Q. I have white powdery mildew on my green, table
grapes. This has not been a problem in
the past. What now? Is this related to
the cool, moist weather?
A. Yes, powdery mildew on grape is seldom seen here
because of our very dry and hot weather. This very cool spring, higher humidity
and recent rains has made powdery mildew, as well as early blight on tomatoes a
problem. Powdery mildew will disappear when it gets hot and dry.
Horticultural oils can help reduce powdery mildew problems |
We can usually prevent powdery
mildew by removing the leaves around grape bunches for better air movement and
keeping bunches dry. Once powdery mildew has started, you may have to apply a
fungicide to keep it at bay or eradicate it.
One of the best organic controls
of powdery mildew on grape are the horticultural oils. Horticultural oils are
mixed with water and sprayed on grape bunches in the early morning hours. There
is a precaution in using oil sprays and not to apply it when temperatures are
high. However, I have had no problem applying oils during the cool early
morning hours.
Insecticidal soaps labeled for
disease control have also given some control as well as dusting dry bunches
with sulfur dust.
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