It has more to do with invasive species than anything. Xyella fastidiosa is native to the gulf coast states in the US. Olives and other species from the old wor

It has more to do with invasive species than anything. Xyella fastidiosa is native to the gulf coast states in the US. Olives and other species from the old world lack any resistance to the bacteria. This same bacteria causes Pierce's disease in Vitis vinifera, the common grape (from Eurasia). Whereas North American Vitis species are resistant to Xf. There's a lot of research going into solving Pierce's disease here in the US from breading programs to bacteriophages. The later may end up helping solve the same problem in Olives.