Issue link: http://winesandvines.uberflip.com/i/62507
GRAPE GRO WING turns out that mealybugs already present in California are quite capable of vector- ing the leafroll virus. Grape mealybug and longtailed mealybug are actually more effi- cient vectors than vine mealybug. Since we have fairly good biological control of these insects by generalist predators and parasi- toids, the mealybug populations are often very low, and most growers aren't even aware of them in their vineyards. There is speculation that even at low numbers, these insects are quite capable of moving leafroll virus from infected vines in older blocks into and around new blocks. It is possible that this has been occur- ring for a long time, but two to three de- cades ago, many vineyards had low levels of leafroll already, since many vines were propagated on rootstock from field-select- ed scion wood. Movement may have been less noticeable. UC researchers Deborah Golino and Neil McRoberts will be leading a team of researchers who will work on epidemiol- ogy studies in the coming years to better understand the mechanics and kinetics of leafroll disease movement from infected to clean vineyards. Insect populations, temperature patterns, wind intensity and direction, disease incidence and severity Foundation Plant Services Process for Propogating Clean Vines, Part I 1 2 3 1. Grape vines grow in sterile nutrient media (from left) to develop roots. 2. Chipbudding into four varieties that are indicators for virus infection. 3. A small growing tip is grown into a new plant. will be some of the factors evaluated in the research. Finally, leafroll virus awareness is not high in all winegrowing districts. In the counties where I work (Lake and Mendo- cino, Calif.), we tend to worry most about it when planting new vineyards, and I have for many years encouraged growers to source only certified virus-free propaga- tion material. We have many old vineyards that have severe leafroll symptoms, but we don't appear to be seeing movement of lea- froll virus into newer vines planted from clean propagation material. Perhaps we are not looking closely enough. At what point of infection should I consider removing leafroll-infected vines? We don't have any good metrics to advise growers when to remove a vineyard based on the severity and incidence of leafroll virus in their vines. We have local vineyards that are mildly infected but yield well and ripen well. Economics is probably the most important issue: Is the winery that makes wine from the infected vineyard willing to continue buying the fruit? Is the resulting wine suitable for the price-point and quality goals? Are yields sufficient to justify keeping the vines in the ground? These questions are probably the most germane to individual growers. AVAILABILITIES CALL NOW FOR 2012 Award-winning quality… …a tradition for over 20 years…has made Vintage Nurseries the perfect pairing for growers desiring the finest, most reliable yields. Our state-of-the-art technology, industry-leading service and wide selection make Vintage Nurseries a California classic. Whether your needs include the finest field-grown dormants, potted green vines, rootstock rootings or own-rooted plants and cuttings, Vintage Nurseries assures you of the finest quality products…every time, for every wine. Place your order today, and capture classic quality from the leader in the field. 661-758-4777 Wasco 800-499-9019 Paso Robles 805-237-8914 209-523-8036 Modesto Santa Rosa 707-542-5510 www.VintageNurseries.com Serving the Wine, Table Grape and Raisin Industries Wines & Vines OCTOBeR 2011 61