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Bt rules

March comes in like a lion and goes out like a lamb, so the saying goes. But sometimes the opposite is true as well. Weather conditions in early spring can change rapidly and change the hybrid-buying decisions you made late last year. If you're now trying to decide whether to hold on to those corn hybrids or exchange them for seed products better suited to current environmental conditions, you must take into consideration some new requirements if you want to plant hybrids containing a Bt gene.

Seed industry leaders stress that if you plan to use Bt in 2002, you must remember you are now contractually bound to grow all Bt corn products in a manner consistent with mandates outlined by the new Insect Resistance Management (IRM) program, which the EPA formalized last October.

Three core mandates make up the bulk of the IRM requirements:

  • Growers must plant at least 20 acres of a non-Bt hybrid for every 80 acres of Bt corn they grow, thereby providing a minimum 20% refuge. However, in corn/cotton-growing areas, growers must plant at least 50 acres of a non-Bt hybrid for every 50 acres of Bt corn, thereby providing a minimum 50% refuge. Most 2002 seed company product use guides provide a list of the counties that fall under this requirement.

  • A non-Bt refuge must be planted within one-half mile of each Bt cornfield, and preferably within one-fourth mile.

  • Non-Bt corn may be treated with conventional insecticides only if target pest pressure reaches economic thresholds. Bt-based foliar insecticides are not to be used within the refuge crop.

Follow through with a plan

Planting season is a hectic time, and industry leaders worry these new requirements will be left behind in growers' haste to exchange hybrids and plant them in a timely fashion. “Weather conditions will create a hassle for some growers this spring, and in the frenzy to get their crop in they may forget about implementing their IRM plan,” says Tom Slunecka, a National Corn Growers Association (NCGA) lead spokesperson for biotechnology. “If farmers plant Bt corn, they've got to follow through with their plan.”

Part of that plan means managing Bt corn and non-Bt corn hybrids similarly. “If planting dates are pushed back due to weather, farmers need to think about maturity and silking dates, drydown and other agronomic traits as they exchange seed,” Slunecka reminds. “That goes for both Bt corn and non-Bt hybrids used for a refuge.”

Prevent insect resistance

Last fall, the EPA formally declared that all Bt products require the implementation of an IRM program, which addresses refuge size, distance guidelines and insecticide use. Greg Wandrey, product stewardship director for Pioneer Hi-Bred International, says the academic community, seed companies and EPA officials were involved in developing the IRM mandates, which were initially discussed in 1999. From the onset, Wandrey says, the goal of the group was to develop a program that would help protect the Bt technology for farmers' long-term use.

Larry Stenberg, channel manager for Dow AgroSciences, agrees. “As technology suppliers, we are committed to the preservation of the technology in order to ensure that growers may continue to reap the benefits,” he says. He adds that the four companies currently marketing the technology — Dow AgroSciences, Monsanto, Pioneer Hi-Bred International and Syngenta — were also required to submit their Bt corn products to EPA's reregistration process. Stenberg says that since last fall, the four companies have worked together and independently to help educate growers on the new EPA mandates. Their efforts have included developing product use guides, designing and implementing grower agreements, holding grower meetings and implementing numerous direct-mail campaigns.

“If you have a formal plan in place for Bt use, the configurations are easy to apply,” Slunecka says. “The requirements are fairly simple and straightforward.”

Wandrey says the new EPA-mandated refuge requirements are in place to help prevent or delay potential insect resistance to the Bt technology. He shares this possible scenario: If a resistant corn borer were to survive in Bt corn, it would encounter and mate with a susceptible corn borer from the refuge corn, and their offspring would also then be susceptible. Wandrey stresses, however, that “there's never been a confirmed report of any resistance problems with Bt corn.”

Complete information on the IRM requirements is available from each of the companies supplying the Bt technology and also on the NCGA Web site at In addition, the association's Know Before You Grow program, also available on its Web site, can help you decide whether to use biotech hybrids and where they offer the best fit.

Consider the odds

In 2001, according to NCGA, about 18% of U.S. corn growers chose to plant Bt hybrids. The association anticipates that growers will plant a similar percentage this year. The majority is planted in the western Corn Belt, including Iowa, Nebraska and southwest Kansas, to protect crops from European corn borer (ECB), southwestern corn borer and corn earworm.

Yield losses of 20 to 30 bu. can be commonplace in insect-infested fields, particularly when ECB populations are high, says Iowa State University research and extension entomologist Marlin Rice. However, Rice is quick to point out that no one is able to accurately predict corn borer populations for a given year. “It's like trying to predict the stock market or rainfall,” he says. (See “Endangered corn borers?” page 20.)

He advises to consider the odds of a pest outbreak. With the cost of the Bt trait running between $5 and $8/acre, depending on the hybrid purchased, Rice says farmers need to gain or protect an additional 4 bu./acre (based on $2 corn) to cover their costs.

Preserve the technology

Each of the four companies supplying the Bt technology has made a significant investment in its products. Pioneer, for instance, offers its YieldGard brand of seed products in every corn maturity found in the United States. Dow is poised to introduce its new Herculex I seed technology this spring. “We are anxious to go to the marketplace with this technology,” Stenberg acknowledges, “but we want everything in place before we do.”

One requirement the EPA has placed on the four technology suppliers is that they must ensure that the growers who buy and plant their products use them responsibly. To address this need, representatives from each of the technology suppliers, led by Wandrey, are developing a compliance assurance program. EPA requires the companies to document that growers using Bt hybrids do implement the IRM program; otherwise, they risk having the registrations pulled for their products. The good news so far, Wandrey says, is that “farmers are doing what needs to be done to comply with the requirements.”

Slunecka says as planting time nears, corn growers need to talk repeatedly about the IRM requirements with everyone involved in the planting process. “Whether you're the guy dumping seed into the planter or you hire custom planters, make sure everyone is brought on board with the plan,” he says. “It's a manageable process, but it's crucial that everyone involved understands their responsibility so we have access to the technology in the future.”

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