the plants; heavy infestations reduce quality and yield of melons. DDT is the most effective insecticide of those tested against the melon leaf hop- per. Applications should be limited to one pound of active material per acre. Malathion and parathion have also given adequate control of melon leaf hoppers. MELON APHID The melon aphid is another wide- spread and destruc- tive melon pest. It sucks cell sap, there- by reducing plant vigor, stunting vines and deforming leaves; size, flavor, and shipping quality of melons are greatly reduced. The aphid has many natural enemies which, unless adversely affected by insecticides, frequently keep it under control until late summer or fall. Effective control of melon aphids can be obtained with a 2 per cent parathion dust at 30 pounds per acre, or its equiva- lent as a spray, if treatments are thor- ough and even. Malathion, dieldrin, al- drin, and heptachlor have shown promise in suppressing aphids before heavy popu- lations are present. DDT in heavy dosage tends to favor increases in melon aphids. This adverse [5] effect can be minimized but not elim- inated by using DDT at a rate not to exceed one pound of active material per acre. AGROMYZID LEAF MINERS Sometimes melons are seriously at- tacked by an agromyzid leaf miner. This pest has increased its activity in recent years, and many believe that this has been associated with the increased use of DDT and closely-related compounds. De- structive populations seldom occur on melons before summer or fall. They may cause serious defoliation. Natural enemies are important in keep- ing leaf miner populations below an eco- nomic level. In California, parasites limit serious damage to a relatively few fields. If parasites seem able to control the miners, control measures should not be applied. In any case, chemical control can safely be delayed until the average number of mines per leaf for the center leaves reaches at least 10 to 15. By then the center leaves will show noticeable injury. Effective insecticides include dieldrin, aldrin, heptachlor, and parathion. Quan- tities of active ingredient per acre fol- low: dieldrin, 0.5 pound; aldrin, one pound; heptachlor, one pound; para- thion, 0.6 pound. SPIDER MITES Several species of spider mites attack melons. The two- spotted spider mite and the Pacific spider mite are the principal northern California species. In southern Califor- nia the dominant species is the Atlantic spider mite. It is not unusual for several species to be present at the same time. Spider mites are found on melon plants from early spring until frost. They do most damage in summer when tem- perature conditions favor rapid develop- ment and multiplication. Major infesta- tions impair the size, flavor, and sugar content of melons. A variety of factors — physiological, physical, biological — favor the develop- ment of destructive populations: for ex- ample, dryness, dust drifting from road- ways, adjacent fields of infested weeds or crops, and stimulation resulting from applying certain insecticides. On the other hand, spider mites have important natural enemies. In melon fields the most effective of these are anthocordis, six-spotted predacious thrips, and predacious laelaptid mites. Parathion, thoroughly applied, gives excellent control of spider mites. It is frequently necessary to repeat the appli- cation to ensure satisfactory results. Parathion should not be applied later than two weeks before harvest. Control can also be achieved with ovo- tran or aramite. MISCELLANEOUS PESTS Among miscellaneous pests that attack melons are seed-corn maggots, wire- worms, darkling ground beetles, crickets, grasshoppers, thrips, and squash bugs. The root-knot nematode is also quite de- structive to melons planted in an infested field. POLLINATION Melons depend on bees for successful pollination. Everything possible should be done to protect these and other bene- ficial insects. Because most insecticides used on melons are poisonous to bees, they should be used only when treatment is clearly necessary. They should be ap- plied only in late afternoon, at night, or early in the morning, when blossoms are closed. [6] Where und How Studies Were Conducted Most of the experimental studies were conducted at Patterson, Stanislaus Coun- ty and at Vernalis, San Joaquin County. Some investigations of a rather extensive nature were carried out at Woodland, Yolo County and at Brentwood, Contra Costa County. Observations and field tests were also made at other localities throughout the state. All experimental treatments were ap- plied with power equipment, which in- cluded ground dusters and sprayers and airplanes equipped for dusting or spray- ing. Plots varied in size from about 0.5 to 20 acres. Where feasible checks were left and if possible treatments were repli- cated from 2 to 4 times. Experimental series were often duplicated in several fields, on different varieties of melons, at various times of the season and in suc- ceeding years. Where leaf samples were used in popu- lation determinations, mature leaves were picked at random from the center of the rows. For counts of the melon leaf hopper, Empoasca abrupta DeLong, 50 to 100 leaves were taken from each plot or treatment and a record made of all nymphs and adults found. The count for each leaf was recorded separately. Comparative abundance of the melon aphid, Aphis gossypii Glover, and spider mites was determined by placing leaves in the following categories: not infested, lightly infested, moderately infested and severely infested-; or by actually count- ing the number of individuals occurring on marked areas of the leaf. In making counts three impressions were made at random on each sample leaf with a thin- walled, beveled-edge brass tube. The in- side diameter of the tube used for melon aphid counts was 31 mm. while that used for spider mite counts was 15 mm. All stages of aphids were counted, while for spider mites all but the egg stage was recorded. On any survey 10 to 25 leaves were taken from each plot or treatment. The agromyzid leaf miner popu- lation was determined by either counting the number of mines on a leaf or by actu- ally counting the number of maggots present in marked sections of the leaves. In either case mature leaves were picked at random from the zone of greatest mag- got activity. Where mine counts were made, 50 to 100 leaves were examined per plot or treatment. Where maggot counts were made, 10 to 25 leaves were taken. Three impressions were made on each leaf with a piece of brass tubing having an inside diameter of 31 mm. All individuals in the marked areas were dis- sected out. The maggots were placed in one of the following categories: alive, dead, or parasitized. Early stages of parasitism sometimes made it very diffi- cult to place the maggots in the proper category. Some error from this source was inevitable, but succeeding surveys tended to clarify the categories. [7] The Results of the Studies CUCUMBER BEETLES Cucumber beetles rank among the most important insects attacking melons in California (Michelbacher et al., 1953b). The two most important species are the western spotted cucumber beetle, Diabrotica undecimpunctata Mann., and the western striped cucumber beetle, Acalymma trivittata (Mann.) . Two other species, the banded cucumber beetle, Diabrotica balteata Lee. and the spotted cucumber beetle, D. undecimpunctata howardi Barber., occur in southern Cali- fornia. Four Stages In Life Cycle All species pass through four stages of development — adult, egg, larva, and pupa. Stages in the life history of the western spotted cucumber beetle are shown in figure 1. The adults of the western spotted and the western striped cucumber beetles are shown in figures 2a and 2b. The immature stages of the two species are rather similar. The larva of the western spotted cucumber beetle is larger and somewhat more robust than that of the western striped cucumber beetle. It is easy to distinguish between the mature larvae of the two species: in the western spotted cucumber beetle two pro- jections that arise from the posterior margin of the dark-pigmented, sclero- tized anal plate are short and robust ( fig- ure 3a) ; in the western striped cucumber beetle they are slightly recurved and slender (figure 3b). Cucumber beetle larvae can be distinguished from other insect larvae that are likely to be found near the roots of melon plants by the flattened, dark anal plate and by the dark head and prothoracic shield. Cucumber beetles lay their eggs about \& Fig. 1 (A-F) Western sported cucumber beetle: (A) egg; (B) 1st instar larva; (C) 2nd instar larva; (D) 3rd instar larva; (E) pupa; (F) tip of abdomen of 3rd instar larva, dorsal view; (G) western striped cucumber beetle showing tip of abdomen of 3rd instar larva, dorsal view. Fig. 2. (A) Western spotted cucumber beetle and (B) Western striped cucumber beetle rest- ing on honeydew melon. [8] Fig. 3. Projections arising from posterior margin of anal plate: (A) Diabrotica undecim- punctata Mann.; (B) Acalymma trivittata (Mann.) (x 16.5). the base of the plants. Upon hatching, the larvae begin to feed on the roots, and in completing their development pass through three larval instars. When ma- ture the larvae construct earthen cells in which they pupate. After a varying period, depending considerably upon temperature, the adult emerges. The wing covers as well as the body of newly- emerged adults are soft, the color is pale and the markings are barely distinguish- able. After a few days the wing covers and body harden, the markings become distinct, and the color brightens. Indi- viduals that have not fully hardened and colored are frequently encountered in melon fields. All species pass through several gener- ations per year. Michelbacher et al. (1943) and Smith and Michelbacher (1949) found that in the lower San Joa- quin Valley the western spotted cucum- ber beetle has three generations a year. These investigators conducted extensive studies in the life history and ecology of this species. This beetle normally spends the winter as an adult in secluded spots of the valley floor and in the foothills. The striped cucumber beetle also passes the winter as an adult. Dr. J. H. Freitag of this Department observed the beetles hibernating in the bark crevices of oak trees (unpublished). The number of generations this insect has per year has not been determined, but it is probably close to three. Both species are active by the time the earliest melons are planted in spring, and are present in melon fields in increasing numbers until the end of the season. The western spotted cucumber beetle attacks a wide variety of plants. Accord- ing to Michelbacher et al. (1943) the lar- vae feed upon grains, cucurbits and leg- umes, while the adults not only feed upon these but also upon many other truck and field crops as well as certain fruits and most flowering garden plants. They also feed upon many uncultivated plants. The leaves and stems of host plants are at- tacked and they are fond of flowers, espe- cially those belonging to the Compositae. The western striped cucumber beetle has a much more restricted host range. In limited laboratory studies the larvae could be reared only on the roots of cu- curbits. Hosts of the species may be limited to this group. In the field they are seldom found in abundance on plants be- longing to other botanical groups. Destructiveness Of Cucumber Beetles Cucumber beetles occur wherever melons grow and may attack plants seri- ously from the time they first appear above ground until harvest. The beetles prefer some varieties of melons to others : the honeydew in particular, closely fol- lowed by the Crenshaw and casaba vari- [9] Fig. 4. Honeydew melon leaf seriously in- jured by adult cucumber beetle feeding. eties. Melons that ate covered with a net- ting, such as the Tersian variety and particularly cantaloupes, are the least subject to injury. If any of the attractive varieties were left unprotected from the cucumber beetles, probably not a single field would escape damage. Some would be com- pletely destroyed. Although the western spotted cucumber beetle inflicts serious injury, the most destructive species is probably the western striped cucumber beetle. Cucumber beetles may injure melons in any or all of the four following ways: adults (1) may feed upon the foliage, or (2) they may scar the fruit, stems and crown; while the larvae (3) feed upon the roots or (4) upon that portion of the melon in contact with the soil. Defoliation by Adults. Adults feed readily upon foliage and a seriously in- jured leaf is shown in figure 4. Under conditions of severe infestations large plants may be defoliated. Most damage by adult feeding occurs, however, on small plants, and if a field is not care- fully watched it is possible that a seed- ling stand may be killed before it has had an opportunity to become established. Destructive populations may occur early in the season. For example, on April 16, 1953, near Patterson, Stanis- laus County, cucumber beetles (mostly western striped) were sufficiently numer- ous in one field to kill young honeydew plants. It was not uncommon to find as many as six beetles in a single hill. Large adult populations should not be tolerated. Under any condition they should be eliminated before they have had an op- portunity to oviposit, for once eggs have been laid about the base of the plants it becomes difficult if not impossible to con- trol subsequent larval stages in the soil. Scarring of Fruit by Adults. Adults are responsible for serious injury to melon fruit. Under conditions of high adult population, they may damage nearly all the fruit. The adults prefer to feed on young, developing melons. After the skin hardens, melons are much less subject to attack. For this reason larger populations can be tolerated than when there are many small melons. With pre- ferred varieties it is a good practice to observe fields closely and treat them as soon as the first sign of adult feeding appears. The adults tend to avoid heat, and as a result feed mainly on the under side of young melons. For this reason young melons should be turned over in survey- ing for injury. On young honeydew melons that are still pubescent the injury appears as an etching of the surface as shown in figure 5. On slightly older melons the feeding is deeper and more pronounced (figure 6) . As the melon matures a considerable amount of scar tissue is formed. This tissue is mostly dark, scabby and some- Fig. 5. (Top) Adult cucumber beetle injury to a young honeydew melon. (Natural size.) Fig. 6. (Center) Nature of adult cucumber beetle injury to melon slightly older than shown in figure 5. (Natural size.) Fig. 7. (Bottom) Adult cucurnber beetle injury as it appears on a maturing honeydew melon. (Natural size.) [10] %%,., what raised as shown in figure 7. As the melons reach full maturity the scabbed areas are distinctly raised and nearly white (figure 8). On other varieties of melons the injury is whitish and scabby and the damaged area may be slightly depressed, sunken or deformed. In figure 9 is shown typical injury to a Crenshaw melon. On water- melons the adults sometimes eat the green epidermis. Adults also scar the stems and crowns of the plants (figure 10). Scarring of Fruit by Larvae. Where large larval populations have been al- lowed to develop, serious injury to mel- ons sometimes occurs. In honeydew fields as many as 50 per cent of the ripe melons have shown evidence of larval feeding. Larvae attack those melons in the later stages of development which rest upon moist soil. They bore into the fruit, leav- ing dark, sometimes rather deep-scarred areas. The wounds tend to cork over but at best present an unsightly appearance. In figure 11 is a honeydew melon show- ing larval injury. Feeding on Roots by Larvae. Seri- ous injury to melons is frequently caused by larval feeding on the roots. The west- ern striped cucumber beetle is believed more destructive in this regard than the western spotted cucumber beetle. Larvae frequently kill young plants and occa- sionally older ones. Also, it is possible that larval feeding may furnish portals of entry for the fungus disease, verticillium wilt. A root system of a honeydew melon which has been seriously fed on by west- tern spotted cucumber beetle larvae is shown in figure 12. Fig. 8. (Top) Characteristic adult cucumber beetle injury as it appears on a mature honey- dew melon. (About Vi natural size.) Fig. 9. (Center) Adult cucumber beetle injury to Cren- shaw melon. (About V2 natural size.) Fig. 10 (Bottom) Honeydew melon: scarring at crown— the result of adult cucumber beetle feeding, while scarring on the lower portion of the root is caused by larval feeding. Sources of Infestation Serious infestations of cucumber beetles arise from several sources. De- structive populations frequently develop from breeding within a field, and damag- ing larval populations are often encoun- tered. Further, examination of soil about the roots often reveals many pupae and newly-transformed adults. Migrating beetles offer a continual problem. Frequently melon fields are rapidly invaded by adults, in flights of considerable magnitude. These beetles originate from other crops that are being harvested or from fields where harvest- ing is completed and which are drying up or are being disked or plowed under. Large numbers of adults may move from alfalfa fields that are cut for hay. Im- portant migrations of the western spotted cucumber beetle may also occur in spring from uncultivated regions where large numbers of the first spring generation develops (Michelbacher et al., 1943; Smith and Michelbacher, 1949). In late fall the authors have observed that beetles may tend to concentrate in melon fields near a foothill area. Cucumber beetles like moisture and dislike heat. Therefore melon fields are especially attractive in hot weather and during and after an irrigation. Control of the Cucumber Beetle Although cucumber beetles are at- tacked by a number of natural enemies, these agencies rarely are sufficiently ef- fective to reduce the population to a level where control with insecticides is not re- quired. The most important parasite is a tachinid fly, Celatoria diabroticae Shini- er, (figure 13) . The maggot of this para- site completes its development within the body cavity of its host, the beetle. By the time it reaches maturity it has consumed practically all of the body contents and occupies the entire space in the abdomen. Although the internal organs appear to be destroyed the host beetle does not die until the parasite maggot has completed its development and is ready to emerge. The western spotted cucumber beetle adult, in the later stages of parasitism, is somewhat lighter in color than a normal individual. Chemical control of cucumber beetles would be rather simple except that some of the most effective materials, such as DDT, are likely to stimulate an increase Fig. 11. Cucumber beetle injury on honey- dew melon. Light-colored, corky tissue is result of adult feeding, while dark, pitted areas are caused by larvae. (About Vi natural size.) Fig. 12. Root system of a honeydew melon plant that has been seriously attacked by larvae of the western spotted cucumber beetle. Plants in this field were a total loss. ^^m if ^B. ^■» ? ^^ H "^ B Fig. 13. The diabrotica parasite, Celatoria diabroticae Shimer: (A) ventral view of two western spotted cucumber beetle adults from which mature parasite maggots have emerged. The body contents have been destroyed and the abdomen breaks away; (B) pupa cases from which the adult parasites have emerged; (C) the adult parasite. [14 in the spider mite and aphid population. Therefore control should be obtained with the lowest dosages and fewest appli- cations. The danger of developing de- structive spider mite or melon aphid populations can be greatly reduced — but not eliminated — by applying not more than one pound of actual DDT per acre, either as dust or spray. The authors have found that this amount assures excellent control of cucumber beetles and gives satisfactory results against other melon pests than can be controlled with DDT. Although cryolite is not nearly as ef- fective as DDT, a 40 or 50 per cent cryo- lite dust is sometimes recommended in early growth stages to control cucumber beetles. This is applied to avoid adverse effects that might result from using too much DDT. Satisfactory results with such a dust can only be obtained if cu- cumber beetles are the only pest to be controlled and if the dust is thoroughly applied by ground equipment. Cucumber beetles can also be controlled on seedling stands by applying undiluted calcium arsenate of low soluble arsenic content with a fertilizer attachment at time of cultivation. The calcium arsenate is al- lowed to dribble out over the rows. Dieldrin at 0.5 pound or aldrin or heptachlor at one pound per acre give excellent control of cucumber beetles but are not recommended where beetles are the only pest to be controlled. A 2 per cent parathion dust at 30 pounds per acre or an equivalent amount applied as a spray, is effective against cucumber beetles. Parathion has been successfully used to protect a crop for its entire growth. Single applications have remained effective for periods up to three weeks. Malathion as a 4 or 5 per cent dust at from 25 to 30 pounds per acre is also effective. Timing of Treatments. Treatments, especially in early stages of growth and melon formation, should be applied as soon as cucumber beetles become notice- able. This is particularly true for pre- ferred varieties such as honeydew, Cren- shaw, and casaba. With the netted melons such as cantaloupe precise timing is not so important. Because the adults are quiet when it is either cold or hot, the best time to esti- mate population size is in the morning shortly after it begins to warm up, or in late afternoon. Beetles are active and easily disturbed when it is moderately warm, and the relative number of indi- viduals can be rather easily estimated by walking through a field. The adult popu- lation is likely to be very uneven. It is not uncommon to find a portion of a field heavily infested while in the rest of the field the population may be below an eco- nomic level. Under some conditions, beetles tend to congregate. In large fields it may be sufficient to treat only the heavily-infested portion of the field. Be- cause large populations cannot be toler- ated, it is often necessary to treat melon fields when cucumber beetles are the only pest present in numbers sufficient to jus- tify the application. On preferred melons satisfactory con- trol for the growth of the crop should usually be obtained with two to four ap- plications of DDT or other effective in- secticide. MELON LEAF HOPPER The melon leaf hopper, Empoasca abrupta DeLong, is a destructive pest of melons particularly in the Central Valley of California. The small green adults measure a little more than % inch in length. The eggs are kidney-shaped and the female inserts them singly in the host just below the surface of the tissue. In completing development an individual passes through five nymphal instars. Stages in the life cycle, and a stem with eggs inserted in it, are shown in figure 14. First instar nymphs are pale or water white in color, and are difficult to see if not looked for closely. The color intensi- fies as the insect develops, but even in the later nymphal instars, the green is [15] Fig. 14. Life cycle of the melon leaf hopper, Empoasca abrupta Delong: (A) egg; (B to F in- clusive) the 5 nymphal instars; (G) adult female; (H) top upper wing, bottom lower wing; (I) habitat drawing of eggs inserted in a young stem of a celery plant. (A to H x 17; I x 5) [16] paler than that of the adult. The insect can be readily distinguished in that it runs with a sideways movement. The species was described by DeLong (1931) and is southwest and western in distribution. According to Poos and Wheeler (1943) it occurs in Arizona, California, Colorado, Kansas, Missouri, New Mexico, Oregon, and Texas. It at- tacks a wide range of plants and, besides melons, may seriously damage such crops as celery and potato. It passes through a number of generations each year and spends the winter in the adult stage. Some rearing studies on celery were conducted in a greenhouse, where the mean temperature was about 70° F. Under these conditions it was found that there was a preoviposition period of about 10 days, and the egg incubation period was close to 14 days. Nymphal development averaged about 19 days, so the time necessary to complete a genera- tion was approximately 43 days. Other species of leaf hoppers in south- ern California sometimes damage mel- ons. On occasion Empoasca solana DeLong or a still different species in- jures melons in the desert area. The melon leaf hoppers prefer to feed on the under surface of the leaves. They apparently like shade and are found in greatest abundance on leaves protected by the upper canopy of foliage. Serious injury may occur on the lower leaves be- fore there is much evidence of feeding on the upper leaves. Large populations are frequently encountered. Of the spe- cies of Empoasca studied by him, Poos (1932) reported that the melon leaf hop- per was the most prolific, with the pos- sible exception of the potato leaf hopper, E. fabae (Harris). DeLong (1938) pointed out that the melon leaf hopper and Empoasca arida DeLong occur in the lower elevations of California, where they are able to pro- duce enormous populations. Out of a col- lection of 18,000 specimens collected in this state he found five species repre- sented. Of these specimens 58.2 per cent were the melon leaf hopper, and 28.3 per cent were E. arida. Destructiveness The melon leaf hopper injures melons by sucking up the cell content of the leaves. According to Smith and Poos (1931) the melon leaf hopper punctures the lower epidermis of the leaf and then feeds in all directions from this point upon the mesophyll tissue. This results in the stippled appearance of the upper leaf surface. Feces that drop on leaves and on developing melons speckle them with tiny, blackish dots. Leaves that have been seriously injured by the pest are shown in figure 15. Destructive popula- tions kill the plants. Serious infestations reduce quality as well as yield of melons. Controlling the Melon Leaf Hopper Little evidence has been obtained to indicate that natural enemies are very Fig. 15. Crenshaw melon leaves that have been seriously injured by the feeding of the melon leaf hopper. Note the stippling and the tiny black specks of dried feces. [17] important in controlling the melon leaf hopper. The pest is usually held under control by cultural practices and through the use of insecticides. Cultural Control Methods. Prob- ably the most useful cultural method is to destroy crops as soon as harvest is completed. By so doing, breeding areas can be eliminated. Where abandoned and young fields are adjacent or not far from one another, treatment of the young field should be delayed, if possible, until the old one is disked under or otherwise de- stroyed. Insecticidal Control. Before the ad- vent of the newer insecticides, the melon leaf hopper was one of the most difficult melon pests to control. The most effective insecticides contained pyrethrum. When DDT first became available for agricul- tural use, Jeppson and Borden (1945) demonstrated that it was highly effective against the melon leaf hopper. Because DDT tends to increase the spider mite and melon aphid problem, investigations were conducted to see if these disadvantages could be eliminated or reduced. Experiments soon deter- mined that the problem could be reduced if DDT was used at a rate not to exceed one pound of actual toxicant per acre. Other insecticides were tested. Benzene hexachloride was not very effective against the pest. Michelbacher et al. (1952) found that aldrin, dieldrin, and heptachlor were ineffective against the leaf hopper and concluded, "After two years of extensive investigations it ap- pears that the principal use of aldrin, dieldrin, and heptachlor in the melon in- sect control program might well be lim- ited to those cases where the leaf miner becomes a problem." During 1952 and 1953 numerous ex- periments were conducted to compare the effectiveness of several insecticides against the melon leaf hopper. In one of these DDT, dieldrin and parathion were Table 1. Treatments and the Average Number of Leaf Hopper Nymphs per Honeydew Melon Leaf on Survey Dates Given (Treated May 29, June 1 9, and July 1 1 ) Survey date (1952 Treatment Check 0.04 0.10 4.76 6.72 9.82 9.14 13.78 13.38 5.50 8.38 10.90 11.40 8.82 DDT, 3' ; Sulfur, 50%* Dieldrin, 1.5% Sulfur, 50% f Dieldrin spray % Parathion, 2%t May 27 0.34 0.10 0.35 0.10 0.06 0.11 0.14 0.05 0.00 0.03 0.01 0.00 0.05 0.34 0.10 2.20 5.24 6.12 3.59 5.20 7.22 4.99 2.95 3.11 2.76 0.98 0.34 0.10 2.02 3.26 3.63 4.70 7.32 11.19 4.68 6.27 6.72 4.70 2.00 0.34 0.10 2.98 7.14 2.02 0.14 1.56 2.54 1.30 0.20 0.96 0.34 0.80 May 29 June 5 June 11 June 17 June 23 June 27 July 2 July 9 July 16 July 23 July 30 Aug. 6 * Approximately 25 pounds per acre per application. f Approximately 20 pounds per acre per application. X 0.35 pounds actual first; 0.65 pounds actual second; 0.86 pounds actual third. [18] compared. Treatments, dates of applica- tions and results obtained are shown in table 1. Best control was obtained when DDT was followed by parathion. The control obtained with dieldrin, either as a dust or a spray, could hardly be con- sidered satisfactory. Results of a second experiment with these same materials conducted in a Persian melon field are given in table 2. Although the leaf hop- per population was much lower than in the preceding experiment, the order of effectiveness of the insecticides remained the same. DDT Most Effective. Of all insecti- cides tested, DDT proved most effective against the melon leaf hopper — so effec- tive, in fact, that it often interfered with studies of other insecticides' effectiveness against the melon leaf hopper. Fre- quently, at the height of the dusting sea- son, DDT used in large amounts to control pests on tomatoes, beans, and seed alfalfa has drifted to melon fields. There it markedly reduced the leaf hop- per population, making it difficult to de- termine whether the control obtained was due to the insecticide used or the DDT drift. Further, it is possible that an additive effect of DDT drift may make an insecticide look better than it actually is against the melon leaf hopper. More than once, experiments have been rendered worthless by DDT drift, and in other cases it has complicated the interpreta- tion of the results. Two experiments were conducted in 1953 to compare DDT, parathion, and malathion in controlling the leaf hopper. One of these experiments was conducted at Patterson, Stanislaus County, and the other in the vicinity of Vernalis, San Joaquin County. Treatments and results obtained in the Patterson experiment are given in table 3. A destructive leaf hop- per population developed in the check plots. However, just prior to the second treatment which was applied on August 18, the influence of DDT drift made its appearance and from this time until the experiment was completed the infestation in the check plots declined. DDT drift also apparently had a favorable effect upon the treated plots, for following the second application they remained nearly free of leaf hoppers until the crop was harvested. The results prior to the second treatment probably give a good compari- Table 2. Treatments and the Average Number of Leaf Hopper Nymphs per Persian Melon Leaf on Survey Dates Given (Treated July 1 1 and August 14) Survey date (1952) July9.. July 16 July 23 . July 30. Aug. 8 . Aug. 13 Aug. 20 Aug. 28 Treatment Check 1.89 2.28 1.18 2.14 2.22 DDT, 3%* 1.89 0.30 0.29 0.28 0.18 0.81 0.00 0.00 Dieldrin, 1.5%t 1.89 1.67 1.87 2.83 3.37 2.39 0.00 0.00 Dieldrin spray % 1.89 1.58 1.21 1.12 1.09 1.65 0.02 0.00 Parathion, 2%t 1.89 0.10 0.68 0.42 0.14 0.52 0.00 0.00 * Approximately 25 pounds per acre per application. t Approximately 20 pounds per acre per application. 1 Approximately 0.80 pounds actual first; 1.0 pounds actual second. [19] son of the relative effectiveness of the three insecticides. If this is correct, it is evident that 5 per cent DDT at 12 pounds per acre was more effective than mala- thion or parathion. Further, 4 per cent malathion at 16 pounds per acre was more effective than 2 per cent parathion applied at the same rate. However, the control obtained with parathion was within economic limits. Information about the Vernalis experi- ment is in table 4. Here again there was some interference from DDT drift. The results, however, substantiate those ob- tained at Patterson: DDT was most ef- fective; 4 per cent malathion was second, and 2 per cent parathion third. Note that the initial control obtained with either malathion or parathion is better than that obtained with DDT. Table 3. Treatments and the Average Number of Leaf Hopper Nymphs per Crenshaw Leaf on Survey Dates Given (Two applications, July 22 and August 18) Survey date (1953) July 21. July 25. July 28. Aug. 4. . Aug. 11. Aug. 17. Aug. 20. Aug. 27. Sept. 3. Sept. 9 . Sept. 15 Check 2.69 7.92 13.35 10.79 11.25 8.55 5.38 6.23 5.92 3.69 1.21 Treatment DDT, 5%* 1.00 0.78 0.58 0.27 0.31 0.00 0.00 0.01 0.00 0.00 Malathion, 4%f 0.18 1.10 1.59 0.79 0.35 0.00 0.00 0.00 0.00 0.00 Parathion, 2% J 0.86 1.56 3.92 1.44 0.22 0.00 0.01 0.01 0.09 0.00 * July 22, applied at the rate of 12 pounds per acre; August 18, at the rate of 21 pounds per acre. f July 22, applied at the rate of 16 pounds per acre; August 18, at the rate of 21 pounds per acre. t July 22, applied at the rate of 16 pounds per acre; August 18, at the rate of 33 pounds per acre. Table 4. Treatments and the Average Number of Leaf Hopper Nymphs per Santa Claus Melon Leaf on Survey Dates Given (Two applications, August 12 and September 1 ) Survey date (1953) Treatment Check DDT, 5%* Malathion, 4%f Parathion, 2% J Aug. 11 Aug. 17 Aug. 25 Sept. 1§ 12.90 3.42 5.88 4.12 0.20 0.24 0.01 0.00 0.72 0.00 0.92 0.52 0.00 0.00 1.92 1.80 0.00 Sept. 9 * Rate per acre August 12, 30 pounds, no second treatment. f Rate per acre August 12, 36 pounds; September 1, 32 pounds. % Rate per acre August 12, 32 pounds; September 1, 28 pounds. § Pre-treatment count. - [20] DDT gives excellent control when ap- plied either as a dust or a spray at the rate of one pound of actual material per acre. Adequate control can be obtained with a 2 per cent parathion dust at 30 pounds per acre or its equivalent as a spray where applications are thorough and even. Slightly better control can be expected with a 4 per cent malathion dust evenly applied at 30 pounds per acre. MELON APHID The melon aphid, Aphis gossypii Glov., is a widespread and destructive pest of melons. It is a rather small, dark species and ranges in color from yellowish green to greenish black. Both winged and wing- less forms are produced. The winged in- dividuals are somewhat slender and are not as robust as the wingless form. A mature individual measures about 1 / 1Q of an inch in length. The melon aphid develops in colonies and prefers the under sides of the leaves. Under favorable conditions its develop- ment and reproduction is rapid. The in- sect passes through many generations each year. Isely (1946) reported that un- der optimum conditions an individual begins producing young within four days after birth. Paddock (1919) reported a maximum of 51 generations in a 12 month period, while Reinhard (1927) stated that during a like period 59 gener- ations were reared in the laboratory and insectary. Goff and Tissot (1932) found that 30 generations were produced in a greenhouse and 20 in an insectary in a 217-day period from November 4, 1930 to June 8, 1931. The average temperature in the greenhouse was 74° F; the insec- tary averaged 61° F. It is interesting to note that Isely (1946) believed that 68° F. was the most favorable temperature for reproduction. Widely distributed throughout the world, the melon aphid is most abundant in the tropics and warmer temperate regions. In these areas sexual forms have not been known to occur, and reproduc- tion is entirely by parthenogenetic fe- males. The insect has an extensive host range and attacks many cultivated as well as uncultivated plants. Among the culti- vated hosts seriously injured are cucur- bits, cotton and citrus. Some wild hosts include gourd, milkweed, Jimson weed, pigweed, plantain and morning-glory. The aphid spends the winter on any of its available hosts. In many melon-pro- ducing sections of California, spring in* festations originate from migrations of winged aphids that have developed on host plants hardy enough to survive the winter, how much the aphid can move from host to host is open to question. Evidence shows that in some cases the aphid cannot freely move from one markedly different host species to an- other. Paddock (1919) noted that the aphid did not migrate from cotton to cucurbits, or vice versa. Isely (1946) re- ported that aphids reared on cotton could not be colonized on members of the cucumber family, nor could aphids reared on cantaloupes and cucumbers be colonized on cotton. Yet despite these findings, the fact re- mains that the aphid easily finds its way into melon fields. The production of winged forms is probably associated with crowding. Rein- hard (1927) stated that crowding is a very important, if not the dominant or controlling factor in stimulating wing de- velopment. Goff and Tissot (1932) also believed that crowding resulted in con- ditioning the plants in a manner to stimu- late wing production. Further, it is a common sight in the field to find winged forms produced in greater and greater abundance as the aphid population de- velops to a highly destructive level. Finally winged individuals are found dis- persed in all directions. The stimulation of wing development induced by crowd- ing and probably by other factors affect- ing the quality of food is certainly an effective measure of nature to insure the survival and spread of the species. [21] Aphid Injures By Sucking Sap The melon aphid causes injury by in- serting its mouth parts into the plant and sucking up the cell sap. Where large pop- ulations are involved the vigor of the plant is greatly reduced. Vines are stunted, leaves curl down at the edges and are distorted, and the melons' size, flavor, and shipping properties are mate- rially reduced. The aphids at first confine their feeding to the under sides of the leaves, but gradually spread to the tips of runners. A seriously infested and dam- aged runner is shown in figure 16. A large amount of honeydew is secreted, and all parts of plants including melons become coated with sticky secretion. Sometimes the ground beneath the plants appears as if it has been sprayed with a syrup solution. A sooty mold fungus grows on the honeydew and infested plants become blackened with this growth. A common sight in heavily-infested fields is to see the whitish cast skins of the aphids stuck to the honeydew coating which covers the vines. Also, where large syrphid fly larval populations have de- veloped upon the aphids, irregular shiny black blotches of excrement, ranging from about % 6 to % square inch in area, are seen over the leaves, stems, and mel- ons. This material is sometimes difficult to remove during washing, when it has been deposited on netted melons. Figure 17 shows a honeydew melon plant seri- ously infested with aphids. Melons are subject to serious attack by the melon aphid in all melon-producing sections of California. While it is most destructive in warmer regions, Chitten- den and White (1926) reported that oc- casionally it is injurious as far north as Maine and Minnesota. Infestations may Fig. 16. A heavily-infested melon runner badly deformed and stunted by the melon aphid. be spotty and it is not uncommon to find part of a field rather heavily infested while the rest may show little evidence of aphids. In general the pest becomes most troublesome late in the season, par- ticularlv in northern California. Natural enemies, so important in helping to keep the aphid below an economic level earlier in the season, frequently fail to do as well late in the season. Highly destructive aphid populations are often encountered in September and October. This may be because the aphid is better adapted to cooler temperatures than are its natural enemies. Isely (1946) , who conducted in- vestigations on cotton, believed that this might be the case. He stated that 68° F was the most favorable temperature for aphid reproduction, and that this was lower than the optimum of its insect enemies. For this reason he concluded that the aphid often appears in conspicu- ous numbers early in the season and again late in the fall but is never an im- portant pest in midsummer unless cotton is dusted. On cotton many investigators have ob- served increases in the aphid population following applications of calcium arse- nate and other insecticides. The problem intensified as the number of dustings with calcium arsenate increased. Insecticide- induced increases on melons have also been observed. Michelbacher and Mid- dlekauff (1950) reported that high dos- ages of DDT were responsible for serious increases in the aphid population. They further reported that tetraethyl pyro- phosphate can give rise to a destructive aphid population if applied under condi- tions which result in a poor kill of the aphid but in a heavy mortality of its nat- ural enemies. Any treatment not effective against the melon aphid but highly de- structive to natural enemies is apt to re- sult in a troublesome aphid problem. Fig. 17. A severe infestation of the melon aphid showing typical injury to the leaves and fruit. CAUTION Always bear in mind that DDT, dieldrin, aldrin, heptachlor, and the other chlori- nated hydrocarbons are apt to stimulate an increase in spider mites. Where a serious spider mite infestation is indi- cated, an acaricide such as aramite or ovotran should be included in one treat- ment when these insecticides are applied repeatedly. Although some damage by the melon aphid can be expected every year, its de- structiveness varies from district to dis- trict and from year to year. Ecological conditions are much more favorable to the aphid in some seasons than others. Control Methods Natural agencies, cultural practices, and applications of insecticides can be utilized in the control of the melon aphid. Natural Control. The melon aphid is attacked by a host of natural enemies. Chittenden and White (1926) stated that there were about 40 species of beneficial insects. Predators are more important than parasites. The most important pred- ators in California, listed in order of im- portance, are ladybird beetles, syrphid flies, and lacewings. The most important ladybird beetle is the convergent lady- bird beetle, Hippodamia convergent Guerin. At times the aphid is heavily parasitized by a small wasp. The under sides of the leaves may be fairly well cov- ered with mummified aphids, and if they are closely examined the small circular holes through which the parasitic wasp emerged can be seen. If insecticide treatments do not too adversely affect natural enemies, they usually control the aphid during the spring and summer. However, in late summer and fall they appear less effec- tive, and serious outbreaks of the aphid are frequent. If conditions are favorable, natural enemies can sometimes reduce a destruc- tive aphid population to a non-economic level in a week to 10 days. The value of natural control and its effectiveness against the melon aphid is clearly shown by Michelbacher and Middlekauff (1950) . They found that natural enemies were not greatly interfered with when DDT was applied to control other pests of melons at a rate not to exceed one pound of actual toxicant per acre. Studies since then have substantiated these find- ings. To minimize adverse effects on natural enemies, insecticides should be thoroughly applied with the fewest treat- ments needed to ensure effective control. Cultural Control. Early in the season it is reported to be a good practice to cut out and bury isolated small plants that are heavily infested (Chittenden and White, 1926). This should be done be- fore the infestation develops to a point where winged forms are being produced in abundance. In this regard, Woodworth (1915), who conducted his investiga- tions in Imperial Valley, stated that when vines first become infested in spring it is usual to find aphids confined to a very few vines, upon which they be- come exceedingly abundant before de- veloping wings and spreading generally over the field. Under these conditions, he added, many growers sprinkled gasoline on heavily-infested vines and set them afire. At present such infestations don't occur except in the earliest melons, but it is likely that timely destruction of heav- ily-infested vines in early season may help establish a better balance between host and natural enemy. Late in the season, fields infested with aphids should be disked or plowed under as soon as harvest is completed. This is important because an infested field that remains unplowed may produce enough aphids to infest melons throughout the countryside. Remember that an increase in aphid population density stimulates the production of winged forms. In melons growing downwind from an [24] £ 8» > *E gB © O O CO O i-H O <+- CO 1 a • ^ *^> O CO iH "^ CM CO "5 © iH 1-i CO 4> c 2? CO CM O > O 4> > eB 4) iH O CM O 4- ffi f>_ Q. > S '4- S 1a 0) CO c jd ^ 00 O CM CO CN O CO O "3 2 >> > eB O O O * ffi ■0 c X c • ■■» CO a. 0) * © 'bo ■ a rH 4a • CO ^•3 O O O 2 1 -Q E d •0 >» ► s " 1 - O CO O > c 4" Q. u 3 eB O O CM O O n (3 « 4^ U) O CO Si 4- (A ■0 c V 4a M 4a a. CO „ O CM O »*■ a 4a • > of 43 bo i-3 CO CM i-H CM O >» Q. 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Oi > •S. • ® bp hi in J3 « w V cS C t o o o o o - S.S. 49 us CO 1-1 ifl ^•35 w bi) S < 0" s c T ! o i O 1 O 1 o M C fl fl fl fl bo O O c 3 a o o. < CO M H o ,4 H P P c£ + tr Eh ^j CO P! c8 CO Pi H-i- Sh i— ^ 01 o3 O It. •■"! 1 ed ++ S ° w E s o> .5 ■" 3 O O fl t- t- *: o. o> O ft ft 1- u CO CO »o CO lO CM lO 1 over melon fields. Avoid fast or unnec- essary driving on dusty lanes and roads. Sprinkling or oiling dusty roads might be profitable if they are in constant use. Insecticidal Control. Increases in spider mite population caused by DDT can be greatly lessened if no more than a pound of actual ingredient is applied per acre (Michelbacher et al., 1952) . Ad- verse effects of DDT and related mate- rials can be restricted if treatments are timely and thorough, so that applications can be held to a minimum. The authors followed spider mite pop- ulations in many experiments where treatments were directed against other melon pests. In one experiment compar- ing DDT, perthane, malathion, and parathion on honeydew melons where the two-spotted spider mite was the principal species (table 11) better suppression of the spider mite was obtained when sulfur was combined with DDT and perthane than when DDT was used alone. Best re- sults, however, were obtained with para- thion and malathion. In another experiment a dieldrin spray was compared to a parathion dust (table 12). Parathion dust checked the spider mite population while dieldrin encour- aged its development. A third trial compared dusts of DDT- sulfur, parathion, dieldrin-sulfur, and dieldrin spray in a honeydew melon field (table 13). Population trends were de- termined by counting spider mites on uniform leaf samples. Parathion was found superior to the other treatments. DDT-sulfur dust was better than dieldrin- sulfur dust. In the dieldrin spray plots the spider mite population was greatly stimulated and vines dried up before har- vest was completed. Even when the DDT- sulfur and the dieldrin-sulfur were ap- plied, the spider mite population de- veloped to a destructive level before har- vest was finished. The quality of melons in later pickings was markedly impaired, and this was particularly true of the dieldrin-sulfur treatment. Melon quality in parathion plots continued good all through harvest and yielded one picking more than any of the other treatments. In 1953 the seasonal trend of spider mite (mostly two-spotted) population was followed in a field of Crenshaw mel- ons where DDT, parathion, and mala- thion were being compared (table 14). Table 12. Treatments and Per Cent of Crenshaw Melon Leaves Infested With Spider Mites, on Survey Dates Given Survey date (1952) Aug. 13. Aug. 20 . Aug. 26 . Sept. 3. Sept. 10 Sept. 17 Sept. 30 Oct. 10 Treatment Check Light 2 5 44 42 63 78 35 % 18 Medium 8 5 7 8 13 28 Heavy 1 1 1 1 54 Dieldrin spray* Light 2 5 30 37 82 70 Medium 1 12 15 25 7 2 Heavy 3 2 3 93 98 Parathion, 2% f Light Medium 2 13 36 1 1 63 1 1 58 98 20 66 23 8 92 Heavy * Airplane application: 0.5 pound actual per acre in 10 gallons of water per application, August 15 and September 6. f Applied by ground duster at rate of 25 pounds per application; August 20 and September 4. j Treated with 2% parathion, by ground duster, September 19. [37] The heaviest infestation occurred in the DDT treatment followed in sequence by malathion and then parathion, which re- mained relatively free of spider mites. To check on the trend of the infestation, an actual count of spider mites was made on September 24, nine days after the last survey given in table 14. Individuals per leaf sample for the three treatments aver- aged as follows: DDT 21.07 Malathion 11.87 Parathion 1.87 These results clearly show that, of the three materials, parathion was much the best in suppressing spider mites. In another 1953 experiment the spider mite population trend was observed in a honeydew melon field. One portion was treated with 3 per cent DDT plus 50 per cent sulfur; the other was treated with 2 per cent parathion. Prior to this time the field had received three applications of dust during the establishment of the crop. These treatments were, in order of application: 5 per cent DDT by ground Table 13. Treatments and Average Number of Spider Mites per Sample of Honeydew Melon Leaf (Treated May 29, June 1 9, and July 1 1 ) Survey date (1952) July 23 July 30 Aug. 1 . Aug. 6 . Aug. 13 Aug. 20 Treatment Check 0.04 0.60 0.19 1.92 DDT, 3'c Sulfur, 50%* 0.87 2.17 5.93 3.97 Dieldrin, 1.5% Sulfur, 50% f 2.10 9.78 4.91 19.22 Dieldrin sprayj 5.67 9.75 10.73 28.42 Parathion, 2%t 0.11 0.03 0.35 0.83 0.72 1.44 * Approximately 25 pounds per acre per application. t Approximately 20 pounds per acre per application. t 0.35 pound actual first; 0.65 pound actual second; 0.86 pound actual third. Table 14. Treatments and Per Cent of Crenshaw Melon Leaves Heavily Infested with Spider Mites Survey date (1953) Treatments DDT, 5%* Malathion, 4% f Parathion, 2%$ Aug. 11 Aug. 17 Aug. 20 1 2 10 16 52 1 2 1 2 5 32 4 Aug. 27 Sept. 3 Sept. 9 Sept. 15 * Two applications: July 22, 12 pounds per acre; August 18, 21 pounds. t Two applications: July 22, 16 pounds per acre; August 18, 21 pounds. j Two applications: July 22, 16 pounds per acre; August 18, 33 pounds. - [38] at 15 pounds per acre; 2 per cent para- thion by ground at 15 pounds per acre; and 5 per cent DDT by airplane at 25 pounds per acre. The trend of the spider mite population in the two portions of the field is given in table 15. The infor- mation clearly shows that the 2 per cent parathion held the spider mite population in check much better than the DDT- sulfur combination. Seeking ways to prevent development of large spider mite populations when DDT is used, the authors compared plots dusted with DDT with DDT-dusted plots that were re-treated the same morning with a 7.5 per cent ovotran dust (table 16). Each treatment was replicated four times. Table 16 also shows the trend of spider mite population in a parathion- treated portion of a field adjacent to the experimental area. The results clearly in- dicate that the DDT-ovotran treatment very effectively, if somewhat slowly, checked the spider mite infestation. The suppression obtained with parathion was also very good. In another experiment ovotran or ara- mite was incorporated with dieldrin dusts. A heptachlor-aramite mixture was also included. These combinations of ma- terials were checked against plots receiv- ing no treatments, a dieldrin dust, a heptachlor dust, and a parathion dust. The experiment was directed against the two-spotted spider mite in a Crenshaw melon field. The treatments, information on rates of application, and the results obtained are given in table 17. When either ovotran or aramite was used in the first application the spider mite popula- tion was held below an economic level. When ovotran was combined with two dieldrin applications, results were even better. Best results, however, were ob- tained when three applications of 2 per cent parathion were applied. Further, ovotran resulted in better control than did aramite. Application of DDT to the dieldrin and heptachlor plots was neces- sary because of a developing leafhopper population in these plots. Neither dieldrin nor heptachlor is very effective against this pest. It is interesting that in this ex- periment the treatments containing ovo- tran exerted a marked suppressing effect upon a destructive powdery mildew in- fection. Other experiments incorporated acari- cides with DDT and related materials. In all of these, promising results were ob- tained that substantiated the data given above. Table 15. Treatments and Average Number of Spider Mites per Sample of Honeydew Melon Leaf Survey date (1953) July 16. July 21 . July 28. Aug. 4. Aug. 11 Aug. 18 Aug. 27 Sept. 3 . Treatment Parathion, 0.20 0.04 0.11 0.09 3.52 0.25 1.02 4.03 DDT, 3% + Sulfur, 50% t 0.57 0.59 2.61 3.30 7.43 3.65 13.09 16.92 * Applied July 19 and August 15, at 25 pounds per acre. t Applied July 24 and August 15, at 25 pounds per acre. [39] Table 16. Treatments and Average Number of Spider Mites per Sample of Melon Leaf Survey date (1953) July 21. July 25. July 28 Aug. 4 . Aug. 11 Aug. 18 Aug. 27 Sept. 3. Treatment DDT, 5%* 2.04 1.94 1.85 1.52 3.16 3.26 17.73 10.18 DDT, 5% + Ovotran, 7.5% t 2.83 1.07 0.04 0.04 0.11 0.57 Parathion, 2%% 0.18 0.12 0.03 0.05 0.22 1.42 * Treated July 25, at 17 pounds per acre. f Treated July 25, at 17 pounds of DDT and with 30 pounds of 7.5% ovotran. t Treated July 22, at rate of 25 to 30 pounds per acre. Table 17. Treatments and Average Number of Spider Mites per Sample of Crenshaw Melon Leaf Treatment Survey date (1953) Oct. 5 Oct. 12 Oct. 19 Check (no treatment) 2 applications of dieldrin, 1.5%. 1 application DDT, 5%* 1 application dieldrin, 1.5% + ovotran, 7.5%. 1 application of DDT, 5% ; and 1 application of dieldrin, 1.5%f 4.65 5.60 0.08 1.58 6.35 0.30 0.05 9.58 28.68 6.27 0.37 2.65 14.67 3.88 0.33 15.63 17.58 1.92 2 applications of dieldrin, 1.5% + ovotran, 7.5%; and one application DDT, 5%J 1.53 1 application dieldrin, 1.5% + aramite, 3%. 1 application of DDT, 5% ; and 1 application of dieldrin, 1.5% § 6.70 2 applications of heptachlor, 3%; and one application of DDT, 5%** 11.53 1 application heptachlor, 3% + aramite, 3%. 1 application of DDT, 5% ; and one application of heptachlor, 3%ff 3 applications of parathion, 2% Jf 8.48 0.57 * Order, date and rate per acre: Dieldrin, August 20, 20 pounds; DDT, September 4, 24 pounds; Dieldrin, September 24, 33 pounds. f Order, date and rate per acre: Dieldrin-ovotran, "August 20, 20 pounds; DDT, September 4, 24 pounds; Dieldrin, September 24, 33 pounds. t Order, date and rate per acre: Dieldrin-ovotran, August 20, 20 pounds; DDT, September 4, 24 pounds; Dieldrin-ovotran, September 24, 33 pounds. § Order, date and rate per acre: Dieldrin-aramite, August 20, 22 pounds; DDT, September 4, 24 pounds; Dieldrin, September 24, 33 pounds. ** Order, date and rate per acre: Heptachlor, August 20, 20 pounds; DDT, September 4, 24 pounds; Hep- tachlor, September 24, 30 pounds. ft Order, date and rate per acre: Heptachlor-aramite, Aug. 20, 20 pounds; DDT, Sept. 4, 24 pounds; Hep- tachlor, September 24, 30 pounds. Xt Order, date and rate per acre: August 20, 20 pounds; September 4, 27 pounds; September 24, 30 pounds. [40] CAUTION Always bear in mind that DDT, dieldrin, aldrin, heptachlor, and the other chlori- nated hydrocarbons are apt to stimulate an increase in spider mites. Where a serious spider mite infestation is indi- cated, an acaricide such as aramite or ovotran should be included in one treat- ment when these insecticides are applied repeatedly. No extensive studies on the control of the brown wheat mite, Petrobia latens (Miiller) have been conducted. However, Reynolds and Swift (1951) reported that parathion was effective against this spe- cies in Imperial Valley, and Michel- bacher et al. (1952) found this insecticide could be successfully used in San Joaquin Valley to control the pest. There is no question but that the addi- tion of sulfur to dust mixtures will help suppress spider mites. This is particu- larly true where the Atlantic spider mite is predominant, for it is readily suscep- tible to sulfur treatments. However, most melon varieties will not tolerate sulfur. It can be safely used only on honeydews and on cantaloupe varieties resistant to sulfur injury. When DDT and related insecticides are used in melon insect control, satisfac- tory control of spider mites can be ex- pected by incorporating an acaricide such as ovotran or aramite — in one of the applications. Best results will be ob- tained when this is done before the spider mite populations reach an economic level. Again, good results will only be obtained if the treatment is even and thorough. Either ovotran or aramite used alone will give satisfactory control of spider mites. Also, note that neither ara- mite nor ovotran exhibits a marked ad- verse effect on natural enemies. The use of parathion, when needed to control other melon pests, has resulted in excellent control of spider mites, pro- vided the applications give even coverage and are begun before a serious spider mite population has developed. MISCELLANEOUS PESTS A number of other pests can cause serious injury to melons. With the excep- tion of thrips, however, they are not en- countered to any great extent. Although thrips are common and are frequently found in large numbers, they are placed in this section because they are usually controlled by treatments directed against other melon pests. THRIPS Thrips are small, slender insects with mouth parts developed primarily for sucking and rasping. Several species are involved and measure about % 5 of an inch in length. The adults have two pairs of fringed wings, carried lengthwise over the back. Both the young and adults cause damage. Their rasping and punc- turing of surface cells result in a silvering and sometimes in deformation of the leaves. Edges of leaves tend to curl down- ward. Serious infestations are sometimes encountered and most damage is done in early growth stages. Control. Most thrips infestations are controlled with treatments directed against cucumber beetles, melon aphid, and the melon leaf hopper. When de- structive populations occur they can be reduced to a non-economic level with ap- plications of DDT, parathion, or mala- thion as recommended for the control of any of the above-mentioned insects. SQUASH BUGS The squash bug, Anasa tristis (De- Geer) (figure 21), is a dark grayish- brown, somewhat speckled, sucking in- sect that averages about % of an inch in length when mature. The visible mar- gin of the abdomen as seen from above is orange or alternately barred with orange and brown. The younger nymphs [41] Fig. 21. Adult squash bug, Anasa tristis (De- Geer). are pale green with pinkish legs and an- tennae. Later, the thorax and appendages take on a blackish hue, while the abdo- men becomes a pale grayish-brown. The shiny light brown eggs which darken with age are usually laid singly in small clusters on the under side of leaves in the angles between veins and on the leaf petiole. The winter is passed as adults. Both nymphs and adults injure plants by sucking the cell sap and possibly by secreting toxic or enzymatic substances. Severely infested plants wilt, dry up, and die. Squash bugs are particularly destruc- tive to squash and pumpkins, but at times seriously attack melons. Destructive pop- ulations have been encountered on young watermelons. Injury is seldom seen on other varieties of melons. Control. Destruction of hosts as soon as harvest is complete will aid in reduc- ing the number of individuals that may pass the winter. Control of the pest with insecticides is difficult. A 20 per cent sabadilla dust at from 30 to 40 pounds per acre will give some relief if it is thor- oughly and evenly applied on calm, still days when the vines are dry. A 2 per cent parathion dust is effective against the nymphs when applied with effective equipment under favorable weather con- ditions. CRICKETS AND GRASSHOPPERS Occasionally crickets or grasshoppers may damage melons. These pests are usually checked by treatments directed against other pests. However, if destruc- tive populations are encountered they can be controlled with dieldrin. aldrin, or heptachlor. DARKLING GROUND BEETLES These are small, dull black or bluish- black beetles that measure only about *4 inch in length. They live in and on the surface of the soil. Occasionally they attack melon plants when they first show above the soil. They sometimes take shel- ter under cantaloupes in the desert areas of southern California. They feed on the netting and cause some scarring. Control. Treatments to control dark- ling ground beetles are seldom necessary because they are usually checked by treatments directed against cucumber beetles and other melon pests. SEED-CORN MAGGOT The seed-corn maggot, Hylemya cili- crura (Rond.) is the larva of a rather small fly. Legless, somewhat wedge- shaped, it has no distinct head and is nearly white. The maggot attacks the ger- minating seed of melons, and is only a pest in early season before the soil warms up. Little damage is likely to occur once favorable growing conditions set in. Control. If early plantings are to be made and damage from the seed-corn maggot is anticipated, treated seed should be used. Investigations by Lange et al. (1953) have demonstrated that ex- ceedingly small amounts of lindane, diel- drin, aldrin, or heptachlor will protect [42] seed from serious attack by the seed-corn maggot. These workers suggest that in- secticides should be used in combination with a fungicide. One ounce of actual lindane treats 100 pounds of seed. If diel- drin or aldrin is used 0.5 ounce of actual material is recommended; for hepta- chlor, one ounce of actual ingredient should be used per 100 pounds of seed. WIREWORMS Wireworms are the immature stages of "click beetles." They have smooth, shiny, cylindrical bodies, tough skin, and are usually yellow or brownish in color. They live in the soil and most of the destruc- tive species measure an inch or less in length. Wireworms injure plants by cut- ting off the roots, or by penetrating into the roots and up into the crown of young melon plants. Wireworms seldom seri- ously injure melons. Damage is most likely to be encountered in early plant- ings and where melons grow on lighter soil types. Control. If a field has a wireworm history, seed that has been treated with lindane should be used. Lange et al. (op. cit.) found that melons can be protected from wireworms if the seed is treated at the rate of one ounce of actual ingredi- ent to 100 pounds of seed. Best results are obtained when lindane is used in combination with a fungicide such as Arasan, Spergon, or Captan. CUTWORMS Serious damage by cutworms is sel- dom encountered. A few individuals may be found but they are hardly ever en- countered in numbers sufficient to justify control measures. Damage to outer rows of melons sometimes results from migra- tions of the western yellow-striped army- worm, Prodenia praefica (Grote) that occur when adjacent infested alfalfa fields are cut. Injury from these migrat- ing caterpillars can be avoided if an 8- inch-wide barrier strip of 5 or 10 per cent DDT, chlordane, or toxaphene is placed along the edge of the melon field that faces the migrating pest. ROOT-KNOT NEMATODE The root-knot nematode is a parasite that attacks the roots of many kinds of plants. A small roundworm of almost microscopic size, it causes the formation of gall-like swellings or knots on the roots of melons. Adult nematodes are im- bedded in these galls. Heavily-infected plants become weakened and may eventu- ally die. First aboveground indications of the presence of this pest are poor growth and stunting of plants. Melons are very susceptible to injury by the root- knot nematode and should not be planted in fields known to be heavily infested. It is sometimes possible to obtain reason- able suppression of this pest by growing such unfavorable host crops as barley, wheat, oats, and other grains before the field is to be planted to melons. Control. The root-knot nematode can be controlled by fumigating the soil with certain chemicals. Satisfactory results de- pend on proper preparation of the soil. It should be in excellent tilth and well supplied with moisture. The most effective fumigants are a mixture of one part of 1,2 dichloropro- pane and two parts of 1,3, dichloropro- pene, sold under the name of D-D, and ethylene dibromide, sold under the name of EDB. D-D usually gives satisfactory control of root-knot nematode when ap- plied at the rate of 200 pounds or more per acre, depending upon soil type. Ethy- lene dibromide should be used at the rate of from 3 to 4 gallons of active ingre- dient per acre. Usually applications of the above fumigants are made on a full cov- erage basis and give effective control for only a single season. Special commercial applicators are available for applying the fumigants. Row treatment is a new method of applying fumigants that shows consider- able promise in nematode control. This type of treatment can be made with from [43] SAFETY WARNING AND PRECAUTIONS On chemicals for use as pesticides read label warnings and cautions before use. Keep pesticides out of reach of children, pets, or irresponsible persons. In case of accidental poisoning, call a physician or get patient to a hospital at once. Always keep pest control materials in original, properly labeled containers. Never give a neighbor or anyone a portion of your pesticide in an unlabeled container. Store in a safe place, away from children and animals. Do not expose to excess sun or cold. Do not keep pest control materials where foods, human or animal, are stored or handled. Observe cautions to prevent poison residue on edible portions of plants. Wash hands and face after spraying or dusting. Do not smoke while spraying or dusting. Avoid inhalation of sprays or dusts. Do not spill insecticides on the skin or clothing. Wash immediately and thoroughly to remove such spillage. Wash clothing each day before re-use. When treating around pet or livestock quarters cover food and water containers. Be careful not to contaminate fish ponds. one-fourth to one-third the amount of material required for full coverage. The amount of material needed per acre would be as follows: 6-foot plantings, D-D, 4.5 gallons or EDB, 0.83 gallons; 8- foot plantings, D-D, 3.4 gallons or EDB, 0.62 gallons. D-D and ethylene dibromide are toxic to plants, and a field should be treated at least two to three weeks in advance of planting. If trees and shrubs grow near- by, treatments should not be made within the drip areas of such plants. The chemi- cals are also toxic to man. If they spill on the skin, wash the affected area thor- oughly with soap and water. Clothing that has come into contact with either fumigant should be cleaned or washed before being worn again. POLLINATION Successful melon production depends on having blossoms pollinated by insects. While the so-called wild bees and certain other insects are of some importance in pollination, McGregor and Todd (1952) conducting investigations in the Salt River Valley of Arizona, found that for cantaloupes honey bees were the only effi- cient pollinators. In some cage tests Mc- Gregor and Todd increased melon pro- duction by placing colonies of bees with cantaloupe flowers. Under these condi- tions the melons set nearer the crown were sweeter, larger, and had more seed than those produced in open plots. Be- cause bees are esential they should be protected carefully. Most insecticides used in melon insect control are toxic to bees and should be used with considerable caution. Among those that are most harmful to bees are dieldrin, aldrin, heptachlor, parathion, and malathion. These as well as other insecticides should not be applied to melons when the blossoms are open. Ap- plications should be made, if possible, late in the afternoon or at night. Where treatments have been applied before the flowers open, little damage to pollinating insects has been observed. In order to reduce the number of treatments to a minimum, all applications should be timely and thorough, using efficient equipment. Poor application makes fre- quent treatments necessary and thus greatly increases the hazard to pollinat- ing as well as other beneficial insects. [44] LITERATURE CITED Baker, Edward W., and A. Earl Pritchard 1953. A guide to the spider mites of cotton. Hilgardia 22(7) :203-234. Chittenden, F. H., and W. H. White 1926. The melon aphid and its control. U. S. Department of Agriculture, Farmers' Bulletin 1499: 1-16. Davis, Donald W. 1952. Some effects of DDT on spider mites. Jour. Econ. Ent. 45(6) : 1011-1019. DeLong, Dwight M. 1931. A revision of the American species of Empoasca known to occur north of Mexico. U. S. Department of Agriculture, Technical Bulletin 231:1-59 1938. Biological studies on the leafhopper Empoasca fabae as a bean pest. U. S. Department of Agriculture, Technical Bulletin 618:1-60. Frick, Kenneth E. 1952. A generic revision of the family Agromyzidae (Diptera) with a catalogue of New World species. Univ. Calif. Pub. in Ent. 8(8) :339-452, 34 figs. Goff, C. C, and A. N. Tissot 1932. The melon aphid. Florida Agr. Exp. Sta., Bui. 252:1-23. Hills, Orin A., and Edgar A. Taylor 1951. Parasitization of dipterous leaf miners in cantaloupes and lettuce in the Salt River Valley, Arizona. Jour. Econ. Ent. 44(5) : 759-62. 1953. Cantaloupe pests have enemies, too — Beneficial parasites should not be killed off with new insecticides. Progressive Agri. in Arizona 5(2) :8 and 10. Isely, Dwight 1946. The cotton aphid. Arkansas Agr. Exp. Sta., Bui. 462:1-29. Ivy, E. E., and A. L. Scales 1950. Dieldrin for cotton insect control. Jour. Econ. Ent. 43(5) :590-592. Jeppson, L., and A. D. Borden 1945. Investigations with DDT in California in 1944. California Agr. Exp. Sta. Lithoprint. 33 pages. Lange, W. H., E. C. Carlson, and L. D. Leach 1953. Pest control by seed treatment — wireworms and seed-corn maggots can be controlled by treating seed with lindane prior to planting. California Agriculture 7(5) : 7, 8. Mayeux, Herman S., and George P. Wene 1950. Control of serpentine leaf miner on pepper. Jour. Econ. Ent. 43(5) : 732-733. McGregor, S. E., and Frank E. Todd 1952. Cantaloup production with honey bees. Jour. Econ. Ent. 45(1) :43-47. Michelbacher, A. E., G. F. MacLeod and Ray F. Smith 1943. Control of Diabrotica, or western spotted cucumber beetle, in deciduous fruit orchards. California Agr. Exp. Sta. Bull. 681:1-33. Michelbacher, A. E., and W. W. Middlekauff 1950. Control of the melon aphid in northern California. Jour. Econ. Ent. 43(4) :444-447. Michelbacher, A. E., O. G. Bacon, W. W. Middlekauff and W. Erwin 1953. Tomato insect investigations in northern California. Jour. Econ. Ent. 46(1) : 73-76. Michelbacher, A. E., W. W. Middlekauff and O. G. Bacon 1952. Mites on melons in northern California. Jour. Econ. Ent. 45(3) :365-370. Michelbacher, A. E., W. W. Middlekauff and O. G. Bacon 1953a. Melon insects in northern California. Western Grower and Shipper. 24(6) :26-29. 1953b. Cucumber beetles attacking melons in northern California. Jour. Econ. Ent. 46(3) :489- 494. Michelbacher, A. E., W. W. Middlekauff and L. C. Glover 1951. Studies with aldrin and dieldrin against melon insects. Jour. Econ. Ent. 44(3) :390-393. Michelbacher, A. E., W. W. Middlekauff, O. G. Bacon and L. C. Glover 1952. Aldrin, dieldrin and heptachlor to control California melon insects. Jour. Econ Ent. 45(3) : 470-475. [45] Paddock, M. S. 1919. The cotton or melon louse. Texas Agr. Exp. Sta. Bui. 257:1-54. Poos, F. W. 1932. Biology of the potato leaf hopper, Empoasca jabae (Harris) and some closely related spe- cies of Empoasca. Jour. Econ. Ent. 25(3) :639-646. Poos, F. W. and Nancy H. Wheeler 1943. Studies on host plants of the leafhopper of the genus Empoasca. U. S. Department of Agri- culture, Tech. Bull. 850:1-51. Reinhard, H. J. 1927. The influence of parentage, nutrition, temperature, and crowding on wing production in Aphis gossypii Glover. Texas Agr. Exp. Sta. Bui. 353:1-19. Reynolds, H. T. and J. E. Swift 1951. Control of Petrobia latens in the Imperial Valley of California. Jour. Econ Ent. 44(5) : 642-645. Smith, F. F. and F. W. Poos 1931. The feeding habits of some leafhoppers of the genus Empoasca. Jour. Agr. Res. 43:267-285. Smith, Ray F., and A. E. Michelbacher 1949. The development and behavior of populations of Diabrotica ll-punctata in foothill areas of California. Ent. Soc. Amer. XLII(4) :497-510. Webster, F. M., and T. H. Parks 1913. The serpentine leafminer. Jour. Agr. Res. 1(1) :59-87. Wene, George P. 1953. Control of the serpentine leaf miner on peppers. Jour. Econ. Ent. 46(5) :789-793. Wilcox, J., and A. F. Howland 1952. Control of a dipterous leaf miner on tomatoes in California. Jour. Econ. Ent. 45(4) :634- 639. Wolfenbarger, D. 0. 1947. The serpentine leaf miner and its control. Fla. Agr. Exp. Sta., Press Bui. 639. 6 pp. Woodworth, C. W. 1915. Aphids on grain and cantaloups. California Agr. Exp. Sta. Cir. 125:1-4. ACKNOWLEDGMENTS The authors wish to express their appreciation to the several chemical concerns which contributed insecticides, help and equipment, and to B. Harlan and T. Dumars, Woodland, and Herman Wood, Patterson, who generously provided melon fields and other help. Thanks are due to the following for field and laboratory assistance : N. B. Akesson, and W. E. Yates, Department of Agricultural Engineering, University of California, Davis; William H. Wade, C. S. Davis, and Earl Oatman, research assist- ants, Department of Entomology and Parasitology, University of California, Berke- ley; and E. E. Stevenson, Farm Advisor, Stanislaus County. Special thanks are due Dr. John N. Simons who, as a graduate student, conducted the studies dealing with the rearing of Empoasca abrupta. [46] In order that the information in our publications may be more intelligible it is sometimes necessary to use trade names of products or equipment rather than complicated descriptive or chemical iden- tifications. In so doing it is unavoidable in some cases that similar products which are on the market under other trade names may not be cited. No endorsement of named products is intended nor is criticism implied of similar products which are not mentioned. Co-operative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture co-operating. Distributed in furtherance of the Acts of Congress of May 8. and June 30, 1914. J. Earl Coke, Director, California Agricultural Extension Service. 10m-4,'55(5610)RMB TOO MANY INSECTS . . . NOT ENOUGH V INSECT-FIGHTERS E ALL THE LAND ANIAAALS on the face of the earth— man in- cluded—don't weigh as much as the earth's insects. In America alone they cause $4,000,000,000 worth of dam- age each year. California, with more than 200 kinds of crops, spends more on insect control than any other state. NTOMOLOGY provides the weapons man needs for dealing with his insect enemies as well as the knowledge he needs to help his insect friends — the honeybee, for example. The war against insects never ceases. It will increase in importance as world population and the need for food and fiber increase. THE UNIVERSITY OF CALIFORNIA'S Department of Entomology and Para- sitology — in Berkeley and at Davis — is recognized as a leading world center of ento- mological training. Many of the teaching staff are outstanding authorities in their fields. Thirty-one undergraduate and graduate courses offer the widest basic and advanced training available on the Pacific Coast. FOR INFORMATION on courses, fees, requirements, write to: E. G. Linsley, chairman Department of Entomology and Parasitology 112 Agriculture Hall University of California Berkeley 4, California