Roundup resistant weeds pose environmental threat

CHAMPAIGN, Ill. (AP) - Farmers hailed the weed killer Roundup when it was introduced in the 1970s because it could kill nearly any plant and allowed them to give up harsher chemicals and reduce tilling.

But now some Roundup resistant varieties of weeds have emerged, and some farmers are being forced to turn to less environmentally friendly herbicides.

Penn State University weed scientist David Mortensen estimates that in three or four years, farmers' use of dicamba and 2,4-D, a weed killer developed during World War II and used in Agent Orange, will increase by 55.1 million pounds a year because of resistance to Roundup.

Mortensen says that unlike Roundup, these older herbicides easily drift beyond the spots where they're sprayed and threaten neighboring crops and wild plants.