LABORATORY AND FIELD TRIALS OF FENTHION AND CYFLUTHRIN AGAINST MANSONIA-UNIFORMIS LARVAE

A laboratory bioassay of insecticides against laboratory-reared late t hird/early fourth-instar larvae of Mansonia uniformis indicated that t he synthetic pyrethroids tested (cyfluthrin and permethrin) were more active than the organophosphate compounds tested (chlorpyrifos, fenthi on, and temephos). The LC(50) values ranged from 0.09 (cyfluthrin) to 7.68 mu g/l (temephos). Field trials of fenthion (Baytex GR2) and cyfl uthrin (Baythroid H10WP) against laboratory-cultured late third/early fourth-instar larvae of Mansonia uniformis in floating screened cages were conducted in small plots on Penang Island, Malaysia. At respectiv e doses of 0.50 and 0.30 g/m(2) (5.0 and 3.0 kg/ha), both fenthion and cyfluthrin caused more than 90% mortality of the Mansonia larvae expo sed at 0 hour post-treatment. The use of these larvicides for the cont rol of Mansonia larvae in open field environments is discussed.