Synergistic effects of verbutin with dibenzoylhydrazine-type ecdysteroid agonists on larvae of Aedes aegypti (Diptera : Culicidae)

There were no significant differences between the activities of RH-5849, te bufenotide, and halofenozide on 4th instars of Aedes aegypti (L.). Methoxyf enozide was almost 10 times more active (LC50 = 0.22 mg kg(-1)) than the ot her ecdysteroid agonists. Halofenozide, methoxyfenozide, tebufenozide, and RH-5849 caused premature wing disk evagination and also caused the larval t horax to bloat on the dorsoventral sides resulting in a larval-pupal interm ediate thorax. Methoxyfenozide induced these effects in the lowest concentr ation. Further molting disturbances (e.g., hanging larval exuvium, head cap sule slippage failure) and a more intense sclerotization and melanization o f the thorax also were noted. Although verbutin did not show significant ef fects with any of the tested ecdysteroid agonists under actual test conditi ons, some improvements could be found in the use of RH-5849 and tebufenozid e.