Monarch butterflies threatened by GM crops in U.S., study says

A sweeping Canadian-led study of environmental influences on monarch butterflies has thrown into sharp focus what appears to be the most crucial factor affecting the migrating insect’s survival: loss of milkweed in the U.S. Midwest due to a change in farming practices. Monarchs lay their eggs on milkweed plants every spring and summer as successive generations migrate northward from Mexico as far as Canada. At the end of the breeding season a single “super generation” heads back south, travelling thousands of kilometres so that the cycle can begin anew. The evidence points to the U.S. corn belt, where increased cultivation of genetically modified corn and soybean crops comes with a devastating side effect for milkweed. When GM crops are planted, fields are sprayed with herbicides to wipe out any wild plants that don`t share the crops’ genetically engineered protection. In the past, herbicides would typically be applied early in the growing season, when milkweed seeds are still underground. With GM crops, the spraying happens later, and any milkweed growing adjacent to the crops is hit hard...more