Currently, we are not receiving many reports of insect problems in field crops in Ohio. People are reporting finding soybean aphids, but only at a few aphids per plant at most. Remember that the threshold is 250 aphids per plant with a rising population (it takes 700-800 per plant to cause economic damage), and these numbers are NOT being seen. As we get into August and the later part of the summer, the susceptibility of soybeans to aphids goes down. However, as in other years with low numbers aphid, we do expect the numbers of aphids to begin to rise prior to the end of the summer. These aphids then will move to buckthorn in the fall and lay eggs, and will overwinter, possibly resulting in problems in 2011.
A few people have asked about twospotted spider mites in soybean with the hot temperatures we have been experiencing. While mite populations might build up in dry areas, remember that the weather has also been very humid, which encourages a natural-occurring pathogen that helps to keep populations down. Before taking action against this mite in soybeans, make sure that it is extensive enough and also an expanding problem.
Although not having received reports of abnormal defoliation occurring in soybean in Ohio, we have heard from other states in the Midwest including Michigan of defoliation occurring from various caterpillars. Growers might want to check on their fields to make sure they are not caught off-guard.
One thing we would like to mention is that we are concerned about a few newer stink bugs that could be creeping into soybean fields in Ohio, as well as large numbers of the regular green and brown ones. This is especially a concern in southern areas of the state. The two new species of stink bugs are the brown marmorated stink bug, an invasive species from Asia, which is currently in eastern states, and the red banded stink bug which is causing new problems in middle and southern U.S. states. Growers in Ohio are asked to make note of the presence of stink bugs that appear to be different than the usually green and brown ones or in unusually high populations over the next few months in soybean. Please let your county extension educator know about any such findings. A fact sheet on the brown marmorated stink bug is available on the Agronomic Crops Insects webpage at http://entomology.osu.edu/ag/images/Marmorated_Stink_Bug.pdf.