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Update on Chlorpyrifos

Saturday, March 23, 2024
filed under: Insects

Editor’s Note:  The following statement was written and released collaboratively in early March by Adam Varenhorst, Patrick Wagner, Stephen Robertson, Amanda Bachmann, Philip Rozeboom, Brad McManus (all SDSU) and Janet Knodel and Patrick Beauzay (NDSU).
        The U.S. Environmental Protection Agency recently announced that currently registered insecticide products with the active ingredient chlorpyrifos will be legal to use on labeled crops during the 2024 growing season.  According to the South Dakota Department of Agriculture, Natural Resources Pesticide Product Search and Kelly Registration System, there are currently 20 products with the active ingredient chlorpyrifos that are registered for use in South Dakota. Of those 20 products, 15 are used for control of agricultural insect pests. These products include 13 liquid and two granular formulations.
        According to the North Dakota Department of Agriculture Kelley Registration System, there are currently (as of March 15) only four chlorpyrifos products registered for use in sunflower in the state:  Pilot 4E, Pilot 4G, Warhawk and Warhawk Clearform.  Growers are
encouraged to view the South Dakota and North Dakota pesticide databases, as more chlorpyrifos products could be labeled prior to the 2024 growing season.
        As a reminder, labels for these products must be followed regarding application rates and the total amount of active ingredient that is allowed per acre during a single season.
        The EPA revoked all food tolerances for chlorpyrifos in August 2021 due to an April 2021 order from the U.S. Court of Appeals for the Ninth Circuit.  In November 2023, the U.S. Court of Appeals for the Eighth Circuit issued a ruling vacating the EPA’s final rule. This was in part because the 2021 decision for food tolerances did not provide an opportunity for public comments or further fact-finding and because a Proposed Interim Decision (abbreviated as PID) issued by the EPA in 2020 (providing chlorpyrifos safety tolerances for 11 crops) was not finalized before the Ninth Circuit’s ruling.
        The legal use of chlorpyrifos during the 2024 growing season has the potential to be very beneficial for sunflower farmers in South Dakota for the management of pyrethroid-resistant RSSWs.  Per current labels, products with the active ingredient chlorpyrifos should not be applied more often than once every seven to 10 days. In addition, you should not apply more than six pints of chlorpyrifos products per acre during a single growing season.  No more than three applications of chlorpyrifos products should be made to a single field during a single growing season.
        Chlorpyrifos is highly toxic to bees that are directly exposed to the treatment or remaining residuals on flowering plants. Per the labels, “Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area.” This indicates that application timing must occur when pollinators are not actively foraging on sunflower and will not be exposed to residuals during foraging activities.
          The EPA will likely issue a new PID for the 11 crops that were identified in the 2020 PID.  Of the 11, alfalfa, soybean, sugarbeet and wheat (spring and winter) are important for South Dakota and North Dakota agriculture.  Unfortunately, sunflower and corn were not included in the 2020 PID.
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