The U.S. Environmental Protection Agency recently released its interim registration review on chlorothalonil.
The Federal Insecticide, Fungicide, Rodenticide Act mandates a periodic review of existing pesticide registrations every 15 years.
During registration review, the EPA determines whether a registered pesticide continues to meet FIFRA registration standards. Where appropriate, the EPA might issue an interim review decision before completing a final registration review decision.
Issuing an Interim Decision is not a decision on whether a pesticide's registration continues to satisfy the FIFRA standard for registration. Instead, the Interim Decision might include mitigation measures and changes to labeling that the EPA has identified that would address risks of concern, identified data or information needed to complete registration review, and include schedules for submitting such data, conducting the new risk assessment and completing the registration review.
The EPA issued this Interim Decision for chlorothalonil on Dec. 26, 2024 to identify risk mitigations that would address risks of concern for chlorothalonil.
One of the world's most widely used turfgrass fungicides, chlorothalonil was first registered for use in the United States in 1966. It also is used to manage fungal diseases in row crops, primarily peanuts, potatoes and tomatoes, according to the EPA.
In October 2023, EPA published the Proposed Interim Decision for registration review of chlorothalonil. Since then, the EPA has identified the need for changes to the annual application rates for non-vulnerable soils for some crops, clarified and updated vulnerable soil language to exclude most cranberry bogs and turf putting greens and included the option to use a vegetative filter strip for turf instead of the ground buffer to aquatic areas as a result of comments received on the PID.
The Interim Decision also addressed changes for vulnerable soils in turf (pages 81, 121), soil organic matter (page 81) and spray drift management (page 124).
Spray boom application rules:
- During application, the sustained wind speed, as defined by the National Weather Service (standard averaging period of 2 minutes), must register between 3 and 10 mph.
- Wind speed and direction must be measured on location using a windsock or anemometer (including systems to measure wind speed or velocity using application equipment). Wind speed must be measured at the release height or higher, in an area free from obstructions such as trees, buildings and farm equipment.
- Do not release spray at a height greater than 3 feet above the ground or crop canopy, except for applications to turf.
- For golf course, sod and turf applications, do not release spray at a height greater than 2 feet above the ground.
- Applicators must select nozzles and pressure that deliver medium or coarse droplets in accordance with American Society of Agricultural and Biological Engineers Standard 572 (ASAE S572).
- Do not apply during temperature inversions.
Chlorothalonil also has some activity as a bactericide, microbiocide, algaecide, insecticide and acaricide. Its exact mechanism of action is not known. Chlorothalonil is registered on a wide variety of sites including turf and row crops and as a mildewicide to be added to paint and other surface treatments.
Click here to read or download the entire EPA Interim Decision.
