Response of woody eastern Canadian forest weeds to fall foliar treatments of glyphosate and triclopyr herbicides

Second-season post-treatment efficacy data are presented for a New Brunswick field study comparing three formulations of glyphosate (VISION®, MON14420, and TOUCHDOWN®) and a single formulation of triclopyr (RELEASE®). Five rates of each herbicide were broadcast applied to a 2-year-old clearcut in early September. Two growing seasons after treatment, percent control values (based on total woody crown area) ranged from 21% at glyphosate rates < 0.25 × label maximum to more than 80% at rates ≥ 0.75 × label maximum. Coefficients of variation for percent control values decreased from 104% at the lower glyphosate rates to 9% at the higher rates. Total woody control provided by triclopyr was generally equivalent to that of glyphosate at rates < 0.5 × label maximum. Beyond this rate, percent control values for triclopyr averaged only 59% and coefficients of variation remained high (40%). At the individual-species level, the three glyphosate formulations provided greater crown volume reduction than triclopyr for w...