Extent of corn rootworm (Coleoptera: Chrysomelidae) larval damage in corn after soybeans: search for the expression of the prolonged dispause trait in Illinois
1992
Steffey, K.L. | Gray, M.E. | Kuhlman, D.E.
Surveys were conducted from 1986 through 1989 to determine whether prolonged diapause in northern corn rootworm, Diabrotica barberi Smith & Lawrence, would lead to subsequent damage by larvae in corn, Zea mays L., planted after soybeans, Glycine max (L.), in Illinois. Overall, 5,406 root systems were extracted from 1,100 fields in 35 different counties in northern and central Illinois and evaluated for corn rootworm larval injury. The incidence of corn rootworm larval damage in corn after soybeans was greatest in the central, northeastern, and eastern regions of Illinois, where annual rotation of corn with soybeans predominates and where northern corn rootworm populations are larger than in other regions of the state. However, only 1.7% of the fields surveyed had a mean root rating of greater than or equal to 3.0. Only 6.2% of the plants examined had root ratings of greater than or equal to 3.0. If a theoretical economic injury level for corn rootworm larval damage is established at a root damage rating of 4.0, none of the fields surveyed in Illinois suffered economic loss as a consequence of rootworm larval injury to corn after soybeans. Results from the surveys indicate that prolonged diapause rarely causes subsequent economic damage in corn after soybeans in Illinois. Corn producers in Illinois rarely need to apply soil insecticides to prevent corn rootworm injury, in corn planted after soybeans.
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