A run-in with corn rootworm resistance in a single 40-acre field four years ago prompted Tim Daly of Bankston, Iowa, to begin rotating hybrids. Now he uses different Bt toxins between fields to prevent future problems.
Part 3 of our "Resistance Reality" story, featured in the Farm Journal 2012 Seed Guide. Click here to start reading from the beginning.
Specific to Bt, Bradshaw says it’s imperative that farmers plant the prescribed refuge for each corn hybrid planted. Plus, he adds, it’s the law.
"All I can say is if you don’t put a refuge in, the longevity of the technology will be shortened," he says.
Corn hybrids with the initial Bt toxin, Cry3Bb1, were first available commercially in 2003. They were followed by hybrids with the Cry34/35Ab1 toxin in 2005 and then mCry3A in 2006. Initially, each of the Bt hybrids required that farmers plant a 20% non-Bt refuge in the Corn Belt. Today, some refuge requirements are as small as 5%, which is the case for the refuge-in-a-bag style products.
Even with reduced refuge requirements, some producers still ignore them altogether. That fact frustrates those farmers, such as Tim Daly, who make every effort to comply with them.
"We need to be putting in these corn refuge acres that the products require," says Daly, who farms with his father, Matt, in Dubuque County, Iowa, near Bankston.
Taylor agrees and adds: "We should not be using neighbors’ corn to provide our refuge."
Most farmers do comply with refuge requirements but struggle with the complexity they present, says Ben Kaehler, Dow AgroSciences general manager, seed affiliates. The company owns six regional U.S. seed companies in addition to its national company, Mycogen Seeds.
He says taking refuge compliance out of farmers’ hands with the SmartStax refuge-in-a-bag-style products is one way technology providers believe they can help growers and, in the process, extend the longevity of the Bt technology.
"SmartStax received the 5% refuge based on field tests and statistical modeling of the evolution of the corn rootworm," Kaehler explains. "Scientists who are familiar with the life cycle of corn rootworm are very confident with the 5% number."
Two entomologists, Bruce Tabashnik at the University of Arizona and Fred Gould at North Carolina State University, want to reform how refuge acres are used. To protect Bt efficacy, they want EPA to increase refuge requirements to 50% for hybrids with one Bt toxin and 20% for hybrids with two toxins.
This summer, for the second year, the major seed companies are working with third-party organizations, such as state seed and crop improvement associations, to audit corn growers’ Bt refuge compliance.
Technology providers are also working with industry and academia via the Agricultural Biotechnology Stewardship Technical Committee, which supports farmer and retailer education and training on best management practices with Bt. Academia has formed two committees, NCCC-46 and NC-205, to address the intensifying issue of Bt resistance.