Source: Iowa State University Extension

Insecticide-resistant soybean aphids have emerged as a new challenge to farmers throughout the upper Midwest. In a new regional publication, we suggest strategies for managing soybean aphids resistant to pyrethroid insecticides.

A few key points for managing aphids are:
•Scout and treat soybean aphids based on the economic threshold (250 per plant on 80% of aphids until R5.5).
•Use sufficient volume and pressure to make contact with aphids and use labeled rates of insecticides.
•Check efficacy of insecticide 3-5 days after application to determine knockdown rate.
•Alternate insecticide groups if fields need to be retreated.

To assist with alternation (rotation) of insecticides, we summarize different insecticides (and their corresponding insecticide groups) available for soybean aphid management. This new publication, entitled “Management of Insecticide-Resistant Soybean Aphids,” is available at the ISU Extension Store.

Management of soybean aphid since 2000 has relied primarily on the use of foliar-applied insecticides. In a recent scientific paper, the first occurrence of insecticide-resistant soybean aphids in North America was documented in the U.S. Pyrethroid-resistant soybean aphids has now been observed over three years and from much of Minnesota and parts of Iowa, South Dakota, North Dakota and Manitoba. Insecticide resistance in this highly mobile pest with a complicated life cycle, will likely continue to pose a challenge to soybean production in coming years. Growers and agricultural professionals should carefully evaluate their soybean aphid management practices.