Aphid response to vegetation diversity and insecticide applications

A field experiment was conducted to determine the effects of vegetation diversity and pesticide disturbance on insect herbivore populations in a broccoli agroecosystem. Varying concentrations of the selective insecticide imidacloprid were applied to patches of broccoli surrounded by bare ground or weedy vegetation during one growing season in western Washington (USA). Aphids responded to an interaction between vegetation diversity and pesticide concentration, and their response varied as a function of time after pesticide disturbance. These results suggest that simplistic, linear predictions of the effects of chemical disturbance and natural enemies on insect herbivore populations will not be forthcoming.