While we were digging roots this week, we noticed that Japanese beetles are still abundant and active in cornfields and soybean fields. In addition, corn leaf aphids were observed in several cornfields. Although we are beyond the pollination period for most fields in the state, high densities of corn leaf aphids can still cause potential yield losses for those fields under severe moisture stress. Bean leaf beetles also were numerous in many soybean fields in our areawide study.|
We have already discussed the importance of monitoring your soybean fields for insect defoliation in a previous issue of the Bulletin. So, with the combined leaf-feeding activities of corn rootworm adults (at least in east-central Illinois), bean leaf beetles, grasshoppers, and a variety of soybean caterpillars, now is the time to take a walk through your soybean field to assess the level of defoliation. Soybean fields that average 20 percent defoliation between bloom through the pod-fill stage of development may warrant a rescue treatment.
A final thought: don't forget that as soybean fields move through the pod-filling stage later this summer, they remain susceptible to many insect pests. We'll address the topic of insect injury to pods in a forthcoming issue of the Bulletin.--Mike Gray, Kevin Steffey