摘要:

Eucelatoria bryaniSabrosky larvae, which had developed for the first 20–28 h in the hostHeliothis virescens(F.), were fed artificial diets for the remainder of the larval stage. The most effective of three amino acid mixtures tested increased mean adult yields ca. l.8-fold over yields obtained with a previous diet. Compared with diets otherwise devoid of proteins, yields ofE. bryaniadults were increased 4.2- to 5.7-fold by the addition of defatted toasted soy flour and 3.3-fold by bovine serum albumin (BSA). The most effective diet tested produced mean yields as high as 39%; this was a 2.8-fold increase in adult yields over the most effective previously reported artificial diet for tachinids. When BSA was replaced by soy flour (which costs 0.015 per liter at the concentration used in the current diet), the cost of the artificial diet was reduced by 4.18 per liter. Highest yields of puparia and adults ofE. bryaniwere obtained when the pH of the artificial diet was 5.5–8.0.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1111

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Five experimental maize hybrids with husk tightness rating on a scale of one (relatively tight) to four (relatively loose) were evaluated for preharvest kernel aflatoxin contamination in Iowa, Missouri, and Georgia. Hybrids were exposed to treatments of European corn borer (ECB),Ostrinia nubilalis(Hübner); corn earworm (CEW),Heliothis zea(Boddie);Aspergillus flavus(AF) Link ex Fr., and combinations of each insect and the pathogen. A control consisted of hybrid plots with no treatment. Each location differed significantly in the parts per billion of aflatoxin contamination, with geometric means of 4, 30, and 214 in Iowa, Missouri, and Georgia samples, respectively. Interactions among locations, hybrids, infestations, and infestation/inoculation treatments were not significant. There was no significant difference in aflatoxin contamination among treatments, but mean values for ECB-infested samples were of lower magnitude than for CEW-infested samples, whether they were inoculated withA. flavusor not. Results demonstrated that kernels of tight-husked hybrids contained significantly less aflatoxin contamination than did those of loose-husked ones.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1116

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Laboratory life tables were constructed forGraminella nigrifrons(Forbes) using Johnsongrass and corn as hosts. Daily mortality and fecundity schedules were established to estimate net reproductive rate and instantaneous rate of population increase on each host. Nymphal mortality on Johnsongrass was greatest in the fifth instar. In general, nymphal mortality was higher on corn and was greatest in the second, third, and fourth instars. Net reproductive rate and instantaneous rate of population increase were higher on Johnsongrass than on corn. This was attributed to higher probabilities of survival to the midpoint of any stage or age interval and higher numbers of female eggs per female per week on Johnsongrass. Mean generation time was essentially the same for each host.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1119

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Three maize cultivars that had shown differences in response toChilo partellus(Swinhoe) adults and larvae were evaluated for their relative ability to withstand larval infestation and damage. Three treatment regimes, protection by insecticides, artificial infestation, and natural infestation, were adopted.C. partelluswas the predominant species during the whorl stage of crop development.Eldana saccharinaWalker appeared during the tassel emergence stage and persisted through harvest. Treatment, cultivar, and interaction effects were significant for maize foliar damage, stalk breakage, and ear drop. Stalk tunneling was affected by treatment and cultivar effects but number of entrance holes per plant was affected by treatment only. A larval survival index, the ratio of exit to entrance holes per stem, was higher for ‘Inbred A’ than for the other cultivars, suggesting some antibiosis in the other cultivars. Yield reduction between the protected and infested treatments was 71.4% for ‘Inbred A’ compared with 3.1% for ‘ICZ2-CM’. Of the primary damage symptoms, foliar damage correlated better with yield loss than stalk tunneling. When the yield reduction and leaf damage responses of each cultivar were partitioned into quadrants, resistance in ‘ICZ1-CM’ and ‘ICZ2-CM’ appeared to be antibiosis perhaps together with tolerance or nonpreference, whereas ‘Inbred A’ had none of these qualities.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1124

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

First instars of common green lacewing,Chrysoperla carnea(Stephens), were selected in the laboratory for resistance to carbaryl. After four selections with carbaryl, mortality of larvae decreased from 98% to between 10 and 20% at concentrations well above field rates. Adults of the resistant strain showed significantly greater survival than those of the unselected strain, but still succumbed to rates of carbaryl commonly used in the field. Genetic analyses demonstrated that the resistance does not fit a model of a single completely dominant gene. Tests using the oxidase inhibitor piperonyl butoxide and the esterase inhibitor phenyl saligenin cyclic phosphonate suggest that both oxidase and esterase enzymes contribute to the resistance. No significant cross-resistance to the carbamates propoxur, methomyl, and carbofuran was found. When reared in absence of carbaryl, the carbaryl-resistant strain exhibited lower larval and pupal survival and produced fewer females than the colony from which it was derived. However, its fecundity was significantly higher and adult longevity slightly higher, which compensated in part for reduced survival of immature stages.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1130

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Simulated tobacco hornworm,Manduca sexta(L.), defoliation was conducted by hand at four growth stages of tobacco,Nicotiana tabacum(L.), to investigate potential compensatory mechanisms for buffering foliar losses. Plants defoliated at plant establishment and posttopping growth stages employed several compensatory processes including a) periods of increased efficiency in assimilating dry matter, occasionally correlated with increases in chlorophyll, soluble proteins, and ribulose 1,5-bisphosphate carboxylase oxygenase content; b) partitioning of assimilates to leaf tissue at expense of support structures; c) increased leaf area per unit of total plant dry weight; d) delayed plant senescence. At maturity, despite these compensatory mechanisms, growth and economic yield were significantly lower among plants defoliated before the topping growth stage. Our results suggest that reduction in growth and yield was related to summation of reduced leaf area and lower net assimilation rate among remaining foliage. Plants defoliated at the posttopping stage, however, showed no significant yield loss or impairment of growth. This study provides additional evidence that plants have evolved physiological mechanisms for minimizing adverse effects of defoliation by leaf-chewing insects

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1137

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Sample trees of European white birch,Betula pendulaRoth, in Albany, on San Francisco Bay in northern California, were characterized according to tree vigor, microclimate, isolation from other birches, and homeowner maintenance practices. Discriminant analysis was used to distinguish between trees that developed large aphid populations and those that did not. The resulting discriminant function correctly predicted aphid population load for 91.3% of all study trees. Shading of the tree canopy was the single most important variable discriminating between tree groups.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1145

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Young adults ofOoencyrtus kuvanae(Howard) were held at different photoperiods and periodically supplied with gypsy moth,Lymantria dispar(L.), eggs while their progeny production and longevity were noted. Females reared at 10:14 (L:D) and 12:12 photoperiods produced fewer progeny but lived longer than those held at 14:10 or 16:8 photoperiods. Switching females from a 10:14 to a 16:8 photoperiod after 12 days (or vice versa) did not influence progeny production; females continued to reproduce as they would have if photoperiods had not been changed. This suggests that the initial photoperiod environment of the adult is important. Dissections showed that number of mature eggs in ovaries of females held at a 16:8 photoperiod increased more than that in ovaries of females held at a 10:14 photoperiod, corroborating progeny production results. Females preconditioned to long or short photoperiods for 2 weeks did not differ in longevity when held subsequently at low temperatures.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1149

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Conidia ofEntomophthora muscae(Cohn), collected from the onion fly,Delia antiqua(Meigen), produced secondary eonidia at vapor pressure deficits from 0.0 to 3.6, but at highly reduced rates when compared with germination in free water. Germ tubes (the invasive stage) were only produced in the free-water and saturated-atmosphere treatments. Germination rates for these treatments were temperature-dependent; the optimal germination temperature was close to 21°C. The upper and lower conidial germination limits were found to be between 26.7 and 32.2°C and 1.0 and 4.4°C, respectively. Germination and survival in the field were affected by the habitat where the conidia were deposited. Onions, carrots, and grassy border areas (the main sites ofE. muscaesporulation in the onion agroecosystem) affected germination and survival differentially based on the amount of cover in each canopy and the location of the conidia within the canopy. On four experimental dates, conidia experienced nearly 100% mortality after a single day of exposure to full sun. Fungicide applications were detrimental to conidial survival in the field.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1154

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Tobacco budworm,Heliothis virescens(F.), and corn earworm,H. zea(Boddie), were reared on diets containing various concentrations of the multiple-embedded, nuclear polyhedrosis virus (NPV) fromH. armigera(Hübner) andBacillus thuringiensis(Berliner) (B.t.) (HD-1 isolate), both individually and as mixtures. Addition of NPV did not significantly affect the 7-day mortality due to normally lethal concentrations ofB.t., but the addition ofB.t.to normally lethal concentrations of NPV reduced mortality. An apparent synergistic relationship occurred between the pathogens at a normally sublethal concentration.H. virescenslarvae fed on NPV were smaller at all concentrations tested, but their weight was not related to concentration of the virus. Weight of survivingH. zealarvae was affected only by high concentrations of NPV. Normally sublethal concentrations ofB.t.affected larval weight of both species, and the weights were inversely proportional to the concentration ofB.t.

ISSN:1754-5692    

DOI:10.1093/ee/15.6.1161

出版商:Oxford University Press    

年代:1986

数据来源: OUP