Citrus tristeza virus

Citrus tristeza virus (CTV) is recognized as one of the most destructive and economically damaging viral pathogens affecting citrus crops globally. The virus belongs to the Closteroviridae family and primarily interferes with the plant’s phloem function, leading to a catastrophic breakdown of nutrient transport from the leaves to the roots.

The disease affects almost all commercial citrus varieties. The severity of the symptoms is often determined by the interaction between the viral strain and the specific rootstock-scion combination used in the orchard. The most severe form, often called quick decline, is typically seen in trees grafted onto sour orange rootstocks, resulting in sudden death of the plant.

Symptoms are highly variable and range from mild leaf chlorosis and stunting to severe canopy dieback. One of the most distinct diagnostic features of this virus is "stem pitting," where the wood beneath the bark develops deep, irregular depressions and grooves, which severely limit the tree's ability to maintain hydraulic conductivity and structural integrity.

The transmission of the virus is predominantly mediated by aphid species, with the brown citrus aphid (Toxoptera citricida) being the most efficient vector. The virus is also spread over long distances through the trade of infected plant materials, such as budwood and nursery stocks, which often do not show immediate signs of infection.

Management of the virus relies heavily on integrated pest management (IPM) strategies. This includes the implementation of rigorous quarantine programs, the establishment of disease-free nurseries, and the removal of infected trees to minimize the inoculum source in the area. Breeding programs focused on developing resistant rootstocks remain the most sustainable long-term approach for citrus industries worldwide.