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College of Food, Agricultural, and Environmental Sciences


Ohio State Scientist: EPA's Alert on Imprelis is Warranted

August 30, 2011

COLUMBUS, Ohio – The U.S. Environmental Protection Agency is taking appropriate action in alerting homeowners and landscape professionals not to use grass clippings that have been treated with Imprelis, as well as trees that may have been injured from Imprelis, for compost or mulch, says an Ohio State University turfgrass science professor.

Imprelis is a herbicide that was sold by DuPont to licensed lawn care professionals. It was used on residential, industrial and institutional lawns and on golf courses. The EPA and DuPont have received numerous reports of injury to trees, including to Norway spruce and white pine, after Imprelis was used.

On Aug. 11, the EPA issued an order to immediately stop the sale, use and distribution of Imprelis, and DuPont is voluntarily implementing a product return program. The active ingredient in Imprelis is aminocyclopyrachlor.

“As a part of the registration process, a company is required to provide the EPA with information regarding the behavior of the pesticide in the environment, such as its potential to leach or volatilize, and also to provide evidence of the persistence of the pesticide after application,” said Dave Gardner, associate professor of turfgrass science and researcher with the university’s Ohio Agricultural Research and Development Center. “Based on this testing, there is some concern that residues of aminocyclopyrachlor in compost or mulch could persist at concentrations that would be injurious to ornamentals.”

In fact, Imprelis carried a warning label about this issue, saying:

“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.”

The new alert extends the warning to trees that were injured after Imprelis was applied.

Gardner said it's unclear how long the herbicide might have a detrimental effect.

“The exact period of time that this would be a concern is quite variable and dependent on environmental conditions after application. Because of this uncertainty, the EPA is taking appropriate precautions in warning the public to avoid use of residues that may contain aminocyclopyrachlor for mulch or compost.”

More information is available from the EPA at:


Martha Filipic
Dave Gardner