JARS v63n3 - Glyphosate with Surfactants and Bark Splitting

Glyphosate with Surfactants and Bark Splitting
Marty Finkel, Master Gardener
Granville County, North Carolina
Reprinted from The Garden Path newsletter, October 2008

A warning when using glyphosate (one brand is "Roundup") with surfactants: the use of the wetting agent causes injury to trees and shrubs such as bark-splitting (usually blamed on cold winter temperatures when bark is exposed to the sun). The herbicide makes the bark structure weak so that it splits open even in comparatively warm winters. It often takes years for plants to break this down with even low doses of glyphosate with surfactant. Extension specialist Hannah Mathers of Ohio State University says this injury shows up on black gum, crabapple, dogwood, hawthorn, maple, mountain ash, magnolia, and numerous species of Prunus and Pyrus . Other injuries show up as stunting, dead branches, witch's brooms, and chlorosis. So don't use it to remove suckers, and keep a 9-metre (30 foot) buffer between the weeds being sprayed and your special "woodies.