Determining Survival of Lobesia botrana Larvae in Grapes Processed for Wine Making to Evaluate the Risk of Dispersal

Lobesia botrana (Denis & Schiffermüller), European grapevine moth, was reported for the first time in North America by USDA–APHIS in October 2009, in vineyards in Napa County, CA. Pheromone traps placed in vineyards subsequently detected moths in 11 California counties. In June 2010, a Federal Order established quarantine areas and with the State’s interior quarantine, safeguarding measures were established to restrict the movement of regulated articles including fruit and winery waste. In two harvest periods, we evaluated the fate of larvae in clusters processed for wine making. In 2010, individual ‘Chardonnay’ clusters, each infested with a single larva were sewn into mesh bags and processed with uninfested clusters in two separate loads (reaching 1.5 and 1.8 bars respectively) in a 200-pound capacity Willmes press at a commercial winery. One larva survived the 1.5 bar press. Each cluster was treated as a single replicate of a completely randomized design and data analyzed by cross tabulation. There was no significant difference in mortality between press loads. In 2011, research on processed winegrapes was conducted inside a Biosafety Level 3 facility at the University of California, Davis, due to State quarantine regulations. Six replications of 46 individual ‘Merlot’ clusters were placed in paper cartons and each cluster inoculated with 5 live larvae of L. botrana then covered and held for 48 hours to allow larvae to web feeding nests. For each replication, 40 clusters were processed through a hand-cranked destemmer-crusher; 6 clusters were not processed to provide baseline mortality due to conditions other than grape processing. Larval status (dead or alive) was evaluated on: 1) 20% of the volume of solids processed; 2) 100% of the cluster stems processed; 3) the processing equipment prior to washing; and 4) rinsate from washed equipment containing berry solids and stem pieces. Total weight of clusters processed and subsequent weight and volume of fruit solids allow results on per cluster basis. Unequal variances of dependent variables were significant regardless of transformation thus preventing ANOVA. Live larvae were found in the solids in 5 replicates and in stems in 2 replicates; up to 0.5 and 0.025 larvae per cluster, respectively.   Live larvae were observed on equipment prior to and post-washing; up to 0.08 and 0.10 larvae per cluster, respectively. Results indicate thorough washing of all equipment in contact with infested clusters is important and at harvest, truck-loads of grapes should be tarped or slack filled.