Toward management guidelines for the soybean aphid in Quebec. I. Feeding damage in relationship to seasonality of infestation and incidence of native predators

Abstract

AbstractA study was conducted in 2004 and 2005 to test the hypotheses that the severity of damage caused by the soybean aphid, Aphis glycines (Hemiptera: Aphididae), is minimized by the activity of predators and declines with the maturity of soybeans, Glycine max (L.) Merr. (Fabaceae), at the time of infestation. In caged subplots where predators were excluded, aphids attained a high density following experimental infestation of soybeans, resulting in severe reductions of yield, particularly when plants were infested early in the season. A guild of generalist predators consisting predominantly of ladybird beetles colonized plants in uncaged subplots, resulting in a low rate of population growth following infestation of soybeans with aphids and a relatively weak impact on the soybean yield. The soybean yield declined as the density of aphids (number per plant), and the maturity of soybeans at the time of infestation, increased. Our results suggest that A. glycines represents an occasional pest of soybean in Quebec, because of (i) temporal asynchrony between the late-season infestation by aphids and the most susceptible phenological stage of soybeans (vegetative or flowering) and (ii) biological control by natural enemies.