The hosts and potential geographic range of Dothistroma needle blight

Dothistroma needle blight, one of the most important foliar diseases of Pinus spp., is caused primarily by the fungus Dothistroma septosporum (Dorog.) Morelet, and to a lesser extent by Dothistroma pini Hulbary. The potential distribution and abundance of Dothistroma spp. was determined by (i) developing a process-oriented model of potential distribution of Dothistroma spp. from known locations, (ii) compiling a comprehensive list of susceptible host species from existing scientific literature and (iii) determining the distribution of susceptible hosts in areas predicted to be suitable for range expansion of Dothistroma spp. Using these three sources of information regions at risk were identified as those that were predicted to be suitable for range expansion by Dothistroma spp. and included significant areas of susceptible host species.The process-oriented distribution model, CLIMEX was used to infer the climatic requirements of Dothistroma spp. from laboratory based measurements and 248 disease records in North America and Asia. When validated against 7594 disease observations from Europe, Africa, South America and Oceania, the model correctly predicted that all observations had a suitable climate for Dothistroma spp. The model indicated that the fungi can persist in climates ranging from sub-arctic through temperate, Mediterranean, continental, subtropical to dry tropical regions. The low level of disease detection in many regions projected to be climatically suitable may be due to the low occurrence of susceptible hosts. When areas that were not suitable for susceptible hosts were excluded results suggest that Dothistroma spp. could further extend their range into south east China, Vietnam, Ireland, Western Australia, Venezuela, Guyana, Suriname, Panama, Turkey, Albania and many countries bordering the Mediterranean Sea.