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MNLA E-Training, Project Plant

What is Imprelis?
Imprelis is a relatively new selective herbicide labeled for use to control broadleaved weeds in turf and lawns.  It is intended for use by professional applicators.  The active ingredient in Imprelis is aminocylopyrachlor, which is a synthetic auxin.

What kind of injury to landscape trees has been observed following Imprelis application?
Homeowners, lawn service operators, and others have observed browning of shoots and needles and twisting and stunting of new shoots especially near tops of trees following application of Imprelis in Spring 2011. Symptoms are usually most severe on current year (outermost or topmost) growth. 

What trees are affected by Imprelis?

Conifers, particularly Norway spruce and Eastern white pine are most commonly affected and show the most characteristic symptoms. Based on site visits and reports from the Purdue University Plant and Pest Diagnostic lab, other conifers that may be affected include Colorado blue spruce, Black hills spruce, firs, Douglas-fir, yews, arborvitae, Dawn redwood and Baldcypress.  Hardwood species may also be affected.  Honeylocust seems to be the most commonly listed hardwood for Imprelis-related injury.  In addition, damage has been reported on Cottonwood, Maple, Lilacs, Boxwood, Redbud, Ginkgo, Willow, Euonymus, Tulip poplar, Viburnum, Mulberry, Rose of Sharon, Paw paw, and River birch.

How widespread is the problem?

University Extension websites from Kansas to Pennsylvania have reported injury to trees associated with Imprelis application to turf and lawns.

What should I do if I suspect injury to trees after applying Imprelis?
DuPont has established an Imprelis Hotline 866-796-4783 where applicators can report damage.  Contact your chemical supplier and make sure they are aware of the problem.  You may also want to contact your customers so they are aware of the situation.

Is the worst of the damage over? 

Because our experience with Imprelis is relatively short, it’s hard to say.  A lot of Imprelis-related injury occurred to new growth early in the season.  Based on casual observation it appears that the July heat wave increased the amount of visible injury on many of these stressed trees.  Of special concern are Eastern white pine trees with severely affected current-year shoots.  White pine trees typically hold needles for two years.  Some Imprelis-affected trees produced few, if any, new needles this year.  This fall when these trees drop their 1-year-old needles they will be essentially defoliated.  This could potentially impact their ability to acclimate and harden off before winter.

Can I test for the presence of Imprelis?
As of this writing (August 3, 2011), testing for Imprelis residues is not widely available.  Several labs including the MSU Pesticide Analytical Lab are developing testing protocols.  At this juncture the best course of action is to collect foliar samples and freeze them for later testing.  Provide enough material to fill a gallon Zip-lock bag to ensure adequate material for testing.  Be sure to label the bags with identifying information and when the sample was collected. 

Can trees recover from Imprelis injury?

Herbicide injury to trees can be dramatic, but trees can often recover over time.  Based on experience with other forms of herbicide injury and other types of environmental damage, trees with minor browning (<1/3 of crown affected) on new growth will likely be able to push new growth and eventually ‘grow out’ of the damage, though this can take one or two growing seasons.  Trees with distorted tops may resume growth, but will likely require corrective pruning to maintain desirable form and symmetry. 

Can anything be done to help trees recover?

The types of trees that are most commonly affected typically grow vigorously and are therefore good candidates for recovery from minor injury.  Reduce drought stress by watering during dry periods.  Avoid over-watering that may cause water-logging.  Fertilization is probably not necessary unless a professional tree care provider determines that a nutrient deficiency exists.

What is DuPont doing about the problem?
DuPont issued statements to applicators on June 17 and July 27, acknowledging Imprelis-related issues with Eastern white pine and Norway spruce.  As noted earlier, they have established a hotline as well as a website: www.Imprelis-facts.com.  According to the website, DuPont has retained 20 arborist firms to assist with evaluating claims of Imprelis damage.

Where can I get more information?

In addition to the DuPont website, several university extension services and the Environmental Protection Agency (EPA) are providing updated information including:


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