New herbicide will contaminate compost
By Ken McEntee
June 17, 2011
In reply to the U.S. Composting Council’s (USCC) request for a special review of the registration for the new herbicide Imprelis, the U.S. EPA Office of Pesticide Programs said it is seeking the advice of legal council about the matter. Imprelis, made by DuPont, can survive the composting process and remain active in a finished compost product.
The product label specifies that clippings from lawns treated with Imprelis should not be used as a mulch or placed in a compost pile.
Imprelis has been registered in every state except California and New York for use by licensed applicators on lawns and other turf areas for control of broadleaf weeds like dandelion, clover and plantain. The Composting Council of Canada said it doesn’t appear that Imprelis is available for sale in Canada, having yet to be registered through Health Canada’s Pest Management Regulatory Agency (PMRA).
USCC last month issued an alert warning composters to watch out for grass clippings contaminated with the new herbicide. USCC said grass from treated lawns could end up in a compost pile, and unlike most herbicides, Imprelis will survive the composting process and still be active in the finished compost. Preliminary research has shown that Imprelis does not break down significantly faster than the leaves and grass in the compost, so the concentration stays about the same. An unsuspecting gardener using contaminated compost could end up damaging their flowers and vegetables, most of which are also broad-leafed.
The product label contains a warning about composting:
“Do not use grass clippings from treated areas for mulching or compost, or allow for collection to composting facilities. Grass clippings must either be left on the treated area, or, if allowed by local yard waste regulations, disposed of in the trash. Applicators must give verbal or written notice to property owner/property manager/residents to not use grass clippings from treated turf for mulch or compost.”
In March, DuPont issued suggested language for applicators to use regarding management of grass clippings from areas treated with Imprelis:
“Today we have treated your lawn with an innovative weed control product from DuPont. The product label requires that you do not use grass clippings from areas treated with Imprelis for mulching or compost, or allow for collection to composting facilities. Grass clippings must either be left on the treated area, or, if allowed by local yard waste regulations, disposed of in the trash.”
"One problem is that the warning is on page seven of a nine page label," said Dr. Stuart Buckner, executive director of the USCC. “Unfortunately not everyone reads or follows the label. We are requesting the U.S. EPA initiate a special review of the registration due to the likelihood of residual herbicide levels in compost damaging non-target plants."
He said he received a reply from the EPA acknowledging the request and saying that the Office of Pesticide Programs is seeking the advice of counsel. No timeframe was given.
USCC said it is unlikely that municipal or commercial compost will contain significant amounts of Imprelis, though it is possible in suburban areas where a large amount of clippings could come from commercially treated lawns. It could especially be an issue for places like schools, recreational fields or golf courses that use their grass clippings to make compost and then use the compost in landscape beds or gardens instead of placing back on turf.
"We are alerting our members to this issue, that they need to make sure their haulers are informed to not bring them grass clippings that have been treated with Imprelis," Buckner said. "We also suggest they work with their state's bureau of pesticide applicator licenses to ensure applicators know about this restriction.”
DuPont said Imprelis, an innovative product to control a wide spectrum of broadleaf weeds, is the “most scientifically advanced turf herbicide in over 40 years.” Imprelis contains a single active ingredient – Aptexor - that is absorbed by the roots and shoots of target weeds providing consistent performance.
Aptexor, the first compound in an advanced generation of carboxylic acid herbicides, has unique properties at both the molecular and whole plant levels that translate into more powerful herbicidal activity. The most noticeable symptoms after application include the bending and twisting of stems and the cupping of leaves.