Mitigating the Economic Impact of Grapevine Red Blotch: Optimizing Disease Management Strategies in U.S. Vineyards

Grapevine red blotch disease (GRBD) is a recently-recognized viral disease found across some of the major grapegrowing regions in the United States. Vineyard managers were surveyed to (i) estimate the economic impact of GRBD on <i>Vitis vinifera</i> cv. Cabernet Sauvignon in Napa and Sonoma Counties in California and on <i>V. vinifera</i> cv. Merlot in eastern Washington and Long Island in New York, and (ii) to identify cost-minimizing management strategies under various disease incidence rates, price penalties for suboptimal fruit composition, timing of disease onset relative to vineyard age, and costs of control. The economic cost of GRBD was estimated to range from $2213/ha in eastern Washington, when disease onset occurs at a low initial infection level and there is a low price penalty, to $68,548/ha in Napa County, when initial infection rates and quality penalties are both high. Our results further suggest that roguing symptomatic vines and replanting with clean vines derived from virus-tested stocks minimize losses if GRBD incidence is low to moderate (below 30%), while a full vineyard replacement should be pursued if disease incidence is higher, generally above 30%. These findings should help vineyard managers in the four examined viticultural regions adopt optimal GRBD management strategies.