On November 3, 2003, Monsanto announced that the U.S. Environmental Protection Agency (EPA) had approved the registration of YieldGard Plus corn, designed to prevent economic damage caused by European corn borers and western and northern corn rootworms. In the press release, Monsanto indicated that, after state regulatory approvals and the required Japanese import clearances are received, sales of YieldGard Plus hybrids may proceed. Monsanto indicated that all YieldGard Plus hybrids also will contain an insecticidal seed treatment that is designed to reduce secondary insect damage. YieldGard Plus hybrids will be marketed through the Market Choices pro-gram. This program familiarizes producers with those markets (does not include the European Union) that are appropriate for food and feed use only in the United States and Japan.
Monsanto describes two refuge options for YieldGard Plus hybrids. We believe the first option that utilizes a common refuge for both European corn borers and corn rootworms is the best choice from an insect resistance management (IRM) perspective. This common refuge approach requires that a minimum refuge (non-Bt corn) of 20% be planted within or immediately adjacent to YieldGard Plus corn. The common refuge approach also is less confusing than the second option proposed by Monsanto. Option two allows for a separate refuge to be used for each Bt technology. Under option two, a corn rootworm refuge would need to be deployed within or adjacent to a Yield-Gard Plus field. A separate European corn borer refuge could be utilized in the YieldGard Plus field or in a separate field (1/2 mile required, 1/4 mile preferred). Can you begin to see how this gets a little confusing? Other specifics related to the IRM program for YieldGard Plus include using the same crop rotation pattern for YieldGard Plus refuges. Although the rotational pattern for corn borer refuges is not an issue, for corn rootworms this is not the case. YieldGard Plus refuges may be treated with corn rootworm soil insecticides to prevent excessive root injury and lodging. We will provide further information and commentary on refuge specifics for YieldGard Plus hybrids as we move through this winter season.
In the December issue of the Bulletin, we will provide the results of our annual fall European corn borer survey. A preliminary review of these data indicates very low densities of European corn borer are present in many areas of Illinois. This follows a pattern that has persisted for several years. Although corn borer pressure was low in 2003, the level of corn rootworm larval injury in rotated corn continued to increase. On-farm surveys of corn rootworm larval injury were conducted in 36 counties by Jared Schroeder, a graduate research assistant in the Department of Crop Sciences, and others in August. Additional details about this survey are provided in issue no. 23 of the Bulletin. Results from Jared's research indicated the percentage of larval injury (percentage of plants with root injury > 3.0) in rotated corn increased greatly from 2002 to 2003 for central (18%), eastern (20%), northeastern (20%), northwestern (20%), and western (9%) regions of Illinois.
We are clearly at an interesting point with respect to implementing pest management programs in corn. In 2004, producers will have the option of planting hybrids that offer corn rootworm and European corn borer protection. In addition, these transgenic hybrids will be treated with systemic seed treatments that offer some protection against secondary insect pests. Is this level of insect protection needed on every acre of corn in Illinois? What are the costs and benefits? What are the risks? Does this approach represent a sound pest management approach for the long-term benefit of producers? We will continue to grapple with these questions for many years to come.--Mike Gray and Kevin Steffey