Issue link: http://read.dmtmag.com/i/114539
GUIDE for grape pest management available W ashington State University's 2013 Grape Pest Management Guide includes recommendations for controlling insects, weeds, diseases, and other pests. The guide also includes results of 2012 fungicide efficacy trials, a table with Fungicide Resistance Action Committee (FRAC) codes for resistance management, and suggestions of fungicide timing. The guide comes in a pdf format or printed bulletin. To order, visit: https://pubs. wsu.edu and search for Extension Bulletin 0762 (EB 0762). inoculated, the less disease there was at harvest. By timing fungicide sprays when clusters are most susceptible to the disease, you can delay disease progression in the vineyard and help clusters escape infection, Moyer said. "If you delay enough the rate of increase and keep disease pressure low, then you can keep fruit from becoming infected. "With powdery mildew, you don't spray based on what you see, but on what you're trying to prevent." Cornell researchers also found that as clusters transition to resistance, the berries that are nearly immune to infection may still support what are known as diffuse mildew colonies. Clusters with diffuse infection appear to the naked eye to be healthy and free of powdery mildew, but symptoms can be seen when examined under a microscope. "These necrotic spots or dead tissue can enhance botrytis later in the season," Moyer said. "They're perfect places for botrytis to set up shop." Fungicide programs WSU extension plant pathologist Dr. Gary Grove, who spoke at the same grape meeting, offered tips for developing an effective disease management program. Grove has spent years studying the efficacy of grape and tree fruit fungicides, calculating optimum spray timing, and developing resistance management strategies. The bottom line in powdery mildew management is timing, he said. "The longer you wait in the infection process, the more inoculant you have on the leaf surface. By the time you can see powdery mildew on the leaves, the disease is already producing millions of spores." Grove advised growers to choose chemicals with protectant activity as they work to protect the grapevine from initial infection. Curative modes of action are used to cure the early infection stages; eradicants are last-ditch fungicides, and there are few effective ones. He urged growers to target their disease management efforts at the early infection stage (see Figure 1). Those who don't use a prevention strategy, risk affecting their grape quality at harvest and jeopardizing relationships with winemakers. www.goodfruit.com "You can fool some of the people some of the time, but you cannot fool the winemaker," Grove said. "Take the period of fruit susceptibility [prebloom to post fruit set] very seriously." Growers must deal with both the fruit and foliar phases of powdery mildew. The fruit phase impacts the quality and marketability of the grapes. The foliar phase only affects the canopy, but sets the vineyard up for increased disease pressure the following season. Spray early Although postharvest or dormant sprays can help reduce primary spores, which are in the fungal overwintering structures called chasmothecia, he doesn't advocate postharvest sprays. "The overwintering spores are usually formed before veraison, and finding an effective material to kill them is the problem." A better strategy, he said, is to start sprays earlier the next season, providing good coverage when shoots are about ten inches long and continuing sprays through fruit set. • When it comes to fungicides, one star seems to stand out. The powerful broad-spectrum disease control of Inspire Super® fungicide stands out above all others. By combining a best-in-class triazole with a second highly effective fungicide, growers of pome fruit, almonds, grapes and many vegetables can depend on its superior performance. Proven across the world, it stops disease in its tracks. For power and reliability, there's no better choice than "top of the class" Inspire Super. ©2012 Syngenta. Important: Always read and follow all bag tag and label instructions before buying or using Syngenta products. The instructions contain important conditions of sale, including limitations of warranty and remedy. All crop protection products and seed treatments may not be registered for sale or use in all states. Please check with your state or local extension service before buying or using these products. Inspire Super® the Alliance frame, the Purpose icon and the Syngenta logo are trademarks of a Syngenta , Group Company. Syngenta Customer Center: 1-866-SYNGENT(A) (796-4368). www.FarmAssist.com MW 10CC2006-Super-NB2 04/12 GOOD FRUIT GROWER March 15, 2013 39