Studies on the impact of genetically modified (GM) corn (Zea mays) on monarch butterfly caterpillars (Danaus plexippus) in the cornfields of Northern America provide more information on the environmental effects of genetically modified crops. Six papers published simultaneously in the on line early edition of Proceedings of the National Academy of Sciences seem to agree that Bacillus thuringiensis corn (Bt corn) has a negligible impact on monarch larvae populations, although it is suggested that one Bt corn hybrid could have sub-lethal effects on non target insect species.

Bacillus thuringiensis was first described in Thuringia, Germany in 1911 and the toxins it produces have been available for pest control in commercial formulations since the 1930s. For many years Bt remained only a minor component of pest management. The bacteria finally received a celebrity status in 1996 when the first genetically engineered Bt corn was cultivated in...

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