David Owens, Extension Entomologist, owensd@udel.edu
Small Grains
Once small grains are planted, begin scouting them for aphids up until cold weather sets in. Last year, aphids remained active up until December, and then because of unusually warm January and February aphid populations increased extremely rapidly. We also had unusually high barley yellow dwarf virus incidence last year. BYDV is unpredictable, and because we had it last year does not necessarily mean we will see much of it this year. Southern states use a threshold of 2-3 aphids per row foot at seedling, 6 per row foot 30-60 days after planting. North Carolina uses a threshold of 20 aphids per row foot when cold weather is not in the forecast. Small grains planted after the Hessian Fly-free date are at lower risk of high aphid colonization. Historically, fly free dates ranged from October 3 (New Castle) to October 10 (Sussex). If, however, we have a late fall, aphids will remain active long after the fly free date. Small grains treated with an insecticide should be protected from 3-9 weeks. If aphid counts are approaching concerning levels in the fall, pyrethroids, neonicotinoids (for barley), and Sivanto are all very effective options.
Soybeans
We received a call earlier this week of high green stink bug counts in a field of late soybean. At early R6 stages, thresholds are around 5 per 15 sweeps, but they start increasing as the field moves through R6 to R7. Some states use a threshold of 7 bugs per 15 sweeps at R6.5 when seeds begin separating in the pods, and closer to 10 bugs per 15 sweeps at the beginning of R7. At this point, they are more of a quality concern than as much of a yield concern. If you encounter a large number of stink bugs, be sure to sweep the whole field and take a field average. Often, stink bugs will aggregate and sometimes aggregations can be very intense but small. Other times, they will be present near a woodline but not extend too much more than 100-150 feet into the field.