Analog-Synergism of Several Carbamate Insecticides1

Combinations of two carbamate insecticides applied jointly were found to increase mortality beyond the expected additive effect on two of the three insect species tested. Dimetilan® (3-methyl-5-pyrazolyl dimethylcarbamate) was found to synergize the more potent in vitro cholinesterase inhibitors Sevin® (1-naphthyl methylcarbamate) and Pyrolan® (5-(3-methyl-1-phenylpyrazolyl) dimethylcarbamate) on German cockroaches (Blattella germanica (L.)) and house flies (Musca domestica L.)) It was suggested that those two species possess a detoxifying enzyme "carbamate esterase" which destroys the carbamate insecticides. Partial inhibition of this enzyme by Dimetilan was suggested as an explanation for its synergistic action with other carbamate insecticides that are broken down easily by the detoxifying enzyme. The relative toxicity of the tested carbamates to the large milkweed bug (Oncopeltus fasciatus (Dall.)) was different from flies and cockroaches and there was no apparent synergism.