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Cause Nonpathogenic, usually associated with adverse growing conditions such as exposure to frost, wind, excessive drought, transplant shock, or overapplication of fertilizer. Azaleas are very sensitive to excess soluble salts in the root zone.
Symptoms Leaves turn brown, especially at the edges and tips. Salt injury may show up as a marginal necrosis of lower leaves and many cultivars may drop these leaves. Leaves of evergreen azaleas may develop a red coloration in response to salt injury. Salt injury may also be one-sided if fertilizer is deposited on only one side.
Cultural control
- Use the best possible cultural methods.
- Plant in protected locations to avoid extreme environments.
- Avoid applying too much fertilizer and apply evenly to pots. Check the media electrolyte concentration at regular intervals.
Reference Linderman, R.G., and Benson, D.M. 2014. Compendium of Rhododendron and Azalea Diseases and Pests, 2nd ed. St. Paul, MN: APS Press.