White leaf spot and gray stem

White leaf spot and gray stem is a fungal plant disease caused by the pathogen Pseudocercosporella capsellae. It is a significant concern for agricultural production, primarily affecting cruciferous crops by reducing photosynthetic area and compromising the structural integrity of the plant stems.

The disease primarily targets plants within the Brassicaceae family. Key crops susceptible to this pathogen include winter oilseed rape and radish. The fungus can also survive on various wild mustard species and crop volunteers, which serve as essential reservoirs for inoculum throughout the agricultural season.

Symptoms initially appear as small, circular, or irregular white to gray spots on the leaves, which may develop dark margins as the disease progresses. When the infection spreads to the stems, it causes grayish necrotic lesions, potentially leading to wilting or premature senescence. Under humid conditions, the pathogen produces conidia, facilitating rapid secondary spread within the canopy.

Environmental conditions play a critical role in the epidemiology of the disease, with moderate temperatures (15–20°C) and persistent high humidity favoring fungal development. The pathogen overwinters as mycelium or conidia on crop residues, making infected stubble from previous harvests a primary source of infection for the following season's crops.

Economic damage stems from reduced seed yield and lower oil quality in rapeseed due to early leaf loss and stem damage. Integrated pest management strategies are essential to control the pathogen, including strict crop rotation, removal of infected crop debris through deep tillage, and the application of fungicides during periods conducive to rapid disease development.

• Implement a crop rotation cycle of at least 3–4 years.
• Deep incorporation of crop residues to reduce primary inoculum.
• Regular monitoring of fields during the rosette stage and early flowering.
• Targeted application of fungicides when climatic conditions trigger infection.