Concave gum

Concave gum is a chronic viral disease that specifically affects various species and cultivars within the Citrus genus. It is caused by the Citrus concave gum virus, which creates long-term systemic infection, often remaining latent for years before distinct structural changes appear on the host tree.

The disease targets commercial citrus plantations, causing significant physiological distress to orange, mandarin, grapefruit, and lemon trees. Once a tree is infected, it remains a permanent source of the virus, posing a constant threat to the health and longevity of the entire orchard population.

The characteristic symptoms include shallow, concave depressions on the trunk and primary limbs. These structural deformities are often accompanied by gum exudation (gummosis) and internal wood abnormalities, such as the formation of porous or discolored tissue. As the disease progresses, the tree's vigor declines, and the structural integrity of the branches becomes compromised.

Transmission of the virus occurs primarily through the use of infected budwood or rootstocks during the propagation process. Because the virus is systemic, every part of an infected tree can act as a source of inoculum. Mechanical transmission can also occur via contaminated pruning tools, which can carry sap from an infected tree to a healthy one if not properly sterilized between uses.

Management of Concave gum is focused entirely on prevention and quarantine. Since there are no chemical or biological cures for infected trees, growers must prioritize the following measures:

• Utilizing certified virus-free nursery stock.
• Rigorous inspection and culling of symptomatic trees.
• Sanitizing pruning and grafting tools using bleach or alcohol solutions.
• Establishing isolation zones around known outbreak sites.