No. 16 Article 1/July 13, 2007

Bt Usage in Illinois Soars: An Update on Corn Rootworm Investigations

In a recent report (July 5, 2007), Adoption of Genetically Engineered Crops in the United States, the USDA Economic Research Service revealed the significant escalation in the use of Bt corn in Illinois and other states. In 2006, 19% of all planted corn in Illinois was characterized as a "stacked gene" variety. In 2007, the use of stacked corn hybrids in Illinois more than doubled and is estimated to be at 40% of planted corn acres. (Figure 1, page 130) In 2006, 55% of corn planted in Illinois was estimated to be a genetically engineered hybrid (Bt only, herbicide-tolerant only, or stacked gene variety). In 2007, that percentage has increased to 74%. Therefore, roughly three-fourths of the corn acreage in Illinois is now planted to a genetically engineered corn hybrid. (Figure 2, page 130) This adoption of the technology is occurring at a remarkable pace. To view the full report, please go to the following Web site.

Figure 1

Figure 2

We began our annual corn rootworm "digs" on July 9 to evaluate the performance of various corn rootworm products, including Bt hybrids, seed treatments, and soil insecticides. Roots were dug at the Orr Agricultural Research and Demonstration Center located near Perry and in our plots located near Urbana. The level of root injury in the untreated check (control) at the Orr Center was inadequate to assess the protection afforded by the various corn rootworm products. We're not sure why the trial at Orr, this year and last, has failed to provide an adequate challenge to our treatments. During the past week, we've received some reports from western Illinois that suggest the overall corn rootworm population may be lower in that area of the state. The "pressure" at Urbana was quite good (nearly 3 nodes of roots destroyed) in the control. We will report the full range of root ratings for the various treatments at a later date. On July 12 and 16, roots will be dug from out experiments located at the Monmouth and DeKalb research and demonstration centers, respectively.

In addition to the standard corn rootworm product trials, we are engaged in an on-farm research investigation at multiple sites in east central Illinois. Dr. Joseph Spencer, an entomologist with the Illinois Natural History Survey, is providing the primary leadership for this USDA National Research Initiative funded project. This season marks the beginning of this multi-year study in which we are seeking to determine the potential management value of late-planted corn strips as trap crops for western corn rootworm beetles in growers' soybean fields. The late-planted corn in some fields is deployed as strips through a given soybean field. In other producers' fields, the corn strips are planted as a perimeter around a soybean field. Densities of western corn rootworm adults are being estimated with vial and Pherocon AM traps in the late-planted corn strips and adjacent soybean field. After harvest, soil samples will be taken in soybean fields and corn strips, and the densities of western corn rootworm eggs determined. In 2008, root injury in both the corn planted after soybeans and the trap crop areas will be estimated. The long-term goal of this research is to assess the potential value of trap crops in concert with Bt or soil insecticides to manage western corn rootworms more effectively. We look forward to sharing the results of this research through the upcoming years.

We also look forward to learning about how your corn rootworm products performed this season. Please share your observations with us when you have a chance.--Mike Gray and Kevin Steffey

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