Phoma stem canker

The causal agent of this disease is the fungus Leptosphaeria conoidea (anamorph Phoma lingam). It is the primary pathogen responsible for Phoma stem canker, a devastating disease affecting various members of the Brassicaceae family, particularly oilseed rape and cabbage.

The disease host range includes winter and spring oilseed rape, mustard, and various cruciferous vegetables. Leptosphaeria conoidea can infect plants at any growth stage, significantly impacting both yield and seed quality through systemic tissue colonization.

Symptoms initially appear as leaf lesions with dark borders containing pycnidia—small black dots. As the disease progresses, it infects the stem base, causing necrosis, dry rot, and stem girdling, which often leads to lodging, stunted growth, or complete plant death before harvest.

The fungus thrives in cool to moderate temperatures with high humidity or frequent rainfall, which facilitate spore dispersal. It persists in crop residues and soil, and it is also commonly seed-borne, allowing for the widespread introduction of the pathogen into new fields.

Economic impact is severe, as Phoma can lead to significant yield losses due to premature ripening and poor grain filling. Integrated pest management, including crop rotation, the use of certified pathogen-free seeds, and timely fungicide applications, is critical for disease control.

• Use of disease-resistant cultivars.
• Strict crop rotation (at least 3-4 years gap).
• Seed treatment with registered fungicides.
• Effective management of cruciferous weeds and stubble debris.