Studies on the insecticide resistance in cotton stainers. Dysdercus Spp. (hemiptera:pyrrhocoridae), in Kenya.

Abstract

1. In the present investigation field and laboratory strains of four species of cotton stainers, Dysdercus fasciatus, Q. nigrofasciatus, D. superstitiosus and Q. cardinalis, were used to study the insecticide resistance phenomenon. 2. Three insecticides, technical grades carbaryl (99.9% pure), lindane (99.9%) and methidathion (92.7%),were used. Each insecticide was diluted with solvent Isobutyl methyl ketone into 9 different concentrations ranging from 29.3 to 10,000 mg/l. 3. The different instars of the two sexes of D. fasciatus showed varying susceptibilities to carbaryl. The 4th instar nymphs (mixed sexes) gave an LC50 of 102.76 mg/l while the 5th instar male and females gave LC50,s of 121.08 .and 371.76 mg/1, respectively. The adult males and females showed LC50,s of 664.20 and 694.20 mg/~respectively. The 5th instar 4-dayold female was found to be the most convenient stage to do bio-assays with.