Pharmacodynamics of Different Insecticides in Microplitis croceipes (Hymenoptera: Braconidae), a Parasite of Lepidopteran Larvae
| Autor: | Edgar G. King, D. L. Bull, N. W. Pryor |
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| Rok vydání: | 1987 |
| Předmět: | |
| Zdroj: | Journal of Economic Entomology. 80:739-749 |
| ISSN: | 1938-291X 0022-0493 |
| DOI: | 10.1093/jee/80.4.739 |
| Popis: | Toxicity and fate of several insecticides topically applied to adults of Microplitis croceipes (Cresson), a larval parasite of Heliothis spp., were compared. LC50’s ranged from 0.008 to 0.658 μg per insect; order of toxicity was methyl parathion > dieldrin > aldrin > malathion > dimethoate > cis -permethrin > trans -permethrin > DDT > fenvalerate. Differences in susceptibility (ca. 2-fold) between the cis and trans isomers of permethrin, and the appreciable tolerance of M. croceipes to these compounds as well as to DDT and fenvalerate, did not appear to be related to differences in rates of penetration or metabolic degradation. These variations in susceptibility may be due to differences in interactions of the compounds with neural receptors. Comparisons of the topical toxicity data for cis/trans -permethrin and fenvalerate on M. croceipes with data reported for unparasitized third instars of the tobacco budworm, Heliothis virescens (F.), indicate that the parasite has a considerable selective advantage over the pest (ca. 25- and 300-fold, respectively). The relatively high level of toxicity of malathion (LC50 = 0.04 μg per insect) to M. croceipes was most likely related to the extremely rapid penetration of the compound, coupled with its metabolic transformation to the highly toxic oxygen analog (malaoxon). Comparative in vitro studies of enzyme activity in homogenate preparations indicated the specific activities of glutathione-dependent transferases in adult M. croceipes abdomens and midguts of fifth instar tobacco budworms were somewhat similar. However, the specific activity of soluble esterases was ca. 100-fold higher in the pest. In vivo and in vitro determinations of aldrin epoxidase demonstrated the presence of an active monooxygenase system in M. croceipes; however, the activity of this enzyme is somewhat less in the parasite than in the tobacco budworm. |
| Databáze: | OpenAIRE |
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