Bad news for Midwest corn growers -- a new study has found some pests have developed an immunity to Monsanto's genetically-altered corn seeds.
In a study by Iowa State entomologist Aaron Gassman, western corn rootworms have developed a resistance to Monsanto's altered plants. The corn plants had been grown with seeds designed to resist the bug by releasing a gene that destroyed the rootworm but was harmless to animals and most other insects.
This is the first time a Midwest bug has evolved to resist a genetically altered crop.
So far the sample of resistant corn that is being harmed by the rootworm is small, only "four northeast Iowa fields have evolved," Gassmann found.
"These are isolated cases, and it isn't clear how widespread the problem will become. But it is an early warning that management practices need to change," Gassmann said.
Monsanto shares fell with the news Monday. The company responded to Gassmann's findings by stating the seeds were working "on more than 99% of the acres planted with this technology."
Corn growers could opt to use competitor's seeds and spray with harsher pesticide to fight the resistant insects.