Powdery mildew (PM) is a fungal disease that damages many crops, including grapes. In California, wine, raisin, and table grapes contributed over $3.8 billion to the value of California’s farm production in 2011 (California Department of Food and Agriculture, 2012). Grape varieties with resistance to powdery mildew are currently being developed, using either conventional or transgenic approaches, each of which has associated advantages and disadvantages. PM-resistant varieties of grapes could yield large economic benefits to California grape growers—potentially allowing cost savings as high as $70 million per year, but benefits range widely across the different grape production systems. The benefits might be even larger if environmental regulations over the use of pesticides were changed to limit some currently effective PM management protocols. On the other hand, grapes produced using non-vinifera or transgenic vines might suffer a price discount compared with conventional alternatives.