Influence of foliar exposure, adjuvants, and rain-free period on the efficacy of glyphosate for torpedograss control

The proportion of torpedograss tissue exposed to glyphosate at application rates of 0.28, 0.56, 1.12, 2.24 and 4.48 kg/ha affected control as measured by regrowth. The effect of tissue exposure was more pronounced as applicat ion rate decreased. This study suggests that higher rates of glyphosate nee d to be used during higher water levels, when less torpedograss tissue is e xposed to herbicide spray and lower rates may be used during periods of low water levels. Addition of the water conditioning agent Quest(R) (0.25% v/v ) to glyphosate spray mixtures diminished the influence of simulated rain e vents following glyphosate application. Twelve other adjuvants did not infl uence the effect of simulated rain events.