Comparison of Two Sampling Methods for Assessing Halyomorpha halys (Hemiptera: Pentatomidae) Numbers in Soybean Fields.

Sampling soybean fields for the brown marmorated stink bug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), can be challenging. Both adults and nymphs have a "startle response" and drop to the ground with even the slightest disturbance. This behavior could reduce the effectiveness of the traditional sweep net and ground cloth sampling methods. In 2013 and 2014, in Virginia, Delaware, and Maryland, we evaluated a visual plant inspection method that consisted of counting the number of brown marmorated stink bug nymphs and adults seen on soybean plants in a 2-min inspection period while walking carefully between two rows. After a 30-min interval, which allowed the stink bugs to reposition in the canopy, the area was resampled using 15 sweeps with a 38-cm-diameter sweep net. In total, 76 soybean fields and 2,042 paired comparisons were used to determine a strong linear relationship between sampling methods (y  =  0.984x  +  0.4359, R2  =  0.6934, where y  =  brown marmorated stink bugs/2-min visual count and x  =  brown marmorated stink bugs/15 sweeps). An average visual count of 5.4 brown marmorated stink bugs in 2 min was estimated as being equivalent to the current economic threshold of 5 stink bugs per 15 sweeps. Visual inspection appears to be an effective method for assessing brown marmorated stink bug populations in soybeans.