Vineyard Management
Whither the wither?
Theremight be little hope for a grower’s current crop, but knowing the cause could save the following year’s. By Gary Strachan
U
nless you’re gambling with a botrytis affected vintage, wrinkled berries in the vineyard are never a welcome sight. You always have this unpleasant feeling, “This is going to cost me money.” It’s about the same as the last words you utter before a car crash — when you politely say, “I think this is going to hurt.”
The real questions should be: “Why is this happening in my vineyard?” and “What can I do about it?”.
The answer to the first question is, “It depends.” And the second answer is “Probably nothing.”
On that reassuring note, let’s look at the problem a little closer.
There are many situations that can cause wrinkled grapes in the vineyard. By the time the grapes have started to wrinkle, the situation probably can’t be reversed. If you can determine the cause you might be able to prevent it happening with your next crop. The problem can either cause you to lose current production or it might not seriously affect crop quality, depending on the cause. In any case, wrinkled berries will lessen production and should be avoided.
Berries wrinkle if the contents are shrinking for some reason, probably from the removal of water. The first inspection to make is to check out the pedicel of the clusters. These are the short stems that connect the berry to the rachis. The rachis runs down the centre of the cluster and connects the berries via the pedicels to the rest of the vine. If the pedicels are green, then the berries have probably acquired an infection of some kind.
British Columbia FRUIT GROWER • Spring 2015 29
With an infection there may be a mix of wrinkled and normal berries or the whole cluster may contain wrinkled berries. If the wrinkling is pre-veraison, the vineyard probably acquired a botrytis infection at bloom.
You can pray for a dry fall and might be rewarded with a wonderful dessert wine. If it’s a wet fall, your clusters might turn to soft clumps of grey fuzzy mush that’s of no use to anyone. It’s time to revise your early-season spray schedule for next year.
If you notice that the new canes have black blotches on them, then the
wrinkling is probably from a powdery mildew infection.
The early stages of a mildew infection are not visible to the naked eye, but it’s risky to assume that an infection isn’t there just because you can’t see it.
Prevention of an early season mildew infection is one of the best practices for a vineyard.
Your spray program should start early in the season by the time the new shoots are about ten cm long. Use the Gubler-Thomas model to
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