Whenever anyone in this part of Texas thinks of a disease of trees, or just thinks of trees dying, they always think of oak wilt. And with good reason. Oak wilt is probably the proximate cause of the death of more mature oak trees in the Hill Country than any cause, other than man. But there is another fungal disease, called hypoxylon or hypoxylon canker (Hypoxylon atropunctatum) that infects and kills oaks.