News

DPR ANNOUNCES RESTRICTIONS TO PROTECT COMPOST

SACRAMENTO -- The California Department of Pesticide Regulation today announced new pesticide restrictions to protect commercial compost from potential contamination.

DPR will restrict sales of the herbicide clopyralid ("clo-PEER-ah-lid") to lawn and turf professionals, instruct those licensees to assure that green waste stays onsite when the herbicide is used, and require dealers to provide written notice of the restrictions when they sell some clopyralid products. DPR will immediately begin drafting regulations to enforce those restrictions, based on concern that clopyralid residue in grass clippings could make compost toxic to non-target vegetation.

DPR expects its restrictions to affect about 15 clopyralid products used in parks, playing fields, and cemeteries. Golf courses were exempted after DPR determined that grass cycling onsite is a standard industry practice, and clopyralid product labels prohibit use on tees and greens. Clopyralid products labeled for farm, rangeland, and forest use are not affected. DPR took initial action on residential uses in March 2002.

Used to control broadleaf weeds, clopyralid is a low-toxicity chemical that poses little hazard to people, animals, and most vegetation. However, even low levels of clopyralid in compost may damage some plants. Some commercial compost facilities in California have detected clopyralid residues, but no cases of non-target vegetative damage have been documented in the state.

"This action underscores our commitment to California's environment in general and to the compost industry in particular," said DPR Director Paul Helliker. "Clopyralid is a useful pesticide, but some applications could cause a problem if residues accumulate in the green waste stream. We've worked closely with the Integrated Waste Management Board to protect the green waste stream while preserving beneficial uses of this herbicide," said Helliker.

"Using organic material to make compost is an essential part of our efforts to prevent valuable resources from ending up in landfills, a major reason why California's statewide diversion rate has grown to 48 percent," said Linda Moulton-Patterson, Chair of the Integrated Waste Management Board (IWMB). "We are very pleased with DPR's determination to further limit the use of clopyralid. It is a crucial step in protecting the viability of compost markets and the continued success of our waste diversion efforts."

In March 2002, DPR announced it would seek cancellation of 15 clopyralid products registered for residential lawn use, citing a potential hazard to compost. Dow AgroSciences, which registered the herbicide in California, subsequently asked the U.S. Environmental Protection Agency for product label changes to address DPR's concerns. Since U.S. EPA allowed Dow time to clear existing stocks from dealer shelves, products with the new labels are expected to appear in the market later this year.

DPR's action today fulfills a charge by Assembly Bill 2356 (Keeley), passed in 2002. It directed DPR to assess the possibility that clopyralid residues could persist in compost and either impose restrictions or cancel registration of those uses. (See Determination of the Director under AB 2356: Clopyralid in Compost PDF, 28kb)

Clopyralid was initially registered for use in California in 1997 to combat yellowstar thistle, a noxious weed that can kill livestock.

DPR and IWMB began investigating clopyralid residues in compost about 18 months ago. The two Cal/EPA agencies co-sponsored a workgroup that included compost industry representatives, Dow, and other interested parties. The group held four meetings in the past year to explore how clopyralid residues enter the green waste stream, what residue levels may pose a risk to non-target vegetation, and other relevant information. Among the findings:

• Compost monitoring data varied. While the frequency of residue detections declined, low levels of clopyralid continued to show up in some samples.
• Sales data from DPR's pesticide assessment database and Dow AgroSciences suggested sales of turf products declined in the past 12 to 18 months.
• Dow AgroSciences has made significant efforts to educate its product dealers and users about compost issues, and Dow advised users to discontinue residential lawn uses of clopyralid after DPR initiated cancellation action for that use.
• Professional lawn and turf associations and the University of California Cooperative Extension Service raised awareness of the issue in meeting presentations, magazine articles, newsletters and Web postings.
• No phytotoxicity from clopyralid in compost has been reported to DPR during the last 18 months. A recently submitted study examined the phytotoxicity of clopyralid to sensitive plants under defined conditions of soil/compost and compost/peat combinations with varying levels of clopyralid. The Dow-funded study suggested a low probability of phytotoxicity on sensitive plants, given detected levels in California compost. Members of the compost industry reviewed a summary of the study and discussed it with DPR.

However, AB 2356's definition for persistent residues in compost covered a broad range of characteristics with potential toxicity: "residues of an herbicide in compost at levels and in a form with the potential to be toxic or injurious to plants." Based on the law and the joint investigation with IWMB staff, DPR acknowledged the potential diverse uses of compost in commercial agriculture, the nursery industry, and home gardens. Under the law's criteria, DPR determined it was possible that persistent residues in compost could occur from turf uses of clopyralid.

One of six boards and departments within the California Environmental Protection Agency, DPR regulates the sale and use of pesticides to protect people and the environment.

FLEX YOUR POWER! For simple ways to reduce demand and energy costs, see www.flexyourpower.com.

Back to News and Publications