Issue link: http://read.dmtmag.com/i/128999
Glyphosate revisited Photo courtesy of david rosenberger Carefully used, glyphosate has less impact on apple tree health than was once feared. Photo courtesy of david rosenberger by Richard Lehnert Basal trunk canker on a Macoun tree. Basal trunk canker showing necrosis beneath the damaged bark. RHINO TURBO SERIES ROTARY CUTTERS fter studying the matter for more than ten years, Dr. David Rosenberger has reached some conclusions about the use of glyphosate (Roundup) herbicide to control weeds in apple orchards: while glyphosate can have negative impacts on apple tree health, those impacts are less significant than initially feared, and glyphosate can be used in apple orchards if applied carefully. Rosenberger, who is a plant pathologist and heads Cornell University's Hudson Valley Laboratory in Highland, New York, plans to retire at the end of this year. He summed up his work in glyphosate while talking to Ohio producers last winter and presented the following guidelines: When applying glyphosate, include a drift inhibitor in the spray mixture to minimize the number of small droplets that can drift upward onto —David Rosenberger apple foliage. Where possible, use a hooded boom sprayer to minimize bounce-back from bare soil that sometimes allows a haze of small droplets to drift upward into the trees. Keep the pressure on herbicide sprayers low (20-30 psi) or use air-induction nozzles to minimize generation of small droplets. Early-summer applications are less likely to create problems than late-summer applications. Cheaper formulations of glyphosate may be safer than the more expensive formulations "fully loaded" with surfactants. High concentrations of surfactants may increase uptake through tree bark, so cheaper products with less surfactant should be safer around trees. Avoid using glyphosate for sucker control on apples as it may reduce winter hardiness, especially if applications are made in August. Nor should glyphosate be applied immediately after suckers are cut because freshly cut stems readily absorb it. Never apply glyphosate with controlleddroplet applicators that disperse concentrated glyphosate from a spinning disk. 1 "What might have been an 'herbicide issue' became a 'plant disease issue.'" 2 TURBO 96 • Turbo 96 2-PT • Dome deck • 8-ft. cutting width • Adjustable offset w/cyl. • Cutting height 1.5 to 12" w/cyl • Blade overlap 4" • Divider box center: 120 HP; outboard: 110HP • Blade tip speed 17,004 FPM • Cutting capacity 2.5" • Side skirt .25" x 10" YAKIMA IMPLEMENT & IRRIGATION 1922 S. First Street • Yakima, Washington 509-452-5867 • 1-800-572-2239 40 May 15, 2013 GOOD FRUIT GROWER 3 4 5 6 7 www.goodfruit.com