Oak wilt disease was discussed in an earlier issue of this newsletter (see issue #8). If you are considering pruning oaks, it is important to know whether oak wilt is present in your area. If you prune oaks during the growing season when sap is flowing, infested beetles may be attracted to your tree, bringing with them the oak wilt fungus. Before pruning oaks, find out what the oak wilt situation is in your area. Most city arborists and state foresters are aware of outbreaks. Horticulture specialists in Extension offices are also aware.|
So far this year the Plant Clinic has confirmed oak wilt in St. Clair and Stephenson counties. In 2004 the clinic isolated the fungus, confirming oak wilt in DuPage, Henry, JoDaviess, Lee, Madison, Marshall, Mason, Stephenson, Tazewell, and Winnebago counties. This information is reflective only of Plant Clinic samples; I do not mean to imply that oak wilt is not in other counties. For example, it has been found in Champaign County but has not been confirmed at the Plant Clinic since 2000. This information still has great value. If you live in one of these counties, know that recently confirmed cases of oak wilt have occurred in your area. Do not prune oaks during the growing season in those areas if possible. Most of the oak wilt literature says not to prune until mid-July. If you can wait until fall to avoid attracting beetles that might carry the oak wilt fungus spores, that would be a safer plan of attack.