Raisin vineyards may be at increased risk from several threats
By CnAgri
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He also advises raisin growers to be prepared for higher powdery mildew pressure in vineyards this season. “I’m hearing more growers talk about the disease this spring,” Zhuang says. “Due to higher humidity levels in the canopies from the increased precipitation this year, there’s the potential for an increase in powdery mildew outbreaks.
Because of its high vigor and tendency to produce dense canopies, the Fiesta raisin grape variety is more susceptible to powdery mildew than others, he notes.
In scouting their vineyards this season, Zhuang advises growers also to be alert for signs of trunk diseases, such as dead spurs, stunted shoots, and cankers. “We saw a lot of trunk disease last year and are seeing it this year,” he says. “In fact, I know several Fresno County growers who lost vines to Esca, as well as Eutypa dieback. Stress from the drought might leave the vines more susceptible to the pathogens.” More information about trunk diseases is available online at www.ipm.ucdavis.edu.
