High risk for oak wilt
On March 18, 2012 Minnesota changed the oak wilt risk status from safe to high. Normally, the risk period for oak wilt would begin in April and continue through July.
Above average temperatures during the past weeks have been ideal for the emergence of Colopterus truncates, a nitidulid beetle responsible for transmitting the oak wilt fungus from diseased to healthy trees. High temperatures and rainy days also cause the oak wilt fungus to form spore mats underneath the bark of dead or dying trees (see picture below). These spore mats have a sweet odor that attract nitidulid beetles and once the beetles come in contact with spores mats they can move fungus to recently wounded oak trees. So for now until the end of July avoid any wounding on your trees and put those pruners away! For more information about oak wilt, please view this article and bulletin.
Stay tuned for more updates!