article_snippet: The plants have been altered through the insertion of foreign genes that create toxins to kill insects or give The plants immunity to spraying with powerful chemical weed killers.
article_snippet: There is evidence from the USA that certain weeds have developed immunity to the same weed killers with the result that certain weeds are taking over many fields.
article_snippet: At the same time, the use of sprays alongside the GM crops is thought to have caused a collapse in the population of the Monarch butterfly, which is now under threat.