Comparison of four glyphosate herbicide formulations for white spruce release treatment

Abstract

An operational field trial was established to compare the efficacy and white spruce (Picea glauca (Moench) Voss.) tolerance of three alternative glyphosate formulations to Vision®, Canada's originally registered forestry formulation. The trial was done at operational scale (minimum treatment unit 7 ha) using helicopter application of all products. The tested alternatives included two new generic formulations, recently registered for forestry in Canada (Glyfos-Forza® and Vantage®), and one widely used formulation in the United States (Accord®). All four formulations provided greater than 90% control of bluejoint reedgrass (Calamagrostis canadensis (Michx.) Beauv.) through 23 months post-treatment (p > 0.27). Assessed over the same period, the three Canadian formulations provided equivalent white spruce tolerance (p > 0.10), with seedlings exhibiting only minor, non-lethal herbicide injury. Accord®, not registered for use in Canada, consistently provided the best crop tolerance, but differences were only statistically significant 11 months post-treatment (p = 0.10). The results suggest that foresters may choose among the glyphosate formulations available in Canada without concern for product-related differences in efficacy and white spruce tolerance. Key words: glyphosate, white spruce, conifer tolerance, Calamagrostis canadensis, efficacy