Wines & Vines

WINE GROWING Preventing spread of Lobesia botrana in grapes processed for winemaking BY Rhonda J. Smith, Monica L. Cooper and Lucia G. Varela, University of California Cooperative Extension were sewn into mesh bags and processed with uninfested clusters in each of two separate press programs with final pressures of 1.5 and 1.8 bars respectively in a 200-pound capacity bladder press at a commercial winery. One larva survived the 1.5 bar program. Acknowledging the press load size was not representative of commercial press loads, survival of vine mealybug (Planococcus ficus) in 6- and 12-ton press loads has been documented, and the survival of an EGVM larva re-emphasizes that unfermented winery waste may pose a risk of pest dispersal.1 In 2011, research on processed winegrapes was conducted inside a Biosafety Level 3 facility at the University of California, Davis. Six replications of 46 individual Merlot clusters were inoculated with five live larvae of L. botrana and held for 48 hours to allow larvae to create feeding-nests (see top photo). For each replication, 40 clusters were processed through a hand-cranked destemmer-crusher. Six clusters were randomly selected per replicate as unprocessed, positive controls. Inspections of control clusters at the same time infested clusters were processed indicated 96% of the inoculated larvae were alive. This recovery rate of live larvae indicated a baseline mortality of appoximately 48 lavae (4%) of the 1,200 larvae innoculated on clusters processed through the destemmer-crusher. For each replication, we evaluated larval status (dead or alive) on 100% of the photo by Monica Cooper D Lobesia botrana larva inside a Cabernet Sauvignon cluster at harvest. photo by rhonda smith iscovery of the European grapevine moth, Lobesia botrana, in Napa County in late 2009 changed how bulk grapes are handled during transport, shipping and processing in areas under a federal quarantine designed to prevent spread of the pest. From a peak quarantine area of 2,331 square miles across portions of 10 California counties, the quarantine area in 2013 has been reduced to include most of Napa County (554 square miles) and small areas in Sonoma and Solano counties within three miles of Napa traps that caught adult moths. European grapevine moth (EGVM) is an exotic pest that has the potential to cause greater damage than other lepidopteran pests in California vineyards because it feeds on grape flower parts and berries. Within the quarantine area the U.S. Department of Agriculture and the California Department of Food & Agriculture have restricted interstate and intrastate movement of regulated articles respectively— which include grapes and winery waste. Current regulations include safeguarding loads of bulk grapes by tarping or filling below capacity, and requiring the exterior of all vehicles, bins, machinery, etc., to be free from debris prior to leaving vineyards and wineries. Depending on the location of the fruit source, unfermented winery waste is required to be transported to an approved composting facility, composted on-site or returned to the source vineyard. An exception is made for berries and clusters pressed to a minimum of 2 bars (28 psi) during the press program. These regulations are designed to reduce the risk of EGVM larvae moving off conveyances holding infested fruit and the potential risk that viable larvae could exist in green waste and overwinter as pupae. To more clearly understand the threat of dispersal of Lobesia botrana in winery waste, we evaluated the fate of larvae in infested clusters processed for winemaking in 2010 and 2011. In 2010, 79 individual Chardonnay clusters, each infested with a single larva, Grape bin trailers can carry berries infested with L. botrana. cluster stems, all surfaces of the processing equipment and in water collected when equipment was washed. A total of two live larvae were located in stems, 10 were found crawling on the destemmercrusher prior to washing and nine live larvae were found in the water collected from washing equipment. We also evaluated larval status on 20% (1.4 gallons) of the must collected when each of the six sets of 40 clusters was processed through the destemmer-crusher. In this investigation, the total number of live larvae recovered from stems and equipment was just under 2% of the total number of larvae we inoculated on the clusters prior to processing. In 1.4 gallons of must, we found 11 live larvae. It is likely that more larvae would have been found if all of the must had been evaluated; however, regardless of the number that can survive a destemmercrusher, both red and white must is fermented and does not pose a risk of larvae dispersal. Although destemmers and presses on winery crush pads are thoroughly and repeatedly washed, the data indicate larvae can move from infested fruit onto a container holding the load in a short length of time. When considering the conveyance of fruit to wineries, this observation supports the continued use of safeguarding measures during transport of bulk grapes and thorough washing of all equipment leaving the vineyard and winery (see photo at left). PWV Bibliography 1. Smith, R.J., Varela, L.G. 2008 "Sidebar: Pomace management reduces spread of vine mealybugs." California Agriculture 62 (4):172–173. pr actica l win ery & vin eya r d AU GU ST 20 13 73

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