U.S. EPA takes action to prevent ecological risks from herbicides aminopyralid and picloram

The U.S. Environmental Protection Agency (EPA) is releasing the interim registration review decisions (IDs) for the pesticides aminopyralid and picloram, finalizing stronger measures to help prevent residues from contaminating compost and damaging non-target plants in sites where compost is applied. The Federal Insecticide, Fungicide and Rodenticide Act requires the agency to periodically re-evaluate pesticides through registration review to ensure that risk assessments and pesticide decisions reflect the best available science. The ID is one of the final stages of the registration review process and implements risk mitigation to address risks of concern.

Aminopyralid and picloram are pyridine herbicides used in both agricultural and non-agricultural settings. Agricultural use sites include pastures and rangeland. Non-agricultural use sites include turf, industrial areas, rights of ways, roadsides and other non-agricultural sites. Aminopyralid and picloram are used to control of a wide range of broadleaf and woody weed species in pasture and rangeland, particularly invasive species and help preserve conservation land due to their ability to target hard to control weeds without damaging native vegetation.

Pyridine herbicides such as aminopyralid and picloram have a history of reported compost incidents. Residues in contaminated compost can persist and damage non-target plants in residential gardens and other sites. Compost contamination occurs when treated materials, or manure from animals that consumed treated materials, are collected and recycled into compost. For many years, EPA has been engaging with stakeholders to identify effective measures to prevent damage to non-target plants where compost is applied. EPA is now requiring the following mitigation measures to reduce the potential for residues of these herbicides in compost:

• Prohibition of off-site use of treated plant materials and manure from grazing animals for compost and animal bedding/feed until 18 months after application to allow for residues to decline;

• Requiring that livestock be grazed on forage that haven’t been treated for three days before moving to a site where manure is collected, or sensitive crops are grown; 

• Requiring pasture applicators to notify the property owners/operators of the compost prohibition, and for the applicator to keep a record of this notification for two years; 

• Updating compost pictogram on pesticide labels showing growers/operators how to manage treated materials; and,  
  Requiring registrants to participate in a stewardship program and provide educational outreach for applicators, growers, land managers/operators, and others affected by herbicide residues in compost. 

EPA will also continue to work with stakeholders to develop additional educational resources for land managers and others affected by herbicide residues in compost.

The IDs finalize enforceable mitigation measures to address spray drift risks of concern, such as a maximum wind speed for applications, medium or coarse droplets, and mandatory spray release heights for ground and aerial applications.

Additional information on the pyridine and pyrimidine herbicides and interim decisions are available on EPA’s website.