Powdery mildew persists as one of the most damaging grape diseases in California. It is responsible for more grape crop losses than any other disease and costs California growers equal to 10 percent of the state’s entire grape crop value in control measures and yield loss.
Rod Yraceburu, PCA and grape grower based in Kerman, Calif., has helped wage the war against powdery mildew since the 1970s. Although powdery mildew control methods have come a long way since then, he says winning against powdery mildew comes down to being proactive.
“Powdery mildew is a disease you have to be ahead of because you can’t play catch-up,” says Yraceburu. “It’s easy to get lulled into a false sense of security when you can’t see any signs of the disease in the vineyard, but powdery mildew can lie in wait in the canopy for weeks until conditions are right for it to rear its ugly head.”
Yraceburu recommends applying wettable sulfur with copper when buds are out about one inch and applying straight sulfur roughly 14 days later when buds are out about three to four inches to get a strong early start in controlling powdery mildew as well as early-season Phomopsis. After the sulfur applications, Yraceburu begins rotating fungicides in 14- to 21-day cycles for continued control. He starts with Viticure® fungicide from Chemtura AgroSolutions.
“Viticure is usually the first fungicide I spray. It has always done a good job for me,” says Yraceburu. “I use it on my grapes and recommend it to my customers.”
As a systemic sterol inhibitor (SI) fungicide, Viticure provides protective and curative control of powdery mildew. Viticure is also labeled for suppression of black rot and Botrytis bunch rot in grapes.
Yraceburu encourages growers to work with their PCA to ensure they are using appropriate materials at the right times for best results with their powdery mildew control programs.