Wallaces Farmer

What’s up with chlorpyrifos and dicamba?

Recent court cases have brought changes to the use of these two pesticides.

Rod Swoboda

June 3, 2024

3 Min Read
closeup of spray nozzles
DICAMBA DECISION: At least for 2024, EPA is allowing the continued use of dicamba herbicide postemergence, to use up existing stocks already purchased.Holly Spangler

The Environmental Protection Agency has announced that currently registered insecticide products with the active ingredient chlorpyrifos and labeled for use on major crops will be legal to use during the 2024 growing season.

Also, EPA is allowing over-the-top application of dicamba herbicide products that are already in the supply chain. The three dicamba weed control formulations are XtendiMax, Engenia and Tavium.

Chlorpyrifos is an organophosphate insecticide (Lorsban, Warhawk and others) that’s been used to control many important crop pests. In the past 15 years, chlorpyrifos, like many organophosphates, has come under scrutiny due to acute toxicity concerns to humans, especially children. In an effort to protect all ages of humans and the environment, EPA began the process of phasing out many uses of organophosphates.

Another big issue is the widely used dicamba herbicide. In February 2024, a federal court ruling said EPA’s previous decision to halt dicamba use postemergence didn’t follow the proper rules for comment in 2020, when EPA issued rules on how dicamba could be used. Thus, EPA now says it will allow existing stocks of dicamba to be sold.

Betsy Danielson, Iowa State University Extension specialist and co-coordinator of the Pesticide Safety Education Program in Iowa, provides the following update.

In late 2023, the U.S. Eighth Circuit court rejected EPA’s 2021 Final Rule revoking all food tolerances for the organophosphate insecticide chlorpyrifos. As a result, all chlorpyrifos products currently registered for use in Iowa may be used according to label directions and uses. To view the list visit currently insecticides registered for use in Iowa.

All previously cancelled products cannot be used in the 2024 crop year. “If you have unusable chlorpyrifos products, you should contact the manufacturer and if necessary, work with the Iowa Department of Natural Resources Regional Collection Centers for disposal,” Danielson says For the location and information about the collection centers, visit Iowa DNR’s Regional Collection Centers.

The EPA plans to propose new tolerance restrictions soon for all food uses of chlorpyrifos, except for the 11 crops identified in the Eighth Circuit Court lawsuit: alfalfa, apple, asparagus, tart cherry, citrus, cotton, peach, soybean, strawberry, sugarbeet, and spring and winter wheat.

In addition, EPA is engaged in discussions with registrants of chlorpyrifos products to further reduce exposures associated with these 11 uses of chlorpyrifos. Notices of tolerances, amendments and cancellations are published in the Federal Register.

Earlier this year, the U.S. District Court in Arizona rejected the 2020 registrations of three dicamba herbicide products previously approved by EPA for over-the-top (OTT) applications. Those three products are XtendiMax, Engenia and Tavium. The court ruled that EPA violated notice-and-comment mandates for new-use pesticide registrations.

EPA has issued an existing stocks order allowing for the use of these products in Iowa following the previously approved label application cutoff dates. Retailers, distributors and suppliers could sell currently registered products containing dicamba until May 13, 2024. Applications of XtendiMax, Engenia and Tavium can be made according to label directions until June 12 or the V4 soybean growth stage, whichever comes first.

Danielson points out that anyone applying dicamba OTT must complete the label-mandated dicamba training. Visit dicamba training for more information.

The good news, at least for this year, is that EPA is allowing continued use of dicamba existing stocks that were already sold. Many farmers buy herbicide products in late fall and in winter. It was previously estimated that dicamba is used on 45% of all of U.S. soybean acres.

Swoboda is an editor emeritus of Wallaces Farmer.

About the Author(s)

Rod Swoboda

Rod Swoboda is a former editor of Wallaces Farmer and is now retired.

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