This article analyzes the causes, consequences and agronomic solutions to increased sun strike in citrus crops, a growing problem that jeopardizes crop quality and profitability.

Introduction: The Hidden Cost Of A Scorching Sun

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.

What Is Causing The Increase In Sun Strike?

1. Climate Extremes Are No Longer An Exception

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.

2. Vulnerable Varieties And Management That Expose To Risk

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

Economic impacts impossible to ignore

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.

What To Do: Tactical Measures And Preventive Strategies

Technical Actions For This 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.

Prevention For Future Seasons

• 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.

Conclusion: Don't Let The Sun Steal Your Harvest

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.