The toxicities of some analogues of dieldrin, endosulfan and isobenzan to bloodsucking diptera, especially tsetse flies

Abstract

AbstractThe dieldrin analogue, 1, 8, 9, 10, 11, 11‐hexachloro‐4, 5‐exo‐epoxy‐2, 3‐7, 6‐endo‐tricyclo‐[6.2.1.02, 7]undec‐9‐ene (HEOM), and the isomeric 3, 4‐exo‐epoxy‐and 3, 6‐endo‐epoxy compounds (HCE and ODA, respectively), incorporating structural modifications of the non‐chlorinated ring system, were tested against adult mosquitoes (mainly Anopheles stephensi List.), tsetse flies (mainly Glossina austeni Newst.) and stable flies, Stomoxys calcitrans (L.). The order of toxicity was ODA > HCE > HEOM. In further tests of residual activity against A. stephensi, ODA was better than HCE but neither was sufficiently persistent to be a promising mosquito toxicant. Analogues of dieldrin (HEOD), endosulfan and isobenzan with reduced numbers of chlorine atoms were tested against G. austeni. In the pentachloro‐analogues of dieldrin and α‐endosulfan, the anti‐bridge chlorine was more important than the syn‐chlorine for toxicity. The general effect of reductive dechlorination was to reduce toxicity, but the effect was small for some endosulfan analogues and in one case there was an increase in toxicity. In the main, toxicities of the endosulfan analogues compared favourably with those of the dieldrin analogues. However, toxicity fell drastically following replacement of the second ethylenic chlorine in isobenzan. The effect of these structural changes on toxicity evidently varied from one series to another and was influenced in an unpredictable manner by the rest of the molecule.