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California Association of Winegrape Growers

Established in 1974, the California Association of Winegrape Growers (CAWG) is an advocate for farmers, providing leadership on public policies, research and education programs, sustainable farming practices and trade policy to enhance the California winegrape growing business and our communities.

In 1986, the California Association of Winegrape Growers funded research by Drs. Marois and Ough, who were studying the effect of Botrytis cinerea and Aspergillus sp. on wine quality. The problem of deterimining the threshold of disease after which wine quality is affected was under investigation; this is critical in determining the pricing of wine grapes at the winery. Their research allowed the winery to decide what level of diseased grapes it can accept and still maintain quality wine.

Their experiment involved taking Chenin Blanc and Zinfandel grapes and inoculating them with B. cinerea or Asperigillus sp. Entire clusters were inoculated and combined with clean clusters at harvest to yield lots of 100 lbs each of 0%, 1%, 5%, 10%, 20% diseased berries by weight. The lots underwent small scale fermentation and were tasted according to protocol to determine the effects of the various disease levels on wine quality.

The berries were monitored during disease development in order to quantify the effect of disease on berry weight. These measurements allowed for better defining of the levels of disease at the inspection stations. This preliminary project allowed the Commission to decide if there was a need to expand the experiments in future years.