“The bacteria is fatal to citrus trees and has decimated citrus groves in Florida and Texas. Now, California growers are holding the line to keep producing the vital crops. As temperatures rise, that gets more difficult.”
EDIT: the tail-end of Wikipedia’s entry points to a Citrus Grower article – seems that cover crops and healthy soil biology seem to help citrus trees weather the disease a lot better
The larger and denser the groves, easier is the transmission. You cannot have healthy cultures in huge monocultures, plants need different species around them as much as we do.