Insect Pests in Soybeans and Corn in August

I had believed that major pest insect populations could increase after the rains that occurred during the last week of July and first weeks of August; however, major pest insects have remained at very low numbers. The drought during June and July and warmer temperatures may have caused this trend on insect populations. This situation is shared by colleagues working on field crops in Indiana, Illinois, and many other states in the Midwest.

In soybeans, the occurrence of major insect pests, such as stink bugs, bean leaf beetles, caterpillars, have not increased during the first two weeks of August. During recent visits to commercial fields in different counties in Central and Western Kentucky, tallies of insects mentioned above remained low. Only grasshoppers and threecornered alfalfa hoppers numbers are high. Soybean plants are resilient, and the damage caused by grasshoppers might not be a problem, but threecornered leafhoppers feeding on the main stem may cause lodging of plants, and this damage can be of concern to farmers.

During these visits, kudzu bugs had been collected in most fields of western Kentucky, although numbers remained low. In addition, egg bundles of second-generation kudzu bugs were found in soybean plants, something that I have not observed before. The latter may be the result of the establishments of kudzu bugs in Kentucky, but this insect may not cause major damage in soybeans.

In corn, insect pest activity has remained calm, although brown marmorated stink bugs had been observed on ears of field corn. Stink bugs can injure kernels, reducing the seed quality. Also, in an experimental conventional field corn (non-GMO traits) at the UK Research and Education Center at Princeton, the presence of corn earworms and fall armyworms were detected injuring plants, although pheromone trap captures for these two species remained low (see insect trap article in this week's KPN). In most commercial corn fields (using corn with GMO traits), the presence of these two species has not been observed.