With all the planting difficulties in 2019 there are soybeans in a much greater variety of growth stages than usual this summer. What does this mean for stink bug management? First, it means that different fields will be in the danger zone at different times. Stink bugs feed on developing pods and seeds, with the potential for damage beginning in R3 and R4-R5 being prime damage time, with damage potential still lingering in early R6. This year peak damage potential may be spread over a larger window of time. Second, the latest soybeans to mature will be at extra risk at the end of the season. Stink bug adults are quite mobile and able to move into new fields. As earlier fields mature they will naturally be attracted to fields that are still green. If only a few fields are still green at the tail end of the season the immigration will be magnified. The same is true for bean leaf beetle and pod feeding. Our monitoring shows that this process can continue into October. Late-maturing fields should receive extra scouting attention.
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 and nymphs combined). If soybeans are being grown for seed or food, the threshold can be dropped to 2 or more stink bugs. When scouting time is tight (and when isn’t it) scout first at the field edges where stink bugs tend to accumulate first. If they are found in the edges move the scouting effort further into the field to assess the extent of infestation. If populations are still mainly on the edge, sometimes an edge treatment can do the job.
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