International crowd gathers at annual conference in Portland, Ore.

The wine industry assembled in Portland for the 66th American Society for Enology and Viticulture (ASEV) National Conference, held June 15-18.

Despite the word “American” in the organization’s name, attendees and speakers from Canada, South Africa and other nations participated, sharing information alongside United States-based researchers and industry professionals.

Research presentations addressed a wide range of enology and viticulture topics affecting the industry, many of which were included in the general viticulture session.

GRN Rootstocks

Of particular interest was an evaluation of GRN rootstocks conducted by Dr. Andy Walker, Louis P. Martini Endowed Chair in Viticulture at UC Davis. The lab continues actively evaluating new plant material for field trials based on broad resistances – including salt, nematodes and drought. GRN-1 was the most resistant, Walker reported. One of its characteristics is vigorous growth with deep roots, which Walker noted is “not for everyone, but (the rootstock) should be available.”

Results of comparing conventional rootstock with so-called “ubervines” – rootstock with a 90 cm cane – were presented by Larry Bettiga, viticulture farm advisor for the University of California Cooperative Extension, in Monterey County. At $5.50 per vine, it was important to determine its benefits compared to purchasing conventional rootstock at $3 per vine. Although labor was not factored into the assessment, he found the additional cost may be justified given the potential for earlier production with the ubervine.

Leaf-Removal Practices

A pair of researchers looked at leaf removal practices in different climates. Kaan Kurtural, associate professor at California State University, Fresno, evaluated strategies specific to Merlot grapes grown in the Central Valley heat in tandem with the fruit’s anthocyanin levels, since fruit with lower levels command a lower price. Based on his findings, a pre-bloom leaf removal is ideal and had no loss of yield.

Dove-tailing with Kurtural’s presentation, Virginia Tech researcher Cain C. Hickey discussed leaf removal practices specific to Virginia vineyards where “getting clean fruit into the winery is a challenge, (and) the rest is gravy.” Exposing fruit through post-fruit set leaf removal optimizes disease management, he found, without decreasing yield.

Pests & Diseases

In addition to sessions on general enology topics, several specialty topic presentation sessions were held, including one on pests and diseases, which began with a survey of grapevine viruses in British Columbia by Sudarsana Poojari, a researcher with Agriculture and Agri-Food Canada Pacific. The most prevalent was the grapevine fleck virus, “which was surprising to us,” said Poojari. Other surprises included finding grapevine red blotch virus in only two of 812 samples, and no positives of Arabic mosaic virus.

Kari Arnold, a UC Davis doctoral student, sought to determine whether plant material age – based on planting booms – was a factor in diseases such as neopviruses and leafroll. Newer blocks were less virus-infected than the older ones, they determined, and infection is more likely from a neighboring vine. They are now updating screening protocols as well as developing an online assessment tool for growers.

Not yet interested in sour rot? Those who attended Cornell University doctoral student Megan Hall’s enthusiastic presentation of her research into understanding sour rot and how to manage it surely came away with a new appreciation for the rarely investigated topic. Sour rot has been seen worldwide, she said, but not fully characterized despite the fruit damage it causes. Using antimicrobial and insecticide treatments in combination are effective controls, while training vines on a top wire system also reduces sour rot, Hall reported. Research on the topic is continuing to solidify her findings.

Bhanu Donda from Washington State University sought to determine how grapevine leafroll disease spreads in newly planted vineyards surrounded by older, infected blocks. Preliminary results have found that the optimal distance for planting new vines from older ones is about 30 meters, but further study is needed. Additional related questions were raised as a result of the work, Donda said.

Progress in using entomopathogenic nematodes (EPNs) to control mealybug populations, which plague both wine and table grapes in South Africa, was explained by Patrique Le Vieux of the University of Stellenbosch in South Africa. Researchers looked at two different nematodes, but found S. yirgalemense was 90% persistent in the field. In the 12 week study, they found those areas with the highest nematode concentrations had the highest mealybug mortality rates.

Jensena Newhouse from Washington State University evaluated different spraying programs to combat powdery mildew. Of nine different programs, including a control program with no spraying, the best result was achieved from using an effective combination of synthetic fungicide and biological controls in rotation.

Tours of Columbia Gorge vineyards and wineries as well as the second Symposium of Nitrogen in Grapes and Wine were also among the conference events.

The next ASEV National Conference will convene in Monterey, Calif., June 27-July 1, 2016.