EFFECT OF ADJUVANTS ON GLYPHOSATE WASH-OFF FROM WHITE BIRCH FOLIAGE BY SIMULATED RAINFALL
Abstract The effect of six surfactant adjuvants on glyphosate wash‐off from white birch (Betula papyrifera Marsh.) foliage was studied at 2 and 6 h after treatment with end‐use mixtures of Vision® at the rate of 1 kg of active material in 35 L per ha area of leaf surface. The investigation consisted of two parts. In Part I, C‐labeled herbicide was used to determine the maximum amount of wash‐off ('Worst Case Scenario') by rinsing treated foliage with water. At 2 h after treatment ca 84% of the applied amount was washed off when no adjuvant was present, and at 6 h the washable amount decreased only to ca 72%. Out of the six adjuvants tested, only Silwet® L‐77, an organosilicone copolymer surfactant, provided the greatest increase in rain protection, since the amount washed off decreased to 51 and 42% at 2 and 6 h rain‐free periods respectively. In Part II of the investigation, non‐radiolabeled herbicide was used, and glyphosate wash‐off was examined at 2 and 6 h after treatment using cumulative rain of 1 a...