In the heart of the Comunitat Valenciana, where citrus farming has long been a pillar of agricultural identity, an increasingly aggressive problem is making its presence known: sunstroke in citrus crops. Once considered a sporadic concern, this phenomenon, triggered by extreme heatwaves and intense solar radiation, is now affecting a growing number of groves, compromising fruit quality, marketability, and grower income. With the climate trending toward hotter and more volatile summers, this agronomic challenge is demanding immediate, strategic action from both seasoned farmers and agri-advisors.
Sunstroke, or “golpe de sol”, occurs when citrus fruits are exposed to direct and sustained sunlight, especially during episodes where temperatures exceed 38°C and remain high overnight. This thermal imbalance prevents the plant from recovering, causing epidermal burns that range from cosmetic defects to total fruit necrosis.
Factors amplifying the issue include:
Extended exposure due to reduced leaf cover
Poor nighttime cooling, leading to persistent stress
Inadequate or mistimed irrigation under extreme heat
The result? Fruits, especially those facing the afternoon sun, literally burned on the tree.
Certain citrus varieties are biologically more susceptible to sunstroke damage. Navelina, Clemenules, Lane Late, and Oronules are particularly at risk due to their structural and physiological traits.
Meanwhile, aggressive pruning practices or natural thinning in some trees can expose fruit clusters to unfiltered radiation. A thin or poorly distributed canopy fails to shield fruit during peak heat hours, increasing vulnerability.
Additional risk factors:
Sparse foliage from over-pruning
Stress caused by poor water availability
Orientation of plantation rows that maximize sun exposure during peak hours
Sunstroke doesn't just affect visual appeal. The economic fallout is serious:
Necrosis of fruit skin diminishes commercial value
Higher classification costs for sorting damaged from healthy fruit
Fruit drop (abscission) in severe cases, reducing total yield
Increased discards, resulting in higher rates of second-category fruit or total loss
For many growers, this means lower price per kilo, less exportable volume and higher postharvest costs: a lethal combination for the season.
Assess exposure after pruning: avoid leaving too much fruit exposed in sensitive areas.
Adjust irrigation according to actual demand: avoid water stress during peak heat hours.
Apply foliar protectants: kaolin and other authorized products can reflect solar radiation.
Monitor temperature extremes: using sensors or agroclimatic stations, plan interventions.
Design more conservative pruning in critical areas to preserve natural shade.
Introduce cover crops to reduce ambient temperatures.
Plan new plantings considering the orientation to minimize direct sun exposure.
Optimize the irrigation system: sectorization and use of humidity probes for more precise control.
Integrate climatic and physiological data in technical advice to make better decisions.
Sunstroke in citrus has ceased to be a one-off incident to become a systemic risk in the Valencian Community. Faced with an increasingly demanding climate, growers and technicians must update their management strategies. Whether you run an export farm or a local field, protecting the fruit from the sun is vital.
Rethinking pruning, incorporating technology and anticipating environmental stress are not options, they are necessities. The time to act is now. The sun does not wait.