Nearly four years ago, Imprelis surfaced as a broadleaf weed control option that some say was as good as it gets. The product, though, created serious, long-lasting issues that still are being resolved.

Howard Richman
Aftermath photo 1

Photos courtesy of Kathy Zuzek,
University of Minnesota Extension.
Photo illustration by Kelly Neis

Read this story in GCM's digital edition

When Imprelis was introduced, Hillcrest Country Club superintendent Joe Aholt never had seen anything like it for broadleaf weed control.

“It was a miracle product,” says Aholt, a 20-year member of GCSAA.

It took just 2 ounces per acre of Imprelis to eradicate weeds at the Boise, Idaho, course, Aholt says, and it performed admirably.

“You knew within a month the weed would be gone,” Aholt says. “You had to be patient with it, but it worked. You could spray it in rain, cold, heat. It was the cleanest my course had been, ever.”

Imprelis appeared to be a game-changer. Like Aholt, others applauded its effectiveness. Unlike some herbicides, where the smell lingers throughout the day, Imprelis was different: It was odorless.

Today, years after being removed from the market, Imprelis remains visible.

Imprelis — the herbicide, created by DuPont for professional use on golf courses, residential areas and institutional lawns — is no longer available for sale. It has been that way for quite a while.

DuPont voluntarily pulled Imprelis from the market in August 2011 before the Environmental Protection Agency (EPA) issued a mandatory stop-sale order on Imprelis after being alerted of numerous reports from golf courses to nurseries that the product was suspected of injuring and, in some cases, killing trees. Norway spruce, white pines and honey locust proved to be among the species of trees that were susceptible.

Imprelis appeared to be a gamechanger. Unlike some herbicides, where the smell lingers throughout the day, Imprelis was different: It was odorless.

In October 2013, a settlement was reached in a class-action lawsuit against E.I. du Pont de Nemours and Co. (DuPont) over Imprelis. More than three-dozen class-action lawsuits originally were filed in multiple federal courts throughout the U.S. Ultimately, the class-action lawsuits were consolidated and transferred into one case and entered into the U.S. District Court for the Eastern District of Pennsylvania.

In some instances, golf courses settled their claims directly with DuPont. Three classes were established in the settlement. Class 1 included property owners who own or owned property in the U.S.; Class 2 was applicators (lawn care professionals); and Class 3 included golf courses and other Imprelis self-applicators. They were eligible to be part of the claim if they used Imprelis between Aug. 31, 2010, and Aug. 21, 2011, as long as they submitted or accepted a claim through the manufacturer’s Imprelis Claims Resolution Process.

New York and California were not included because Imprelis was not approved for use in those states.

Approximately 38,000 claims have been submitted through the Imprelis Claims Resolution Process, DuPont spokesman Gregg Schmidt told GCM in March. DuPont estimates there will be $1.175 billion in total charges to compensate customers, according to Schmidt.

States that participated in the class-action lawsuit were Connecticut, Delaware, Indiana, Kansas, Kentucky, Maryland, Michigan, Minnesota, Missouri, New Jersey, North Carolina, Ohio, Pennsylvania, South Dakota and Wisconsin.

Settlements vary in scope and payouts, according to published reports. Two examples: The Owatonna People’s Press in Owatonna, Minn., reported that the city received a check last year from DuPont for $1.85 million for damage to trees at Brooktree Golf Course. Lake County Forest Preserve District in Illinois received nearly $836,000 from DuPont for damages, according to the Chicago Tribune.

“We are pleased with the progress we have made in resolving claims for damage,” Schmidt says via email. “To date, we have made offers of resolution to approximately 90 percent of claimants.”

GCM attempted to speak with several superintendents and others in the industry for this story. Some, because of claims that have not yet been processed, declined, a sure signal that Imprelis has not completely vanished from the radar.

Aftermath photo 2

A mature white spruce shows signs of damage from Imprelis.

What’s in a name?

For years, DuPont was committed to superintendents through its work with major universities for turf field research. DuPont regularly disseminated its research through sales representatives, associations, distributors, webcasts and one-on-one meetings.

For example, in 2010 DuPont updated its Weevil Trak website, which offered superintendents more features to help control annual bluegrass weevil.

Also that year, the EPA conditionally registered aminocyclopyrachlor. That is the active ingredient in Imprelis. According to the EPA website, “the studies originally submitted were adequate to make a statutory finding for registration.”

The EPA determined aminocyclopyrachlor was 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.”

The EPA also stated that DuPont conducted “roughly 400 efficacy and phytotoxicity field trials” and that “they (DuPont) reported to EPA that they did not observe adverse effects to trees.” Imprelis posed minimal risks to people and pets.

Aftermath photo 3

One of the signs of Imprelis damage in white pine
is stress or death of the tips of branches.

Before Imprelis was made available, Scott McElroy, Ph.D., an associate professor of turfgrass and weed science at Auburn University, participated in research trials of aminocyclopyrachlor about eight years ago when he was an assistant professor of plant sciences at the University of Tennessee. He says its broadleaf control in tall fescue was outstanding.

“It’s still probably the best broadleaf control herbicide I ever worked with,” McElroy says. “Don’t get me wrong. We still have some great herbicides. But for a single active ingredient at low rates and with the ability to control a wide spectrum, specifically cool-season turf, there’s nothing like it.”

Labeled for use rates of 3.0 to 4.5 fluid ounces per acre, Imprelis was made to be absorbed into the ground and destroy the root system of weeds. But when it came into contact with certain tree roots, particularly shallow, succulent roots, some of the results proved to be traumatic.

The signs appeared in different ways. Needles on firs turned orange or brown. Leaves curled up. Some fell to the ground. Tips of branches and buds showed stress. Tumor-like growths appeared.

Aftermath photo 4

Tumor-like growths on a honey locust indicate
damage in this species.

As part of its investigation into reports of possible damage to trees, the EPA sought to determine whether the damage was a “result of product misuse, inadequate warnings and use directions on the product label, persistence in soil and plant material, uptake of the product through the root systems and absorbed into the plant tissue, environmental factors, potential runoff issues or other possible causes.”

DuPont responded with action following the onslaught of damage claims.

The company established open lines of communications for customers. It engaged multiple independent, certified arborist companies to work with customers and evaluate their claims. Among the companies that Du- Pont listed for those filing claims under its Qualified Tree Replacement process was one that is well-known to golf course superintendents, The Davey Tree Expert Co., who agreed to pricing and terms for tree replacement included in the Claims Resolution Agreement (CRA) that DuPont established. Davey, as did other arborist companies, agreed to provide a limited warranty for the trees that the company plants. One superintendent tells GCM the tree recovery process included slow-release fertilizers, pest treatments and pruning.

As part of the CRA, DuPont announced it would pay for care programs and replanting. The company also provided a two-year warranty to program participants for all replacement trees and paid for efforts to assist recovery of other trees impacted by Imprelis use.

DuPont launched a website, http://, to feature the latest information and provide an avenue to report problems to the company. DuPont also started a toll-free hotline to handle concerns. More than one superintendent told GCM that DuPont was helpful and followed through during the claims process.

"I think in the future, product testing will be strengthened. Probably because of it, I don’t foresee it ever happening again."
— Jared Hoyle, Ph.D.

The size of a settlement depended on the size of the tree. For example, a 1-foot-tall tree was $30; a tree 96 to 100 feet high equaled $19,000. DuPont asked those who were making claims to document damage by taking digital photos prior to removal.

DuPont compensated golf courses for removal and disposal of impacted evergreen trees unlikely to recover. DuPont also offered credits or refunds, depending on a distributor’s policy, on unused Imprelis.

Imprelis had a short shelf life. It was introduced in August 2010. Twelve months later, it was gone. Late in 2012, Syngenta announced that it had acquired the DuPont Professional Products insecticides business, which included the brands Acelepryn, Advion and Provaunt. The closing price for the acquisition was $125 million.

That same year was DuPont’s last one as a Silver Partner through GCSAA’s Partner Recognition Program. As a Silver Partner from 2008 to 2012, DuPont spent a minimum of $100,000 in support of GCSAA member services and programs.

DuPont also was a member in the Champions Club of GCSAA’s philanthropic organization, the Environmental Institute for Golf (EIFG). DuPont was recognized as a member of the Champions Club for the cumulative total of its contributions to the EIFG ($250,000 to $499,999) since 1987. Part of DuPont’s contribution included donation of products to the EIFG’s Silent Auction.

Moving forward

In some cases, spaces where trees have been removed because of Imprelis are no longer vacant, another symbol of the healing process for an issue that rocked the industry.

“They are replanting on some sites where trees have been removed without any problem,” says Kathy Zuzek, assistant extension professor for the University of Minnesota.

Imprelis, if anything, serves as a cautionary tale for manufacturers and superintendents. Jared Hoyle, Ph.D., an assistant professor in horticulture, forestry and recreational services at Kansas State University, imagines the Imprelis saga could benefit the industry down the road.

“I think in the future, product testing will be strengthened,” Hoyle says. “Probably because of it, I don’t foresee it ever happening again.”

At The Country Club of Muirfield Village in Dublin, Ohio, GCSAA Class A superintendent Dave Gribler encountered issues with some of his trees because of Imprelis. He anticipates, and welcomes, the day when he can fully focus on what happens below his feet.

“I spend too much time looking up instead of looking down at the ground,” Gribler says.

HowardRichman is GCM’s associate editor.