Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/2/2002
Publication Date: 7/14/2002
Citation: ELLSBURY, M.M., CLAY, S.A., CLAY, D.E., MALO, D.D., CARLSON, C.G. POPULATION TRENDS IN NORTHERN CORN ROOTWORMS (COLEOPTERA: CHRYSOMELIDAE) AS EVIDENCED BY GEOREFERENCED ADULT EMERGENCE DATA. INTERNATIONAL CONFERENCE ON PRECISION AGRICULTURE ABSTRACTS & PROCEEDINGS CD-ROM. 2002. p. 242-246. Interpretive Summary: This long-term study was done to determine how the numbers of emerging northern corn rootworm adults varied spatially within fields farmed as corn rotated with soybean. During the period of sampling overall populations of northern corn rootworm increased. During this time progressive increases in root injury and harvest loss attributable to lodging also were noted. The results suggest that a cropping system or management strategy as an alternative to the two-year corn and soybean rotation practiced in the northern Great Plains may be needed if pesticide use is to be reduced or avoided for management of extended diapause northern corn rootworms. The grower cooperating in this study has instituted a three-year rotation comprising two years of corn following soybean done in part in an effort to reduce infestations of extended diapause northern corn rootworms. Site-specific pesticide application also is a possibility where spatial variability in rootworm populations exists. Successful application of this concept will depend on development of methods to predict where rootworm infestation will exceed economic thresholds within a field.
Technical Abstract: Georeferenced grid samples for northern corn rootworm, Diabrotica barberi Smith and Lawrence (Coleoptera: Chrysomelidae) were taken over a 6-year period from two study sites in eastern South Dakota. A site in Moody County, SD was sampled in 1995, 1997 and 1999 and the second site in Brookings Co., SD was sampled in 1996, 1998, and 2000. Both sites were farmed in corn rotated with soybean. Spatial variability in adult emergence at each site was characterized by semivariograms for each year of sampling and adult emergence distributions were graphically interpreted as contour maps overlaid on elevation for each field. The data indicate that during the period of sampling overall population levels of northern corn rootworm were increasing. The results suggest that a cropping system or management strategy as an alternative to the two-year corn/soybean rotation as practiced in the northern Great Plains may be needed to avoid pesticide use for management of extended diapause northern corn rootworms.