Invariably I get asked, “What do you do this time of year?” or “Are the bugs dead yet?” The answers last week would’ve been: counting aphids in small grain plots, and not quite. Aphid populations coming out of winter are pretty low in research plots at Carvel in Georgetown, DE and at the Wye in Queenstown, MD. This is consistent with reports coming from other folks in the field. It may be tempting to tank-mix a pyrethroid with the initial nitrogen application for small grains in the next few weeks (assuming things dry out), but in the vast majority of cases, you will help your bottom line by leaving out an early insecticide. These low aphid populations also serve as important food for beneficial insects, and an insecticide will take them out, releasing spring migrants from predation. In fact, there are only two situations where we are concerned with the physical feeding injury caused by aphids, 1) infestations of Greenbug aphids and 2) English grain aphids feeding on small grain heads. However, aphids are important because of the role they play as vectors of Barley Yellow Dwarf Virus (BYDV). At this point in the growing season, an insecticide application may be warranted if you find ten or more aphids per row-foot. Remember, you may hit a small colony in one sample that has 10 or 15, but then go several samples without any. The only way to know how many and what species of aphid you have in your field is to scout it.
Read this fact sheet for more information about Barley Yellow Dwarf Virus: https://cdn.extension.udel.edu/wp-content/uploads/2015/10/14051904/BYDV-Final-Draft-9-12-16.pdf
Click here for a photo library of common aphid species in DE: https://www.flickr.com/photos/139973317@N03/sets/72157664513242564/
Click here for a photo library of Barley Yellow Dwarf Virus Symptoms: https://www.flickr.com/photos/139973317@N03/sets/72157666301880210/