ALBERT

Description: First-season herbicide efficacy and crop tolerance results are presented for a range of glyphosate (VISION®) rates (0–1.00 kg acid equivalent per hectare) aerially applied with two different dispersal systems (AU5000 Micronairs® and conventional hydraulic nozzles). Derivative-free nonlinear regression was used to model post-treatment raspberry cover (Rubusidaeus L. var. strigosus (Michx.) Maxim.) as an exponentially decreasing function of chemical deposit (R2 = 0.87). Similar methods were used to model post-treatment crown area as a function of chemical deposit and pretreatment crown area for pin cherry (Prunuspensylvanica L.f.) (R2 = 0.92), red maple (Acerrubrum L.) (R2 = 0.79), white birch (Betulapapyrifera Marsh.) (R2 = 0.93), elderberry (Sambucuspubens Michx.) (R2 = 0.85), and aspen (Populustremuloides Michx.) (R2 = 0.96). Acceptable first-season control (〉60% cover reduction) of raspberry, pin cherry, elderberry, and aspen was achieved with rates of deposit ≥0.50 kg acid equivalent per hectare. Red maple and white birch crown area reduction averaged 60% at the highest rate tested (1 kg acid equivalent per hectare). Significant differences in efficacy attributable to the different dispersal systems were found only for pin cherry: the Micronair system resulted in 30% greater efficacy on one of the four blocks tested (P 

Description: Experimental methods and resulting on-target deposit data are presented for an operational field trial designed to evaluate glyphosate (Vision®) efficacy using two different dispersal systems (AU5000 Micronairs® and conventional hydraulic nozzles). A range of glyphosate rates (0, 0.25, 0.50, 0.75, and 1.00 kg acid equivalent per hectare) was aerially applied in a randomized complete block design to four cutover sites in New Brunswick. Formulation, tank-mix, droplet, and chemical analyses were conducted to quantify actual on-target deposit for each treatment. Data for the calibrated portion of each swath suggested that the Micronair system produced a slightly narrower drop-diameter spectrum (0–677 μm, volume median diameter = 300 μm) than the hydraulic system (0–1085 μm, volume median diameter = 425 μm). Analysis of variance and orthogonal contrasts indicated that on-target deposit for the Micronair system (average accountability = 71%) was not significantly different from that of the hydraulic system (average accountability = 82%) for three of four rates tested. Unrepresentative meteorological and site conditions affecting Micronair treatments in two blocks resulted in reduced deposit for the treatment of 1.00 kg acid equivalent per hectare. Substantial variability within treatments was observed for both dispersal systems (41 and 47% coefficient of variation for Micronair and hydraulic systems, respectively). Overall, results suggest no significant differences between the two dispersal systems (as calibrated) in terms of on-target deposit efficiency or variability. Both on-target droplet density and chemical deposit data reflected differences associated with blocks. This fact highlights the need for further studies on meteorological and operational factors on deposit.