Glyphosate Herbicide: An Assessment of Forestry Potential
Environmentally safe, yet potent in controlling herbs, grasses, and woody species, with possibilities for selective use, glyphosate (Roundup®) has great potential usefulness in forestry.In the small study reported here, twelve.01 ha plots were established in August, 1973 in dense 6-year-old shrub and hardwood post-fire regrowth near Chapleau, Ontario. In each plot, 16 rising 3 + 0 white spruce (Picea glauca [Moench] Voss) were planted centrally at.9 m ×.9 m spacing. Six treatments with two replications were applied at random the next day: 1, control; 2, all woody vegetation cut off at ground level; 3, all woody vegetation cut off in central planted area of plot; 4, sprayed with 60 mL glyphosate in 1.892 L of water; 5, sprayed with double strength glyphosate; 6, sprayed with sextuple strength glyphosate. Eight trees in each plot were shielded during the spraying. Browsing affected 16% of the spruce after 2 weeks, 96% by spring. Half of each plot was replanted with eight white spruce (four of them caged against browsing) in May, 1974.The objectives were to observe the effect of glyphosate on hardwood and shrub competition, to assay this effect by white spruce outplantings, and to evaluate the resistance to glyphosate of newly planted white spruce. Glyphosate was highly effective in killing trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), and beaked hazel (Corylus cornuta Marsh.): pin cherry (Prunus pensylvanica L. f.) resprouted with moderate vigor. White spruce responded significantly (P.01) to first-year non-herbicide (i.e., immediate) weed control, but second-year height increment was significantly (P.001) less than that of the first year: second-year height increment in the glyphosate treatments was significantly (P.001) greater than in the non-herbicide treatments. Growth and survival were both affected by non-treatment disturbances, but shielding during spraying improved second-year survival significantly (P.001).