In this photo two oak trees have died from oak wilt (yellow dots). One tree is currently wilting and dropping its leaves (purple dot).

In August, I reported that we’d found oak wilt in Cloverland Township in Vilas County, in Arbor Vitae Township northeast of Woodruff, (on the southern border of Boulder Junction Township), and along Nabish Lake Road in Boulder Junction and Plum Lake Townships.

So, what’s new since then? Another tree killed by oak wilt was identified on the western side of Plum Lake in Plum Lake Township in Vilas County; another tree died in Washington Township just north of the city of Eagle River. I’m still waiting on results from a suspicious tree in northern Three Lakes Township in Oneida County. In many cases spring storms, which occurred during the high-risk period for overland transmission of oak wilt, were to blame for new oak wilt infections. But in some cases, disease was due to logging or pruning that occurred during the high-risk period for overland transmission of oak wilt. It’s important to know where oak wilt is and to minimize your risk.

For more information, visit the DNR oak wilt web page.

Oak wilt is generally not common in the northwoods, so, if your oaks suddenly wilted and dropped their leaves in July or August, please report those trees. To minimize new infections of oak wilt it’s important not to prune, wound, or harvest during the high-risk period in the spring, which is April 15 – July 15 in the north. For more information about minimizing the risk of overland spread of oak wilt, or for info on controlling oak wilt infections that are already present, visit the Wisconsin DNR oak wilt page.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.