Sunburn
Non-pathogenic (abiotic — solar radiation damage)
10 host plants
Last updated
Sunburn shows up as bleached, tan, or whitish patches on leaves, particularly affecting camellias, filberts, and rhododendrons on the south or southwest side of plants. The affected tissue remains connected to green veins, giving leaves a distinctive pattern. This damage typically appears during rare heat events when temperatures exceed 90°F combined with low soil moisture, even on plants that normally tolerate shade.
Once leaves are scorched, there's no remedy except waiting for new growth to cover the damage. The real issue is that sunburned areas invite secondary fungal infections that can complicate the picture. Prevention means understanding which cultivars are susceptible, maintaining consistent soil moisture during hot spells, and providing afternoon shade for sensitive plants. Camellias especially benefit from pruning shortly after flowering and supplemental water during dry summers.
Quick Reference
Management
Another type of sunburn occurs with new growth in spring during cloudy weather.
Cultural Controls
- Prevention is the key as there is no remedial action that can be taken once leaves are scorched by the sun, but effects are not fatal and new leaves will eventually cover damaged ones.
- Move the plant to a more shaded location.
- Provide some shade where it is now planted.
- Maintain watering during summer, especially during extreme heat events.
- Reference Linderman, R.G. and Benson, D.M. 2014.
- Compendium of Rhododendron and Azalea Diseases and Pests, 2nd ed.