(Adds details on dicamba, quote from EPA administrator)
CHICAGO, Oct 31 (Reuters) - The U.S. Environmental Protection Agency said on Wednesday it would allow farmers to spray a controversial weed killer made by Bayer AG's Monsanto Co and BASF SE for two more years, with additional restrictions on use.
Farmers have complained that the herbicide called dicamba drifts away after it is sprayed on soy and cotton plants that Monsanto engineered to resist it. The chemical then damages nearby crops that cannot tolerate it, according to farmers and agronomists.
The EPA said dicamba was an important tool for controlling weeds in crop fields. However, the agency said it would prohibit applications on soybeans 45 days after planting and on cotton 60 days after planting to address "potential concerns to surrounding crops and plants."
EPA approval for dicamba to be sprayed on resistant crops expires this autumn. Farmers have been anxiously awaiting the agency's ruling amid uncertainty about whether to buy dicamba-resistant crops for planting next year.
"By extending the registration for another two years with important new label updates that place additional restrictions on the product, we are providing certainty to all stakeholders for the upcoming growing season," EPA Acting Administrator Andrew Wheeler said.
Bayer bought Monsanto and its portfolio of dicamba-resistant soy seeds, sold under the Xtend brand, for $63 billion this year in a deal that created the worlds largest seed and pesticides maker.
Bayer sells dicamba herbicide, along with rivals BASF SE and DowDuPont Inc. The companies have previously said the chemical can be used safely and is needed to control tough weeds.
Representatives could not immediately be reached for comment after normal business hours.
Bayer is banking on Xtend soybean seeds to dominate soy production in the United States. They are seen as a replacement for Monsanto's Roundup Ready line of seeds, engineered to tolerate the weed killer glyphosate, which has lost effectiveness as weeds develop tolerance to the chemical.
During the summer of 2017, after farmers planted Monsantos dicamba-resistant soy seeds en masse, the herbicide drifted onto nearby farms and damaged an estimated 3.6 million acres of non-resistant soybeans, or 4 percent of all U.S. plantings.
Farmers also reported problems during the 2018 growing season.
In another new restriction, the EPA limited the number of applications on growing cotton plants to two times from four, according to a notice. Applications on dicamba-resistant cotton and soy will also be restricted to one hour after sunrise to two hours before sunset. (Reporting by Tom Polansek; Editing by Richard Chang and Grant McCool)