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Growers Should Remember to Plant Non-Bt Corn Refuges If They Plant Bt Corn

April 12, 2002
In an article in the Bulletin last year (issue no. 24, November 9, 2001), I reported that the United States Environmental Protection Agency had approved Bt corn for use for another 7 years. I also shared EPA's strong intent for corn growers to comply with resistance management strategies recommended by seed companies and university and government entomologists. It is critical that corn growers "follow the rules" this year and in the future so that we can reap the benefits of Bt corn, and other transgenic crop technology, for pest management programs for years to come. Recommendations for resistance management are not made lightly; a lot of effort and thought went into the development of these resistance management strategies. So, for the benefit of everyone in agriculture, we urge growers to comply with the following recommendations:

· At least 20% non-Bt corn refuge should be planted on each farm.

· Non-Bt corn refuges should be planted within 1/2 mile of Bt corn. However, we (University of Illinois entomologists) recommend that the refuge be planted adjacent to or within Bt cornfields. The objective of the refuge is to generate European corn borer or southwestern corn borer adults that have not been exposed to Bt. These adults would mate with any rare individuals that emerge from Bt corn. Therefore, the closer the refuge is to Bt corn, the more likely the moths from the two types of fields will mingle and mate.

· Non-Bt corn refuges can be planted in a number of ways:

· Adjacent to, or at least nearby (within 1/2 mile), fields

· Blocks of non-Bt corn within a field of Bt corn (e.g., a 16-acre block within an 80-acre field)

· Split-planter strips--some planter boxes with Bt corn, other planter boxes with non-Bt corn (e.g., three boxes of non-Bt corn in a 12-row planter is a 25% refuge). Non-Bt corn strips must be a minimum of four rows wide. This approach obviously is not an option for growers with air planters.

· Perimeter plantings--non-Bt corn planted along the sides and in the turn rows of cornfields.

Non-Bt corn refuges can be treated for control of European or southwestern corn borers if their densities exceed economic thresholds. Consequently, if a grower intends to protect his or her refuge, the "split-planter strips" option is not the favored approach.

Insect resistance management is a new concept to most corn and soybean growers in the Midwest. However, cotton growers have been implementing insect-resistance management strategies for years. If they can do it, so can we. Our stewardship of this technology should ensure its continued use. Remember, planting non-Bt corn refuges is the right thing to do.--Kevin Steffey

Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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