Treating Leaf Spot Disease on Magnolia Trees

A young Susan magnolia shows expanding red leaf spots, slow growth, and no response to fungicide. This matches leaf spot fungi—various fungi causing yellow, brown, or black blotches that merge into larger dead patches.

Management Strategy

• Sanitation: Remove and destroy fallen leaves to reduce spores.
• Preventive spraying: Apply fungicide at bud break in spring, repeating three times at 12-14 day intervals.
• Products: Look for mancozeb or chlorothalonil (Daconil) at local nurseries.

Fungicides protect new growth but don't cure existing infections. On small trees, spraying is practical; on mature trees, sanitation often suffices.