Nuttall/Shumard Oak Lichen: Not Harmful but Indicates Stress

6-year-old oaks have greenish-gray lichen on trunks/branches; branches losing leaves and breaking where lichen is heavy. Live oaks unaffected.

Lichen Facts

Copper sprays (Bordeaux) can suppress but won't improve health.
Best: improve tree vigor (water, fertilize, mulch) to densify canopy, shade limbs, naturally reduce lichens.

Plant Diseases: Green Flat Fungus on Oak Trunk: Likely Lichens—Harmless, but Photo Needed for Certainty; Blue-Gray Growth on Tree Trunks: Lichens—Harmless, Indicate Light, Not Cause of Fruit Tree Decline; White Powdery Growth on Oak: Powdery Mildew or Insects?; Orange Bumps on Oak Leaves in Florida: Likely Gall Insects; Lichens on Oak Trees: Harmless Epiphytes or a Sign of Stress?; Greenish-White Scale on Oak: Lichens, Not a Disease; Lichens on Oak and Roof: Harmless Epiphytes; Lichens on Trees: Harmless Epiphytes or Hidden Threat?; Gray Fungus on Large Trees: Lichens, Not a Disease; Lichen on Red Oaks: Cosmetic, Not Harmful

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