ISA Urban Forest Professional Practice Test

Oak wilt is a fungal vascular wilt that specifically affects oaks, caused by Ceratocystis fagacearum. It interferes with the tree’s water transport system, so leaves wilt, scorch, and die starting at the tips or margins, with red oaks often showing rapid decline and white oaks sometimes surviving longer but still ultimately affected. The fungus spreads mainly through beetle vectors that fly to fresh wounds and through root grafts between neighboring trees, making infected areas difficult to contain once established. This combination of being caused by a fungus and targeting oaks is what sets oak wilt apart from the other diseases listed. Dutch Elm Disease attacks elms, Chestnut Blight attacks chestnut, and Fire Blight is caused by a bacterium that affects apples and pears, not oaks.