Phoma stem canker

The disease known as Phoma stem canker is caused by the fungal pathogen Plenodomus biglobosus. This fungus is a significant threat to agricultural production, particularly for crops in the Brassicaceae family. It is a necrotrophic pathogen that colonizes host tissues, causing lesions and compromising the structural integrity of the plant.

The pathogen primarily affects oilseed rape (canola), but it can also infect other cruciferous plants. It targets multiple organs, including cotyledons, leaves, stems, and pods. The infection process can occur throughout the growing season, starting from early seedling emergence until the crop reaches maturity.

Symptoms initially appear as light-colored, necrotic spots on leaves, often surrounded by a dark margin and speckled with tiny black pycnidia. As the disease progresses, these lesions can expand to the stem, causing significant necrosis at the stem base, often referred to as blackleg, which leads to lodging and reduced yield potential.

The development and spread of Plenodomus biglobosus are highly dependent on environmental conditions, particularly high humidity and rainfall, which facilitate the dispersal of fungal spores. Temperature also plays a crucial role, with moderate ranges being optimal for fungal growth and tissue colonization.

Integrated pest management strategies are essential for control. These include using resistant crop varieties, practicing crop rotation to reduce soil-borne inoculum, and ensuring the destruction of infected stubble. Fungicide applications during critical growth stages are also commonly employed to mitigate the economic impact of the disease.