EPA Releases Interim Review Decision on Oxadiazon

On April 28th, 2022 The U.S. Environmental Protection Agency (EPA) released its Interim Review Decision on several pesticides as part of its periodic review of pesticide registrations. One active ingredient that is of key interest to sod producers is oxadiazon, a pre-emergence herbicide labeled for use on many weed species of annual grasses, primarily crabgrass and goosegrass.

TPI has been working with EPA on this registration review since at least August of 2021 when the Proposed Interim Registration Review Decision was posted to the EPA’s public document in the U.S. Federal Register. As a result, TPI and nine individual sod producers from the states of Georgia, North Carolina, South Carolina, Tennessee, and Texas submitted comments for EPA’s consideration on oxadiazon’s importance in sod farms and the potential impacts of this registration review decision on those who use it.

Most of the proposed changes to the oxadiazon label revolve around rate reductions, limitations on liquid applications, post-application irrigation, and others. A summary of the EPA’s recommendations from the Interim Registration Review are as follows:

For Sod Farms

  • Oxadiazon will be classified as a Restricted Use Pesticide (RUP)
  • A yearly maximum application rate of 6.0 lbs ai/acre/year for all use sites, reduced from a previous maximum of 8.0 lbs ai/acre.
  • A single maximum application rate of 3.0 lbs ai/acre, reduced from a previous maximum of 4.0 lbs ai/acre.
  • Up to two liquid applications per year of oxadiazon
  • A 60-day re-treatment interval is required between applications
  • A 10-foot vegetative buffer is required between treated areas and surface water
  • Thorough post-application irrigation is required as soon as possible on the same day of application

For other Turf Sites (golf courses, parks, athletic fields)

  • Oxadiazon will be classified as a Restricted Use Pesticide (RUP)
  • A yearly maximum application rate of 6.0 lbs ai/acre/year for all use sites
  • A single maximum application rate of 3.0 lbs ai/acre, reduced from a previous maximum of 4.0 lbs ai/acre.
  • Limit of one liquid application per year at a max rate of 3 lbs ai/acre
  • Golf courses only – Restrict treatment of up to 30% of golf course managed turf with a required 10-ft vegetative surface water buffer
  • Golf courses only – Allow up to two granular applications at 4lbs ai/A in areas of heavy weed pressure only
  • Prohibit Mechanically Pressurized Handgun (MPHG) on all sites except golf course turf
  • Restrict liquid backpack applications in turf to spot treatments only (1,000 sq ft or less)

One particular comment worth noting is that continued registration on non-agricultural, non-golf turf sites (athletic fields, parks, institutional turf, etc.) will currently be allowed until a pending review of new required studies are complete regarding the transfer of residue under these new labeling requirements.

TPI will continue to work with EPA to provide public comment on these recommended changes in the Interim Review Decision for oxadiazon. A Federal Register Notice has announced the availability of the oxadiazon Interim Decision, and a final registration review decision for oxadiazon will only be made after EPA completes additional requirements.

As always, we seek and welcome input from sod producers on these and other regulatory affairs. Last but certainly not least, thanks to those sod producersand representatives of other industries who logged onto provide public comment on this important product. Thanks also to EPA staff for working with our industry on this and addressing many of our needs in this decision.

 

About the Author

Casey Reynolds, PhD
Dr. Casey Reynolds is the Executive Director at Turfgrass Producers International

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