WASHINGTON — Imprelis, a DuPont herbicide used to control weeds that has been reported to be harming a large number of  Norway spruce and white pine trees, has been ordered off the market by the U.S. Environmental Protection Agency.  The EPA told E.I. DuPont de Nemours to immediately halt the sale, use or distribution of it.

The action follows EPA’s investigation into why a large number of evergreens and other trees have been harmed following the use of the herbicide. EPA said it is investigating whether tree deaths resulted from product misuse, inadequate warnings, persistence in soil and plant material, uptake of the product through the root systems into the plant tissue, environmental factors, potential runoff issues or other causes.

In June DuPont warned professional applicators against the use of Imprelis where Norway spruce or white pine trees are present on, or in close proximity to, the property being treated. Last month DuPont acknowledged that there has been damage to trees associated with Imprelis use, and on August 4, DuPont voluntarily suspended sales of Imprelis. EPA's said in its announcement banning the sale of Imprelis it would study whether trees were harmed because of misapplication of the herbicide, or from some other cause.