Sunburn

Sunburn is a non-infectious physiological disorder in plants caused by prolonged exposure to intense direct sunlight and extreme heat. Unlike biotic diseases, it is not caused by pathogens, but the resulting tissue damage often makes the plant highly susceptible to secondary infections by bacteria and fungi.

A wide range of crops is susceptible to sunburn, with soybeans, vegetable crops like tomatoes and peppers, and young fruit trees being particularly at risk. The susceptibility increases significantly when plants are subjected to sudden changes in light exposure, such as after a prolonged cloudy period or transplanting.

The symptoms of sunburn typically manifest as bleached, yellowish, or white necrotic patches on the leaves or fruits directly exposed to the sun. In severe cases, the tissue loses turgor, turns dry and brittle, leading to irreversible damage to the photosynthetic apparatus and significant reduction in the plant's overall vigor.

The development of sunburn is driven by high levels of solar radiation combined with moisture stress. When soil moisture is insufficient, the plant cannot maintain adequate transpiration rates to cool its tissues, making it defenseless against the damaging effects of ultraviolet rays and high ambient temperatures.

Management and prevention focus on maintaining proper soil moisture and using agricultural practices that reduce heat load. Key strategies include:

• Ensuring adequate irrigation during heat waves.
• Applying anti-transpirant sprays to reduce water loss.
• Using row covers or shade cloths for sensitive crops.
• Managing crop canopy density to provide natural shading.
• Choosing cultivars that are adapted to local climatic conditions.