No. 20 Article 2/August 27, 2010

No European Corn Borer Survey Planned for 2010

The corn harvest has begun in some areas of Illinois, and some may wonder about the annual European corn borer survey. For 2010, the survey will not be conducted. It has been well documented that densities of this once-prominent insect pest of corn have continued to hit historically low density levels for many successive years. The survey was stopped for two years (1997 and 1998) after the commercial introduction of Bt hybrids in 1996 and was renewed in 1999.

Corn harvest has begun (Champaign County, August 25).

In the past three years, it has been increasingly difficult during the survey to find European corn borers in most producers' fields (Figure 1), and moth flights have been negligible. If in the future we confirm elevated levels of European corn borer injury and note increases in moth abundance, we may elect to renew some targeted survey efforts. For now, we are likely to redirect some of our survey resources to western corn rootworm adults (summer 2011) and to potentially new insect pests of soybean (like the redbanded stink bug).

Figure 1. Results of European corn borer surveys for Illinois, 1943 to 2009.

Data from this survey, begun in 1943, have never consistently predicted subsequent infestations of European corn borers, as the original architects envisioned. However, the survey did offer a look in the rearview mirror regarding how much yield loss could be attributed to this insect pest. It's not unreasonable to estimate that during outbreak years, such as 1949, 1989, and 1991, European corn borers took 15% to 20% of the yield for themselves. No wonder so much time and so many resources were initially devoted to developing IPM strategies and ultimately to commercializing Bt hybrids to combat this formidable insect. We are fortunate to date that no field-level resistance by the European corn borer to Bt has been confirmed; however, insects are adaptable, and we should not take this transgenic technology for granted.--Mike Gray

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