Iowa State University Extension and Outreach experts recently shared their evaluation of the 2019 growing season and how insecticides affected planting. As they note, the year was particularly challenging for producers across the state, as several species of insects were observed in soybean crops amidst the cold, wet conditions of the spring.
Thistle caterpillar was the most abundant insect observed across Iowa, but it was not the only troublesome pest. Multiple species of caterpillars, Japanese beetle, soybean aphid, and soybean gall midge were all problematic for producers.
The exponential growth of soybean aphid occurred in August, with peak aphid populations occurring in early September. However, yield differences among treatments were not dramatic, as infestations occurred late in the season.
High numbers of the Japanese beetle were observed during the growing season, but the level of defoliation was low and did not result in measurable yield loss.
The emergence of soybean gall midge was continuous throughout the summer months in the state. ISU Extension and Outreach researchers observed the pest at the ISU Northwest Research Farm in Sutherland and a commercial soybean field near Griswold, Iowa. Compared to Sutherland, midge pressure appeared to be greater at Griswold, but this was a controlled observance over the course of the season.
The ISU Soybean Research Laboratory conducts its research annually. More information on their results can be found on the ISU Extension and Outreach website.