Testing the areawide pest management concept on the western corn rootworm (Diabrotica virgifera virgifera LeConte) in northwestern Indiana and east-central Illinois

Corey Kent Gerber, Purdue University

Abstract

Since the early 1970s, corn producers in the eastern Corn Belt have used a corn/soybean rotational system to manage the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte. However, an adaptation by the WCR (variant) to this rotational system occurred in northwest Indiana and east-central Illinois. This adaptation resulted in significant WCR egg deposition in soybean. Therefore, in first-year cornfields, larvae hatched and fed extensively on corn root systems not protected with a soil insecticide. As a direct result, soil insecticide use dramatically increased in areas where the WCR variant existed. Due to this rise in soil insecticide use, alternative management strategies for the WCR variant have been investigated. In 1996, a WCR areawide management program was initiated in northwest Indiana and east-central Illinois. This program was designed to test the suppression of WCR adults with two semiochemical-based low rate insecticide baits, SLAM and Invite EC. A 3,726 ha management zone was established to test the effectiveness of each bait. A comparison zone, which did not receive bait treatments, was established around the management zone. To evaluate the impact of the baits on the WCR population, hectares treated in the management zone were compared by year, and WCR larval damage. WCR adult emergence, and yield estimates were compared within and between years for the management and comparison zones. Based on the data, an overall decrease in area treated in the management zone from 1997 to 2001 was not detected. A consistent decrease in root damage and beetle emergence, and a consistent increase in yield were also not detected. Predicting the potential damage by WCR larvae in subsequent cornfields, strictly based on WCR adult density estimates in soybean, is crucial for producers in the eastern Corn Belt. To predict this damage, an economic injury level and an economic threshold for WCR beetles in soybean have been determined. Results revealed that at a root damage rating of 3.5, the economic injury level and economic threshold for WCR adults in soybean are seven and five WCR beetles per Pherocon AM trap per day, respectively.

Degree

Ph.D.

Advisors

Edwards, Purdue University.

Subject Area

Entomology|Agronomy

COinS