Resistance Management Under Fire

Large scale cultivation of Bt maize may lead to the development of insects resistant to the Bt proteins. To date, no maize pests have developed resistance to Bt proteins. To prevent this, farmers in the USA are required to plant 20% percent of the field with non-Bt plants in the vicinity of Bt maize fields. Non resistant European corn borers and Western corn rootworms can survive in these fields and may delay the development of resistance.

However, a survey conducted by the Center for Science in the Public Interest, an American consumer organization found that the percentage of farmers complying with the refuge requirements is declining. Seed companies on the other hand are developing new genetically modified maize varieties which they hope will make it possible to relax the resistance management requirement. A report however shows that resistance can take ten to fifteen years to develop. Genetically modified Bt crops have been grown in the USA since 1996. First populations of Bt-resistant pests were found in Bt cotton between 2003 and 2006, and a recently published study shows that the cotton bollworm can develop multiple resistance. Against this background, the report recommends waiting a few years before relaxing the resistance management requirements for Bt maize.

For details, see: http://www.gmo-safety.eu/en/news/726.docu.html