Viruses and related pathogens have no cure and impose large costs on plant production. These diseases are typically spread through infected planting stock and plant propagation material. However, virus spread can be minimized if clean stock is used. We examine the costs and benefits of a virus testing and certification program for Grapevine Leafroll-3 in the North Coast region of California. We compare grower costs and benefits from using certified stock, and we extrapolate to the industry as a whole to estimate costs and benefits to consumers and producers of winegrapes, for the North Coast region. We find that the benefits from certification are large—in excess of $50 million per year for the region—and that they substantially outweigh the costs. We also find large potential benefits from roguing and replacing diseased vines rather than leaving them in the vineyard where they can spread disease. Additionally, we find large costs associated with disease entering from neighboring properties—nearly $300 per acre annually, using our baseline parameterization.