This technique can be used in a couple of ways. We have successfully used it on small invasive woodies and brambles by swiping their stems in winter. You can successfully swipe stems that are brushcut to a heighth of 4-12″ tall or not cut at all. Whether you cut or not depends on your ability to traverse the woody area you need to manage.
We have also used the PVC herbicide pipe when we’re mitigating Tall goldenrod. Some areas of our land have enough diversity around the Tall goldenrod that mowing would create too much collateral damage. Yet, those places are too thick to efficiently use the lop and treat method. In these areas, with a brushcutter, we cut the stems to 8-12″ tall. Then we walk through with the PVC herbicide pipe and swipe the stems.
The PVC herbicide pipe is an inexpensive tool and needs to be part of your management toolbox. The Nature Conservancy has created a diagram and instructions for making this tool.
The herbicide we use is 20% trichlopyr mixed in bark oil blue. That is 64oz of trichlopyr to 2 gal of bark oil. This method will not work using herbicide mixed with water.