Brown marmorated stink bug is showing up at treatable levels in some soybean fields across many counties in the northern Piedmont of North Carolina.
Stink bug thresholds in soybeans vary by row spacing and can be found here.
Brown marmorated stink bugs are best sampled with a sweep net, but “best” is a relative term. These critters will evade your net as you pass through the field by hiding or dropping off plants.
Ames Herbert, Virginia Tech. Extension Entomologist, recommends spraying if you see five or six stink bugs on the plants surrounding you in all directions. Focus on R4-R6 stages to protect the yield and R7-R8 to protect quality.
A rule of thumb may be to double the threshold for R7-R8 beans.
Herbert also recommends treating with pyrethroids, especially bifenthrin, pre-mixed combination products (such as Endigo and Cobalt Advanced), and Orthene at 12 ounces or higher.
These recommendations are based on several trials in Virginia over the past two years.
Remember that this pest is most prevalent on field edges. In 2011, border treatments seemed to manage this insect well. However, these edge treatments aren’t working as well in all cases this year.
I still think it’s worth a shot trying to spray the edges of fields this year, especially when you take into account avoiding loss from driving over beans that have pods.