They are attracted to sap from a wound in the bark of a live oak or red oak
Wounds from pruning
Wounds from limbs breaking off in the wind
Wounds from accident damage (e.g. by a lawnmower scraping the tree)
Local spread from tree to tree through roots
Insect carriers are always responsible for infection of the first oak in a neighborhood of otherwise healthy oaks. After the first oak has been colonized, the fungus moves through the roots to surrounding oaks, creating an oak wilt disease center.