Rootworms Are Eating Their Way Through Bt Corn

Diabrotica virgifera

Diabrotica virgifera

On November 28, 2011, the U.S. Environmental Protection Agency (EPA) released a memo which identified the failure of Monsanto’s Bt corn to prevent “unexpected” rootworm damage to the corn crop. The EPA stated that at least four states, Iowa, Illinois, Minnesota, and Nebraska, are seeing “severe efficacy issues” for Monsanto’s Bt corn. The agency also noted problem areas in four additional states, Colorado, South Dakota, Minnesota, and western Wisconsin, and asked that they be monitored in the future.

Shaking its regulatory finger at Monsanto, the EPA said in no uncertain terms that the company’s resistance monitoring is “inadequate and likely to miss early resistance events.”

“It’s one of those delectable reports written not by political appointees or higher-ups, but rather by staff scientists reporting what they see,” commented Tom Philpott, the food and agricultural blogger at MotherJones. Monsanto, for its part, is sticking to its PR talking points and denying the existence of a problem. Although the company reportedly is taking the EPA’s report seriously, “Monsanto continues to believe there’s no scientific confirmation of resistance to its Bt corn,” a company spokesperson told Bloomberg news. This mirrors the sentiments the company expressed in September, a month after the Iowa State University published a study showing resistance by rootworm after ingesting the company’s Bt corn. “Our Cry3Bb1 protein is effective, and we don’t have any demonstrated field resistance,” assured a company representative in September.

Despite the company’s assurances, the EPA report paints a different picture.

In its November report, the EPA identified that resistance to Monsanto’s insecticidal poison producing corn has been reported as early as 2004 — a mere year after the product was released. And while the number of resistance reports kept coming in, “Monsanto reported [to the EPA] that none of [the company's] follow-up investigations resulted … in finding resistant populations [of rootworms].”

In case you are wondering, part of the condition for registration of Monsanto’s corn in 2003 was a requirement that Monsanto monitor the performance of its product and report to the EPA data collected from farmers and the company’s investigations. During the registration of Monsanto’s corn, there was also a debate as to the size of the buffer zone of non-GMO corn that farmers should be required to set aside nearby when planting Bt corn to avoid resistance.

In deciding on the size of the buffer zone, the EPA approved Monsanto’s recommendation of a 20% buffer zone and ignored the recommendation of its scientific advisory panel (SAP), which recommended a 50% buffer zone. In discussing the reasons for EPA’s decision, a 2003 Nature article reported that:

the EPA decided to go with a 20% refuge [instead of SAP's recommended 50%]  because they received additional data from Monsanto that showed it would be acceptable using conservative assumptions. The EPA calculated that even if 100% of crops were transgenic, resistance wouldn’t occur for 7-15 years.

But resistance occurred as as soon as 2004.

The EPA also noted in its November report that Monsanto’s problem assessment is “insufficient” as the company collects beetles 1-2 miles away from the problem field, which the EPA says is too far. Since “the majority of adult corn rootworm may not disperse long distances,” says the EPA, “the greatest probability of capture of resistant genotypes should be in the problem fields, possibly in adjacent fields, but less likely in fields 2 miles away during that particular year.”  The EPA went further to comment that “[i]f the resistance monitoring program is to be meaningful, a more proactive, effective approach must be adopted.”

The EPA also found problems with Monsanto’s trigger point measurement for resistance in the crop as too high and therefore likely to miss early resistance.

All of this spells trouble for the company’s latest product, Smartstax corn, which it developed with Dow AgroSciences. The EPA approved Smartstax in July 2009, contains 6 traits for insecticidal resistance (Bt toxins) and two traits coded for herbicide tolerance. Monsanto got the EPA to approve a mere 5% buffer zone for Smartstax but now the EPA says that “a 5% refuge … will be substantially less durable and could ultimately compromise the second unrelated toxin used to control the pest.”

Bill Freese, the Science and Policy Analyst at the Center for Food Safety told GMO Journal that “EPA must put independent agronomists in charge of monitoring for insect resistance, since Monsanto can obviously not be trusted to do this job.”