Below is an open letter from Wendy Longpre, Assistant Director for the City of East Lansing Parks and Recreation Department in response to a question we had on how to keep the roots from spreading on a tree that was to be cut down.

"Below is some great information about process and chemicals to use to treat the stumps of willow or other trees, so that they don't re-sprout. The information came from Mike Vasievich who is one of our Park and Recreation Advisory Commissioners, is a Forester, and has helped with our invasive species removal program for years....You can also feel free to share the information with anyone who may need."

"Glyphosate (aka Round-up) will work just fine.... but there are some specifics. We use 25% glyphosate in water, mixed with an adjuvant (primarily an emulsifier) and some dye so we can see where we put it. The concentrate we get is about 48% glyphosate in a water-soluble formulation.

Homeowners may have problems buying such concentrated material. Most of the glyphosate (aka Round-Up) in small containers on the shelves at Meijer and other garden center outlets is 18%. This concentration would probably work to prevent without the additives if painted on full-strength (18%) around the outside circumference of the stump soon after the tree is cut. On a large tree, there is no need to paint the center, only the outside inch or two. Waiting a day or two (or more) after cutting will reduce the effectiveness.
Also, the season when the tree is cut and treated may have an effect. Winter is OK, early spring when the sap just starts flowing is less effective, summer and fall are good times to treat.
If the tree does sprout, perhaps months after cutting, my recommendation is to just chop out the sprouts with a hatchet or axe and paint the cut wounds with the same concentration.

Other chemicals will also work on willow, including triclopyr (aka Garlon), which we use for spraying buckthorn sprouts, but the concentration may vary from what we use with glyphosate. These chemicals are relatively safe and are not EPA restricted use herbicides. Also, careful targeting (ie. painting on a stump) is considerably safer than broadcast spraying. I certainly recommend that homeowners use rubber gloves and be particularly careful about spills or contamination outside the target plant."