Good Fruit Grower

October 2016

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38 OCTOBER 2016 Good Fruit Grower Antibiotics and Apogee continue to top the list of control products. by Dave Weinstock A new study by researchers in New York shows that antibiotics remain the tool of choice for fire blight prevention in con- ventional apple orchards and that Apogee can be used in young blocks without lim- iting growth. Fire blight hit Eastern New York growers especially hard this year and never stopped, thanks to a one- two punch of heat and some untimely early summer windstorms in the Lake Champlain and Hudson Valley apple growing regions. "All it takes is a few storms and 30 to 40 bacteria and you've got trouble," said Kerik Cox, Cornell University School of Integrative Plant Science associate professor. Apple growers use two chemical tools to control fire blight: antibiotics to suppress growth of the bacterial pathogen Erwinia amylovora, in its blossom blight phase and also later in the season, and Apogee (prohexadione calcium) to slow down and toughen tender growth during the shoot blight infection phase. H o w e v e r , c o n c e r n s about antibiotic resistance have raised questions about whether they should be used widely, and grow- ers are hesitant to apply Apogee to young trees, even though they are espe- cially susceptible. Researchers in New York infected four plots in one orchard with fire blight to evaluate best treatments last spring and summer. They then treated the trees with var- ious fire blight control products; some trees were treated after infection with Apogee and a systemic acquired resistance inducer. "Overall, most of the products did fairly well con- trolling both blossom and shoot blight," though the anti- biotics showed the strongest effects, said Amelia Zhao, a senior neuroscience major at Hobart and William Smith Colleges in Geneva, New York, who conducted the study with Cox. In the study, streptomycin, kasugamycin and oxytet- racycline topped the list of fire blight control products. Luckily, antibiotic resistance is not a problem in New York — yet. Nineteen orchards there reported strepto- mycin-resistant disease in 2012 and 2013, but there have been no reports since. "There have been no reports of kasugamycin and oxytetracycline of fire blight pathogen resistance in New York," Cox said. Zhao presented the findings at the 2016 Cornell Fruit Field Day, attended by Finger Lake region growers and International Fruit Tree Association New York Study Tour participants in mid-July. Trial setup Fire blight is a bacterial infection exacerbated by early summer's heat, which helps the bacteria multiply. It spreads by means of rain, birds and insects (see "Blight and bugs," Good Fruit Grower, September 2016). There were four blocks in the research orchard, pro- viding four replicates for each treatment. Zhao and Cox applied treatments at pink, 20 percent bloom, 40 percent bloom and 80 percent bloom using a motorized backpack application. On May 12, the day after the 80 percent bloom application, they used hand pumps to inoculate the orchards with fire blight bacteria. Control trees, which were untreated, presented 60 percent blossom blight incidence and 23 percent shoot blight incidence. For the three most effective treatments — streptomy- cin, kasugamycin and oxytetracycline — incidence of blossom blight was under 10 percent and shoot blight was under 5 percent. Biocontrol products were less effective at controlling fire blight, reducing blossom blight to 20 percent and shoot blight below 10 percent. But Zhao and Cox enhanced their effectiveness to levels similar to those of antibiotics by adding fungicides to two of them. Adding Magna-bon CS 2005 (copper sulfate penta- hydrate) to Regalia (Reynoutria sachalinensis), a SAR Fighting fire blight IFTA New York study tour Kerik Cox DAVE WEINSTOCK/GOOD FRUIT GROWER Participants in the International Fruit Tree Association New York Study Tour saw lots of orchards with fire blight in them alongside the roads of Orleans and Monroe counties. Amelia Zhao "One year after I watched my neighbor save most of his apple crop with Orchard-Rite ®wind machines (while I lost three quarters of mine), I decided I should do something on my farm to help ensure that I have fruit to sell every year. I purchased three Orchard-Rite ® wind machines and placed them where I had good trees but couldn't set good crops because of frost. One year the tart cherry orchard where I have a machine that covers the lower two-thirds of the orchard yielded 3 times more cherries than the one-third of the orchard that was not covered. That one machine in that one year paid for itself and half of another.We were able to raise the temperature 4 to 5 degrees (Fahrenheit). We have since added four more machines. With Orchard-Rite ® wind machines we are able to have a more consistent crop from the top of the tree to bottom every year on both apples and cherries. We are very pleased with the service we get on the wind machines. The Superior Wind Machine Service guys give them the once-over every year, keeping them in top-notch condition for the upcoming season!" -- Bob Bush Bush's Apples New Era, MI "With Orchard-Rite® wind machines we are able to have a more consistent crop from the top of the tree to bottom every year on both apples and cherries." 6919 Kra Avenue Caledonia, MI 49316 Phone: 616-971-8177 Fax: 616-971-8178

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