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Japanese Plum (Loquat) Yellow Powder on Limbs: Cytospora Canker

20+ year Japanese plum (likely loquat, Eriobotrya japonica) with half tree dying, yellowish powder on limbs, dead wood: Cytospora canker (fungal) entering through wounds, stress. Yellow powder = fungal spores.

Management (No Cure Once Infected)

Prune out dead/diseased limbs 6–12 inches below visible canker.
Sterilize tools between cuts.
Water deeply in summer drought.
Fertilize in spring; avoid late summer nitrogen.
Keep soil cool/moist with mulch.
Prevent wounding (mowers, trimmers).

Key

Fungicides ineffective once fungus inside. Prevention via vigor is only control. Tree may survive years with management.

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