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FS ShieldForest Health Protection, Southern Region


Disease Agent Injury Control
Powdery mildew, caused by Microsphaera spp., Phyllactinia spp. and others. These fungi overwinter on dead leaves. Spores are windblown to healthy leaves. A white, powdery mold occurs on leaves and buds. Leaves may be distorted, stunted and fall prematurely. 2, 3
Leaf blister, caused by Taphrina spp. This fungus overwinters on bud scales. When buds expand, infection of new leaves occurs. Spores produced on leaves are disseminated by wind. Yellowish-green to purple blisters appear on leaves. Blistered leaves remain on the tree. 1, 2, 3
Leaf spots, caused by various fungi. Fungi overwinter in leaf tissue; spores are disseminated by wind and rain. Small round to angular spots, variable in size and color appear on leaves. Defoliation may occur in extreme cases. 1, 2, 3
Nutrient deficiencies. These physiological conditions are soil related. Soil condition, such as pH, may make nutrients unavailable to plants, or the soil may be exhausted of some nutrients. Leaf tissue turns yellow to brown; often this happens first along the veins. Some leaf fall may occur. Dieback may occur later if uncorrected. 4

Controls for Urban Trees
  1. Rake and destroy fallen, infected leaves.

  2. Maintain high vigor through cultural practices.

  3. Control with chemical fungicide.

  4. Control with appropriate fertilizer.


There are EPA registered chemicals for the control of these leaf diseases. Consult a specialist if the damage appears to be unusually severe and chemical control is needed.

Leaf blister on oak

Leaf blister on oak.
(Click for detail. JPG 24K).
Leaf spots

Leaf spots.
(Click for detail. JPG 38K)