last year we bought two grape vines, planted in our home garden, 6-10 feet...

Asked August 10, 2014, 12:07 PM EDT

last year we bought two grape vines, planted in our home garden, 6-10 feet tall, many leaves have many brown spots or whole leave become brown, wonder what caused the problem and how to fix? Also like to know how many years it will take for the grape vine to produce fruits? Thanks

San Diego County California viticulture

3 Responses

These almost look like old powdery mildew infections.

Powdery mildew can be managed early in the season with sulfur sprays, but please refer to the appropriate pest management guide for your area before selecting a management strategy.

Dear Jodi
Thanks for your help, from the reference page, I know that Powdery mildew is caused by a fungus,
then can I use common fungicide to kill powdery mildew?
I did some research on sulfur spray, found the following info:
"Sulfur is only effective as a fungicide when applied to healthy, disease-free plant tissue, notes the University of California’s Statewide Integrated Pest Management Program. Plants already infected with fungicide must be treated with an alternate method." Since my grape already infected, what I should do to fix it? thanks

Correct, sulfur should be used earlier in the season before infections are out of control. Stylet oil and neem oil could probably be used at home. Some potassium salt formulations are effective on current infections (Nutrol, etc.), but be sure that this is actually powdery mildew before spraying anything (leaves covered with white, "powdery" mycelia). It is not entirely clear from the picture what's going on. It could also be a nutrient deficiency.

According to the UCDavis IPM page:
"Sulfur, horticultural oils, neem oil, jojoba oil, and Serenade are registered for controlling powdery mildew in home vineyards."