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Popular herbicide loses approval, use allowed until end of month

Farmers who rely on a pesticide called dicamba caught a small break.

A recent decision by the U.S. Court of Appeals overturned the approval of dicamba-based herbicides, but the U.S. Environmental Protection Agency said farmers are allowed to use dicamba until the end of the month.

Virgil Schmitt, extension field agronomist, said there were a lot of people who planned on using the dicamba products and had planted the specific soybeans, so it is was good the deadline was extended to July 31.

“If they couldn’t execute their plan, they were going to be in a world of hurt,” Schmitt said.

Schmitt said the products containing dicamba are extremely popular in Iowa, although it is a love/hate relationship.

It does work, Schmitt said, and often works better than people thought it would on the Roundup-resistant weeds, particularly the water hemp, but at the same time, they are temperamental.

Schmitt compared it to using nitroglycerin as an explosive.

“It’s a great explosive, but you never quite know when it’s going to go off,” Schmitt said.

A challenge some farmers face with dicamba is its volatility and the drift issues it causes. This volatility is increased by factors including warm, humid temperatures that cause the product to turn into a vapor and drift to other plants that are not resistant, Schmitt said.

On June 3, the U.S. Court of Appeals for the Ninth Circuit said the EPA had violated FIFRA in approving the three dicamba herbicides, XtendiMax, Engenia and FeXapan.

FIFRA is the Federal Insecticide, Fungicide, and Rodenticide Act that governs the registration, distribution, sale and use of pesticides, according to the EPA.

“We hold that the EPA substantially understated risks that it acknowledged and failed entirely to acknowledge other risks,” the ruling said.

The court overturned the EPA’s two-year registration of the dicamba-based herbicides to Mansanto and two other companies for use on dicamba-tolerant soybeans and cotton.

Schmitt said the future of dicamba is unknown, but the registration was up for renewal at the end of this year already.

Dicamba is an herbicide discovered in 1957 and approved for use in 1962. In the United States, there are more than 1,000 products sold that include dicamba, according to the National Pesticide Information Center.

Grass, corn and wheat are naturally resistant to dicamba, but it is detrimental to soybeans and other broad leaf plants, Schmitt said.

Dicamba became a popular ingredient in herbicides in the early 2000s after weeds developed a resistance to a commonly used herbicide called glyphosate, the main ingredient in Roundup products, Schmitt said.

Monsanto and DuPont created products XtendiMax and FeXapan which has “vapor grip technology,” and they are said to have something in it to keep the product from volatilizing, Schmitt said. BASF created a product, Engenia, made of a different salt of dicamba that was less volatile.

As the 2017 season progressed a report by Professor Kevin Bradley of the University of Missouri said there were 2,708 dicamba-related injury cases under investigation by various state departments of agriculture and approximately 3.6 million acres of soybeans were injured by off-site movement.

On June 11, an emergency motion was filed by the plaintiffs seeking to halt dicamba use and hold the EPA in contempt.

The motion was denied and farmers were allowed until July 31 to use products purchased before June 3.