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Greenish-White Scale on Oak: Lichens, Not a Disease

Identification

Greenish-white scale on oak limbs with brown rubbery strings that melt in sun = lichens (fungus + alga symbionts). The “strings” are the fungal partner rehydrating and fruiting.

Key Facts

Lichens are epiphytes, not parasites.
Indicate clean air (won’t grow in pollution).
No treatment needed; they don’t harm the tree.

Enjoy the biodiversity indicator.

Plant Diseases: Grapefruit Tree Greasy Spot Fungus: Organic Treatment Option; Lichens on Oak Trees: Harmless Epiphytes or a Sign of Stress?; Maple Tree Lichens: Harmless Epiphytes Indicating Canopy Thinning; Nuttall/Shumard Oak Lichen: Not Harmful but Indicates Stress; English Oak Sap & Insects: Oak Borer Attack; Orange Fuzz Balls on Post Oak: Woolly Leaf Galls; Oak Leaf Galls: Wasp-Induced, Cosmetic Only; Lichens on Oak and Roof: Harmless Epiphytes; Oak Trunk Fungus (Conks): Decay Fungi Management; Gray Fungus on Large Trees: Lichens, Not a Disease

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