The effect of the systemic fungicide benomyl on survival and reproduction of the bird cherry aphid (Rhopalosiphum padi)

Weight gain and intrinsic rate of population increase (r_m) of Rhopalosiphum padi were measured on wheat plants given soil drenches of benomyl at various concentrations. Reduced weight gain occurred with concentrations as low as 3.125 ppm. Mortality of aphids significantly exceeded control mortality at 25 ppm, and no aphids survived concentrations above 50 ppm. Development time was extended at 12.5 ppm and above. Reductions in fecundity and r_m became statistically significant by 25 ppm. Topical application of benomyl at 100 ppm or above increased aphid mortality, which reached 97% at 400 ppm. Weight gain of aphids was also reduced by topical application at 100 ppm. A factorial experiment showed absence of interaction between the effects on aphid weight of soil drench application to plants and topical application to aphids.