Soybean aphids have been recovered this week from both soybeans and buckthorn at the Rosemont Research & Outreach Center. This is the earliest that soybean aphid has been collected from soybean in Minnesota. Plants at Rosemont are mostly in the VC stage, just emerging from the ground, to V-1 (first true leaves). In addition, colonies of soybean aphids were found on buckthorn bordering fields on the St. Paul campus. Surveys in the NW part of the state have not indicated the presence of soybean aphid yet, nor have they been found in SWROC in Lamberton according to Bruce Potter.

This is not necessarily cause for concern. Early appearance doesn’t necessarily indicate early problems in commercial fields; much depends on how well the colonies become established and how quickly they grow in number. Weather conditions across the state are generally favorable for aphid reproduction at the moment but there are chances for showers and thunderstorms in most of the state by late in the week. In addition, establishing aphid populations are very susceptible to predation and there is an abundance of ladybird beetles observed in soybean fields so aphids may never reach damaging levels.

Treatment thresholds for soybean aphids are 200-250 aphids per plant with more than 80% of the plants with a population that is still on the increase. It is not advisable to treat aphids before they reach treatment thresholds, especially early in the season. At this point even using insecticides with longer residual activity against aphids will not eliminate the risk of re-infestation later in the season. Populations may also come under natural control and not require subsequent treatment. Scouting is the key.