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Slime Mold and Trunk Decay on Mature Maple: Separate Issues

Crusty Beige Fungus = Harmless Slime Mold

The light beige, powdery-topped, sooty-underneath growth at the base of your 40-50 year old maple is a slime mold (likely Fuligo). It feeds on bacteria and organic matter in the mulch—not a plant pathogen.

The Real Concern: Trunk Crack and Sap Flow

The 2-foot vertical split weeping sap suggests internal decay or bacterial wetwood (slime flux). These are chronic, non-treatable conditions.

Long-Term Management

Water deeply during drought.
Fertilize moderately.
Avoid bark injury (mowers, trimmers).
Monitor canopy each spring; if dieback accelerates, plan for removal.

The slime mold is a curiosity; the trunk crack is the structural issue to watch.

Plant Diseases: Hypoxylon Canker on Green Ash: Signs and Management; Fungus at Oak Base: Understanding Root Rot Conks and Tree Longevity; Maple Trunk Cavity with White Fungus: Internal Decay—Manage, Don’t Treat; Maple Trunk Fungus: Decay Fungus Fruiting Body—Natural Cycle, No Spray Needed; Sugar Maple Northern Tooth Fungus: Emergency Branch Removal Protocol; Bird's Nest Fungus at Elm Tree Base: Harmless Mulch Dweller; Orange Fungus at Base of Japanese Maple: Mulch Decay, Not Tree Disease; Black Spot Fungus on Mature Maple: Why Fall Cleanup Beats Spring Spraying; Decay Fungus on Mulberry: Management for Longevity; Large Fungus at Base of Pecan Tree: Cut or Keep?

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