Imprelis herbicide killing trees
Imprelis, sold by DuPont Professional Products and widely used by landscapers, is an herbicide that may be damaging and causing thousands of mature trees to die across the country. DuPont™ has released a statement to the turfgrass industry and distributors of Imprelis® informing them of the potential for damage to nontarget trees and shrubs. The trees affected generally show severe symptoms, however there are many locations where the product was used and no damage has occurred to surrounding trees. The current hypothesis is that herbicide drift and volatilization are only minor factors in the injury process. The product likely moves into the soil water and as the tree starts to put on new growth in the spring, the roots uptake the water from the soil to support the newly emerging leaves and needles, absorbing the herbicide along with it. The active ingredient in the herbicide is absorbed through foliage and roots, is translocated in the xylem, and accumulates in the meristematic regions (i.e. growing points) of the shoots and roots. The active ingredient has a 44 day half-life; a relatively long residual activity in the soil. It can affect tree roots far beyond a treeʼs dripline as tree roots often extend 3-5 times the height of the tree, thus damage can occur with application of the product to lawns growing around or near trees.
Imprelis was introduced to the market in October 2010 and aggressively marketed to lawn care professionals as an environmentally friendly way to kill weeds like dandelion, ground ivy, creeping charlie, wild violet and clover. Homeowners, golf courses, cemeteries, and park managers that used this product are now reporting that mature evergreen trees were damaged or killed after Imprelis was applied to their lawns. Norway spruce, Black Hills spruce, Colorado blue spruce and eastern white pines are the most common species reported to have been damaged when in contact with the Imprelis herbicide.
Herbicide damage generally causes the tips of the branches to twist and curl up in a distorted fa
shion. Browning and needle de
ath results. Damage can very greatly from tree to tree. Generally large more mature trees tend to be worse off with Imprelis damage.
|Imprelis damage on Norway spruce tree|
What can I do to help my trees and shrubs recover? Trees usually recover from slight herbicide injury. Irrigating the trees during a drought as well as all newly planted material is imperative to help alleviate moisture stress. Use of soaker hose around the bases of trees is recommended, however, avoid flooding the surrounding soil with water as this may increase the risk of bringing additional herbicide into the soil solution where it could be taken up by tree roots. Fertilization of trees during times of pest and disease activity, drought, or herbicide injury will generally only exacerbate the problem; promoting new growth which can be more easily damaged. For lightly damaged plants, prune out the dead branch tips. If branch dieback occurs, delay pruning of entire branches until the extent of damage and potential development of new buds for next year can be better evaluated.
For many trees, the next yearʼs vegetative and flowering buds are set in midsummer and mature during late summer and fall. Further decline of branches may continue into the next year and long-term severity of the damage is unknown. Complete tree removal is not necessarily recommended at this time. Avoid planting new evergreens and other trees, shrubs, and perennials into soil that was previously treated with Imprelis® during the same season. Do not compost or use as mulch any grass clippings from lawns treated with Imprelis®. Avoid planting evergreens after mid-October, as there is inadequate time to establish new roots before the ground freezes. Many late fall planted evergreens may show significant winter injury the following spring. Most deciduous trees can be planted in autumn without injury, though some species do not do well when dug from the field and planted in fall (oaks, birches, magnolias, hickories, etc.). Those species should be dug in spring and planted as soon as possible.
If damage from Imprelis® is suspected, please contact your lawn care provider, the Plant Disease Diagnostic Clinic at UW-Madison (http://pddc.wisc.edu) or the Turfgrass Diagnostic Lab (http://www.tdl.wisc.edu).