Soybean Aphid - Management

Management

The use of insecticides to control populations of soybean aphids in soybean is the most effective management tactic in North America. Insecticides available to soybean producers for controlling soybean aphids include both foliar-applied treatments and seed-applied treatments. Although seed-applied treatments have proven to be a convenient delivery method for insect control, studies have experienced inconsistent results regarding their efficacy against the soybean aphid. Management decisions should be made with an understanding of soybean aphid life history and sound scouting practices rooted in the principles of integrated pest management.

The current economic threshold for soybean aphids states that an insecticide application is warranted when soybean aphid densities reach 250 soybean aphids per plant, 80% of sampled plants are infested, the population is currently increasing, and few natural enemies are observed in the field. This recommendation is only valid from the R1 (beginning bloom) to R5 (beginning seed) growth stages and is based on an economic injury level of 674 soybean aphids per plant. Due to the clumped spatial distribution of soybean aphids, Onstad et al. (2005) recommend that 50 plants should be sampled within a field to attain an accurate representation of densities of soybean aphids. Soybean producers can choose from a variety of foliar insecticides from the carbamate, pyrethroid, and organophosphate chemical families to control soybean aphids.

Evidence indicates that foliar insecticide applications can reduce symptoms associated with soybean aphid infestations, including curled leaves, shortened stems, stunted plants, and premature defoliation. Foliar insecticide applications can also prevent yield loss associated with high densities of soybean aphids. However, some risks are associated with the use of foliar insecticide applications, especially if integrated pest management principles are abandoned. A single, well-timed application may not sufficiently control soybean aphids and prevent yield loss, especially if large quantities of soybean aphids are surviving on lower leaves. Foliar insecticide applications can work detrimentally if nontarget effects are experienced, such as the unintended death of beneficial natural enemies.