Citrus tristeza virus

Citrus tristeza virus (CTV) is a viral pathogen of the genus Closterovirus that causes one of the most destructive diseases in citrus production globally. The term «tristeza» means «sadness» in Spanish and Portuguese, reflecting the dismal appearance of infected trees.

The virus infects various citrus species, such as oranges, grapefruits, and limes. The severity of the disease often depends on the specific strain of the virus and the rootstock-scion combination. The use of sour orange rootstock is particularly prone to the most severe forms of the disease, leading to rapid decline.

Symptoms of the infection can range from slow decline, characterized by sparse foliage and twig dieback, to a sudden collapse known as quick decline. Internal tissue examination often reveals a characteristic brown stain at the bud union, indicating the blockage of nutrient flow in the phloem.

Transmission of the virus occurs via insect vectors, primarily aphids such as Toxoptera citricida, and through infected grafting materials. Because aphids are highly efficient at moving the virus between trees, orchards can be devastated within just a few growing seasons if left unmonitored.

Management focuses on strict biosecurity and integrated pest management (IPM). Key strategies include:

• Planting certified virus-free nursery stock.
• Implementing rigorous quarantine protocols to prevent entry into new areas.
• Monitoring and controlling aphid populations using targeted insecticides.
• Prompt removal and destruction of infected trees to eliminate the source of the virus.

Given the lack of a cure, excluding the virus from the orchard remains the primary objective. Ongoing research into resistant rootstocks provides hope for long-term control, but strict vigilance remains the best tool for current citrus growers worldwide.