Imprelis and Investigation of Damage to Trees

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August 2011

The Environmental Protection Agency has received reports from numerous states that E. I. du Pont de Nemours and Company's (DuPont) herbicide, Imprelis, which contains the active ingredient aminocyclopyrachlor, may be causing injury to certain species of evergreen trees, particularly Norway spruce and white pine. We have launched an investigation.

Actions in Response to this Issue

We are very concerned about this issue and are working closely with state officials and others to determine the cause of the damage being reported.
We will conduct an independent evaluation on an expedited basis so that appropriate actions can be taken to prevent the potential for any future incidents.
We are also in contact with DuPont, whose turf development team is investigating the reports to determine what may be causing the damage to these trees.
We are requiring the company to expedite submission to the Agency of detailed information about incidents, and are also requiring DuPont to determine what is causing these injuries.
EPA and DuPont are currently advising professional applicators and residential consumers to not use Imprelis where Norway spruce or white pine trees are present on or near the property being treated.

Imprelis and EPA Registration

Aminocyclopyrachlor is a selective, low- toxicity herbicide that provides pre- and post-emergent control of broadleaf weeds, woody species, vines and grasses on several non-food use sites, such as rights of way, wildlife management areas, recreational areas, turf/lawns, golf courses and sod farms.
In August 2010, EPA conditionally registered the active ingredient aminocyclopyrachlor.
- The studies originally submitted were adequate to make a statutory finding for registration.
- The required studies are intended to confirm the conclusions from the existing data.
  - The conditional registration requires submission of a toxicity study for an environmental degradate and resubmission of avian and invertebrate reproduction studies.
Aminocyclopyrachlor is a low-risk pesticide.
- The human health and ecological risk assessments found that the herbicide poses low risk to both humans and non-target terrrestrial and aquatic organisms, except for plants.
- The risk assessments and proposed labels were placed in the docket, and EPA sought public comment on the proposed decision to register aminocyclopyrachlor before making its final registration decision.
- The registrant responded to the Agency’s request for comment; EPA received no other comments.
Aminocyclopyrachlor is related to other herbicides, including clopyralid and aminopyralid, which have caused plant damage, but not siginficant damage to trees, when present in compost or manure as a result of their use on turf and/or pasture grasses.
- Aminocyclopyrachlor shares characteristics with these herbicides (persistence in soil and plant material, systemic nature in plants, and high seedling emergence toxicity), which are thought to have contributed to carryover in compost/manure and subsequent plant damage.
- In roughly 400 efficacy and phytotoxicity field trials that the manufacturer, DuPont, conducted in their development of the chemical, they reported to EPA that they did not observe adverse effects to trees.
- Aware of the potential for aminocyclopyrachlor to cause similar problems, the Agency required labeling restrictions to reduce the risk of plant damage from aminocyclopyrachlor-contaminated compost.
- These restrictions prohibit the use of grass clippings from treated areas in compost or mulch and require commercial applicators, such as lawn care company personnel, to notify residential consumers not to use treated grass clippings in mulch or compost.
The product was first used in Fall 2010.

Next Steps

Receive and review incident data from DuPont
Determine whether further regulatory or other actions are warranted.

Related Information

Letter to DuPont on Stop Sale, Use, or Removal Order (PDF) (9 pp, 164k, About PDF)
Case Letters: E.I. DuPont de Nemours and Company (PDF) (4 pp, 67k, About PDF)
Letter to DuPont requesting information about incidents (PDF) (3 pp, 917k, About PDF)
DuPont Web page on Imprelis
Registration docket for aminocyclopyrachlor

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