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6 4 V I N E YA R D & W I N E RY M A N A G E M E N T | J u l y - A u g 2 014 w w w. v w m m e d i a . c o m prior to visual observation of PM on vines. In Solano County, Gubler noted, "We caught the first spores on the PM spore trap rod, and the beetles showed up about a week later. The spore rod tells you that spores are there, and the beetles tell you whether you have the disease." The beetle lives throughout the U.S., but its presence in vineyards can vary by location. In one study in Oregon, the beetle appeared four weeks after PM spores were detected in traps. Gubler said vine canopy tem- peratures ranging from 70°F-86°F drive PM epidemics by enabling PM to reproduce by sporulation every five days. Higher tempera- tures ranging from 86°F to 92°F reduce spore production and can slow fungal reproduction to every 15 days. The PM Risk Index is based on local weather conditions and allows growers to vary fungi- cide application intervals so that no more, and no less, fungicide is applied than needed to prevent PM damage. Leaf removal in the canopy around berry set can provide up to 50% PM control early in the sea- son, because the spores are thin- walled and negatively affected by UV light. High temperatures also harm PM. "The first heat spell of not be used together, and no soon- er than 14 days apart when apply- ing one after the other, because the two products together can cause phytotoxicity on vines. It is recommended that different fungicides with different modes of action be rotated during the season to prevent PM from developing fun- gicide resistance. Soft chemistry products are recommended when disease pressure is low to mod- erate, although JMS Stylet Oil or PureSpray are sometimes used all season by organic growers. Newer fungicides testing posi- tively in recent trials include Pris- tine, Quintec, Luna Experience and Inspire. "We have a variety of effective fungicides in existence, and more will be available in the future," Gubler said. "Sulfur dust is still one of the best products we have for PM protection." Field-trial reports for 2013 and previous years are posted at http:// plantpathology.ucdavis.edu/Coop- erative_Extension. Ted Rieger, CSW, is a writer and photographer based in Sacramento, Calif., and has been a contributing editor for V&WM since 1990. Comments? Please e-mail us at feedback@vwmmedia.com. the season will knock it back, but we now know that PM fungi have the ability to acclimate to and sur- vive at higher temperatures than we previously thought," Gubler said. Recent evidence indicates the fungus can survive at tempera- tures higher than the previously known limit (above 92°F), and in some cases, may not be negatively affected until temperatures reach 94°F-96°F. PM FUNGICIDES Gubler has conducted field tri- als in a Clarksburg, Calif., chardon- nay vineyard annually for 28 years to test applications of a wide range of fungicides, including new prod- ucts and combinations. The trials include soft chemistry products such as biologicals (Serenade and Sonata), sulfurs and organic oils, and synthetic chemistries such as sterol-inhibitors and strobilurins. "The first spray application to use should be an insecticidal oil (such as JMS Stylet Oil or Pure- Spray Oil) and you should put on the first application when you see the spores or the bug," Gubler said. Oil offers a better chance of early- season eradication, whereas sulfur acts better as a protectant more than an eradicant. He cautioned that sulfur and oil products should Custom Winemaking Services • All inclusive services from crushing to bottling • Specializing in small lots, as little as one barrel. Can scale upwards • Grape sourcing available • State of the art winery conveniently located on the Silverado Trail, Napa Valley • Small lot custom blending options available "THE place for custom crush winemaking in Napa Valley" - Food and Wine Magazine 2332 Silverado Trail Napa, CA 94558 · 707-255-2332 · www.napamicrocrush.com