Thomas G. Cullen

Insecticidal activity and mode of action of 2,4-diaminopyrimidines

Three 2,4-diaminopyrimidines were tested against several insect species. They were active against lepidopteran pests with LC 50 values <3 mg liter -1 for most species tested. They were also active against two-spotted spider mite, Tetranychus urticae, (LC 50 10-40 mg liter -1 ). Folinate, but not hypoxanthine or thymidine was found to be an effective rescue agent, requiring a concentration of 100 mg liter -1 diet to rescue half of the intoxicated larvae. The results confirm dihydrofolate reductase to be the site of action for these insecticides and are consistent with the mode of action of folinate rescue in mammals.