Control of Aspen Regrowth in Western Canada When There Is an Understory of Established Alfalfa

Abstract

The use of 2,4-D alone and in a mixture with 2,4,5-T was evaluated, when applied during the dormant season, for the control of aspen and balsam poplar regrowth in pastures previously seeded with a mixture of bromegrass and alfalfa. When 2,4-D was applied at 2.2 kg/ha for two consecutive years, sufficient control of aspen top growth was achieved to reduce the physical barrier presented by the trees and allowed uniform cattle grazing. An adequate kill of aspen was not obtained until the herbicide rate was increased to 4.4 kg/ha. Herbicide retreatments were required after 5 or 6 years. Balsam poplar canopy cover was not adequately reduced following the use of 2,4-D alone or in a mixture with 2,4,5-T. Grass, alfalfa, forb and woody plant yields were not affected by the herbicide treatments. The use of phenoxy herbicides during the dormant season for pasture improvement is discussed.