The first confirmed case of Herculex corn rootworm resistance was confirmed this week in a single field in Delaware County, Iowa. The National Corn Growers Association is engaged directly with the technology provider, Corteva, to assure appropriate and aggressive measures are taken to keep the seed technology viable.
“This announcement is significant and troublesome given the potential economic implications for corn farmers, so we are watching it closely,” said Bob Hemesath, Decorah, Chairman of NCGA’s Freedom to Operate Action Team. “With that said, there are protocols in place to deal with resistance. NCGA wants to recognize the extraordinary measures taken by Corteva that are well beyond the steps required by the U.S. Environmental Protection Agency.”
Corteva has reported the development to the EPA, which regulates these Bt traits, and Corteva is working with farmers in Delaware County to limit the spread of this resistance.
“These corn rootworm traits are very valuable for corn growers, and every effort is being made to ensure these traits remain an effective tool for as long as possible,” Hemesath said. “Corteva is working with the grower and their neighbors to rotate susceptible fields into soybeans next year and will accelerate pyramid stack adoption in the county and ag reporting district.”
The specific product involved is Herculex RW (Cry34/Cry35) which is a Bt trait designed to provide season-long rootworm protection for the entire root system to safeguard yield potential. The biotech trait in certain corn seed includes two proteins that control rootworm larvae and reduce adult rootworm beetle emergence.
“This reported case highlights the need for continued implementation of the work we have done with other stakeholders on the Take Action initiative. Take Action focuses on pre-emptive steps farmers can take to avoid potential issues with resistance to pest management products.
Insect pests can have a devastating impact on a corn crop. Many farmers turn to in-plant insect protection traits to help protect yield potential and profitability. Take Action is an industry-wide partnership that advocates a diverse approach to weed, disease and insect management to avoid resistance.
NCGA and the Agricultural Biotechnology Stewardship Technical Committee (ABSTC), a consortium of Bt corn registrants, are part of the Take Action program that helps farmers develop insect resistance management plans and refuge strategies for their farms.
Through the Take Action program, farmers have access to the latest tools and information to manage insects and prevent resistance development. Take Action advocates three steps farmers can use today to help preserve current insect protection technologies and avoid resistance:
- Plant the required refuge based on geography and corn product. For corn-growing areas, refuge requirements are 5 percent or 20 percent. For cotton-growing areas, refuge requirements are 20 percent or 50 percent. Farmers should refer to their corn product’s Insect Resistance Management (IRM) guide for specific refuge details.
- Use multiple IRM strategies such as crop rotation, using pyramided traits, rotating Bt traits, and rotating and using multiple modes of action for insecticide seed treatments, soil-applied insecticides and foliar-applied insecticides.
- Scout fields in-season to determine the efficacy of control measures in place and to identify whether further action is necessary for effective control.
Iowa Corn Growers Association has been proactive in working closely with Iowa State University for years developing and promoting a program called the Iowa Pest Resistance Management Program (IPRMP). This Iowa-specific effort addresses pests--including weeds, insects and diseases--that can adapt and become resistant to chemical, genetic, and agronomic control practices. The IPRMP outlines approaches for effective, integrated management solutions that will sustainably control pests. By fostering methods to detect resistance, resistance can be delayed or even prevented, limiting the spread of pest resistance.
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