Mal secco

Mal secco is a devastating vascular disease affecting citrus crops, caused by the fungus Plenodomus tracheiphilus (formerly Phoma tracheiphila). It is recognized as one of the most serious threats to citrus cultivation globally, characterized by its ability to colonize and block the plant's xylem vessels.

The primary host range includes various Citrus species. Lemons and bergamots are particularly susceptible to the infection, showing high mortality rates once established. While other species like oranges and grapefruits possess varying degrees of tolerance, they remain potential reservoirs for the pathogen.

Symptoms typically begin with leaf chlorosis, followed by wilting and the progressive dieback of twigs and branches. A diagnostic feature is the distinct reddish-brown or orange discoloration of the wood found beneath the bark when a cross-section of an infected branch is examined.

The pathogen thrives in cool to moderate temperatures with high humidity, conditions that frequently occur in Mediterranean climates. Spores are primarily disseminated by wind and rain splash, though human activities, including pruning with contaminated tools, play a critical role in the rapid spread of the disease.

• Regular inspection and immediate removal of symptomatic branches.
• Rigorous disinfection of all pruning equipment using effective sanitizers.
• Propagation and planting of certified disease-free nursery stock.
• Application of copper-based fungicides to protect healthy canopy tissues.
• Breeding and adoption of resistant citrus cultivars and rootstocks.

The economic impact of Mal secco is profound, as there is no definitive cure once the fungus has systemically invaded the tree's vascular structure. Management strategies must focus on strict preventative hygiene and long-term horticultural practices to minimize infection risks within the orchard.