Lichens on Trees: Not the Killer You Fear

The "spidery light green fungus" and flat growths on your pine, fir, apple, and birch are almost certainly lichens—a symbiotic partnership of fungus + alga. Lichens do not kill trees.

Why They're There

• Lichens colonize slow-growing or stressed trees with open canopies (more light on bark).
• They're indicators of good air quality—sensitive to pollution.
• The dead trees you removed likely declined from other causes (drought, insects, root disease), and lichens simply colonized the dying bark.

What's Actually Killing Trees?

In the Upper Peninsula, common killers of pine/fir include:

• Bark beetles (ips, pine engraver)—look for pitch tubes, boring dust.
• Root diseases (Armillaria, Heterobasidion)—crown thinning, resin at base.
• Drought stress—especially on shallow/rocky soils.

Action Plan

1. Contact MI DNR Forestry (link in original) for a free forester visit. They'll ID the real killer.
2. Do not treat lichens—wastes money, harms nothing.
3. Monitor surviving trees for beetle signs, crown thinning, resinosis.
4. Thin dense stands to reduce competition and beetle risk.

Lichens are innocent bystanders. Focus on finding the true cause of mortality.