EPA revises Reregistration Eligibility Decision for sulfometuron herbicides

Under federal law, the U.S. Environmental Protection Agency (EPA) must conduct reviews of the human health and environmental effects of registered pesticides to determine whether the pesticides are eligible for reregistration. After reviewing a pesticide, EPA prepares a Reregistration Eligibility Decision (RED) in which the agency may propose new restrictions on use of the pesticide.

Sulfometuron methyl (SM) is the active ingredient in the herbicide Oust®, which is used to control annual and perennial broadleaf and grass weeds. The reregistration process for SM has been underway for several years. NCASI submitted comments at several stages of this process.

In September 2008, EPA issued a RED for SM in which the agency proposed a number of risk mitigation measures that would have drastically curtailed uses of Oust® in forestry operations. These measures included (a) 500-ft no-spray buffer zones around water bodies for aerial applications and 100-ft buffers for ground applications; (b) application height no greater than 10 ft above the forest canopy; and (c) allowing applications in some areas only when a 60% or greater chance of precipitation has been forecast.

NCASI’s comments addressed two main points: (a) industry concerns about the cost and safety implications of the risk mitigation measures proposed by EPA; and (b) the availability of practical alternatives.

EPA recently released an amendment to the RED that addressed many of the issues raised by NCASI and others (Federal Register Vol. 75, No. 12, pp. 3233-3234, January 20, 2010). The key revisions are:

  • Rather than prohibit spray applications more than 10 feet above the canopy, applicators are now directed to release spray at the lowest level consistent with pest control and flight safety.
  • Aerial applications are restricted to rotary wing aircraft.
  • The maximum single application rate for forestry use is 0.199 lb ai/A.
  • All applications must be made using extreme coarse droplet size (>500 VMD) or larger, according to ASABE (S572) definition.
  • No-spray buffer zones around aquatic vegetation for aerial applications are set at 75 feet.
  • No-spray buffer zones around aquatic vegetation for broadcast ground applications are set at 50 feet.
  • No-spray buffer zones around aquatic vegetation for hand-held applications are set at 30 feet.

For additional information, contact Dr. Vickie Tatum at the NCASI Southern Regional Center.

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