Psorosis of citrus

Psorosis is a serious viral disease that affects various citrus species worldwide. The primary pathogen is the Citrus psorosis virus (CPsV), which causes a systemic infection in the tree. The disease is characterized by a long latent period, meaning an infected tree may appear healthy for many years before structural symptoms develop on the bark.

The virus impacts major commercial crops including oranges, mandarins, and grapefruits. It is considered one of the most destructive diseases in citrus cultivation because it slowly causes the decline of tree vigor, reduces fruit yields significantly, and eventually leads to the death of the tree.

The most distinctive sign of the disease is the scaling and flaking of the bark on the trunk and primary branches. Beneath the loose bark, one can often observe wood lesions, necrosis, and gumming. In some cultivars, early symptoms appear as translucent spots or streaks on young leaves, which can be observed when held up against sunlight.

The main route of transmission is through budding or grafting using infected budwood. Additionally, the virus can spread naturally through root grafting between adjacent trees in an orchard. Environmental conditions do not necessarily cause the disease, but they can influence the rate at which bark scaling progresses over the tree's lifespan.

Since there is no curative treatment for infected citrus trees, disease management focuses on prevention and containment:

• Sourcing certified pathogen-free budwood and nursery stock.
• Regular inspection of groves to identify and remove symptomatic trees.
• Rigorous sanitation practices for pruning tools between individual trees.
• Establishing strict quarantine protocols for introducing new varieties into an orchard.