Controlling Honey Locust (Gleditsia triacanthos) with Cut Stump- and Basal Bark-Applied Herbicides for Grazed Pasture

Abstract

Honey locust is a deciduous tree that is now present throughout most of the United States. Fire suppression and introduction of honey locust into shelter belts has allowed honey locust to increase in pastures of mixed grass prairie. Because locust trees can produce abundant sprouts, mechanical measures also require herbicides to effectively control trees. Each year for 2 yr, trees were treated with one of five combinations of herbicides and application methods. Treatment combinations, on a v/v basis, included (1) triclopyr 25% + diesel 75% and (2) aminopyralid 5% + bark oil 95%, both applied to the lower 38 cm of basal bark including the root collar area of live trees, as well as (3) triclopyr 25% + diesel 75%, (4) aminopyralid 10% + water 90%, and (5) dicamba 33% + 2,4-D 2% + water 65%, all applied immediately to the outer cambium layer of cut stump surfaces. One year after treatment, aminopyralid applied as a basal bark or as a cut-tump treatment had the best control and averaged over 97% dead trees. The triclopyr + diesel cut-stump treatment had the fewest dead trees (just over 50%) and produced many new sprouts. In grazed pasture, treating cut tree surfaces with dicamba + 2,4-D + water or aminopyralid + water and treating standing live trees with a basal bark application of aminopyralid + oil are three effective control options. Triclopyr + diesel displayed better control on live standing trees with a basal bark treatment rather than as a cut-stump treatment.