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Imprelis and Investigation of Damage to Trees
Resources
June 2012
In the summer of 2011, the Environmental Protection Agency 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 have caused injury to certain species of evergreen trees, particularly Norway spruce and white pine.
Imprelis is no longer on the market because the EPA issued a stop sale order in August 2011: Letter to DuPont on Stop Sale, Use, or Removal Order (PDF) (9 pp, 164k, About PDF). The agency is conducting an independent evaluation and has required the company to expedite submission to the EPA of detailed information related to the situation to determine what caused the injuries.
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.
- 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