Issue link: http://read.dmtmag.com/i/123973
E. necator fruiting bodies called chasmothecia form on vines in late summer and overwinter on the vine. In spring, or the early growing season, ascospores produced within the chasmothecia are released under favorable moisture and temperature conditions as vine growth begins, providing inoculum for infection. These spores can cause primary infections that develop into lesions that produce another kind of spore, conidia, that can cause secondary infections for the remainder of the growing season. Growers commonly apply sprays at regular intervals during the growing season to prevent and suppress PM outbreaks using fungicides such as sulfur, chemical formulations such as strobilurins and demethylation inhibitors, or organic products such as JMS Stylet-Oil. Applications are made at regular intervals as suggested by product labels, or based on environmental conditions measured at a nearby weather station in conjunction with forecasting models such as the Gubler-Thomas Powdery Mildew Risk Index, commonly used in California, or the PearsonGadoury Model, sometimes used in wetter and cooler climates such as western Oregon and New York. Suggested fungicide application guidelines, and the risk models, tend to be conservative and err on the side of caution in order to prevent PM outbreaks. After working with Northwest growers over several years, Mahaffee and Grove realized that growers did not always need to spray for PM when they did so, and that the PM spore inoculum was not always present in these vineyards at all times during the growing season. The researchers sought to develop cost-effective methods to trap and analyze for E. necator spores. By determining when E. necator inoculum was actually present in the vineyard, growers were often able to delay their first early season spray, and in some cases, expand the period between spray intervals during the growing season. "Over about a six-year study period, growers were able to make an average of 2.4 fewer fungicide applications during the growing sea- son once bud growth started in the vineyard," Mahaffee observed. SPORE TRAP DESIGN AND PLACEMENT Mahaffee has been working to develop simpler, cost-effective JMSWineDex20112.pdf 1 11/15/11 spore traps and analytical proce- dures to enable vineyard managers to test for and quantify PM spores in the field. Ready-made spore traps commonly used by researchers are available from suppliers, ranging in price from about $700 each to $5,000 for a Burkard impaction spore trap, considered the gold 3:48 PM standard by researchers. • Powdery Mildew? JMS Stylet-Oil® Choice • Mites? For Powdery Mildew and Mite control, grape growers choice: have a JMS Stylet-Oil alternative to early-season sulfur treatment. C M Y CM MY CY CMY • Outperforms sulfur as an eradicant on powdery mildew - University researched and rated 10/10. • JMS Stylet-Oil is a stand-alone product for powdery mildew. • Eliminates early season inoculum growth that can cause late-season epidemics. • Unlike sulfur, JMS Stylet-Oil works well in cool weather, protects around the clock, and harmlessly degrades without potential air pollution. K w w w. v w m media.com Apply this clean white oil early for mite control throughout the season. JMS Stylet-Oil is now available in its conventional formulation or an organic formulation that is OMRI listed for use in an organic program. Contact JMS for complete information and product data. Headquarters 73585 Williams Lane 4423 5th Place SW Vero Beach, FL 32968 Pendleton, OR 97801 Mobile: (772) 713-0758 Office: (541) 276-8566 Fax: (541) 276-6245 Fax: (772) 562-7202 styletoil@eoni.com styletoil@aol.com www.stylet-oil.com M a y - J u n e 2 0 13 | V I N E YA R D & W I N E RY M A N A G E M E N T 65