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50% bud-break for our Chardonnay plus Phomopsis risk


Our 5-yr old Chardonnay is about 50% bud break stage as of today.

At this time of the year, the number-one concern is Phomopsis cane and leaf spot. They produce spores on old infected cordons and trunks during the spring, and they can infect tissues even if temperature during a rain event is in 40s. Only option we have against this disease is a protective application of fungicide, such as mancozeb, captan, and Ziram. A QoI fungicide such as Abound and Pristine are also effective; however, I would recommend keeping them for the later part of the season. 

Since they can be active under cold rain event, my recommendation is to protect even when shoots are about 1-3 inches long. The decision to spray for Phomopsis also depends on the history of the vineyard. The vineyard with previous history of Phomopsis tends to carry the same issue year after year. 

You are probably wondering about the risk of Phomopsis from this week's rain.  At our vineyard, we received a very long (~48 hours) wetness that started in 28 April and ended in 30 April, and the average temperature was 48F. This certainly was a Phomopsis infection risk event, on the other hand, it was too cold for black rot.
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