When the EPA’s Preliminary Interim Decision on thiophanate methyl was issued in Spring 2023, GCSAA and its members were concerned about the proposed changes to the label, which included a significant reduction to the rate and number of applications annually. GCSAA and its members commented that reducing the application rate and number of applications permitted on turf as proposed would not be efficacious for disease management, and that this may have been brought about by EPA’s grouping of residential and golf course turf uses of TM.

In the Jan. 6, thiophanate methyl Interim Decision, EPA shared that they agree with this assessment and separated residential turf and golf course turf uses for this ID. EPA has revised the turfgrass rate mitigation in response to the review of public comment. Consequently, golf turf uses do not require rate reduction.

Some key provisions of the thiophanate methyl Interim Decision:

• Soil application restrictions: TM products cannot be applied where the depth to groundwater is 20 feet or less, the soil texture is sand or loamy sand, and the soil has less than 2% organic matter (addresses groundwater risks). If using this product on golf courses, this mitigation applies to tees and greens only if the underlying native soil is sand.
• TM commercial soil applications to landscape, nursery, or field grown ornamentals - Reducing the maximum application rate from 26 lb ai/A to 12.5 lb ai/A with a 5,000 sq. ft treatment area and restricting application to no more than 0.287 lb ai/1,000 sq. ft, no more than 5,000 sq. ft treatment area within any given acre per year, and no more than 1.435 lb ai in an acre per year.
• TM liquid drench or directed spray application for ornamentals in fields/outdoors - Restricting application to no more than one application per year at a max of 5,000 sq. ft treatment area within any given acre, preparing a drench solution containing [amount of product equivalent to 0.5 lb ai]/100 gallons of water as a drench or directed spray over a maximum of 5,000 sq. ft within any given acre, and not applying more than 3.1 lb ai/A per year.
• TM granular applications to ornamentals - Restricting application to no more than one application per year at a max of 5,000 sq. ft treatment area within any given acre, not applying 0.625 ai/1,000 sq. ft over a maximum of 5,000 sq. ft within any given acre, and not applying more than 3.1 lbs ai/A per year.
• Reg. No. 1001-70 on outdoor ornamentals - Restricting application to no more than one application over a maximum of 5,000 sq. ft treatment area within any given acre per year, applying 26.5 lb. of product/1,000 sq. ft (equivalent to 0.55 lb ai/1,000 sq. ft) over a maximum of 5,000 sq. ft within any given acre, and not applying more than 2.75 lb ai/A per year.

Implementation

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

The thiophanate methyl ID states that registrants must submit revised labels within 60 days after posting of the ID. The EPA approval timeline for amended thiophanate methyl labels is unknown. GCSAA will continue to provide more information as the timeline unfolds and more details become available.  

Here is a copy of the final thiophanate methyl Interim Decision.