Powdery mildew is one of the most damaging grape diseases in California causing more grape crop losses than any other disease. The annual cost of control measures and yield loss equals nearly 10 percent of the state’s total crop value so it is crucial to get ahead of the disease.
Rod Yraceburu, PCA and grape grower based in Kerman, Calif., has helped fight 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 about 14 days later when buds are out about three to four inches. This will give a strong early start to controlling powdery mildew as well as early-season Phomopsis.
“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 DMI fungicide with different chemistry than the triazole chemistry found in most other DMIs, Viticure has been more active against powdery mildew than other DMI products in trials. In addition to controlling powdery mildew, it suppresses black rot and Botrytis bunch rot. Viticure is also great in rotation with strobilurin or quinoxyfen fungicides for resistance management. Best use recommendations for Viticure are outlined here.
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.