By Ada Szczepaniec
Winter wheat planting will begin soon and implementing several preventive measures is important to protect the crop from a few relevant arthropod pests.
By far the most cumbersome of pests attacking winter wheat are wheat curl mites. These microscopic arthropods prefer to feed on young and lush plant tissues and a new winter wheat crop is a very attractive food source. These mites cause curling of leaves, hence their common name, but their main impact comes from a virus they vector: wheat streak mosaic virus (WSMV). Wheat infected with WSMV is stunted, and has mottled, streaked leaves. Severe yield losses are associated with WSMV infections and managing the vector, wheat curl mite, is essential especially in fields with history of WSMV.
Wheat curl mites move from maturing wheat to nearby wild grasses, where they usually spend the hot summer months before moving to volunteer wheat coming up in fields in late summer or early fall. They often colonize the new wheat crop from these volunteer wheat plants. Thus, managing this green bridge connecting the emerging winter wheat with the summer hosts is crucial. Maintaining the crucial period of about two weeks of volunteer wheat-free environment is essential to managing the mites and the virus they vector. There are no insecticides or miticides that can be used to manage these mites and clearing volunteer wheat is the only method of preventing WSMV infection.
Grasshoppers have generally remained in low to moderate in numbers this summer, but several central counties of South Dakota have seen moderately high populations of these pests. Grasshoppers will move to the emerging winter wheat crop as nearby grasses and weeds senesce, and vulnerable winter wheat should be protected. One of the recommendations is double-seeding wheat in field margins to compensate for grasshopper feeding. Unless these pests are very high in number, this preventative method should decrease their impact on the crop.