Skip to content
for a responsible, fair & sustainable food system

Monsanto EU GM Maize Plans Undermined by Damning US Report Resistance in maize pest reported in four states

Immediate release (7 Dec 2011)

Calls to: Pete Riley 07903 341065

A review by the US Environmental Protection Agency (US EPA) [1] describes Monsanto’s insect resistance monitoring strategy for Bt maize in the US Midwest as “inadequate and likely to miss early resistance events”. It also highlights how the crop itself may be causing the problem and how a failure to enforce mitigation measures, like refuges and rotations, is making it worse.

The review confirms that in Iowa and Illinois a major pest of maize, the western corn rootworm, has developed resistance to the toxic Cry3Bb1 protein present in Monsanto’s MON863 and MON88017 Bt maizes. It goes on to report “severe efficacy issues for Monsanto’s Cry3Bb1 trait” in Minnesota and Nebraska.

Monsanto has applied for authorization to grow MON88017 in the European Union. GM Freeze published a review of insect resistance in Bt crops earlier this year [2] and is releasing today a critique of the European Food Safety Authority’s support for approval of EU cultivation of MON88017. [3]

The EPA findings are not a surprise. Laboratory breeding experiments with western corn root worm have demonstrated that, “Resistance evolved after just three generations of selection on Cry3B maize.”

Monsanto’s approach to monitoring the problem comes in for severe US EPA criticism because of:

  • Sampling insects too far from damaged crops.
  • Adopting too high a damage threshold before further action is taken.
  • Failure to sample for resistant adults from problem fields.
  • Failure to take follow up samples in the next season if adults were not sampled.

The US EPA review suggests the breakdown in effectiveness of GM maize is caused by a number of factors including:

  • Bt plants producing too low a dose of toxin to kill pests, and hence fostering resistance developing in those that survive.
  • Farmers failing to plant non-GM crops refuges to ensure sufficient non-resistant adults are present to mate with resistant individuals, preventing the recessive resistance from becoming dominant in the population.
  • Continuous cultivation of the same Bt maize on the same land for several years without rotation.

The US EPA also presents data showing the amount of toxin needed to kill the western corn root worm in problem areas has increased by as much as one hundred times.

The Agency warns that merely resorting to other GM maize varieties using several Bt toxins may not provide a lasting solution:

If Cry3Bb1 resistance has indeed developed (ie, ‘confirmed resistance’), a 5% refuge for pyramids (ie, SmartStax expressing Cry3Bb1 and Cry34/35 targeting corn rootworm) will be substantially less durable and could ultimately compromise the second unrelated toxin used to control the pest (ie, in this case Cry34/35).

So far US farmers have responded to the crop losses caused by the outbreak of the insect resistance in Bt maize by using additional pesticides to “bomb” adult beetles, adopting other GM varieties with different Bt toxins present, or a combination of approaches. This increases the number of biotech companies involved, but may not be effective and increases the environmental burden of industrial agriculture.

Commenting Pete Riley of GM Freeze said:

Monsanto’s approach to monitoring resistance in this major pest of maize has rightly been heavily criticized by the US EPA.

Predictably all Monsanto and the US EPA can suggest is more pesticides and more GM. It seems likely that these will also breakdown – then what?

What’s happening to Bt crops in the US Midwest underlines that GM is not a panacea and it is not sustainable. There is an urgent need for scientists and farmers to develop new systems of agronomy based on agroecology, which we know is an system effective over time.

Europe’s precautionary approach to GM crops is proving very wise as time passes and more and more problems with GM come to the fore. Now is no time to change.


[1] US EPA, Office of Chemical Safety and Pollution Previention, 2011. Updated Biocides and Pollution Prevention Division Review of Unexpected Cry3Bb1 Corn Rootworm Damage (doc ID EPA-HQ-OPP-2011-0922-0003 – pdf also available from GM Freeze upon request)

2. See GM Freeze Insect Resistance to Bt Toxins in GM Insect Resistant Crops

3. See GM Freeze Papering Over the Cracks: EFSA’s opinion on cultivation GM MON88017 maize in Europe – Mitigation is not enough