AN ECONOMIC ANALYSIS OF PREVENTATIVE PRACTICES FOR MANAGING TRUNK DISEASE IN TABLE GRAPE VINEYARDS MONDAY, APRIL 19, 2021. BY KENDRA BAUMGARTNER, PHD, USDA, JOHNATHAN KAPLAN, PHD, CSU SACRAMENTO, & MAX NORTON, PHD, CSU SACRAMENTO. California is the nation’s leading grower and sole exporter of table grapes [California Department of Food and Agriculture, 2017], with over 99% of US commercial table grapes grown in California [California Table Grape Commission (CTGC), 2017]. In 2016, the state’s 85,166 bearing acres of commercial table grapes produced 939,294 metric tons of grapes, valued at $1.85 billion [CTGC, 2017; CTGC, 2016]. Most of this acreage is located in the southern San Joaquin Valley. Trunk, or wood-canker diseases, including Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback, present a serious challenge to the productivity of vineyards of all types. The majority of California vineyards over age 10 are likely infected [Hillis et al., 2015]. Rain during the dormant season induces spore production, liberation, and dispersal. The vineyard climatic conditions at this time of year prolong the time it takes for pruning wounds to heal, increasing the susceptibility of the vine. If untreated, yield losses can potentially reach over 90% near the end of a 25-year lifespan [Munkvold et al., 1994]. Further, trunk diseases take many years to develop and do not start to show symptoms until around 10 years old, years after the initial infection has already occurred, at which point management options are limited. Preventative management practices are available (see Table 1), but growers often exhibit hesitancy to start using them in newly established vineyards, possibly due to uncertainties about cost-effectiveness and disease control efficacy (DCE) [Hillis et al., 2015].