A Synoptic Analysis of the Temporal and Spatial Aspects of Grapevine Leafroll Disease in a Historic Napa Vineyard and Experimental Vine Blocks

Abstract

Five Grapevine leafroll-associated virus 3 (GLRaV-3) epidemics were analyzed utilizing a standardized approach to robustly characterize the temporal and spatial parameters. Published data included in the analysis are from Spain, New Zealand, and Napa Valley, CA together with new data from a historic vineyard in Napa Valley, CA. Linear regression analyses of logit-transformed incidence data indicated a maximum average increase of 11% per year in disease incidence, with considerable variation among locations. Spatial analyses, including distribution fitting, examination of the effective sample size, and evaluation of the parameters of the binary power law fitted to variance data for disease incidence, indicated a high degree of consistency among the data sets. In all cases, except at very low disease incidence, a high degree of spatial aggregation was noted, with evidence that the degree of aggregation varied as a function of mean disease incidence. The polyetic dynamics of disease follow a logistic-like pattern over multiple seasons, consistent with limitation by inoculum availability (infected vines) at low incidence and limitation by disease-free vines at high incidence.

Incidence of Grapevine Leafroll Disease: Effects of Grape Mealybug (Pseudococcus maritimus) Abundance and Pathogen Supply

“…Studies of spatial distribution patterns in vineyards demonstrated a generally high degree of spatial aggregation of leafroll-diseased vines, consistent with vector-mediated movement of the pathogen (Habili and Nutter 1997, Cabaleiro and Segura 2006, Arnold et al 2017. These studies included measures of disease incidence, but with few exceptions, did not include structured, consistent sampling procedures to measure vector incidence and distribution.…”

Virus surveys of commercial vineyards show value of planting certified vines

“…Using PCR-based assays increases efficiency by screening a sample for multiple viruses at once and enhances reliability by screening registered increase blocks for viruses not previously targeted. The updated sampling protocol also provides analytics to measure success and facilitate future improvements (Arnold et al 2017;McRoberts et al 2003). With the support of industry stakeholders, FPS has also invested in genetic sequencing technology to improve unknown virus detection in plant material (Al Rwahnih, Daubert et al 2015).…”

Investigating time and economic costs of botrytis bunch rot sampling using interpolated data

“…Kasimatis and Vilas (1985) studied sampling strategies for soluble sugar content and found that any sampling that focused on berry sampling rather than cluster sampling did not reliably represent vineyard maturity. Sampling studies have also been conducted for a range of insect pests, including mealybugs (Geiger & Daane 2001), European grapevine moth (Ifoulis & Savopoulou-Soultani 2006), and ant populations (Mgocheki & Addison 2009), and diseases, including Downy mildew (Seem et al 1985), Pierce's disease (Park et al 2006;Park et al 2011), and leafroll virus (Arnold et al 2016).…”