Blue-Gray Growth on Tree Trunks: Lichens—Harmless, Indicate Light, Not Cause of Fruit Tree Decline

Identification

Blue-gray crusty growth on pines, apples, crabapples, pears = lichens (fungus + alga). Diverse colors/shapes.

Key Facts

• Not parasites—use bark for support only.
• Need light → grow on open/exposed branches.
• Fruit trees decline from Midwest climate (hard to grow), not lichens.
• Lichens on dying limbs because light penetrates.

Resource

OSU lichen fact sheet