By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties
A local landowner contacted me this winter, concerned about his ten acres of young trees and whether they had been damaged by herbicides. In May 2014, a year after the trees were planted, grass was coming in thick, so he hired a contractor to do a release spray. We don’t know what the exact spray mixture was, but the landowner thought it may have been a formulation of glyphosate such as Accord. Glyphosate is known to damage Douglas-fir seedlings (and many other conifers) during the active growing season – the time from when buds begin to swell in spring until resting buds are formed and hardened off in fall.
Affected trees showed several symptoms characteristic of herbicide damage. The least affected trees simply had stunted growth. On many others, the leader and branch tips were droopy and dead. Some seedlings were completely dead. Continue reading