Citrus chlorosis

Citrus chlorosis is a physiological condition commonly observed in citrus crops, characterized by the yellowing of leaf tissue due to a lack of chlorophyll. While it is not a pathogen in the sense of a virus or fungus, it is a critical pathological state that significantly impairs the photosynthetic capacity of the plant.

This disorder typically affects all species within the genus Citrus. It is most commonly associated with deficiencies in essential micronutrients such as iron, magnesium, or zinc. The condition is prevalent in commercial groves and home gardens alike, wherever environmental conditions prevent the plant from utilizing nutrients effectively.

The biology of the condition involves the inhibition of chlorophyll synthesis. In soils with high alkalinity or poor aeration, iron becomes immobilized and cannot be absorbed by the roots. This disruption leads to interveinal chlorosis, where the veins remain green while the surrounding leaf tissue turns yellow, eventually leading to stunted growth and branch dieback.

Development and spread are primarily driven by soil conditions, such as high pH levels, excessive lime content, and waterlogged soil which leads to root hypoxia. Environmental stress factors, such as sudden temperature changes or improper irrigation, exacerbate the condition and make the trees more susceptible to further damage.

The economic impact of chlorosis includes reduced fruit quality, smaller harvest yields, and the long-term weakening of the plant structure. Integrated control measures include:

• Applying iron chelate treatments through foliar spraying or soil drenching.
• Monitoring and adjusting soil pH to keep it within the optimal range for citrus (5.5–6.5).
• Improving soil drainage to prevent oxygen depletion in the root zone.
• Using appropriate rootstocks known to be tolerant of calcareous soil conditions.