Soybean aphid control with seed-applied insecticides

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Seed treatment insecticides such as Cruiser and Gaucho have been marketed for early season soybean aphid and bean leaf beetle control. Results from two years of performance trials conducted in Michigan indicate that soybean yield response to these seed-applied insecticides depends primarily upon the aphid pressure experienced during the early growing season.

In 2004, when aphid pressure was light, the soybean yield response to Cruiser and Gaucho averaged just under 1 bushel per acre over six locations across the state. Conversely, in 2005, with heavy early season aphid pressure, yield response to these seed applied insecticides averaged 6 bushel per acre across four Michigan locations. Results of the 2005 trials showed there was early season suppression of aphid populations through the R1 (flowering) growth stage. However, as aphid pressure increased over the growing season, the level of population suppression seen by the seed-applied insecticide treatments decreased significantly. Based on this data, it appears unlikely that an insecticide seed treatment would keep aphids from reaching economic threshold and prevent the need for a foliar-applied insecticide application during a heavy aphid pressure year. However, some yield benefit may be gained if early season aphid pressure is high.

Late summer scouting in 2005 and early season scouting this spring suggests that aphid levels may be down in 2006 throughout most of the state. However, some areas, especially those with nearby Buckthorn infestations, which serve as the overwintering host for the aphid, may experience high localized soybean aphid populations. In deciding whether to invest in these insecticidal soybean seed treatments, it is important to assess expected early season aphid pressure and weigh that against the cost of the product.

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