Warm weather is upon us and is expected through the weekend and into next week. The mercury hit 96 degrees in Sonoma yesterday, but temperatures should be more moderate from today on. Walking the vineyards this week, I noticed some shatter – the failure of berries to develop due to incomplete pollination during flowering.

Shatter can be the result of too much heat or wind or moisture during bloom that prevents the setting of fruit. Timing is everything, as different sites, clones or selections and varieties develop at different rates. We expected some shatter with the onset of heat last month around bloom time as all the pent-up energy stored in the vines during the cool weather was unleashed in a growth spurt. We see elongated rachises (grape cluster axes) as a result of that spurt.

A little shatter is good for quality because it opens up the cluster, allowing berries to size up and air to circulate, promoting even ripening and preventing rot. Now I’m waiting on berry counts for the different clones and selections, and then we can speculate on potential yields.

On Tuesday, I attended a seminar on viruses at the University of California at Davis. In the old days, conventional wisdom said that virus was spread by propagation and you either had it in dirty rootstock or got it from new plant material, in infected scion wood. Now we know that it can be spread by soft-bodied insects like the grape mealy bug, so we assume scale and white flies can carry it, too. We’re still uncertain as to whether phylloxera can spread it.

In the old days, it’s possible that heavier pesticide use and broader spectrum materials may have kept mealy bugs in check. It may be that newer rootstocks tend to express viruses more as well. Now we realize that viruses can jump rows and get into a clean vineyard from a neighboring vineyard, and there isn’t much you can do about it.

One way to approach it would be to obtain clean plant material together with your neighbor. Each grower will have to assess their situation and determine what is economical for them. Viruses delay ripening, lower yields and lessen color although they can also raise acidity and perhaps add flavor complexities.

The beauty of our industry is that it’s so democratic. We face challenges together and so we are forced to work together to meet them.

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