The U.S. EPA proposed significant changes to the chlorothalonil labels in the fall of 2023 by issuing a Preliminary Interim Decision. GCSAA worked with golf course superintendents and turfgrass scientists to weigh in on the proposed label changes. After review of all public comments in the federal docket, and working with  registrants, the EPA published their Registration Review Interim Decision (ID) on chlorothalonil on Jan. 6, 2025. GCSAA’s government affairs team is reviewing the lengthy document but wanted to share the most important updates:

VULNERABLE SOILS definition for turf sites

(page 81; also listed on page 121)

For products with turf use sites other than sod farms (i.e. industrial, athletic fields; golf courses), the following label language for vulnerable soils is needed:

              “Do not apply more than 6.2 lbs chlorothalonil active ingredient per acre per year in vulnerable soils. Turf putting greens constructed to USGA or California green specifications or constructed as push up greens are not considered vulnerable soils and 45.2 lbs chlorothalonil active ingredient per acre per year may be applied. For other turf, vulnerable soils are soils that meet all three of the following criteria: (1) The soil texture of the application area is over 50% sand, loamy sand, or sandy loam soil as defined by USDA’s soil classification system without a restrictive layer that impedes the movement of water through soil, (2) having less than 2% organic matter content (thatch/mat included), and (3) the water table occurs at a depth of 30 feet or less from the surface. If any one of these three criteria are not met, the soil is not considered vulnerable.”

Supplemental soil organic matter and soil texture determination language

(page 81)

To provide instructions for a user to determine whether they have vulnerable soil, additional labeling language about determining organic matter content and soil texture is needed:

“Supplemental Recommendations for Determining Soil’s Organic Matter Content: If you need to determine the organic matter content of your soil to confirm soil vulnerability, do so before applying chlorothalonil. To obtain a representative soil sample for soil testing, take a composite of several soil samples collected throughout the intended application area. Ideal soil sampling depth varies depending on use site. Consult local extension publications for additional information on recommended soil sampling procedures and soil testing methods. Annual, or more frequent, soil testing for organic matter provides more accurate soil characteristic identification.

Supplemental Instructions for Determining Soil Texture:

If you need to determine soil texture to confirm soil vulnerability, see USDA’s Web Soil Survey tool which may be found here: https://websoilsurvey.nrcs.usda.gov/app/.”

NON VULNERABLE SOILS -- turf use rates – no change from Proposed Interim Decision

(page 78)

Mandatory spray drift language

(page 124)

“MANDATORY SPRAY DRIFT MANAGEMENT

Ground Boom Applications:

• During application, the Sustained Wind Speed, as defined by the National Weather Service (standard period of 2 minutes), must register between 3 and 10 miles per hour.
• 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 heigh greater than 2 feet above the ground.
• Applicators must select nozzle and pressure that deliver medium or coarser droplets in accordance with American Society of Agricultural & Biological Engineers Standard 572 (ASAE S572).
• Do not apply during temperature inversions.”

 Aquatic habitat buffer language

(page 125)

Spray Drift Buffer to Aquatic Habitats

“For aerial and airblast applications, this product must not be applied within 150 feet of water bodies (estuarine/marine and freshwater).

For ground applications, this product must not be applied within 25 feet of water bodies (estuarine/marine and freshwater). If applying to turf, you may choose to construct and maintain a 10-foot vegetative filter strip of grass or other permanent vegetation between the field or application area edge and nearby aquatic habitat (such as, but not limited to, lakes; reservoirs; rivers; streams; marshes or natural ponds; estuaries; and commercial fish farm ponds) in lieu of the 25-foot buffer. If using a vegetative filter strip, only apply products containing chlorothalonil onto fields or application areas where a maintained vegetative filter strip of at least 10 feet exists between the field or application area edge and down-gradient aquatic habitat.”

Implementation 

A Federal Register Notice will announce the availability of the Chlorothalonil Interim Decision - done on January 6, 2025. A final Registration Review decision for chlorothalonil will only be made after EPA (1) completes effects determinations and (2) meets EPA’s Endangered Species Act section 7 obligations.

The Chlorothalonil ID states that registrants must submit revised labels within 60 days after posting of the ID. The EPA approval timeline for amended chlorothalonil labels is unknown, but it could be anywhere from 6 months to 2 years, possibly longer. Once amended labels are approved by the EPA, registrants will have 12 months to sell products with the "old" label.

GCSAA will continue to provide more information as the timeline unfolds and more details become available.  

Here is a copy of the final Chlorothalonil Interim Decision.