Follow-Up on Rhizome Injection for Knotweed – Evidence of Control from Winter Application of Herbicide

In our last couple posts you saw the rhizome injector system that we have been experimenting with.  We did applications throughout the winter and early spring. The injections were through the dead hollow stems. We cut the stems at ground level and inserted the needle down into the rhizome.  A few weeks ago, I noticed the shoot clumps were starting to send up aerial shoots.  I was concerned that the herbicide might not be having an effect. However, glyphosate is slow-acting, so I kept reminding myself to be patient.

We are finally starting to see results.  They are encouraging.  Here are photos of several of the treated stems.

Knotweed plants dying: two brown ones have collapsed and one in middle is showing effects of herbicide. Note hollow stem to which injection was done at bottom of photo.

Rhizome Injection to cut hollow stem in middle of photo. One dead stem and another showing herbicide injury.

Rhizome Injection on March 23, 2012. Brown dead plant showing effects of injection. Injection was through hollow stems that show some coloration from dye.

Healthy untreated knotweed stems nearby.

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