Late-season brown marmorated stink bug populations
Brown marmorated stink bug populations are increasing in soybean fields across southern Pennsylvania. We have not seen or heard about high populations in central or northern parts of the state, so it seems the action is in the southern tier of counties. These populations are, of course, increasing as soybeans begin to senesce, which decreases, but does not eliminate, the risk posed by stink bugs. According to research from Ames Herbert (Virginia Tech), Galen Dively (U. of Maryland), and Joanne Whalen (U. of Delaware), stink bugs do not reduce yield when they are attacking soybeans in growth stage R6 or later, but they can decrease soybean quality. Dr. Herbert recommends treatment only when populations are substantially higher than five bugs per fifteen sweeps with a typical insect net, so get out there and assess the populations you encounter.
A few things to keep in mind: First, recall that brown marmorated stink bug populations tend to accumulate on field edges; therefore, if populations levels warrant a treatment, consider just spraying the edges of fields where the populations are gathered. This will target the bugs where they are feeding and reduce the amount of direct damage to soybean fields caused by running over the beans with a sprayer. Second, remember that once they reach adulthood, stink bugs should begin leaving fields and seeking places to overwinter. This movement tends to begin in mid-to-late September—then you can enjoy them in your homes!