CLIMEX modelling of the potential global distribution of the citrus black spot disease caused by Guignardia citricarpa and the risk posed to Europe

Citrus black spot disease is caused by Guignardia citricarpa and has a global distribution range that is restricted to some regions with summer rainfall and is absent from winter rainfall regions. Some countries restrict the import of fresh citrus fruit from countries where G. citricarpa occurs. A CLIMEX model was previously used to predict the climatic suitability of Europe for potential establishment of the organism, but the European Food Safety Authority criticised aspects of that study. Distributions in South Africa, Australia and Taiwan were used to develop a new set of parameter values that provide a better fit to the known distribution of G. citricarpa and provide confidence that the model is a distinct improvement over that of previous modelling efforts. The new CLIMEX model correctly reflects climatic suitability of all regions in the world where the organism is known to occur. The model indicates that most of Europe is completely unsuitable for the establishment of G. citricarpa. Within European citrus producing regions, suitable areas are highly constrained, never more than marginally suitable, and all have lower levels of suitability than any area in South Africa and Australia where G. citricarpa is known to occur. It is concluded that the potential risk of G. citricarpa establishment in these regions is exceedingly low.

► Parameter values were set using distribution in South Africa, Australia and Taiwan.
► Globally the model correctly reflects climate suitability of known occurrence areas.
► Deficiencies in an earlier model are removed.
► The potential global distribution is predicted.
► It is concluded that the risk of Guignardia citricarpa establishing in Europe is very low.