Caused by a fungus (Ceratocystis fagacearum), oak wilt was first discovered in Wisconsin in the 1940’s and has since caused significant oak death in the Midwest, including South Eastern Minnesota.
This pathogen affects all oak species and is difficult to treat. However, by simply pruning oaks at the proper times (Only in the fall and winter – never in April, May or June – the spread of this deadly fungus can be curbed. When an oak in a woodland area becomes infected, oak wilt disease spreads through interconnected root systems.