Stem Treatments to Control Tanoak Sprouting

Abstract

Abstract Applying 2,4-D, triclopyr, and picloram + 2,4-D to cut surfaces of tanoak (Lithocarpus densiflorus) on southwest Oregon sites in November or February increased mortality and reduced total sprout length and clump area relative to May or August applications. Injecting the same herbicides into stem frills caused 80 to 99% mean crown dieback for November, February, and May applications, but only 47% for August applications. Spraying triclopyr diluted with diesel oil to 1 5 or 3.0% on stem bases caused 64% mean crown dieback for August applications but only 28% averaged over the other three dates. Both frill and spray treatments reduced by about 1.5 to 3.0 times the sprout length and clump area of trees felled within 3 months of treatments, compared to untreated trees. Tanoak can be effectively controlled by treating cut surfaces when felling, and by stem injection or basal spray 3 months before harvesting or slashing for site preparation. Cut-surface application or injection from fall through early spring is likely to be most effective. West. J. Appl. For. 2(2):41-45, April 1987.