Using oxadiazon for annual weed control on golf courses is prevalent in the Southeast. It is a crucial active ingredient in several widely used products for both warm- and cool-season turf, including Ronstar and Andersons Goosegrass/Crabgrass Control. In August 2021, the Environmental Protection Agency (EPA) put oxadiazon up for registration review and proposed eliminating all golf course usage except for fairways. Using oxadiazon on sports fields would also have been prohibited.
After the review, the EPA allowed a period for public comment from the industry to voice concerns and problems with the proposed restrictions. A collaborative group of turfgrass weed scientists and national associations, as well as industry partners with oxadiazon in their portfolio, wrote letters and communicated the importance of oxadiazon for controlling difficult weeds on golf courses and sports fields. This communication was well received by the EPA and in March of 2022 the final re-registration decision on oxadiazon was announced. The following are key label changes for oxadiazon that the EPA will put into place:
Oxadiazon will continue to be available for weed control on golf courses, sports fields and for sod production.
Oxadiazon will become a restricted-use pesticide and will be limited to use only by certified applicators.
Applications will be allowed on all golf course playing surfaces. However, the significant change is that annual usage will be limited to 30% of maintained turf acreage.
The single maximum application rate will be 3 pounds of active ingredient per acre, with a maximum total application limit of 6 pounds of active ingredient per acre per year from all formulations, both liquid and granular.
Golf courses can make single applications of up to 4 pounds of active ingredient per acre with a maximum yearly limit of 8 pounds per acre, but only in specific areas with heavy weed pressure and only using granular formulations. These areas will count toward the 30% of total turf area and liquid formulations are prohibited in the same area that year.
If using the liquid formulation, it must be applied before the granular treatment and can only be used once in a calendar year.
The interval between applications in turfgrass must be 60 days or more.
Golf courses and sod farms must include at least a 10-foot vegetative buffer when treating areas near surface water.
Post-application irrigation on the same day will be required.
Applications with backpack sprayers will be limited to spot treatments of 1,000 square feet or less. Golf courses may continue to apply oxadiazon with mechanically pressurized handguns.
You may be asking when all of these label changes will take effect and impact agronomic plans. The new registration will not affect the oxadiazon label in 2024 but the EPA hopes to have a final stamp of approval in the spring of 2024. Once the EPA approves it, manufacturers will have one year from that date to make the required changes to the label. This should give golf courses time to determine which 30% of their maintained turf acreage will be treated and to find alternative products if need be.
Southeast Region Agronomists:
Chris Hartwiger, director, Agronomy – chartwiger@usga.org
Jordan Booth, Ph.D., director, USGA Course Consulting Service – jbooth@usga.org
John Rowland, Ph.D., agronomist – jrowland@usga.org
Chris Neff, agronomist – cneff@usga.org