EPA announces interim registration review decision for hexazinone

Recently, the U.S. Environmental Protection Agency (EPA) announced the availability of a Proposed Interim Registration Review Decision for hexazinone (https://www.regulations.gov/document?D=EPA-HQ-OPP-2009-0755-0028).

Hexazinone is used in forestry in all regions of the US for site preparation, herbaceous weed control, and release. In the interim decision, EPA has proposed several mitigation measures and label changes relevant to forestry use of hexazinone.

For all dry flowable/water dispersible granule formulations:

  • Reduce maximum aerial application rate for forestry operations from 5.0 to 3.4 lbs. a.i./acre.
  • Reduce maximum “Mechanically Pressurized Handgun” application rate for forestry operations from 2.0 to 1.12 lbs. a.i./gallon.
  • Occupational handlers must wear PF10 respirators.

For all granular and pelleted formulations:

  • Registration for aerial applications of granules for the forestry use is cancelled.

For all liquid formulations:

  • Reduce maximum aerial application rate for forestry operations from 5.0 to 3.4 lbs. a.i./acre.
  • Reduce maximum “Mechanically Pressurized Handgun” application rate for forestry operations from 2.0 to 1.12 lbs. a.i./gallon.
  • Occupational handlers must wear PF5 (aerial application mixer/loader) or PF10 (Mechanically Pressurized Handgun mixer/loader/operator) respirators.

New label language related to reducing spray drift has been proposed:

  • For aerial applications, the distance of the outer most nozzles on the boom must not exceed three-fourths of the length of the wingspan or rotor diameter. To further reduce drift, use on half of the length of the wingspan or rotor diameter at the edge of the field.
  • Applicators must only spray when wind speed is 10 miles per hour or less.
  • Applicators must not spray during temperature inversions.
  • For aerial applications, the release height must be no higher than 10 feet from the top of the crop canopy or ground, unless a greater application height is required for pilot safety.
  • For groundboom applications, apply with the nozzle height no more than 4 feet above the ground or crop canopy. For all other ground applications, the nozzle must be no more than 4 feet from the target vegetation.
  • For ground and aerial applications, select nozzle and pressure that deliver medium or coarser spray droplets as indicated in nozzle manufacturer's catalogues and in accordance with ASABE Standard 572.1.

EPA also proposes to remove information about volumetric mean diameter (VMD) from all hexazinone labels where such information currently appears.

Comments on the decision, which is available at https://www.regulations.gov/document?D=EPA-HQ-OPP-2009-0755-0029