Citrus psorosis

Citrus psorosis, often referred to as scaly bark, is a severe systemic viral disease that affects citrus species worldwide. Caused by the Citrus Psorosis Virus (CPsV), this pathogen is notorious for its long latent period, during which an infected tree may appear healthy while still acting as a reservoir for the virus.

Taxonomically, the agent is classified within the family Ophioviridae. Unlike fungal pathogens that spread via spores, the virus is primarily transmitted through vegetative propagation—specifically through grafting with infected budwood. Mechanical transmission via contaminated pruning tools also plays a significant role in spreading the infection within a grove.

The disease is characterized by the scaling of the bark on the trunk and primary branches, which gives the trees a rough, flaky appearance. As the lesions expand, they cause the death of the cambium, leading to reduced vigor, sparse foliage, and significantly diminished fruit production. Foliar symptoms, such as chlorotic flecking or patterns resembling oak leaves, often emerge on young, developing leaves.

Environmental conditions do not directly trigger the virus, but tree stress can exacerbate the progression of bark symptoms. The disease typically manifests in trees that are between 5 and 15 years old. Once the bark lesions reach a critical stage, the structural integrity of the tree is compromised, eventually leading to the decline of the entire plant.

Since there are no chemical treatments available to cure a virus-infected tree, management relies entirely on prevention and quarantine:

• Use of certified virus-free budwood and rootstocks.
• Strict sterilization of all pruning and grafting tools between trees.
• Rigorous inspection and removal of symptomatic trees to limit viral spread.
• Implementation of regular health monitoring programs in commercial citrus orchards.