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Two of the majestic oak trees adorning the hillside leading down from Woodlawn Boulevard into the park on the far south end of the park have been confirmed to have oak wilt. The damage to the trees observed by the MPRB’s arborists is assumed to have occurred in June’s violent storms. The trees that tested positive for the fungus Ceratocystis fagacearum are being removed in hope of preventing the spread of the disease to neighboring trees.  Trenches are also being dug in the spring to separate the roots of healthy trees from the diseased ones.

The fungus infects oak tree’s water carrying cells, preventing water and nutrients from travelling from the roots to the crown of the tree.  This process is what causes the wilting of the infected tree and eventually its death.  The fungus spreads through root grafts under the soil (in closely spaced trees, such as occur on this hillside and via sap feeding beetles which carry the fungal spores from infected to healthy trees.

The removal and trench line method of containment for oak wilt has been utilized successfully in the park before (near 50th street and the parkway) and we hope for the same success this time.  Replanting will not be done, both because it is not recommended to replant oaks where wilt has been confirmed, and because of the area’s designation as a natural area.  Natural areas are minimally managed by park staff, and are left to be replanted by mother nature and the squirrels when trees die or are removed due to disease.

More information about diseases of oak trees, including oak wilt can be found on the University of Minnesota’s Extension website: http://www1.extension.umn.edu/environment/trees-woodlands/oak-wilt-or-anthracnose/

OAk wilt location

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