The lower branches are affected last but the tree ordinarily loses all its leaves within a week or two and dies during that summer. There is no cure. On white and bur oaks, twigs with wilting and dead leaves may be scattered throughout the crown while some branches remain outwardly healthy. Those leaves usually become light brown and may not fall off. Oak wilt spreads in at least two ways.
Nobody knows how.
The spores of the fungus may be carried by beetles or other insects, by tree-climbing animals such as squirrels, or by woodpeckers and similar birds. That vital question is being feverishly investigated. The other way is underground from tree to tree. It is the only control measure known, now. They support major industries using oak wood for lumber, flooring, heavy timbers, barrels, railroad ties and other purposes.