Arborvitae Sudden Death: Root Disease, Not Drought

Bay Area arborvitae/Italian cypress turned brown in August (one tree only). Water/fertilizer worsened it. Now completely dead. Others healthy.

Diagnosis: Root Disease (Phytophthora/Armillaria)

• Single tree in row = localized pathogen, not drought
• Drought affects all equally
• Watering worsened it = water-mold pathogen (Phytophthora)
• Fertilizer stress = added salt to damaged roots

Immediate Actions

1. Remove dead tree completely (roots too)
2. Do NOT fertilize others—conifers rarely need it
3. Contact CA Forestry/UC Extension for forester visit
4. Monitor others for early symptoms
5. Improve drainage if possible

Why Not Drought

Drought stress = gradual, uniform, all trees. Sudden single-tree death in summer + worsened by water = root rot.