By Ron Hammond and Andy Michel, The Ohio State University Extension
With the growing season coming to an end, there are a few insect pests that we should discuss, including which ones are still a concern and those of interest. The main insect that growers should continue to monitor are bean leaf beetles on soybean, especially in fields that remain green into September. The final adult generation will feed on pods and seeds, resulting in both fewer seeds as well as quality issues. Beetles will tend to go to late maturing fields to feed prior to overwintering, and often cause more damage to seeds than expected. See this fact sheet for information on pod feeding by bean leaf beetles. This is probably a more widespread problem than realized.
Another pest to watch out for, albeit we do not expect it to be a concern, is the brown marmorated stink bug. This is a potentially new crop pest in Ohio that so far has not caused many problems except for homeowners and renters in the fall. However, we expect it to sooner or later begin feeding on soybeans in late summer. Growers might want to monitor their fields, especially along field edges nearest wooded areas, for the presence of this new pest. See a fact sheet for more information.
As we predicted, this past summer was a "low" soybean aphid year, with very few aphids being found. If things hold true like in past years, we will begin to see some aphids on soybeans over the coming weeks. However, these will not reach levels to cause concern, especially at the late growth stages that soybeans will be at. But it will be these aphids that will produce the eggs that will later be found on buckthorn that will overwinter. We would point out that trying to control any late occurring soybean aphids to prevent an overwintering population will not work; so do not apply insecticide sprays for these aphids. We will monitor the buckthorn this coming fall, and more importantly, remind growers to keep a watch for aphids next summer.
Finally, Ohio is now experiencing cooler and wetter conditions, both of which appear to be causing twospotted spider mite populations on soybeans to diminish. Before making any further treatments for mite control, definitely check to see if most mites are still alive. We think you will find that most mite numbers have finally dropped.