Basal Bark Treatment
Alternatively you take the herbicide and mix it with a dilutant such as diesel fuel or bark oil. The herbicide solution gets put on the bark, usually at the basal area right above the crown or base of the plant. The herbicide is applied in a full ring, usually one inch for every inch of DBH. If your tree is 8 inches around, you need an 8 inch ring around your plant to get enough herbicide in it to kill it.
This last method is called basal barking or basal bark herbicide treatment. Basal barking is done without cutting the tree down first. There is always an alternative way to do things.
Basal bark herbicide treatment is a control method in which an oil soluble herbicide is mixed with an oil carrier instead of water and applied directly to the bark of woody plants less than 6 inches in diameter.