Oak Wilt
Bretziella fagacearum (formerly Ceratocystis fagacearum)
Overview
Oak wilt is a lethal vascular disease of oaks caused by Bretziella fagacearum. Red oaks often die within weeks of infection; white oaks usually decline more slowly. The fungus spreads through root grafts between neighboring trees and via sap-feeding beetles attracted to fresh wounds. Landscape and woodland stewardship focuses on avoiding spring pruning wounds, disrupting root connections, and carefully handling infected wood so beetles do not carry spores to healthy oaks.
Symptoms
In red oaks, leaves brown from the margins inward, often starting high in the crown, followed by rapid wilting and heavy leaf drop. Trees may die in four to six weeks. White oaks show slower branch dieback over years, with some leaves flagging while others remain green. Vascular streaking may be visible under bark. Clusters of neighboring red oaks dying in sequence often signal root-graft spread.
Environmental Conditions
Variable
Prevention
Do not prune oaks from spring through midsummer when beetle vectors are most active; if wounds are unavoidable, paint them immediately. Avoid wounding trunks with equipment. When planting, mix species so an entire canopy is not one susceptible oak type. Report suspicious rapid oak death to local extension or forestry services for confirmation and community response.
Management
For high-value trees, professional propiconazole trunk injections are sometimes used preventively or early; this is not a casual home remedy. Trench to sever root grafts well beyond symptomatic trees when a local outbreak threatens a grove. Remove and properly dispose of infected red oaks promptly; debark, chip, or cover wood so beetles cannot breed. Do not move firewood from wilt areas. Keep remaining oaks watered during drought to reduce secondary stress.