Troubleshooting a Declining Deodar Cedar
A well-established deodar cedar (Cedrus deodara) suddenly dying suggests a recent environmental change, not old age.
Top Suspects in Order
- Excess water: Cedars demand excellent drainage. Recent heavy rain, irrigation changes, or drainage alteration = root rot. Most likely.
- Soil pH shift: Cedars need neutral to alkaline soil (pH 7.0+). Acidification from fertilizers, mulch, or runoff kills them.
- Light reduction: New structure/tree shading it out (rare for established tree).
- New pest/disease: Bagworms (check for bags), spider mites (tap test), or root pathogens.
Diagnostic Steps
- Test soil pH at dripline (target 7.0+).
- Check drainage: Dig 12" hole, fill with water. Should drain in < 1 hour.
- Spider mite test: Tap branch over white paper. Moving specks = mites.
- Inspect for bagworms: Spindle bags on branches.
Treatment by Cause
- Water: Stop irrigation, improve drainage, hope for dry weather.
- pH: Lime to raise pH (slow process).
- Spider mites: Ferti-lome Triple Action Plus (insecticide/miticide/fungicide) or horticultural oil.
- Bagworms: Hand-pick bags; Bt (Bacillus thuringiensis) for young larvae.
Recovery Outlook
Cedars recover slowly. If the cause is corrected, improvement may take a full growing season. Don't fertilize a stressed cedar—it worsens root rot.
Water is the #1 killer of established cedars. Check drainage first.
