Aphid populations in winter wheat continue to be observed in South Dakota. The major questions now are whether or not aphid populations are at economic threshold and if spraying is really necessary. Most of the winter wheat across the state is either at or past the milky ripe stage and progressing towards the medium dough stage. During this time, the thresholds for the two aphids that are being observed (English grain aphid and bird cherry oat aphid) is a field average of 10 or more aphids at the milky ripe stage and more than 10 aphids at the medium dough stage. In addition, many of the fields where aphids are present are also inhabited by aphid predators such as lady beetles and lacewings. These predators help to maintain low aphid populations when the aphid populations are not growing rapidly. Predators can also help to reduce aphid populations in nearby fields.
Spring wheat should continue to be scouted to ensure that aphid populations don’t exceed the thresholds for it. A lot of spring wheat is somewhere between flowering and the milky ripe stages. During the flowering stage the threshold is an average of 5 aphids per plant.
For more information regarding identification, scouting, and management of aphids in winter wheat and spring wheat, please refer to an earlier article, “Aphid Populations Being Observed in Wheat.”
For information on the insecticides labeled for wheat in South Dakota, see the 2019 South Dakota Pest Management Guide: Wheat.