Issue link: http://read.dmtmag.com/i/561374
w w w. v w m m e d i a . c o m S e p t - O c t 2 015 | V I N E YA R D & W I N E RY M A N A G E M E N T 5 9 Over the past several years, VineView has been comparing its technique and results to field map- ping and laboratory tests conduct- ed by Cooper, as well as several of the company's clients. The com- pany made the service available to growers commercially in the fall of 2014. (The per-acre cost varies, but company officials say it is compa- rable to the cost of replanting just a few vines.) "Our preliminary work was done on the ground using a hand-held hyperspectral instrument to mea- sure diseased and non-diseased vines and leaves," Cooper said. "We detected a spectral signature for GLRaV-3 in Cabernet Sauvignon consistent with published research. In our next phase, we transitioned to imaging with an airborne camera. We worked in four vineyards in 2013 and nine vineyards in 2014. In each vineyard, ground surveys recorded the incidence of visual symptoms of AERIAL IMAGING AIDS MANAGEMENT The positive, rapid and accu- rate aerial imaging techniques being developed by VineView and tested by Cooper offer several advantages in managing the dis- ease over more traditional detec- tion methods. Biological indexing, which is widely used in clean plant programs as a fundamental assay for identifying GLD viruses, can be a two- to three-year process. The rapid detection of GLD virus using ELISA (enzyme-linked immunosor- bent assay) or molecular assays can involve extensive sampling, mak- ing it challenging to employ across large vineyards. "The reason we initiated this work is to help growers find a cost- effective, reliable and automatable method for mapping the incidence of leafroll disease in their Caber- net Sauvignon vineyards," Cooper said. "Removal of diseased vines is a critical part of leafroll disease management in our region and disease; hyperspectral maps gener- ated by VineView recorded disease incidence from the air. "We are in the process of analyz- ing and comparing data generated from visual (ground) vs. hyperspec- tral (airborne) mapping to minimize inconsistencies and optimize the process of aerial imaging. We are also using laboratory testing to con- firm the virus status of a percent- age of vines at each site." Visual identification of the dis- ease is unreliable and can be com- plicated for vines with mixed virus infections. Foliar symptoms of GLD are apparent during late sum- mer and fall, vary with cultivar and are usually most conspicuous in red-fruited vinifera cultivars, with reddening of leaves in addition to cupping and primary leaf veins remaining green. In white-fruited vinifera cultivars, symptoms are less pronounced, consisting of slight leaf chlorosis and cupping. Also, nutritional disorders, mechan- ical damage and other stresses can mimic foliar GLD symptoms. + A new aerial imaging tech- nique, tested by UCCE Farm Advisor Dr. Monica Cooper, aids in managing grapevine leafroll disease. + The practice of identifying diseased vines requires crews to be highly trained to recognize symptoms. This tool uses aerial hyper- spectral imaging to auto- mate the process. + Aerial maps identify the location of infected vines, help locate the origin of the disease and direction of spread, and determine the overall amount of infection. + To date, the work has focused on Cabernet Sauvignon vineyards, but researchers hope to explore whether other dis- eases show unique hyper- spectral signatures. AT A GLANCE Melissa Staid of VineView (left) and Emily Kuhn, former assistant to Dr. Monica Coo- per, measure the reflectance of diseased and healthy leaves using a handheld spec- trometer. Photo: Monica Cooper, UCCE