Table C.4: Yield loss on vine grapes

Overview of the results of the Expert Knowledge Elicitation (4th EKE question)
Parameter	Incidence in vine grape plants
Stratification	Grapevine production areas in the EU with average yearly temperature above 17°C as average of the coming 30 years
Question	What is the average percentage of infected plants by Xanthomonas citri pv. viticola in vine grape production sites as yearly average of a 30‐year production cycle in the risk area? [%]
Results	P1%	P2.5%	P5%	P10%	P16.7%	P25%	P33.3%	P50%	P66.7%	P75%	P83.3%	P90%	P95%	P97.5%	P99%
Elicited values	0.50%					5.00%		10.0%		25.0%					40.0%
EKE results	0.50%	0.56%	0.71%	1.23%	2.25%	3.99%	6.2%	12.0%	19.4%	23.8%	28.7%	33.1%	36.7%	38.7%	40.0%
Fitted distribution	BetaGeneral(0.59122,1.0967,0.00485,0.41)
Figure (C.4a): Comparison of elicited and fitted values/density function to describe the remaining uncertainties of the parameter							Figure (C.4b): Cumulative distribution function (CDF) of the likelihood of the parameter

Summary of the evidence used for the evaluation
The assessment was done in comparison to the level of infection on table grape production sites, using the same evidence. The influences of the differences between the two productive systems (for table grapes vs wine production) on the infection rate were discussed esp. the influence of the higher frequency of pruning activity, the absence of covers, the different use of irrigation (vineyards are frequently rainfed) and mechanisation, the use of varieties that could be more tolerant to the pathogen, the different harvesting period. References suggest differences between rootstock varieties, rootstock vs. main plants, and white/red grapevine varieties. Grapevine varieties used in EU wine production systems. Differences in the production cycles (pruning, winter period) between the EU and countries of origin, i.e. India, Brazil. Some reference report natural incidence: Lima et al., 2000; Melo et al., 2000; Rodrigues Neto et al., 2011.
Main uncertainties
References may report new outbreaks, highest observed incidences and/or only incidence on symptoms on leaves/plants. Composition and susceptibility of EU grapevine varieties in wine production systems. Influence of climatic differences between reporting countries (e.g. India) and the EU, as well as possible adaptations of Xcv. Proportion of asymptomatic grapevine plants in the EU or duration of the asymptomatic period of infections. Influence of artificial inoculation on the infection rate. Effect of measures applied in the countries of origin as well as treatments already applied in the EU. Frequency of existing spread mechanisms including pest pressure from natural environments in the EU.
Reasoning for a scenario which would lead to a reasonable high proportion	The judgement on the upper limit considers that Grapevine varieties used in wine production systems (with seeds) are susceptible. Higher proportion of mechanisation in grapevine for wine production systems. Stronger pruning, no protection in grapevine for wine production systems. (The remaining scenario of table grapes remains unchanged) Less importance of climatic differences or adaptation of Xcv to EU climates. High proportion of asymptomatic infected plants (not reported with the incidence of symptoms). Infection level of artificial inoculation is similar to the stable infection level after long‐term presence of Xcv. Specific measures at the country of origin lower the prevalence, while treatments non‐specific to Xcv in the EU are less effective. High pest pressure from the environment with effective spread into the vineyards.
Reasoning for a scenario which would lead to a reasonable low proportion	The judgement on the lower limit considers that Grapevine varieties used in wine production systems (with seeds) are less susceptible. Less/no irrigation in grapevine for wine production systems. Shorter vegetation period in grapevine for wine production systems. (The remaining scenario of table grapes remains unchanged) Tropical climate with high humidity promotes infections, thus EU climates are less suitable. Short symptomless period of infections. Artificial inoculation overestimates the incidence under natural conditions. Ineffective measures at origin countries, while EU vinicultural practices are effective, e.g. pruning. Low pest pressure from the environment with slow spread into the vineyards.
Fair estimate as judgement on the weighted evidence	The judgement on the median considers that Varieties for wine production seem in general less susceptible than table grapes. That the EU situation is less favourable for infections, due to different climatic and vinicultural conditions.
Precision of the judgement as description of remaining uncertainties	The judgement on the interquartile range considers that The uncertainty below the median is high and above the median is as well high due to missing specific information on the behaviour of Xcv under EU conditions.