Risk assessment of Xanthomonas citri pv. viticola for the EU

Abstract

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of Xanthomonas citri pv. viticola (Xcv). This pest causes bacterial canker of grapevine and is reported from Brazil and India. Two scenarios were considered: scenario A0 (current practice) and A2 (additional control measures). For the fresh grape import pathway, scenario A0 results in an order of magnitude of about one entry per 10 years (median; 90% uncertainty interval between ca. one entry per 18,000 years and ca. five entries per year). For the Vitis spp. plants for planting for research/breeding purposes import pathway, the risk of entry is several orders of magnitude smaller than the risk due to fresh grape import. This outcome is also obtained under scenario A2. The key entry uncertainties include import volume and transfer (for plants for planting), transfer and the disaggregation factor (for fresh grapes) and the limited availability of epidemiological data. The extent of the area favourable for Xcv establishment in the EU is uncertain, illustrating the limitations of climate suitability assessments when based on few data points and little epidemiological information. Nevertheless, the risk of Xcv establishment is only slightly lower than the risk of Xcv entry, i.e. no major establishment constraints are expected for most entries. Similarly, the risk of Xcv establishment is assessed as only slightly lower under current climate compared to the climate of 2041–2060. For grapevine growing areas in the EU with average yearly temperature above 17°C, the lag phase between establishment and spread is expected to be about 3 years (median; 90% range between ca. 6 months and ca. 6 years). Under the same scenario, the rate of spread by natural means is assessed to be ca. 300 m/year (median; 90% range between ca. 35 and ca. 800 m/year). The spread rate would be considerably higher considering movements of plants and cutting tools or machinery. The percentage of grapevine plants infected by Xcv in production sites as yearly average over a 30‐year production cycle is estimated to be ca. 17% (median; 90% range between ca. 1.5% and ca. 46%) in table grapes and ca. 12% (median; 90% range between ca. 0.7% and ca. 37%) in wine grapes. Impacts have been reported to be severe in Brazil and India, but the estimates provided here show that there is considerable uncertainty about expected impacts in the EU.

Risk assessment of Resseliella citrifrugis for the EU

“…In the assessment of potential spread, it is assumed that the founder population of R. citrifrugis occupies a limited proportion of available habitat (citrus plants or orchards located in a restricted area) with a small local population size (i.e. a fraction of the habitat's carrying capacity), in agreement with previous spread assessments (EFSA PLH Panel, 2022 ). Similarly, it is assumed that the initial increase in population size and the initial dispersal rate of R. citrifrugis are limited due to (a) (epi)‐genetic factors (lack of fitness of the species in a new environment) and (b) suboptimal environmental conditions reducing the fitness of the pest.…”

“…Note that one of the input parameters is a disaggregation of consignments factor (d) used to disaggregate the infested material entering into the EU to different locations in the risk assessment area, as in previous Panel PRAs (EFSA PLH Panel, 2017 , 2022 , 2023 ). For example, for d = 1, one ton of citrus fruit is delivered to one location, whereas if d = 2, one ton of citrus fruit is delivered to two locations (in consignments of 500 kg each).…”

Risk assessment of Citripestis sagittiferella for the EU

“…In the assessment of potential spread, the Panel assumed that the founder population of C. sagittiferella occupies a limited proportion of available habitat (citrus plants or orchards located in a restricted area) with a small local population size (i.e. a fraction of the habitat's carrying capacity), consistently with previous spread assessments (EFSA PLH Panel et al, 2022). Similarly, it is assumed that the initial increase in population size and the initial dispersal rate of C. sagittiferella are limited due to: a) (epi)-genetic factors (lack of fitness of the species in a new environment), b) suboptimal environmental conditions reducing the fitness of the pest.…”

Including climate change in pest risk assessment: Current practices and perspectives for future implementation

“…The first quantitative pest risk assessment which included a climate change scenario informing establishment likelihood was published for the pathogen of grapevine Xanthomonas citri pv . viticola (EFSA PLH Panel, 2022). Factors such as the appearance of heavier storms owing to the tropicalization of climate around the Mediterranean and effects on host plants distribution and phenology were considered when evaluating climate change scenarios.…”