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Browning shoots and needles, twisting and stunted shoots, especially near the tops of evergreen trees and shrubs, are signs that those plants may have injuries associated with the herbicide Imprelis.

Browning of evergreen trees could indicate Imprelis injuries

Browning shoots and needles, twisting and stunted shoots, especially near the tops of evergreen trees and shrubs, are signs that those plants may have injuries associated with the herbicide Imprelis. Michigan State University Extension recently published “A Homeowner’s Guide to Imprelis Herbicide Injury to Landscape Trees” to help identify and deal with suspected Imprelis injuries to conifers.


“Symptoms are usually most severe on the current-year, outermost or topmost growth,” Michigan State University Extension specialist and MSU associate professor Bert Cregg said. “Unlike most conifer insect and disease problems, suspected Imprelis damage occurs rapidly – usually within two to three weeks of application. The most commonly affected trees are Norway spruce, Colorado blue spruce and eastern white pine. Other conifers and some hardwood trees may also be affected.”


In reports of tree damage, it appears that trees may be taking up Imprelis that has been applied to turf near the tree’s drip line. Affected trees are showing symptoms commonly associated with herbicide injury: twisting or stunting of new growth and needle browning.


Imprelis is a relatively new selective herbicide intended for use by lawn care professionals. It is part of a group of selective herbicides designed to control broadleaf weeds in turf by interfering with a plant’s normal hormonal balance. Imprelis was developed and marketed to provide control of several, difficult-to-control turf weeds, such as ground ivy and wild violet. It works by both direct uptake through the foliage as well as root uptake and provides good residual control.


Cregg said that depending on the level of damage, affected trees may recover since herbicide injury in trees can initially look worse than it really is. He recommends that if possible, homeowners give trees time to recuperate on their own.


“Trees can often overcome what initially appear to be devastating injuries and emerge relatively unscathed in the long run,” Cregg said. “The best plan for an affected tree at this point is to try to keep the patient comfortable, and let the tree’s recuperative abilities kick in.”


To care for the tree while it’s recovering, MSU Extension recommends that homeowners irrigate trees during warm, dry weather, but avoid waterlogging. DuPont has issued a statement (http://www.agry.purdue.edu/turf/tips/2011/images/07052011_Infosheet_Treesunderstress.pdf) advising against fertilizing affected trees for at least one year. For more information from Dupont about potential Imprelis damage contact Karen.Hartman@usa.dupont.com
“Symptoms of herbicide exposure are often dramatic and very characteristic, especially twisting of new shoot growth,” Cregg said. “We have seen affected trees where herbicide was applied to adjacent property, so it’s worthwhile to talk to your neighbor if you suspect damage but have not had anything applied to your lawn.”


For additional information on suspected Imprelis damage, visit the Michigan State University Extension News for Ag website. Creggs’ research is supported by AgBioResearch at MSU.

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