Trunk or wood canker diseases pose a serious threat to winegrape growers. Despite high prevalence and substantial consequences, growers routinely wait to adopt field-tested, preventative practices (delayed pruning, double pruning, or application of pruning wound protectant) until the vineyard presents symptomatic vines (~10 years old). We investigated why growers are not adopting preventative practices earlier. To do so, we quantified the gains from adopting practices at different ages in infected vineyards by simulating winegrape production in different crush districts in California using a bioeconomic model parameterized with scientific evidence on trunk diseases, preventative practices, and vineyard costs and returns. We found growers are better off adopting a preventative practice when the vineyard is infected and are best off adopting in a three-year old vineyard. The profitable lifespan of an infected vineyard can increase by >50% when practices are adopted in young vineyards. However, it takes two to 10 years for practices adopted in year three to outperform no action; 0 to eight years when adopted in year five; and 0 to four years when adopted in year 10, likely leading growers to perceive preventative practices as less effective than they are. When practice costs are <$100 per acre and the perceived risk of infection is >1%, early adoption is preferred to waiting. When practice costs are >$200 per acre, however, adoption occurs when the probability of infection is close to one, indicating many will wait for certainty before adopting. Lastly, at very low levels of perceived infection risk, the earliest adoption may not be optimal because gains in net returns from adopting early in an infected vineyard do not outweigh the costs if the vineyard is healthy. To alleviate delay in adoption until symptoms are present, we see a need to further inform growers of the benefits of early adoption using effective extension tools.

Funding Support: United States Department of Agriculture