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Assessing the benefits of disease management by interpreting an ecological survey of grapevine viruses when contrasted with “planting booms”
K. ARNOLD (1), D. Golino (1), M. Cooper (2), R. Smith (3), V. Klaassen (4), N. McRoberts (1). (1) University of California-Davis. Department of Plant Pathology, Davis, CA, U.S.A.; (2) University of California Cooperative Extension, Napa, CA, U.S.A.; (3) University of California Cooperative Extension, Santa Rosa, CA, U.S.A.; (4) University of Calif

Grape virus diseases are economically caustic to industry. Readily spreading vector transmitted viruses like GLRaV-3 can make the use of certified planting material seem futile when planting certified material near infected material. We conducted a multi-virus survey in 2014 in the north coast wine growing region of California in order to assess the benefits of disease virus management. We surveyed 112 vineyard blocks stratified in age to capture historical “planting booms”. Age classes were: 1880-1980 (old material); 1981-1995, replants due to AXR#1 rootstock removal due to phylloxera failure; 1996-2010 representing blocks culled in response to virus infected field selections grafted onto rootstocks not tolerant of viruses present in the material, and 2011-2014 representing a group of “new” material. 27-29 blocks were randomly selected in each age class and sampled using a simple random sampling strategy, in a “W” pattern to ensure subsample separation. Subsample intensity was dependent upon block acreage, and subsamples were tested using qRT-PCR for eight different viruses. The resulting disease incidence data are interpreted in relation to changes in virus distributions over time and the positive impact of grape certification and clean plant programs. Shifts in distributions of virus incidence are modeled by fitting disease incidence data to Beta distributions and plotting the trajectory of disease incidence in the Beta distribution parameter space.

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