Managing Internal Decay in Mature Fruitless Mulberry Trees

Managing Internal Decay in Mature Fruitless Mulberry Trees

A 30-year-old fruitless mulberry (trunk circumference 76 inches, height ~40 ft) has several dead branches but 90% of the canopy appears healthy. An old pruning wound shows holes.

Diagnosis: Internal Decay

The holes at the old pruning cut suggest decay fungi or bacteria entered the wound. Decay is a slow, progressive process that weakens wood from the inside.

What to Do Now

1. Monitor canopy density each spring. Thinning foliage indicates advancing decay.
2. Water deeply during dry periods (1 inch per week).
3. Fertilize annually with a balanced fertilizer (e.g., 10-10-10) at 1 lb per inch of trunk diameter, spread to the drip line.
4. Avoid wounding: Keep mowers and string trimmers away from the trunk.
5. Do not fill cavities—this traps moisture.

Long-Term Outlook

The tree may live many more years. When canopy thinning becomes severe (e.g., <50% leaf cover) or large branches fail, removal is advised—especially if the tree poses a hazard to people or property.

Proactive Care Extends Life

Consistent watering, nutrition, and wound prevention are the only ways to slow decay progression. There is no cure for established internal decay.