[Factors affecting the efficacy of 2 growth regulator compounds, OMS 3010 (phenoxycarb) and OMS 3019 (ethoxypyridine), on larvae of the Simulium damnosum complex].

Two insect growth regulators (IGR'S) acting as juvenile hormone analogs (JHA'S), OMS 3010 (phenoxycarb) and OMS 3019 (ethoxypyridine) were selected after a screening of several compounds proposed by industry on black fly larvae of the Simulium damnosum complex (Diptera: Simuliidae) the vector of onchocerciasis in West Africa. Bioassays were designed to study two parameters: larval age and exposure time. The results showed that these compounds are more efficient on old larvae (6th and 7th instars) than young larvae (3rd, 4th and 5th instars). However, exposure time seems essential. The black fly larvae live in fast running water courses. Thus, it is difficult to insure a prolonged exposure time in natural conditions. Though being active on black fly larvae, three factors are limiting the prospects for operational use of these two compounds: high dosages, limited effectiveness on young instar larvae and exposure time.