Updated February 15, 2019:
1. Comparing two sample units (Sets of 10 vs 25 sweeps) to estimate stink bug numbers in soy: As in 2017, in 2018 the majority of stink bus sampled were Euschistus brown stink bugs. The figure below shows the highest stink bug population, which occurred at the end of August or first week of September, in the seven fields sampled. Each field is represented by a different color bar; the bars show the estimated stink bug population based on taking 10 or 25 sweeps. Regardless of 10 vs 25 sweeps, all data is scaled to and reported as the number of stink bugs per 25 sweeps, because the conventional threshold for stink bug is soybean is 5 per 25 sweeps. In six of seven fields, taking smaller sets of 10 sweeps gave the same estimate of stink bug abundance as taking sets of 25 sweeps. The only exception was a field on the MSU campus, which was much smaller in size than the commercial fields. This data was provided to the University of Minnesota, which is pooling and analyzing it with similar data from other states. Of interest - in contrast to 2017, two fields actually exceeded the threshold for stink bugs. Both fields were in Clinton County, west of St Johns. This was my first time seeing such high numbers in soybean. 2. Stink bugs in food grade soybeans (an extra study to assist Dr. Singh & Dr. Wang). Goal: Determine if certain food grade soybean lines are at greater risk for stink bugs Result: Two food grade trials were sampled. Dr. Manni Singh and Dr. Dechun Wang evaluated agronomic traits of food grade soybeans in 2018. Because food grade beans have a very low tolerance for stink bug damage, I suggested sampling the entries at trial locations in Saginaw and East Lansing, taking five sweeps per plot. The samples were sorted to record the number of stink bugs, Japanese beetle, and bean leaf beetle. As this was an extra project, analysis isn’t done yet.
In preparation for an increase in stink bugs in the future, stink bugs were sampled in Michigan fields and the data pooled with that from other states to identify what species were there and tweak sampling plans in soybeans.