David Owens, Extension Entomologist, owensd@udel.edu
Be sure to scout for aphids in small grains. Warm weather in October and November will favor higher than usual aphid populations. Examine 10-20 sites per field, and at each site, 1-5 row ft. Fall aphids of most concern are greenbug and bird cherry oat aphid. Greenbug is a light green aphid with a blue-ish stripe down the middle and small, green cornicles or tailpipes. The most common aphid this time of year is English grain aphids, which look similar. EGA tend to be a bit darker, tend not to have the stripe down the back, and have long, black cornicles. I say tend to because there are exceptions. Bird cherry oat aphids are pear-shaped, dark green, and have red patches around the cornicles. Winged BCOA are black. Unfortunately, there is a huge disparity in recommendations for thresholds in the fall, but most range between 10-30 per linear row-ft, with areas showing aphid stress. This is especially true for greenbug. Greenbug saliva is toxic to plants, and both greenbug and bird cherry oat aphids are very good vectors of barley yellow dwarf virus.