LINCOLN, Neb. (DTN) -- The U.S. Environmental Protection Agency on Tuesday approved two new herbicide active ingredients designed to combat waterhemp and Palmer amaranth in corn, soybeans and other crops, according to documents posted by the agency on regulations.gov.

Diflufenican is a selective contact Group 12 herbicide registered by Bayer CropScience as Convintro.

A memorandum posted by the EPA describes it as an herbicide for preplant and preemergence control of waterhemp, Palmer amaranth and other pigweed species in corn and soybeans.

According to EPA, it could be rotated with other herbicides to slow the development of resistance in waterhemp and Palmer amaranth.

"The Weed Science Society of America classifies diflufenican as a Group 12 herbicide, which makes diflufenican the first effective PDS inhibitor herbicide for control of waterhemp, Palmer amaranth, and other pigweed species in corn and soybean," the agency said in a memorandum. "This is a novel mechanism of action that could be a valuable rotation tool for pest resistance management in the registered crops."

EPA also approved a new burndown herbicide active ingredient from Valent U.S.A. LLC called epyrifenacil, for use on canola, field corn, soybeans, wheat, fallow land and non-crop areas.

The herbicide trademarked as Rapidicil is designed to provide broad-spectrum control of both broadleaf and grass weeds, according to EPA, including weeds already resistant to other PPO-inhibitor herbicides.

"The use of epyrifenacil as a complementary burndown herbicide in glyphosate-tolerant cropping systems would also help extend the benefits of such cropping systems," EPA said in a memorandum in support of the registration.

"The agency finds that the benefits of an additional broad-spectrum PPO-inhibitor herbicide outweigh any potential risks. This herbicide provides effective control of problematic weed species and target-site-based PPO inhibitor-resistant weed biotypes."

The approval comes five days after the U.S. Supreme Court ruled that federal law preempts state failure-to-warn laws, handing Bayer a victory in the ongoing legal saga of glyphosate-based Roundup.

This week Monsanto, which is owned by Bayer and its subsidiary, Ruevon LLC, also filed a petition with the International Trade Commission alleging glyphosate from China is sold in the U.S. at below fair-market value.

In response to the approval, agriculture groups touted the registrations as important in combating an ever-increasing threat to crops posed by weeds.

"We appreciate EPA Administrator Lee Zeldin and the agency for advancing registrations for a suite of new crop protection tools to ensure U.S. farmers have access to cutting-edge technologies that promote efficient agriculture production," said Scott Metzger, president of the American Soybean Association and a soybean farmer from Ohio.

"Soybean farmers across the country continue to combat new and mounting challenges related to weeds and other pest diseases. To produce the world's most environmentally efficient and reliable soybeans, crop protection tools must evolve alongside modernizing farm practices, making access to these innovative crop protection technologies critical to maintaining the competitive advantage of U.S. soybeans."

American Farm Bureau Federation President Zippy Duvall said in a statement that the group appreciates EPA's "rigorous review process" and that the herbicides would "enable farmers to do more with less."

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