Green Ash Heart Rot: Storm Reveals Internal Decay

Central Minnesota: green ash broke in half in thunderstorm. Externally healthy. Interior: light brown, balsa-like, spongy, sawdust-like, with bore holes. No insects recovered.

Expert Diagnosis

Heart rot decay fungi. Common on green ash: Fomes fraxinophilus (most common), Polyporus sulfureus, Phellinus punctatus. More severe in mature/overmature native woodland trees.

Decay Progression

• Cross-section: irregular rotted area, often one-sided
• Normal wood: light yellow
• Early decay: brownish stain
• Advanced: whitish wood surrounded by brown active zone
• Annual rings: spring wood white first, then summer wood
• Final: soft, crumbly (balsa-like)

Key Insight

Storm exposed advanced heart rot that developed over years. Bore holes suggest insect activity in decayed wood. No treatment for established heart rot; structural failure was inevitable.