Soybean Aphids Hot Topic
One of the major meetings held every year in December is the Fertilizer and Pesticide Short Course at the Minneapolis Convention Center. It is sponsored by the Minnesota Crop Production Retailers Association and the University of Minnesota Extension Service. There is a big trade show and different sessions on a wide variety of agronomic topics. One of the hot topics was soybean aphids and the pyrethroid class of insecticides.
University of Minnesota Extension Entomologist Robert Koch Ph.D. has documented some populations of aphids in Minnesota do have resistance to pyrethroids. Those areas are mainly in northwestern and southwestern Minnesota. Other areas in Minnesota pyrethroids are still effective at this point. The concern is that there are only 3 classes of insecticides that can be used to control soybean aphids.
If we lose the pyrethroids that means two classes left to control soybean aphids. There are environmental groups lobbying the EPA and Minnesota Department of Agriculture to have a regulatory review of some of the remaining insecticides. We are not there yet but there could be a day when there is little we can do to control soybean aphids.
Fortunately we do not have soybean aphid outbreaks every year. In fact I have not seen threshold levels on my farm for 3 years. But I sure want to be able to control soybean aphids if I need to. I have seen data that shows that soybean aphids can decrease yields by 10 to 15 bushel an acre.
Robert Koch Ph.D. said University of Minnesota soybean breeders are working on aphid resistance soybean varieties but they are a few years away yet. In the mean time save your bullets. Make sure you are at threshold levels before you apply an insecticide for soybean aphids. After applications evaluate aphid levels and use a different class of insecticides if a retreatment is needed.