Phoma stem canker

Phoma stem canker, caused by the fungus Leptosphaeria cylindrospora (anamorph Phoma lingam), is a significant agricultural disease affecting brassica crops. It poses a persistent threat to oilseed rape production worldwide, potentially leading to substantial economic losses if left unmanaged.

This pathogen infects oilseed rape, mustard, and other cruciferous plants throughout their lifecycle. While the initial infection usually occurs on leaves via airborne spores, the fungus subsequently grows systemically towards the stem base, leading to the development of deep cankers and vascular blockage.

Symptoms are primarily characterized by pale grey leaf lesions dotted with dark pycnidia. As the disease progresses, necrotic cankers appear on the root collar, causing the stem to crack and the plant to lodge. In severe cases, the entire vascular system is compromised, which significantly impairs water and nutrient uptake.

The development of the disease is highly dependent on environmental conditions, particularly humidity and moderate temperatures, which facilitate the dispersal of ascospores from crop residues. Stubble management and crop rotation are critical, as the fungus persists on decaying plant tissue, serving as a primary inoculum source for subsequent seasons.

The economic impact of the disease is profound, resulting in reduced seed yield, lower oil content, and increased susceptibility to lodging. High levels of infection can lead to early senescence and, in severe outbreaks, total crop failure, necessitating an integrated approach to disease management.

• Selection of resistant or tolerant cultivars.
• Utilization of certified, fungicide-treated seeds.
• Strict adherence to crop rotation, with at least 3-year breaks between host crops.
• Management of crop residues through deep ploughing to bury inoculum.
• Targeted application of foliar fungicides during the autumn and spring growth phases.