As of noon yesterday (4/28/09), our Chardonnay was 100% bud break with more than 50% of them with lower two leaves unfolded. Some were as advanced as the picture. Cabernet sauvignon varied with vines, but some were close to 70% bud break with a few buds with lower leaves unfolded, and others were about 30%.This morning, we had a shower (~0.08 inch from 6:40 am to 8:45 am, average temperature was around 52F). The rain was short, but RH has been fairly high after the rain, thus it may be enough for Phomopsis to cause light infection; however, considering how dry we have been, it may not have much activity by this fungi to initiate spore production and release.
This rain was little shy for condition for powdery mildew fungi to release its spore (ascopsore) to the air (it requires 0.1 inch or more plus 2.5 hr of wetness at >50F) . We are expecting series of short rain events in next few days. I'll keep track of them as much as I can.
I'm heading to a vineyard meeting at Horton vineyard today. If you miss the meeting, here's my handout about early season disease management on Phomopsis, Black Rot, and Powdery Mildew.
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