This question already has an answer here:
I am planning to eradicate a stand of Japanese knotweed by injection of imazapyr. This bamboo-like plant develops a rhizome system far below the ground and the only way to kill it is allow it to absorb a herbicide into the rhizomes.
The problem is that there are two basic approaches. One approach is to cut off the stalks, then inject the herbicide into the resulting cup-like cavity. The other approach is to use a syringe to inject the herbicide into the stalk without cutting it first.
Which approach will be more effective in ensuring that the herbicide reaches the rhizomes?