2018 ASHS Annual Conference

The reformulation of low-drift dicamba (Xtendimax +Vapor Guard Technology®) and 2,4-D (Enlist One + Colex-D Technology®) and their subsequent use alone or in combination with glyphosate on herbicide-resistant row crops have resulted in numerous cases of off-target movement and injury to horticultural plants. A study was conducted to evaluate the sensitivity of one-year-old apple, elderberry, grape, peach, pecan, eastern black walnut, raspberry, and strawberry plants following the application of three driftable fractions (1/2X, 1/20X, and 1/200X) of the labeled rate of dicamba (0.56 kg ae·ha^-1) or 2,4-D choline (1.09 kg ae·ha^-1), with or without glyphosate (1.12 kg ae·ha^-1). By 28 days after treatment, dicamba-treated plants had symptoms of chlorosis and inward cupping of young foliage and 2,4-D-treated plants generally expressed symptoms of epinasty or leaf distortion. At the 1/2X rate, visual injury was more severe for apple, peach, pecan, and elderberry plants treated with dicamba compared with 2,4-D. In contrast, injury to walnut and grape plants treated with 2,4-D was more severe than that of dicamba at the 1/2X rate, but raspberry and strawberry injury was similar for both herbicides. The addition of glyphosate to either herbicide increased injury of all plants except grape.