Treatments for Basal Bark Application

triclopyr ester (Garlon 4 Ultra, Garlon 4, Element 4, Triclopyr 4, and others)

Rate 10-20% product v/v in oil carrier for low volume basal applications in an approximately 15-inch band on basal bark portions of tree or shrub stems. See remarks below for other rates and treatments.

Time Apply between January and early November for best performance. Treatments in midwinter have seen variable control. Applications during the dormant season when branches are bare allows for less labor and ease of application.

Remarks Low volume basal treatments of 10-20% product in oil provide the best combination of ease of application, reduced spray solution and cost. This method uses low volumes of solution to just cover bark on stems of individual target plants. Conventional basal applications of 1-5% require larger volumes of spray solution to thoroughly flood stems and root collars. Thinline treatments use undiluted product applied directly on and across tree and shrub stems that can result in more material applied than needed with added cost if users are not careful

Use only oil as a carrier. Commercial basal oils, kerosene, or plant-based oils work well as carriers. Diesel oil is not as good of an option since it can damage bark before the herbicide can move through the plant. Apply when bark is free from water or ice. Complete coverage around the total circumference of the stem is critical to good control. In some cases, removing dead leaves or moss at the base of the tree or clump can improve coverage and control.

Low volume basal is effective on bigleaf maple trees and sprout clumps, other maples, alder, oaks, Scotch broom, Ceanothus spp., myrtle, tanoak and many other shrubs and trees.

Caution Avoid contact with conifer foliage, especially ponderosa pine. Triclopyr ester is volatile and vapors can move off site during warm temperatures and damage conifers or other desirable plants. New growth on conifers actively growing in spring and early summer is extremely sensitive to spray drift and vapor movement.

Site of action Group 4 synthetic auxin

Chemical family Pyridine