Survival of Ceratocystis fagacearum in branches of trees killed by oak wilt in Minnesota

The survival of Ceratocystis fagacearum in the branches of Quercus ellipsoidalis killed by oak wilt in Minnesota depends on the time of year when the trees die. In trees, which wilt in May or June, the pathogen can be isolated from the xylem for only 1–2 months. In trees which die later in the summer it may persist through to the following spring. Observations on oak bark beetles (Pseudopityophthorus spp.) breeding in the dead trees do not suggest that these beetles are important vectors of the disease in Minnesota.