The effect of sub‐lethal dosages of the synthetic pyrethroid fenvalerate on the reproductive rate of the aphid Myzus persicae

A series of experiments in the laboratory and greenhouse, were designed to test the possible causes of the field resurgence of the aphid Myzus persicae . Stimulation of reproduction occurred at topical dosages of around the LD 5 value. Residual film tests indicated a significant depression in fecundity when aphids were held on sub‐lethal deposits of fenvalerate, even at dosages below the LD 5 value. Trends in the population build‐up experiments in the greenhouse suggested there may be some stimulation when aphids are confined to aged deposits of fenvalerate 7 days after treatment, but the slight increase was not significant.