Showing papers in "Journal of Economic Entomology in 1962"

Insecticide Resistance in the Adult Western Corn Rootworm in Nebraska

Abstract: Adults of the western corn rootworm. Diabrotica virgifera LeConte, collected from two widely separated areas in Nebraska, were assayed for susceptibility to aldrin, Diazinon® ( O,O -diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), and heptachlor. Dosage-mortality curves and LD50 values were determined for each insecticide. Results indicated that adults of D. virgifera collected from the central part of the State required about 100 times as much aldrin or heptachlor per insect to produce an LD50in 2 hours as adults collected in eastern Nebraska. LD50 values for Diazinon tested on beetles from the two areas were virtually the same. The reasons for such differential resistance are considered.

A Comparative Study of Toxicological Test Methods on a Population of the Two-Spotted Spider Mite (Tetranychus telarius)

Abstract: Three toxicological test methods were investigated for their practical value in testing a population of the two-spotted spider mite, Tetranychus telarius (L.), using Kelthane® (1,1-bis( p -chlorophenyl)-2,2,2-trichloroethanol), Meta-Systox-R® ( O,O- dimethyl S-2-(ethylsulfinyI)ethyl phosphorothioate) and TEPP as toxicants. Mites were treated by a Slide Dip Method, a Cage Spray Method and a Leaf Dip Method. In terms of least variability the Cage Spray Method gave the best results at intermediate sensitivity followed by the Slide Dip Method which showed greater variability and the highest sensitivity. The Leaf Dip Method is characterized by the greatest variability and least sensitivity. By combination of different test methods differentiation between topical and topical plus residual effect of toxicants could be demonstrated. Similarly a strong inactivation of TEPP by the plant was detected. The Slide Dip Method and the Cage Spray Method appear well adapted for exact toxicological tests and tests on population dynamics. The Cage Spray Method is indispensable in cases where the survivors of a treatment are needed for further experiments as is the case in selection programs. The relatively small amount of work involved with the Leaf Dip Method makes it well suited for screening work, where a small variability is not essential.

Mechanisms of resistance in diazinon-selected multi-resistant Musca domestica.

Abstract: Studies were made in three strains (a susceptible, a low-resistant, and a high-resistant) of house flies ( Musca domestica L.) to determine whether resistance to Diazinon®( O,O -diethyl O-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), parathion, and DDT is attributable to differences in absorption rates. Penetration studies with Diazinon (P32) showed less rapid absorption by resistant flies and it was concluded that reduction in permeability of the cuticle is a factor in resistance to Diazinon. This is not the only defense mechanism, however, since flies which were 125-fold resistant by topical measurement still showed some tolerance (14-fold) when the insecticide was injected. Similarly, the low-resistant strain (15-fold topically) was 3-fold resistant to injected Diazinon. More rapid detoxication is precluded as the additional resistance mechanism, since the susceptibles contained higher amounts of water-soluble metabolites than resistant flies. Resistance to Diazinon was higher by oral application than by either injection or topical treatment. Ali-esterase activity of the strains was inversely proportional to the level of Diazinon resistance; this fact confirms previous reports on other o-p resistant house flies. There were only slight differences among the strains in cholinesterase level and in sensitivity to in vitro inhibition. In parathion- and DDT-resistance, penetration appears not to be an important factor, since the differences between the tolerances measured by injection and by topical application were small compared with the levels of resistance. DDT-dehydrochlorinase activity was high in resistant flies and it appears that this activity may constitute at least the primary defense mechanism against DDT-type compounds, since the highly resistant strain was only slightly (2-to 3-fold) tolerant of DDT analogs in which dehydrohalogenation is sterically hindered.

Chemical Sterilization of the Screw-Worm

Abstract: Treatment of the screw-worm ( Cochliomyia hominivorax (Coquerel)) with apholate (2,2,4,4,6,6-hexa(1-aziridinyl)-2,4,6-triphospha-1,3,5,triazine) resulted in complete sexual sterility in many instances. Sterilization was accoumplished in either the larval, prepupal, or adult stage, but pupal treatment resulted in only partial sterility. Sterilization was achieved by treatment of media containing the larvae, by dusting prepupae or adults, by dipping prepupae, by topical applications to adults, or by feeding the adults the apholate. Treatment with the compound also caused a reduction in the number of eggs produced. In nearly all tests, females were more affected than males. Slight differences in the age of the insect within each stage treated affected the control of reproduction. Some mortality was experienced when larvae or prepupae were treated, but no noticeable mortality occurred with adults treated at sterilizing dosages. Morphological examination showed a reduction in the size of the ovaries and testes and a distortion and reduction in number of the eggs in the ovaries. Treatment of larvae caused a marked change in the shape and form of the resulting pupae and adults.

The Biology and Control of the Western Bean Cutworm in Dent Corn in Nebraska

Abstract: Studies were conducted on the western bean cutworm, Loxagrotis albicosta (Smith), in irrigated corn in Dundy County, Nebraska, in 1961. Adults appeared the early part of July. At the peak of the flight 4,144 adults were collected by a light trap in a single night. Eggs were laid on the corn plants, usually on the upper side of the leaves. Larvae fed on various portions of the plant and finally on the ears where they destroyed as much as 40% of the kernels. Controls were applied by airplane on a heavily infested field. Treated plots were compared with untreated plots and differences in insect population, number of ears damaged, percentage of damage per ear, and yields of shelled corn were recorded. The insecticides ranked from highest to lowest in control provided on the basis of the comparisons were: Thiodan® (6,7,8,9,10, 10-hexachloro-1 ,5,5a,6,9,9a-hexahydro-6, 9-methano-2,4,3-benzodioxathiepill-3-oxide), endrin, DDT (granules), DDT (EC), Sevin® (1-napthyl N -methylcarbamate) and Diazinon® ( O,O -diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate).

Effect of Infestation by the Rice Stink Bug, Oebalus pugnax, on Yield and Quality in Rice

Abstract: Studies were conducted during 1960 and 1961 to evaluate effects or rice stink bug ( Oebalus pugnax (F.)) infestations on rice in Louisiana. Five varieties of rice grown under screened cages were infested during the early heading stage with adults and late-instar nymphs. Infestation levels were varied to determine effect on quality and yield. Quality was affected to the extent that federal support prices for four varieties were reduced even at the lowest infestation which averaged between seven and eight stink bugs per 1,000 panicles. Consistent and severe losses in yields resulted from infestations which averaged approximately 230 or more bugs per 1,000 panicles. Viability of kernels was lowered by injury resulting from stink bug feeding. Greatest reductions occurred in damaged kernels which were injured in the germ region or which were severely atrophied.

Mode of Action and Insecticidal Value of a Diatomaceous Earth as a Grain Protectant

Abstract: An inert diatomaceous earth of Arizona origin trade named Perma Guard was evaluated as a grain protectant, insecticidal and pathological properties being studied. Dosage-mortality curves are presented for eight test species confined in wheat dusted with Perma Guard at the rate of 2 to 7 pounds per ton, Ranking in order of decreasing susceptibility these species were: flat grain beetle, Cryptolestes pusillus (Schanherr); rice weevil, Sitophilus oryzae (L.); granary weevil, Sitophilus granarius (L.); lesser grain borer, Rhyzopertha dominica (F.); saw-toothed grain beetle, Oryzaephilus surinamensis (L.); dermestid larva, Trogoderma parabile Beal; red flour beetle, Tribolium castaneum (Herbst); and confused flour beetle, T. confusum Jacquelin du Val. Only the flat grain beetle mortality attained standards of commercial kill during the two weeks' exposure period at the commercially recommended dosage (4 pounds per ton) or below. Mortality exceeded 95% at 5 and 6 pounds per ton for this species. At the peak dosages used, the mortality of the remaining species did not approach the criterion for commercial kill, The results indicate that of the two moisture levels (12% and 14%) of wheat used in this study, the lower level contributed to mortality in both weevil species, the lesser grain borer and the saw-toothed grain beetle. The dust was directly applied to five test species. Significant differences in losses in weight were observed between test and control groups for the lesser grain borer, the confused flour beetle and the red flour beetle. Overall differences in losses in weight between test and control lots of rice and granary weevils were not significant. A drastic difference between test and control first-day mortality in the rice weevil may be indicative of an unknown lethal factor in the dust. The significant differences in loss in weight were ascribed to the dust's abrasive action on the water barrier portion of the epicuticle. The toxicology of this diatomaceous dust was studied. Dissections, epicuticular staining. and histological sectioning showed little that could be construed ns epicuticular damage.

Transmission of Cabbage Viruses A and B by the Cabbage Aphid and the Green Peach Aphid

Abstract: Experiments were conducted to determine the modes of transmission of cabbage viruses A and B (CVA and CVB, respectively) by the green peach aphid, Myzus persicae (Sulzer), and the cabbage aphid, Brevicoryne brassicae (L.). Experiments using varying times of acquisition feeding and virus retention showed that both aphids transmitted CVA nonpersistently. M. persicae transmitted CVB similarly. B. brassicae transmitted CVB semipersistently. Transmission was efficient after long acquisition feeds. Plotting per cent transmission against acquisition time resulted in a bimodal curve with peaks around 5 minutes and 5 hours. It was hypothesized that B. brassicae transmitted CVE nonpersistently after short acquisition feeds and persistently after long feeds. Further evidence for the hypothesis was obtained from retention and serial transmission tests using either short or long acquisition feeds corresponding to the peaks in the bimodal curves. B. brassicae retained CVB longer after a long acquisition feed than after a short feed. Formaldehyde (0.25%) applied to viruliferous feeding cabbage aphids in solution through a membrane or directly to exposed stylets was used to inactivate CVB. The chemical in most instances prevented transmission by aphids given short (1 to 2 minutes) acquisition feeds. Using acquisition periods of 4 hours to 2 days, much less reduction of transmission resulted regardless of length of stylets treated, It was concluded that during short acquisition feeds, only the tips of sty lets were involved in CVB transmission. After long acquisition feeds, the transmissible virus apparently was not on the stylets or was protected in some way from virus inactivators. This conclusion lends further evidence to the hypothesis of bimodal transmission.

The Hydroxylation of Naphthalene-1-C14 by House Fly Microsomes

Abstract: Techniques used in isolating a sub-cell fraction of house fly ( Musca domestica L.) tissue capable of converting naphthalene to l-naphthol and 1:2-dihydro-1:2-dihydroxy naphthalene are described. Incubation conditions studied include pH, temperature, time, substrate level, microsome level, and co-factor requirements. The hydroxylating activity of house fly microsomes appears to vary with the growth and development of the life stages, with older adults exhibiting greatest activity and larvae the least. The co-factor TPNH seems to be more critical in the microsomal activity of mature adults.

Infestation Patterns of Douglas-Fir Beetle in Standing and Windthrown Trees in Southern Idaho

Abstract: To facilitate population studies, the infestation patterns of Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, were investigated in standing and wind thrown trees in southern Idaho. Three infestation zones were recognized in most standing trees. The basal zone was infested least densely, progeny did not result from about one-fourth of the galleries, and the infestation varied more than in the upper portions. Typically, a middle zone comprised four-fifths of the infested stem, and the infestation there was densest and most successful as well as least variable. At the top of the infestation, the proportion of unsuccessful galleries again increased and fewer live progeny were present. In windthrown trees, the infestation varied circumferentially, but lengthwise stratification was not demonstrated. Both galleries and progeny were denser on the shaded underside than on the sun-exposed upper side of down trees. Although lengthwise differences were not demonstrated, the infestation was least variable mid way along the infested length, thereby favoring the underside in that vicinity for sampling of down trees.

Vertical Distribution and Persistence of Insecticidal Residues in Soils as Influenced by Mode of Application and a Cover Crop

Abstract: To determine, the effect of mode of application and a cover Crop on the persistence and vertical distribution of insecticides in soils, field tests were conducted over a 3-year period. Aldrin and heptachlor were applied either to the soil surface only or incorporated into the soil by rototilling to approximately 5 inches. Recoveries of insecticidal residues ranged from 2.7% to 5.3% of the applied dosages, 4 months after a soil-surface application. However, incorporation of insecticidal deposits into the upper soil layers increased the persistence of the residues by a factor of 10. One year after treatment of the upper soil layers, 90% of the recovered residues were located within the upper 3 inches of the soil. The highest concentration of the insecticides was found within the second in the of the soil layer. A deeper penetration and a more equal distribution of the insecticidal residues was noticed 3 year after soil treatment. Two to 3 times more insecticidal residues were recovered from alfalfa-covered plots than from fallowed ones. Volatilization appears to be the major factor in the loss of insecticidal residues. Their longer persistence after having been incorporated into the soil, may be extended by reducing the volatilization of the insecticides at the soil-air interface with a dense cover crop.

Oiketicus kirbyi (Lepidoptera: Psychidae) A Pest of Bananas In Costa Rica

Abstract: The bagworm, Oiketicus kirbyi Guilding, became a new leaf feeding pest of bananas in southern Costa Rica the latter part of 1958. Eggs hatched in 27 to 32 days. The larval stage varied from 207 to 382 days. The female pupal period lasted 10 to 33 days as compared with 39 to 111 days for the male pupae. The larva-like female adults lived up to 14 days. One female deposited 6,756 eggs. Male moths reared in the insectary lived 3 to 5 days and rarely mated in cages. Applications of 0.75 pound of actual dieldrin or 2 pounds of actual toxaphene per acre by helicopter or hose controlled small and medium-sized larvae. Two dipterous parasites, Sarcophaga (Sarcodexia) lambens Wiedemann and Achaetoneura sp., attack medium and large bagworns. Lphiau1ax sp., a braconid, parasitizes all sizes of larvae whereas Psychidosmicra sp. (? brethesi Blanch.), a chalcid, attacks only small larvae. Both parasites are considered important in the control of this bagworm. Psychidosmicra sp. is hyperparasitized by Spilochalcis sp. Other hymenopterous parasites occasionally found in smaller bagworms are Perisiorola sp., two new genera and species of Cryptinae, Phobetes , sp., Carinodes sp., and a new genus near Echthrus. Christolia sp., Casinaria sp., and Spilochalcis femorata (Fabricius) are suspected as bagworm parasites. Predacious ants frequently attack larvae of all sizes. Egg masses are attacked by unidentified mites. A microsporidian, Nosema sp., and a fungus, Beauvaria bassiana (Balsamo) Vuillmen, infect all larval stages. Two unknown larval predators, thought to be Anolis lizards, and a bird account for a major part of natural control.

Studies on the Flight Habits of Some Marked Insects

Abstract: Several thousand phosphorous32-and fluorescent-marked stable flies (Stomoxys calcitrans (L.)), several hundred horn flies (Haematobia irritans (L.)), and house flies (Musca domestica L.), and several thousand mosquitoes (Culex tarsalis Coquillett, C. peus Speiser, and Aedes dorsalis (Meigen)) were released in Lake County, Oregon, in September 1961. Labeling was efficiently accomplished by placing P32 in the diet of the insects at the rate of 1 microcurie/ml. Marked stable, house, and horn flies were recovered 1 and 5 miles from the release site. Activity of mosquitoes was apparently curtailed by low nightly temperatures since none were caught. The stable flies showed the most rapid dispersion with specimens being recovered .5 miles from the release point in slightly less than 2 hours.

Effects of Antimicrobial Agents on Micro-Organisms and Pink Bollworm Development

Abstract: Potassium sorbate and sodium benzoate were ineffective in controlling contaminants in nutrient agar at the concentrations tested. Sorbic acid, methyl paraben (methyl p -hydroxybenzoate) and butyl paraben (butyl p -hydroyxbenzoate) at 0.1% and formaldehyde at 0.05% controlled microbial growth for 15 days when incorporated into nutrient agar; however, the first three agents were less effective in wheat germ medium. In general, higher concentrations of the antimicrobial agents effectively controlled growth of contaminants but significantly lengthened larval and pupal development of the pink bollworm ( Pectinophora gossypiella (Saunders)). The formulation of 0.05% formaldehyde plus 0.15% methyl paraben controlled contamination and resulted in larval development equal to cotton squarereared pink bollworms.

Activation of Guthion by Tissue Preparations From the American Cockroach

Abstract: Activation of Guthion® ( O,O -dimethyl S-(4-oxo-1,2,3-benzotriazin-3-(4H)-ylmethyl) phosphorodithioate) and degradation of its active metabolite and P(O)S Guthion by whole tissues and tissue homogenates of the adult, female American cockroach, Periplaneta americana (L.), were estimated manometrically by inhibition of house fly ( Musca domestica L.) head cholinesterase. A Guthion-activating enzyme system is present in several tissues of the American cockroach. The most active whole tissues, in descending order, were: Malpighian tubules, fat body, heart, nerve cord, ovaries and caeca. The fat body probably has the greatest capacity for anticholinesterase production per insect. Because P(O)S Guthion and the active metabolite of Guthion were degraded by tissue homogenates, the activation of Guthion by tissue homogenates was studied by blocking degradation of the active metabolite with 0.01 M sodium fluoride. Under these conditions, homogenates of the midgut and caeca were most active, followed by Malpighian tubules, fat body, foregut, and hindgut. Activation with homogenates required oxygen and NADPH2 or other nicotinamide nucleotides as cofactors.

Development of Insecticidal Resistance by Soil Insects in Canada

Abstract: Tests on soil insects collected from a number of areas in Canada indicated that the dipterous insects are rapidly becoming resistant to the cyclodiene insecticides. Four species of root maggots were found to be resistant; the onion maggot, Hylemya antiqua (Meigen); the seed-corn maggot, H. cilicrura (Rondami) and the closely related species, H. liturata (Meigen); and the cabbage maggot, H. brassicae (Bouche). The spotted root fly, Euxesta notata (Wiedemann), exhibited a high degree of tolerance to aldrin and dieldrin. Diazinon® (D,O-diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), Trithion® ( O,O -diethyl S-p -chlorophenylthiomethyl phosphorodithioate), ethion, and V-C-13 ( O -, 2,4-dichlorophenyl O,O -diethyl phosphorothioate) were all highly toxic to adult flies of the Anthomyiidae. The Common cutworm species of economic importance in southwestern Ontario, Agrotis ipsilon (Hufnagel) and Peridroma saucia (Hubner), showed no indication of cyclodiene resistance. The organophosphate insecticides were generally less toxic to cutworms than the cyclodiene insecticides. The dark-sided cutworm, Euxoa messoria (Harris), was highly tolerant to dieldrin, DDT, and Diazinon. Cyclodiene resistance has developed in areas where broadcast applications of insecticides have been applied to the soil over several consecutive years. It was suggested that, in order to slow the development of oregano phosphate resistance, procedures other than broadcast applications should be utilized with the oregano phosphate insecticides when feasible.

Potentialities and progress in the development of chemosterilants for insect control.

Abstract: The possible use of chemosterilants for insect control represents an extension of the sterility principle which involves the rearing and release of insects made sterile by exposure to gamma radiation, as was done in the eradication of the screw-worm fly ( Cochliomyia hominivorax (Coquerel)) on the island of Curacao and from the Southeastern United States. Certain chemical compounds, classed as alkylating agents, have been found to produce sterility in several species of insects including the house fly ( Musca domestica L.), Mexican fruit fly ( Anastrepha ludens (Loew)), and the stable fly ( Stomoxys calcitrans (L.)). Apholate (2,2,4,4,6,6-hexahydro-2, 2,4,4,6.6-hexakis(1-aziridinyl)-1,3,5,2, 4,6-triazatriphosphorine) and aphoxide (tris(1-aziridinyl) phosphine oxide) are among the most active chemosterilants currently under investigations. When administered orally or by contact these compounds produce irreversible sterility without apparent adverse effects on the mating behavior and length of life of the insects. Although chemosterilants may prove equally or more useful than gamma radiation in the production of sterility in insects for release, they offer possibilities for achieving sterility in the natural population if safe and effective ways of using them can be developed. If ways of producing sterility can be developed in the natural population it would not be necessary to rear insects. This procedure for applying the sterility principle offers several important ad vantages over the conventional method of killing insects. Insects that are sterilized cannot reproduce and thus such effect is equivalent to killing the insects. In addition, the sterile insects compete with the normal insects to further decrease chances for reproduction. This bonus effect represents the greatest advantage over the conventional way of controlling insect populations. In addition, however, sterile insects in the population are capable of limiting reproduction because of "time" and "space" effects, factors which are absent in the killing procedure. Figures are presented which show the theoretical effects on boll weevil ( Anthonomus grandis Boheman) populations which are subjected to control by an insecticide and by a sterility agent.

An Investigation of the Cattle Louse Problem

Abstract: In a study on gains in weight versus louse infestations, 30 of the lousiest feeder heifers in a feed lot containing approximately 3,000 were selected. Two lots of 10 each were sprayed with insecticides for louse control, and the third was sprayed with water. After 42 days gains in weight of the treated lots were not significantly different from those of the control lot. Before treatment, louse infestations averaged light to moderate on all lots; 37 days after treatment, infestations in the control lot averaged very light to light, and only four lice were found in the two treated lots. A Hereford steer, very heavily infested with Haematopinus eurysternus (Nitzsch), under close observation for 4½ months, developed severe anemia, and would have died in the absence of louse control. When the lice were destroyed he improved markedly in gains in weight and feed efficiency. Rancher surveys, cattle buyer records, and population studies on slaughter cattle, indicated that infestations of this magnitude, although they occur regularly throughout Montana, do not ordinarily affect more than 1% or 2% of the cattle. Infestations on the rest of the population are probably of minor economic significance. Louse population studies on the freshly removed hides of 3,188 slaughter cattle indicated that in Montana, Herefords are most frequently and most heavily infested, and that Angus are least so; that H. eurysternus is economically the most important species, followed in order by Linognathus vituli (L.), Solenoptes capillatus End., and Damalinia bovis (L.); and that different breeds of age classes of cattle tend to he infested differently by the four different species of lice. From a n economic standpoint, louse control measures are probably justified on 5%, or fewer, of the cattle in Montana.

The Synergism of Substituted Phenyl N-methylcarbamates by Piperonyl Butoxide

Abstract: The toxicity of 40 substituted phenyl N -methylearbamates to the house fly, Musca domestica L., was re-evaluated with piperonyl butoxide as a synergist. There was no correlation between house fly toxicity and fly brain anticholinesterase activity when the carbamate was used alone. In general, the use of piperonyl butoxide with the carbamate increased the toxicity to levels which parallel anticholinesterase activity. An approximately linear relationship between the logarithm of toxicity and cholinesterase inhibition was obtained. The data support previous suggestions that variability in the toxicity of carbamates used alone is due to different detoxication rates in the insect.

Biology of the banded cucumber beetle, Diabrotica balteata, in Louisiana.

Abstract: The banded cucumber beetle, Diabrotica balteata LeConte, has become an increasingly important pest of sweet potato in Louisiana since 1958 In Louisiana, there are 6 or 7 generations per year Beetle activity was observed in the field during every month of the year Eggs were deposited in the soil singly or in clusters In the field as many as 12 were observed in a single cluster Under laboratory conditions, 20 to 100 eggs were laid during a 24-hour period Oviposition usually occurred at intervals of 2 to 3 days beginning when the female was about 3 weeks old and lasted from 2 to 8 weeks The number of days during which oviposition occurs ranged from 2 to 15, a single female laying as many as 849 eggs in a lifetime Three larval instars were observed during the larval feeding period Mean larval developmental period was 17 days at 80° F and 23 days at 70° F, when larvae were reared on sweet potato Pupation takes place within a pupal cell near the soil surface and the pupal period lasted 7 to 9 days at temperatures of 70°F, and 80°F

A Field Experiment in the Control of House Flies with Chemosterilant Baits

Abstract: Cornmeal baits containing 0.5% of aplioxide (tris(l-aziridinyl) phosphine oxide), a chemosterilant, were applied on an isolated refuse dump in the Florida Keys for the control of house flies ( Husca domestica . L.). Applications were made each week for 9 consecutive weeks, except during the second week. House fly populations were reduced from 47 per grid to 0 within 4 weeks, the proportion of egg masses (from females collected at the dump) containing at least 1 viable egg was reduced from 100% to 10% within 4 weeks, and the per cent hatch among all eggs laid was reduced to 1% within 5 weeks.

Initial Field Observations in California on Trioxys pallidus (Haliday) a Recently Introduced Parasite of the Walnut Aphid

Abstract: The aphidiine beaconed Trioxide pallideas (Holiday) was imported from Europe to California in 1959 and was successfully established on the walnut aphid, Chromaphis juglandicola (Kaltenbach) soon thereafter. The parasite has spread most rapidly in coastal San Diego County and is now distributed over approximately 1,000 square miles in that area. Strong foci also occur in Orange, Santa Barbara, and Ventura Counties. During 1961, study plots were established at three San Diego County localities, Rancho Santa Fe, Escondido, and Pauma Valley. Trends in parasitization of C. juglandicola were followed through most of the walnut-growing season. Parasitization was extremely heavy at Rancho Santa Fe and Escondido in late spring. Parasite activity remained intensive throughout the year at Rancho Santa Fe but slackened perceptibly in the summer at Escondido and Pauma Valley. This reflects, perhaps, adverse effects of more rigorous climatic conditions at these two stations. There was It general uptrend in parasitization at Escondido and Pauma Valley in the fall. Under favorable conditions T. pallidus appears to be an extremely effective parasite. It is fully synchronized with its host both spatially and temporally. Diapause is a key factor in this synchronization. Both aestival and hibernal diapause occur, assuring survival and presence of the wasp through periods of host absence or scarcity, and through climatic adversity.

The Host-Parasite Relationship of the European Corn Borer, Ostrinia nubilalis, and the Protozoan, Perezia pyraustae, in Delaware1

Abstract: A high incidence of Perezia pyraustae was found in European corn borer larvae collected in the Autumn of 1959. Four hundred additional larvae were collected in April 1960 and subjected to controlled laboratory studies of the host-parasite relationship. Of the 114 adults that emerged from these larvae, P. pyraustae was found in 85%. Eighty per cent of a sample of 50 dead larvae examined contained spores of this pathogen. P. pyraustae significantly reduced adult longevity in both males and females. The fecundity of infected females was greatly lowered as compared with no infected females. The number of viable eggs laid by infected females was somewhat lower, suggesting that the pathogen may also have adversely infuenced embryonic development. The results of this investigation, coupled with recent findings of workers in other areas of the country, suggest that P. pyraustae may be an important biotic factor in the regulation of the population density of the European corn borer in Delaware.

Chemical Induction of Sterility in the Stable Fly

Abstract: Three compounds, apholate (2,2,4,4,6,6-hexahydro-2,2,4,4,6,6-hexakis (1-aziridinyl)-1,3,.5,2,4,6-triazatriphosphorine), aphoxide (tris(1-aziridinyl)phosphine oxide), and methaphoxide (tris (2-methyl-1-aziridinyl)phosphine oxide), induced sterility in male and female stable flies ( Stomoxys calcitrans (L.)) when applied topically to adults. One microgram of apholate or methaphoxide per fly caused almost complete sterility when treated males were mated with treated females. Male stable flies were more sensitive to apholate and aphoxide than the females. Apholate sterilized adult stable flies even when applied after the females had begun laying fertile eggs. Apholate induced sterility when adults were exposed to a residual film. A 48-hour exposure was required with a film of 10 mg. per ½-pint jar. However, a film of 100 mg. per jar was effective with all exposure of I hour. When treated jars were stored indoors, the film was effective for 24 weeks.

Seasonal Biology of the Balsam Woolly Aphid on Mt. Mitchell, North Carolina

Abstract: Studies of the seasonal biology of the balsam woolly aphid, Chermes piceae Ratzeburg (Adelgidae: Homoptera), were carried out in 1960 following discovery of a severe infestation of this insect on Mt. Mitchell. Observations of aphid development were made in the field on 3- by 3-inch plots of bark on living trees. In addition, microscopic counts of aphids on bark samples were made at frequent intervals in the laboratory. Observations within the plots revealed as many as three generations per year. Data obtained from bark samples showed that most of the aphid population completed two generations.

The Ingestion of Dry Sugars by Adult Entomophagous Insects and the Use of This Feeding Habit for Measuring the Moisture Needs of Parasites

Abstract: The belief that adult insect parasites must acquire their foods from liquid or semifluid sources has made it difficult to assess accurately the moisture needs of different entomophagous species. It was found that many adult entomophagous insects can feed upon completely dry sugar. Parasitic Hymenoptera dissolve the dry sugar with a lapping movement of the glossa moistened with salivary fluids. Some adult predators use regurgitated fluids for dissolving the sugar before its ingestion. By comparing the survival of adult parasites supported on dry sugar at 0% relative humidity with that of adults given moist sugar at optimum moisture conditions, the aridity tolerance of a species may be assessed without interference by starvation or by liquid food intake. Examples of the use of this simple method for assessing the moisture needs of four species of parasites are presented.

The Effect of Plant Nutrition on the Fecundity of Two Strains of Two-Spotted Spider Mite

Abstract: Two strains of two-spotted spider mite ( Tetranychus telarius (L.)), widely different in susceptibility to organophosphorus acaricides, produced more progeny on lima bean plants as nitrogen supply and absorption were increased, However, in studies with resistant mites, a reduction in the number of progeny occurred on plants supplied the highest nitrogen level. The resistant mites produced more progeny on plants supplied high potassium levels, and the nonresistant mites on plants supplied high phosphorus levels. Increases in the number of progeny produced by either strain were correlated with the carbohydrate content of the leaf tissue. when carbohydrate was increased, with a corresponding increase in nitrogen supply and absorption, mites produced more progeny. At certain higher level of nitrogen supply and absorption, however, carbohydrate content of leaf tissue decreased and mites produced fewer progeny of failed to produce more progeny even though nitrogen absorption of the plant increased. Phosphorus and potassium supply alone and in combination with certain levels of nitrogen supply affected nitrogen absorption and total carbohydrate content of the leaf tissue.