Green Horizons

This spring, DuPont released Imprelis, a lowvolume herbicide containing the active ingredient, aminocyclopyrachlor, that by all accounts gave solid control of a wide range of weeds, including dandelions, clover, and hard-to-eradicate species like ground ivy and wild violet.

But since Memorial Day, applicators and university researchers in the Northeast and Midwest have been reporting curling needles, severe browning and dieback in trees near turf that had been treated with Imprelis. University and state researchers from Michigan and Indiana say they've seen symptoms in evergreens, more specifically conifers, and mainly Norway spruce and white pine trees.

On the spruces, newly emerging shoots will brown up or wilt, followed sometimes with a twisting appearance to them. In most cases reported to date, the whole tree is affected. The damage is so extensive that the EPA is in contact with departments of agriculture from several states to gather information about a possible link between Imprelis and the trees.

In a June 17 letter to Imprelis customers, DuPont said it is investigating the incidents, and has found them to have the following variables in common:

• A majority of the reports involve Norway spruce or white pine.

• In most cases, Imprelis was not applied alone, but in a mixture with other herbicides, either pre-emergent, post-emergent and/or with a liquid fertilizer.

• Some reports indicate there may have been errors in use rates, mixing practices and/or applications to exposed roots or the tree.

The company also stressed that the majority of applications have not resulted in these symptoms. If you or your contract lawn care company have applied Imprelis and you are observing problems among your Norway spruce or white pine trees, contact the Missouri Department of Agriculture at aginfo@mda.mo.gov or 573-751-4211.