David Owens, Extension Entomologist, owensd@udel.edu
Continue to scout small grains for aphids. In the last couple of weeks, we have looked at over a dozen small grain fields, mostly barley, and have seen only very low numbers of aphids. Thresholds vary depending on the state, with most between 6 and 20 per row foot in the fall. None of the fields we have looked at thus far have approached the 6 per row ft number, and, with the exception of two days in next week’s forecast, temperatures are going to be rather cool. Cool to cold weather slows aphid reproduction quite a bit. Because barley is more susceptible to barley yellow dwarf virus, I think an appropriate threshold would run 6-10 per row foot. If we have exceeded that and have warmish weather, a fall treatment of Endigo, either by itself or tank mixed with a herbicide targeting winter annuals, is an excellent treatment. If we are not over threshold and have cool weather (such as currently), I think a lambda cyhalothrin treatment would do just fine. The rate range is 1.28 to 1.92 fl oz. Wheat is generally more tolerant to BYDV, but check with your seed dealer. Looking at extension guidelines, I think an appropriate wheat threshold would be 15-20 per row foot. At least in the fields we have looked at, we are nowhere near that level, and we have cool weather in the forecast. Thus, I think most fields should be aphid safe. If you decide to treat for aphids with a fall herbicide pass, keep in mind Endigo is not labeled for wheat, but the pyrethroids generally do an excellent job.