Camellia Dieback: Root Rot or Algal Leaf Spot?

Saving Remaining Camellias After Mass Loss

Losing 3 of 5 camellias (Camellia japonica) with leaf drop and greenish trunk growth suggests a root zone crisis, not just a foliar issue. The “green fungus” is likely algal leaf spot (Cephaleuros virescens), which is cosmetic, but the rapid decline points to Phytophthora root rot in poorly drained, shaded sites.

Immediate Diagnostic Steps

1. Check soil moisture: Dig 6–8 inches deep near the root ball. Soil should be moist, not saturated.
2. Inspect roots: Gently expose roots. Healthy = firm, white/cream. Rotted = brown/black, mushy, sloughing cortex.
3. Assess site: Is the area low-lying, heavy clay, or irrigated by sprinklers hitting the trunk?

If Root Rot Is Confirmed

• Improve drainage: Regrade, install French drain, or replant on a raised mound (12–18 inches high).
• Fungicide drench: Apply mefenoxam (Subdue Maxx) or phosphorous acid (Agri-Fos) per label. These suppress Phytophthora but won’t resurrect dead roots.
• Reduce irrigation: Water only when top 2 inches are dry. Convert to drip irrigation.

If Algal Leaf Spot Is Primary

• Prune for airflow. Apply copper fungicide (e.g., Kocide) in spring at bud break. Algal spot rarely kills camellias alone.

Act fast: camellias with advanced root rot rarely recover. Propagate cuttings from healthy wood as insurance.