We hit 90 F this afternoon.  This warm weather made things go little faster than we would hope.  About 50-60% of our Chardonnay and Merlot are in the stage of bud break, my Cabernet Sauvignon is still holding tight, but I saw Cabernet sauvignon in the other vineyard is about 40-50% bud break stage.  (FYI, last year we hit 50% bud break around 4/25.)

Some of us are expecting to see some showers on this Thursday to Friday. It will depend on the history of your vineyard and also the condition of the rain, but if you: 1) experienced severe Phomopsis outbreak in the recent years; 2) see your early varieties are already breaking buds; and 3) are expecting that the rain will sustain for a long time (5-6 hours), then you may need to think about a treatment against Phomopsis.

For example, at Winchester, it looks like we have 60% chance of rain from 2 pm Thursday and the temperature is forecasted to be in 70’s.  It will be in the same condition until the middle of the night.  If we would have a rain event, it takes about 4 hours under 60-70F for Phomopsis to cause infection.  I did not see much of Phomopsis development during the last season, so, if I were a vineyard manager, I may decide to go without a treatment, assuming that the risk of having the inoculum (spores) is not high.  However, since many of the vines in our experimental field did not receive any treatments last year because of the experiment (i.e., there is a chance that Phomopsis population increased over a year), I am thinking about putting a treatment down, just to be on the safe side.  There is no curative (or kick-back) fungicide against Phomopsis.

Note: The chance of rain are less as we go to the south of the state, thus this may not apply to your vineyards. Please check your local weather forecast.