The news that pests are becoming resistant to genetically modified corn is a potentially major issue in southern Minnesota, where corn is king.

Besides the enormous economic impact at stake, any decline to so-called Bt corn could also have a heavy environmental impact.

When Monsanto released Bt corn in 2003 it promised to be a boon for agriculture and the environment. The seed naturally produces a toxin that poisons western corn rootworms — pests that eat corn roots.

The naturally resistant plants meant farmers could use fewer pesticides on fields.

While most scientists expected pests would eventually build up some immunity to the Bt corn, they are finding rootworm resistance is happening much more quickly and has been found in Minnesota and across the corn belt.

Farmers bear a good share of the blame. Scientists say two things would reduce rootworm resistance: rotating crops each year from corn to soybeans and planting some non-Bt corn in fields to give rootworms a “refuge” area where they can feast on toxin-free corn roots, thus preventing them from building immunity to Bt corn.

With record-high corn prices, fueled by ethanol production and demand for livestock feed, more and more farmers have moved away from traditional crop rotation and are planting all Bt corn on the same ground year after year.

The story is all too reminiscent of past experiences in which society put too much faith in a single scientific advancement only to see it quickly grow useless. DDT was once seen as the way to virtually end insect problems and related human and plant diseases. But overuse quickly brought widespread resistance among pests.

While advances in technology has and will help in the fight against pests, there is still no replacement for a long-term, integrated pest control approach for farms, orchards, cities and gardens.

— Mankato Free Press, Jan. 2