Grape Grower's Notebook July 24, 1999

Botrytis

Botrytis, like Black Rot, is a vineyard sanitation problem. If you remove junk from the vineyard (discarded and broken shoots, failed flower clusters and berry clusters, etc.) and clean trellis wires in the spring, you eliminate the principal hosts of the Botrytis fungus and its ability to winter over. Botrytis and Black Rot are two good reasons not to mulch underneath grapevine rows (except with black plastic). Shredded mulch and bark mulch make excellent hosts for the spores of both fungi.

A dormant spray of the vines with lime sulfur will help the anti botrytis cause a great deal. Subsequently, three sprays of Benlate, one at bloom, one at berry set and one before the berries touch are very important.

You should be aware of varietal susceptibility, and take extra care to clean out mid season "junk" (discarded shoots, hedged material, etc.) in areas where highly susceptible varieties are growing.

Unlike Black Rot, you may see foliar symptoms long before fruit is impacted. This permits you to spray the susceptible clusters with Rovralor Vangard. In small plantings, where the fruit zone is well organized, application with a handgun directly into the clusters will save money.

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