What’s up with Chlorpyrifos and Dicamba?

March 12, 2024 10:24 AM
Blog Post

Recent court cases have brought changes to two pesticides with agricultural uses.

Chlorpyrifos legal for 2024

In late 2023, the Eighth Circuit court rejected the Environmental Protection Agency’s (EPA) 2021 Final Rule revoking all food tolerances for the organophosphate insecticide, chlorpyrifos (e.g., Warhawk). As a result, all chlorpyrifos products currently registered for use in Iowa may be used according to label directions and uses. All previously cancelled products cannot be used this season. Individuals with unusable chlorpyrifos products should contact the manufacturer and if necessary, work with the Iowa DNR’s Regional Collection Centers for disposal.

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, sugar beet, and spring and winter wheat. In addition, the 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.

Dicamba OTT legal until June 12

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

EPA has issued an Existing Stocks Order that allows for the use of these products in Iowa following the previously-approved label application cutoff dates. Retailers, distributors, and suppliers may 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, 2024 or the V4 soybean growth stage, whichever comes first. Anyone applying dicamba OTT must complete the label-mandated dicamba training.


Elizabeth Danielson Extension Specialist

Betsy Danielson is an extension specialist for Iowa State University Extension and Outreach in the Pesticide Safety Education Program (PSEP).