DIFFERENCES IN INSECTICIDE SUSCEPTIBILITY BETWEEN ADULT AND LARVAL CNAPHALOCROCIS-MEDINALIS GUENEE (LEPIDOPTERA, PYRALIDAE)

The rice leaf folder, Cnaphalocrocis medinalis GUENEE, is a serious pe st of rice plants in southwest Japan, and is a main target of chemical control. The susceptibility of adults and larvae to insecticide was c ompared by topical application. The LD(50) of cartap for adults was sm aller than that for larvae. However, in the case of monocrotophos and acephate, the LD(50) values for adults were much larger than those for larvae. Analysis of the fate of the insecticides showed that the inta ke of monocrotophos and acephate was larger for adults than larvae. Fo r acephate, less methamidophos was produced in adults than in larvae, but a homogenate of adults produced more methamidophos from acephate t han for larvae. There were no differences in sensitivity to those orga nophosphorus insecticides of acethylcholinesterase between adults and larvae. It is believed that monocrotophos and acephate are stored in s ome tissues in adults.