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Bur Oak Blight (BOB)

Bur Oak Blight (BOB)

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Bur Oak Blight (BOB)

Bur Oak Blight (BOB) is a fungal disease that causes leaves to develop wedge-shaped, brown lesions and remain on the tree into winter. Treatment involves fungicide trunk injections by a qualified Arborist, and leaf litter removal can reduce fungal spores.Preventative measures like maintaining tree health and proper watering also help, but BOB is best managed with professional diagnosis and treatment.  

 
What is Bur Oak Blight?
  • Cause: A fungal disease that primarily affects bur oak trees in the Midwest. 
     
  • Symptoms:
    • Purple-brown lesions along the leaf veins. 
       
    • Wedge-shaped areas of yellowing or browning on the leaves. 
       
    • Leaves turning brown, curling, and frequently staying attached to the tree through winter. 
       
    • Black pustules or scars at the base of the leaf stalks. 
       
  • Environmental Factors: Wet seasons and increased rainfall create ideal conditions for the fungus to thrive. 
     
How to Get Rid of It
  1. Professional Diagnosis:
    A qualified arborist should first inspect and confirm the diagnosis, as symptoms can resemble other tree conditions. 

     
  2. Fungicide Treatments:
    The most effective treatment is fungicide, typically delivered as a trunk injection, which can provide control for several years. 

     
  3. Timing of Treatment:
    • Early season fungicide applications during wet periods may be necessary. 
       
    • The fungicide is infused during the tree’s growth and absorption cycle. 
       
  4. Integrated Pest Management (IPM):
    • Remove Litter: Clean up and remove fallen leaves and twigs from under the tree to reduce the number of fungal spores for the next season. 
       
    • Maintain Tree Health: Provide adequate watering and air circulation to keep the tree strong. 
       
    • Proper Composting: If composting leaves, ensure they reach temperatures of at least 140°F to eliminate the fungus. 
       
Important Considerations
  • Fungicide treatments should be done by a certified professional due to the complexity of the application and the use of specific products. 
     
  • Repeated defoliation from BOB can weaken the tree and eventually lead to its death, making treatment crucial for high-value trees. 
     
  • A single fungicide treatment may be sufficient for several years, but follow-up treatments may be needed for heavily infected trees.

If you are unsure of what is going on  with your  tree, contact Johnson Ops  Tree care, and meet with  one of our Certified Arborist for a PHC (Plant Health Care) consult.

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