Winter Weed Control: Woody plant control—basal bark treatment
The basal bark technique is a method of applying herbicide to the lower trunk of trees and shrubs to get the herbicide absorbed through the bark into the vascular tissue. It is then translocated through the plant.
This technique works best on shrubs and young trees as they have thin bark and the herbicide can move easily to the vascular tissue. Also, because the herbicide needs to penetrate the bark use oil-based herbicides.
The ester formulation of triclopyr (Garlon 4 Ultra, Relegate, Forestry Garlon XRT, Pathfinder II) can be added to a penetrating oil or diesel (read the label) and applied to the lower 12 – 15 inches of the trunk. The spray should cover all sides of the trunk all the way to the ground.
This application technique works well on young Russian olive and Siberian elm, as well as shrubs such as salt cedar. It is very targeted in that the only non-target plants that may get some overspray are those that are close to the trunk.
Basal bark herbicide application, combined with mechanical removal has been used to very good effect on older Russian olives. Russian olive roots need to be close to the soil surface to sprout root suckers. The herbicide doesn’t kill the older trees, but it does kill the latent buds on the lower trunk of the tree. Then, when the top is removed below the upper spray line, the roots don’t sucker and will eventually starve. Apply the herbicide two weeks before mechanical removal.
Be sure the target weed and crop or landscape situations and application techniques are listed on the product label. Always read and follow herbicide label directions.