Risk of Western Corn Rootworm (Coleoptera: Chrysomelidae) Damage to Continuous Corn in Virginia

Abstract

Information on the risk of western corn rootworm, Diabrotica virgifera virgifera LeConte, damage to continuously-grown corn previously was lacking in Virginia, as well as other mid-Atlantic states. A field study was conducted in 1993 and 1994 comparing root damage, whole-plant yields, and silage quality in insecticide-treated and untreated sections of 32 continuous corn fields in Virginia. Approximately 28% of the fields had serious root damage exceeding a rating of 3.5 (1–6 scale) in sections not treated with a soil insecticide. Also, 19% of the fields had an economic loss in whole-plant yield due to corn rootworm feeding damage. Silage quality, as evidenced by percent crude protein and acid detergent fiber, was not significantly affected by corn rootworm feeding. Because much of the continuous corn acreage in Virginia is treated preventively with soil insecticides for corn rootworms, the results of this study suggest that a large percentage of this insecticide use is unnecessary.