Oak Wilt is caused by the fungus Ceratocystis fagacearum. The first confirmed case of Oak Wilt was in Wisconsin in the early 1940s. It was not confirmed in Texas until 1960. It is comparable to Dutch Elm Disease, a fungal infection that has destroyed entire elm populations in the Midwest and Northeast United States. Although all oak species can contact Oak Wilt, Red or Spanish Oak and Live Oak are the two most susceptible.

Oak Wilt should not be confused with Oak Decline. Decline is a catch-all term used when a tree under stress falls prey to any number of diseases or insects. Oak Wilt invades the water and food tissues of oak roots and limbs. It is a true wilt disease.