Oak Wilt in Illinois
CRITICALDisease
Oak Wilt is currently active in Illinois. Watch your susceptible trees closely and act early.
About Oak Wilt
A lethal fungal disease that affects all oak species, with red oaks dying within weeks of infection. It spreads through root grafts between neighboring oaks and via sap-feeding beetles. White oaks are more resistant but not immune.
Symptoms to watch for
Rapid wilting from the top of the canopy downward in red oaks, leaf discoloration with browning at margins, defoliation within weeks of symptom onset, fungal mats under bark that crack the bark open
Trees at risk in Illinois
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Treatment options
Root Graft Disruption (Trenching)
Mechanical severing of root connections between infected and healthy oaks using vibratory plow trenching to a depth of 4-5 feet. The primary method to stop underground spread in oak groups.
Propiconazole Fungicide Injection
Macro-infusion of the fungicide propiconazole (Alamo) into root flares of high-value oaks as a preventive or therapeutic treatment. Provides 1-2 years of protection.
Avoid Pruning During Risk Period
Do not prune oaks from April through July when nitidulid beetles that carry the fungus are most active. Paint all wounds immediately if pruning is necessary during risk period.
Recommended Products & Tools
Helpful supplies for managing Oak Wilt. Always read and follow label directions, and confirm a diagnosis before treating.
Seal oak wounds immediately if pruning in the growing season.
Protectant spray for many bacterial and fungal diseases.
For the rare case sealing is advised (e.g., oaks in oak-wilt season).
Sharp, clean cuts to remove affected wood — a tree-care essential.
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Browse all Illinois arborists →Frequently asked questions
Is Oak Wilt in Illinois?
Oak Wilt is currently active in Illinois. Watch your susceptible trees closely and act early.
What does Oak Wilt look like?
Rapid wilting from the top of the canopy downward in red oaks, leaf discoloration with browning at margins, defoliation within weeks of symptom onset, fungal mats under bark that crack the bark open
What trees does Oak Wilt affect in Illinois?
It affects Red Oak, Live Oak, White Oak. Susceptibility varies by species.
How do I treat Oak Wilt?
Options include: Root Graft Disruption (Trenching), Propiconazole Fungicide Injection, Avoid Pruning During Risk Period. Confirm the diagnosis before treating, and consider a certified arborist for high-value trees.