Abstract
Synergism of carbamates and organophosphorus insecticides against an organophosphate-resistant strain of rice stem borer, Chilo suppressalis WALKER, was investigated. Although no synergism was observed with the combination of fenitrothion and each of four substituted phenylcarbamates, carbaryl, methomyl or bendiocarb, a remarkable elevation of co-toxicity was observed with the combination of pirimicarb and fenitrothion. Pirimicarb, a selective aphicide, showed a high synergistic action with all dimethylthiophosphates tested, especially with compounds having a hetero ring in their structure. However, synergism was not observed with diethylthiophosphates, phosphates and dithiophosphates other than malathion. Pirimicarb showed no synergistic action with organophosphorus insecticides against the susceptible strain.
