摘要:

Parasitism rates were analyzed forHelicoverpa armigerafeeding on four different crops in western Tanzania (1982–1985), during a period in which all crops were inhabited by the insect. The major parasitoid species differed markedly in their crop associations, withPalexorista laxa,Apanteles diparopsidis, andChelonus curvimaculatusstrongly associated with sorghum,Cardiochilesspp. mostly associated with cotton, andCharopssp., mostly associated with the weed–cropCleomesp. ForP. laxa,Cardiochilesspp., andCharopssp., the crop effect explained about 50% of the variance in parasitism among crop, month, and year. This was less forA. diparopsidisandChelonus curvimaculatus, which were erratic in their occurrence from year to year. Implications of parasitoid–crop associations for biological control ofH. armigeraare discussed.

DOI:10.1093/ee/19.4.1141

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Five species of carabids (Pterostichus melanarius Illiger,Pterostichus lucublandusSay,Bembidion quadrimaculatum oppositumSay,Clivina fossorL., andAnisodactylus santaecrucisF.) were offered carrot weevil eggs, fourth instars, pupae, teneral or overwintered adults in single and multiple food choice tests. In single food tests, all species consumed three or more stages of carrot weevil. The smaller carabids (B. quadrimaculatum oppositumandC. fossor) were the best consumers of eggs; the largest carabid,P. melanarius, was the only species that consumed high numbers of teneral and overwintered adults. All species were good consumers of fourth instars and pupae. In multiple choice food tests,P. melanariusandC. fossorconsumed the same stages as in the single food tests and showed no preference for any particular weevil stage. In contrast,A. santaecrucisandB. quadrimaculatum oppositumhad a preference for pupae, whereasP. lucublandusselected fourth instars. These preferences were not shown in the single food tests indicating the importance of multiple choice food tests for assessment of polyphagous predators. In voracity tests,P. melanariusandP. lucublandusconsumed three times more thanA. santaecrucisorB. quadrimaculatum oppositum.

DOI:10.1093/ee/19.4.1146

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A multiple-embedded nuclear polyhedrosis virus (MNPV) was isolated and characterized from a field-collected, fourth-instar yellowstriped armyworm,Spodoptera ornithogalliGuenée, in Boone County, Missouri. The LC50value of this virus was determined to be 0.42 occlusion bodies (OB)/mm2for first instar and 7.0 OB/mm2for third instar.Heliothis zea(Boddie),S. frugiperda(J. E. Smith), andPlutella xylostella(L.) larvae were not susceptible to this MNPV. Mortality was observed inTrichoplusia ni(Hübner) larvae challenged with high concentrations; however, no occlusion bodies were observed in or recovered from tissue of survivors or cadavers, and liquefaction of cadavers did not occur. This MNPV appears to be specific forS. ornithogalli; further studies against otherSpodopteraspecies may be justified.

DOI:10.1093/ee/19.4.1150

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Three exotic larval parasites,Allorhogas pyralophagusMarsh andDigonogastra kimballiKirkland from Mexico andCotesia flavipes(Cameron) from the Indo-Australian region, were evaluated in enclosures in commercial corn fields in Castro County, Tex., against the southwestern corn borer,Diatraea grandiosellaDyar. Experiments conducted in 1986 measured the functional and numerical responses of the three parasites to varying host density. The effect of varying the number of searching parasites on parasitization and reproductive capacity was evaluated in 1987. The functional responses of the three parasites to host density were markedly different.D. kimballiexhibited the strongest response, which is hypothesized as a reflection of the coevolutionary history between this parasite and the southwestern corn borer. The responses of parasites to varying parasite density were not different among the three species. In both experiments, encapsulation of immature parasites ofC. flavipeswas observed. The numerical responses of the three parasites were weak; onlyC. flavipesproduced a greater number of female progeny than the number of females introduced per enclosure.

DOI:10.1093/ee/19.4.1155

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The pathogenicity ofBeauveria bassiana(Balsamo) Vuillemin andPaecilomyces fumosoroseus(Wize) Brown&Smith to the onion maggot,Delia antiqua(Meigen), was studied at 50% RH in the laboratory. Conidiospores ofP. fumosoroseussprayed on puparia of the onion maggot at the concentration 1 × 108ml−1(=4 × 105cm−2) increased pupal mortality to 47.5% as compared with 6.6% in the controls. There was no latent effect on adults that emerged from treated puparia. Spores ofB. bassianasprayed at the same concentration had no effect on pupal and adult mortality. Sixteen additional species of fungi were recovered from test puparia during reisolation ofB. bassianaandP. fumosoroseus. Species from the generaAspergillus,Fusarium,Geotrichum,Penicillium,Mucor, andScopulariopsiswere isolated,A. clavatusDesmazières being the most common among them. This fungus grew faster than the entomopathogens in vitro and might have inhibited their action in vivo.

DOI:10.1093/ee/19.4.1163

出版商:Oxford University Press    

年代:1990

数据来源: OUP

DOI:10.1093/ee/19.4.1168

出版商:Oxford University Press    

年代:1990

数据来源: OUP

DOI:10.1093/ee/19.4.1169

出版商:Oxford University Press    

年代:1990

数据来源: OUP

DOI:10.1093/ee/19.4.1170

出版商:Oxford University Press    

年代:1990

数据来源: OUP

DOI:10.1093/ee/19.4.1171

出版商:Oxford University Press    

年代:1990

数据来源: OUP