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An Herbicide Goes Awry


Eastern White Pines are among the types of conifers included in recent reports of widespread tree loss that may be linked to the commercial herbicide IImprelis. Image: Wikipedia.

Sometimes, becoming more environmentally-friendly is a one-step-forwards, two-steps-backwards process, a reality that can be both frustrating and costly, despite good intentions. In the case of recent widespread reports of dying conifers like Norway Spruces and White Pines, the "cost" of using an approved and environmentally-conscious herbicide may be measured out in tree loss.

Tree problems around the country have been linked to the use of an herbicide called Imprelis. Manufactured by DuPont and sold for commercial use by landscapers, Imprelis was released onto the market last October in the U.S. (excepting New York and California) with a "conditional" seal of approval from the Environmental Protection Agency. The herbicide, which contains a single active ingredient, is marketed by DuPont as an environmentally-friendly approach to treating a common gardener's gremlin—broadleaf weeds like dandelion and clover.

Unfortunately, despite all the testing prior to its release, the effects of Imprelis are not limited to pesky weeds. Approximately six months after landscapers began using the product, some varieties of conifers (plants that produce seed cones, like pine trees), have been turning up in various states of decline, from browning to outright dying. Tree owners and landscapers alike are up in arms over the unforeseen problem, and landscapers have been put in the position of replacing and paying for lost trees.

Up a Tree

According to the New York Times' coverage of the story, "Imprelis went through about 400 trials, including tests on conifers, and performed without problems, according to experts at DuPont and at the EPA." It sounds like a lot of testing, but even so, the article notes that while the EPA approved the product, the 23 months of review they conducted before giving their "conditional" thumbs up wasn't enough to conclusively determine the product safe.

Investigations into the cause of the tree problems is ongoing, and there are suggestions that problems could be related to methods of application, quantity, the preparation of the herbicide for use, or even the effects of the herbicide coming into contact with other products. Getting to the root of the problem could take a long time—and a lot of research.

While DuPont has reportedly suggested that many of these trees may return to health, the sad reality for affected tree-owners right now is what seemed like an environmentally-conscious choice...has turned out to be a bad one.

Making Connections

For students, the fate of conifers and other trees with shallow root systems that have come into contact with Imprelis offers a real-world look at both the importance and the challenge of testing&madash;and the need to test in a variety of conditions. Change one variable, and the entire outcome can change, a reality that can make it difficult to know for sure that a new chemical is safe for a specific use and safe over time and with repeated use.

For gardeners, landscapers, and those interested in plant biology, exploring issues of plant survival and heartiness also involves understanding what "else" is in the area and what impact plants or other agents in the soil have upon one another.

The following two Project Ideas allow students to conduct investigations that can be revealing in terms of plant health. These projects may also offer insight into the kinds of investigatory work that will be involved in trying to determine why Imprelis turned out to be detrimental to conifers—when it had appeared to be safe.

(Note: Imprelis labeling and instructional information contains warnings about proper disposal of clippings from treated areas. Clippings are not safe for compost.)


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