Sunscald identification & organic treatment
N/A — abiotic (heat/UV injury)
How to identify sunscald
Direct sun exposure on fruit that's lost its protective leaf canopy (from disease, pruning, or wilting) bleaches and blisters the exposed skin.
Symptoms
- Pale yellow-to-white blistered patch on the sun-facing side of the fruit
- Affected skin can become papery, wrinkled, or leathery
- Secondary mold often grows on the damaged patch afterward
- Damage limited to the exposed side; shaded side is normal
Host crops
Tomato, Pepper, Apple.
How it spreads
Not contagious; caused by sun/heat exposure, not a pathogen, though it often follows defoliation from a real disease.
Favorable conditions
Intense sun combined with reduced leaf cover from disease, over-pruning, or heat-driven wilting; hot, cloudless stretches are highest risk.
Progression
- Canopy loss (From disease, pruning, or wilt) — Fruit loses its shading leaf cover.
- Sun exposure (Hot, sunny days following) — Exposed skin bleaches and blisters.
- Secondary rot (If left on the plant) — Mold colonizes the damaged tissue.
Organic treatment for sunscald
- 1. Provide shade cloth · medium effort
Hang 30-40% shade cloth over exposed fruiting rows during heat waves.
When: During hot, sunny stretches once canopy is thin
- 2. Avoid over-pruning · low effort
Leave enough foliage to shade developing fruit; prune only for airflow, not to expose fruit to full sun.
When: Ongoing pruning decisions
- 3. Address the underlying defoliation cause · medium effort
If sunscald follows a leaf disease, treat that disease so the canopy regrows and shades new fruit.
When: As diagnosed
Prevention
- Keep plants healthy and full-leafed through good disease management.
- Avoid removing more than a third of the foliage at once when pruning.
- Choose varieties with good leaf cover for hot climates.
Easy to confuse with
Blossom end rot (bottom of fruit, not sun-facing side), Herbicide injury.