Sunscald
Sun exposure (physiological injury, not pathogenic)
Overview
Sunscald is tissue injury from intense sunlight and heat, often after sudden exposure. On fruit such as tomato, pepper, and apple, scald appears when leaves that once shaded the fruit are lost to pruning, disease, or pests. On thin-barked trees, winter or summer sunscald cracks the southwest side of trunks when freeze-thaw or heat cycles damage cambium. Preventing abrupt exposure and keeping living shade over fruit is more effective than treating scorched tissue after the fact.
Symptoms
Fruit develops pale, bleached, or paper-white patches that may later sunken, dry, or become infected by secondary molds. Tomato shoulders are classic sites. On tree trunks, elongated dead patches of bark appear on sun-exposed sides, sometimes splitting open the following seasons. Leaves can bleach or crisp when shade-grown plants are moved abruptly into full sun. Damage faces the strongest light exposure and lacks the pathogen structures of true fruit rots at the start.
Environmental Conditions
Hot
Prevention
Harden transplants gradually into full sun. Train tomatoes and peppers with enough leaf cover over fruit. Control defoliating pests and diseases early. Plant orchards with attention to sun angle and avoid over-pruning the south and west sides of young trees in one season. Mulch and irrigate to reduce heat stress that worsens fruit scald. Choose sites and cultivars suited to intense summer light in your region.
Management
Provide temporary shade cloth over fruiting vegetables during extreme heat waves if canopy is thin. Avoid heavy leaf removal that suddenly exposes fruit clusters. Maintain plant health so foliar diseases do not strip shade. For thin-barked trees, use proper pruning to retain some canopy shade on trunks, and consider white trunk paint or guards on young trees in harsh winter sun climates. Harvest scalded fruit for immediate kitchen use if only cosmetic damage is present.