Potential Risk Levels of Invasive Fire Blight in Apple Orchards Around the World

Fire blight, a disease of apple trees caused by Erwinia amylovora, occurs worldwide except in South America, South-Central Africa, and most of Oceania. Ecological niche models can determine the potential distribution of species and measure the risk of pest invasion. This study aims to develop global climate suitability models using MaxEnt software for E. amylovora and to determine the regions in which apple cultivation and the bacterium are most likely to co-occur. Most occurrence data for E. amylovora (93%) are from the northern hemisphere, distributed between 63.90 to 14.56 degree days in regions of Africa, Central America, North America, Asia, and Europe. The only country in the southern hemisphere that this bacteria has been detected is New Zealand (Oceania). Apples are cultivated on every continent except Antarctica, between 61.55 to 44.41 degree days. We find that regions of South-Eastern Africa, Argentina, Australia, Southern Brazil, Bolivia, Chile, China, the United States, Madagascar, Morocco, Mexico, New Zealand, Peru, Tunisia, Uruguay, and the majority of Europe are suitable for both E. amylovora and apple cultivation. These results provide information on the potential worldwide distribution of E. amylovora in apple production area.