During the later stages of June and early July, it will become increasingly important to monitor corn and soybean fields for some important pests warns University of Illinois Professor of Entomology and Crop Sciences Extension Coordinator Mike Gray. "For many areas of Illinois, the dry and hot weather makes this recommendation even more important because crops are increasingly vulnerable to yield loss under these stressful conditions," he says.
Photo by USDA ARS, Bugwood.org
Japanese beetles can now be found throughout the state of Illinois. They can cause injury and subsequent yield loss in both corn and soybeans. In soybeans, Japanese beetles are one of many defoliators to monitor. Rescue treatments may be warranted if defoliation levels reach 30% prior to bloom and 20% between bloom and pod fill.
In corn, the key concern is the potential for excessive silk clipping. Plants that are under severe moisture stress are vulnerable to this type of injury because they cannot grow sufficient silk tissue to keep up with the beetles' clipping activity. During the reproductive phase of plant development, a rescue treatment may be needed if there are three or more beetles per ear and pollination is not finished.
Densities for this pest tend to be greatest along field margins in both corn and soybean fields. "Treatment decisions should be made only after scouting field interiors and border rows," Gray warns.