Quaking Aspen Cytospora Canker: Orange Spores Indicate Stress

Three 8-yr aspens, 5,300 ft elevation. Rusty powder (wipes off) from base to top: limb bases, trunk, scratches. Cold, snowy winter. Just leafing out.

Diagnosis: Cytospora Canker

Fungus enters wounded/stressed trees. Wet weather: orange hair-like spore coils from bark (rain/wind/animal spread). Sunken dead bark, discolored wet wood, odor. Orange fruiting bodies/tendrils. Indicates tree stress (drought, injury, sunscald, fire, other diseases).

Treatment

1. Sanitation: Remove infected limbs (smooth cut at base, preserve branch collar). Prune dry days only.
2. Tool disinfection: 70% alcohol, Lysol, or 1:9 bleach between cuts.
3. Wound care: Clean to healthy tissue (fresh wounds ≤1 month). Remove loose bark only on old wounds. Don't damage callus. No tar/paint—let dry.
4. Fertilize: 10-10-10 at 1 lb/inch trunk diameter, scattered, watered in (before rain).

Expert insight provided by Steve.