Evaluation of two new insect growth regulators against mosquitoes in the laboratory

Biological activity of two new IGRs was studied under laboratory conditions against 2nd- and 4th-instar larvae and pupae of Anopheles quadrimaculatus, Aedes aegypti and Culex tarsalis. The IGR S-21149, an oxime [0-(2-(4'-Phenoxyphenoxy)ethyl propionaldoxime], produced an overall mortality or inhibition of emergence of 95% (when 4th instar treated) at 0.0047, 0.0013 and 0.00041 mg/liter in the three species, respectively. The EI95 values for the second IGR S-31183, a pyridine compound, [1-(4'-Phenoxyphenoxy)-2-(2'pyridyloxy) propane] were 0.017, 0.0026 and 0.00032 mg/liter for the three species, respectively. Both materials in general were less active against 2nd than 4th-instar larvae, except that the 2nd- and 4th instars of An. quadrimaculatus were equally susceptible. Pupae treated at up to 0.1 mg/liter showed no mortality in the pupal or the ensuing adult stages.