Oak Wilt
Bretziella fagacearum
Range: Eastern and central United States; severe in the Upper Midwest and central TexasSee it on the alert map
Symptoms & signs
- In red oaks, rapid leaf bronzing from the margins inward and total defoliation within weeks, often killing the tree in one season
- in white oaks, slower branch-by-branch dieback
- vascular streaking in the sapwood
- fungal mats under the bark of red oaks that crack the bark
Treatment & management
- Avoid pruning oaks April–July
- paint any wounds immediately year-round in active areas
- Trench or vibratory-plow to sever root grafts between oaks
- Preventive macro-injection of propiconazole protects high-value, not-yet-infected white and live oaks
- Remove and properly handle red oaks that may form spore mats
- do not move oak firewood
Host species
Northern Red OakQuercus rubraWhite OakQuercus albaLive OakQuercus virginianaPin OakQuercus palustrisBur OakQuercus macrocarpaWillow OakQuercus phellosScarlet OakQuercus coccineaSwamp White OakQuercus bicolorChestnut OakQuercus montanaWater OakQuercus nigraShumard OakQuercus shumardiiPost OakQuercus stellataChinkapin OakQuercus muehlenbergiiNuttall OakQuercus texanaSouthern Red OakQuercus falcataBlack OakQuercus velutinaEnglish OakQuercus roburSawtooth OakQuercus acutissimaOvercup OakQuercus lyrata
Common questions
When is it safe to prune oaks to avoid oak wilt?
Prune during the dormant season (mid-winter is safest) and never from April through July in affected regions. Always seal fresh oak wounds immediately with pruning paint.
Why do red oaks die faster than white oaks?
Red-group oaks cannot effectively wall off the fungus in their open vessels, so they wilt and die within weeks, while white oaks have narrower, tylose-plugged vessels and decline more slowly.
Related diseases
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