Malsecco disease

The fungus invades the xylem tissues, where it produces enzymes and toxins that lead to vascular clogging and wilting of the host.

The disease is classified as a quarantine pest in many citrus-growing regions due to its rapid spread and destructive potential.

Identification is confirmed through laboratory isolation of the fungus or observation of its characteristic pycnidia on dead branches.

The pathogen is highly specialized and restricted to species within the Rutaceae family, particularly the lemon tree (Citrus limon).

The infection causes systemic wilt, leading to leaf drop, branch dieback, and eventually the death of the entire tree.

Citrus orchards can suffer total loss within a few years if the disease is not managed through strict containment measures.

Young trees in nurseries are extremely vulnerable, as the pathogen can travel through the vascular system and kill them rapidly.

Reduced fruit production and poor fruit quality are inevitable consequences of the systemic stress caused by the fungus.

Economic impact includes not only the loss of trees but also the significant costs associated with quarantine measures and orchard eradication.

Infection occurs most frequently during rainy and mild seasons, with spring and autumn providing the optimal conditions for disease spread.

High relative humidity and temperatures between 20°C and 25°C facilitate the release and germination of conidia.

During dry and hot summer months, the disease progression may appear to slow down, but the fungus remains active inside the tree tissues.

Pruning activities are high-risk periods, as rain can splash spores onto fresh wounds created during the pruning process.

Wind and water run-off are the primary vectors for transporting the pathogen from infected trees to healthy neighboring plants.

The most distinctive symptom is the wilting of foliage, often starting from the top of the tree and moving downwards (hence the name "Malsecco").

Cross-sectioning the infected branches reveals a characteristic reddish or salmon-orange discoloration of the wood, known as xylem staining.

Leaves become chlorotic and drop prematurely, leaving behind brittle, dry branches that lose their structural integrity.

Necrotic lesions may appear on the bark, sometimes accompanied by gummy exudates in advanced stages of the disease.

• Salmon-orange internal wood discoloration.
• Progressive leaf chlorosis and drop.
• Branch dieback from the tip downwards.
• Vascular system clogging visible under microscopy.

The primary control strategy involves planting certified, disease-free nursery stock to prevent the initial introduction of the fungus.

Strict sanitation protocols must be followed, including the immediate removal and destruction of symptomatic branches by burning.

All pruning tools must be disinfected with appropriate fungicides or bleach after every single cut to avoid transmitting the fungus.

Protective sprays, particularly copper-based fungicides, should be applied during high-risk rainy seasons to prevent spore entry.

Integrated pest management, including windbreaks and protection from hail, helps reduce the mechanical wounds that serve as infection sites.