Mulberry Tree Issues: Leaf Spot, Bark Splitting, and Wetwood

Two Mature Mulberries in South France

One tree: leaves brown/yellow drop mid-summer, bark splits on branches. Other: healthy except one branch bleeding near trunk after pruning.

Diagnoses

1. Leaf Spot (Fungal): Moist seasons promote fungi causing spots, leaf death. Reduces growth/fruit but rarely kills. No treatment for large trees; not concerning if green leaves remain.
2. Bark Sloughing: Common on old mulberries. Weight on limb ends causes cracking.
3. Wetwood (Slime Flux): Bacterial disease. Fermenting sap seeps from wounds/cracks, attracts insects. Gas pressure forces sap out. Two types: alcoholic (foul smell) and acidic (vinegar smell). May stop naturally. No cure. Wash trunk with 1 pint bleach per gallon water to deter bugs. Maintain vigor, minimize wounds.

Key Point

More damage can be done trying to cure wetwood than the flux causes alone.