Stink bugs in soybeans
Last week Ohio State University mentioned to be on the lookout for the brown marmorated stink bug, although they were not expected to be a concern. That thought has changed somewhat over the past week in regards to this potential pest and the rest of the stink bug complex that occur in soybeans.
Some soybean fields have been found with much higher numbers of stink bugs than are normally seen, with some fields reaching a level that might need treatment. Since the article last week, reports of brown marmorated stink bug have come in from a few fields. With support from the Ohio Soybean Council, scouting trips have confirmed brown marmorated stink but in soybean. At this time only adults are being seen, but observations last year suggest that larger numbers of nymphs will start occurring within a few weeks. But greater numbers of the green stink bug and a smaller stink bug that is also green but with a reddish shoulder, this latter one being called the red shouldered stink bug are being found. This is a new stink bug that has not been seen very much in Ohio. It is not the red banded stink bug that is causing significant concern in southern states, but it nevertheless might be a potential problem. At this time, little is known about its damage potential. For the time being, it is recommend to group all stink bugs together for determining the need for treatment. Through Ohio Soybean Council support, sampling for stink bugs over the next few weeks across the state will be expanded.
To sample for stink bugs, take multiple 10-sweep samples with a sweep net in multiple locations throughout the field. Average the number of stink bugs in the 10-sweep samples. The threshold to treat is 4 or more stink bugs, adults or nymphs. If soybeans are being grown for seed, the threshold can be dropped to 2 or more stink bugs. Pods should still be green. Because stink bugs often occur mainly on the field edges, especially next to woody areas, it is suggested to sample both field edges and within the field to determine which parts of the field might require treatment.
See the soybean insect images page, http://entomology.osu.edu/ag/pageview3.asp?id=1152, on our website for pictures of the various stink bugs. The ones most likely to be in Ohio soybean fields include the brown marmorated stink bug, the green and red shouldered stink bugs, the brown stink bug (with rounded shoulders) and the spined soldier beetle (with pointed shoulders), this last one actually being a beneficial predator.