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Home > Ag Chemicals & Fertilizers > Pesticides > Imprelis Information

Information about the herbicide Imprelis


The Purdue Plant & Pest Diagnostic Laboratory has released an Imprelis® update that includes information on the potential for tree recovery, new symptom development, and replacement of damaged trees. Notably, soil samples were taken at sites where Imprelis® was detected last year and found Imprelis® levels decreased by an average of about 97 percent from June of 2011 to May of 2012. It is yet unknown if the amount of Imprelis® in the soil is high enough to damage newly planted trees or other plants.

The Minnesota Pollution Control Agency (MPCA) in collaboration with the Minnesota Department of Agriculture (MDA) will temporarily allow disposal of yard material that has been affected by DuPont’s Imprelis® herbicide at waste incinerators or landfills. This is a temporary, limited exception to the MPCA’s enforcement of the yard material disposal ban. Materials not affected by Imprelis remain subject to the ban. 

The University of Minnesota has a blog post with updates on Imprelis. The safety of replanting new materials in soils where Imprelis was applied is still unknown. Michigan State University Extension makes some general assumptions about when it might be safe to replant based on Imprelis half-lives in soil. They suggest a conservative approach of waiting until fall 2012 before planting into soil where trees were severely impacted.

Suspected Imprelis® Damage not Seen in 2011

If Imprelis® was applied in 2011 and damage was not seen, but in 2012 there are symptoms of herbicide damage that could be related to an Imprelis® application or a claim was filed in 2011 with DuPont and new potential Imprelis® damage has been identified on previously undocumented trees, then contact DuPont at 866-796-4783. When calling request a site visit and the forms you’ll need to file a claim or an amendment to your claim, respectively.  

Testing

The MDA has received inquiries on the availability of laboratories that will test soil and plant tissue samples for the presence of Imprelis. The MDA’s laboratory does not accept samples from homeowners. The Montana Department of Agriculture will test for Imprelis residues in soil and on plant tissue. For more information visit their website. There may be other laboratories that test for the presence of Imprelis, but as of this update, the MDA is not aware of any.

Removal/Replacement of Trees

If a tree has potential Imprelis damage and is required to be taken down for safety or aesthetic reasons, caution should be taken when disposing of wood and installing a new tree. Consult your local arborist to determine if your tree should be removed.

Removal

Very little is known about the fate of Imprelis in wood that has been cut down due to potential Imprelis damage. EPA recommends that these trees should not be used for mulch. In a document titled “General Information for Managing Trees Under Stress,” DuPont claims that trees may be used for lumber or for use as firewood. In May of 2012, MPCA granted a temporary, limited exception to the enforcement of their yard material disposal ban for yard material affected by Imprelis.  Materials not affected by Imprelis remain subject to the ban.

Replacement

DuPont recommends waiting approximately 4-5 months before replanting where Imprelis treatments have been made. Furthermore they recommend not using Imprelis-treated soil to backfill around newly planted trees. A link to DuPont’s “General Information for Managing Trees Under Stress” can be found in the Links section.

Grass Clippings

Grass clippings from lawns treated with Imprelis should not be used as compost, or be used as mulch around trees, ornamental bed or in gardens. If clippings are not left on the lawn, they can be disposed of in the trash, but only where allowed by local yard waste regulation. A temporary waiver issued by the MPCA exempts grass clippings and other yard material from the yard material disposal ban and allows yard material to be disposed of at landfills, solid waste incinerators, and biomass facilities. Clippings not affected by Imprelis remain subject to the ban.  Clippings should not be added to garden compost or collected for composting facilities.

Advice for Homeowners

Homeowners should still monitor the health of their trees and ornamental plants through the 2012 growing season. It is unknown how persistent Imprelis will be in soils and plants. If you see signs of damage contact your lawn care company to report the damage. Concerned homeowners can also contact DuPont's Imprelis hotline at 1-866-796-4783.

Background

In 2011, reports from Minnesota and other states have linked a lawn herbicide called Imprelis (active ingredient: aminocyclopyrachlor) with damage to certain kinds of trees, primarily White pine, White and Norway spruce. Typical symptoms on coniferous trees include twisting and curling, possibly followed by browning of needles, shoots and branch tips, which is consistent with herbicide injury. Injury has also been seen on various other ornamental plants and deciduous trees. The Purdue Plant and Pest Diagnostic Laboratory has compiled a more complete list of species suspected to be affected by Imprelis. It is important to note that other environmental factors or pesticide products can cause similar damage. In a letter dated July 27th, 2011 to turf management professionals, DuPont (the manufacturer and registrant of Imprelis) stated that it has observed tree injuries associated with Imprelis.

EPA Action

On July 2nd 2012 the EPA issued a Notice of Noncompliance and Request to Show Cause (PDF: 3.22 MB / 6 pages) to DuPont based on information obtained as part of EPA’s ongoing investigation into “DuPont Imprelis Herbicide” (EPA Reg. No. 352-793), including data and information submitted to EPA by DuPont. Based on information collected as part of the investigation, EPA has determined that DuPont has violated FIFRA as follows: DuPont distributed and/or sold misbranded pesticides and DuPont failed to submit timely information to EPA. DuPont now has an opportunity to show why EPA’s information is not correct and why EPA should not file an administrative complaint for civil penalties for these alleged violations.

On August 11, 2011, the U.S. Environmental Protection Agency (EPA) issued a Stop Sale, Use or Removal Order to DuPont concerning its herbicide product called Imprelis. Prior to this Order, on August 4, 2011, DuPont announced it was suspending sale of Imprelis and would begin a product return and refund program.

MDA Response

MDA is concerned about the reports of damage to trees and ornamental plants, and has collected information from various sources. An informal survey of pesticide managers was conducted with the cooperation of the Minnesota Nursery & Landscape Association, Minnesota Turf and Grounds Foundation, and the Minnesota Golf Course Superintendents' Association, to assess the scope of the issue in Minnesota. MDA has been in contact with the EPA and other states to assess the extent of Imprelis injury around the country and to gather other information. The University of Minnesota Extension Service is working closely with MDA to inform interested parties about Imprelis-related plant injury. Finally, MDA has been in contact with DuPont, communicating the issues facing Minnesotans and inquiring into actions DuPont is taking to address those issues.

DuPont’s Actions

In the fall of 2011, DuPont initiated their claims process and product return and refund program. The claims process is currently under way and is aimed at addressing trees that are unlikely to recover or trees that have been impacted by Imprelis-related injury, but may be recover.  The return and refund program’s purpose is to collect all remaining full and partially-full bottles of Imprelis and refund lawn care professionals for their purchase.

Links to Additional Information 

As always, anyone wishing to report a suspected case of pesticide misuse in Minnesota may call MDA at 651-201-6333 or use the Pesticide Misuse Complaint Form to file a complaint online.