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Issue No. 4, Article 4/April 15, 2005

A Little Clarification About Practicing Safe S.E.X. in 2005

I received feedback from readers who questioned some of the comments I made in the article "Practice Safe S.E.X. (Sensible, Erudite [use of] Xenobiotics) in 2005," published in issue no. 1, March 16, 2005, of the Bulletin. I appreciate the feedback, which prompted me to offer some clarification.

Specifically, a couple of readers challenged the following two statements:

  • Increasing the rates of application of soil insecticides almost never has improved performance of granular or liquid insecticides for rootworm control.
  • Applying a granular or liquid insecticide to YieldGard Rootworm corn exposes the rootworm population to three active ingredients--the chemical active ingredient in the granular or liquid soil insecticide, the nicotinoid active ingredient in Cruiser or Poncho (all YieldGard Rootworm corn is treated with one or the other), and the Bt protein expressed in YieldGard Rootworm corn. In addition, this approach toward rootworm control violates the principles of insect resistance management associated with transgenic corn.

My clarifications for these statements are relatively simple:

  • Regarding increasing rates of application of soil insecticides, I probably should not have used the word "never." It is possible that increasing rates of insecticide application could result in short-term, slight improvements in insecticide performance. However, the history of insect control is replete with long-term problems as a consequence of increasing rates of insecticide application. Therefore, increasing rates of application of an insecticide is not an appropriate solution to rootworm-control problems. The long-term problems that could arise should trump the short-term gains. And quite honestly, the record of short-term gains by increasing rates of insecticide application for rootworm control is not impressive.
  • A few readers pointed out that using products with different modes of action for controlling a pest is an accepted resistance management strategy. This is true. In fact, "tank-mixing" products with different modes of action is a possible short-term strategy for delaying the onset of resistance. (I used "tank-mixing" in quotes to accommodate consideration of a soil insecticide, a seed-applied insecticide, and YieldGard Rootworm corn as a "tank mix.") However, the effects of rotating control products with different modes of action are optimized when the products with different modes of action are applied to different generations (e.g., different years for corn rootworms). Exposing the same generation of western corn rootworms to multiple modes of action ultimately places a great deal of selective pressure on rootworm populations.

A great resource for insecticide resistance information is the Web site for the Insecticide Resistance Action Committee (IRAC). You can spend quite a bit of time browsing through some very interesting and helpful information. I encourage everyone to learn more about insecticide resistance and its management. Following insecticide resistance management strategies (regardless of the insecticide used, and including transgenic Bt crops) would benefit all of us. As the title of one IRAC publication states, "Resistance Is Everyone's Problem."--Kevin Steffey

Kevin Steffey

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