Chocolate spot

Systematic position and pathogen type. Chocolate spot is caused by the fungus Botrytis fabae, an ascomycete pathogen specifically adapted to infecting faba beans (Vicia faba). It is a necrotrophic pathogen that secretes toxins to kill host cells, allowing it to colonize the plant tissue and derive nutrients from the decaying organic matter.

Diseases and host crops. The disease, commonly known as chocolate spot, primarily affects faba beans. Symptoms manifest as small, circular, reddish-brown spots on leaves. Under aggressive conditions, these lesions enlarge rapidly, becoming necrotic and irregular, often leading to total defoliation, stem breakage, and collapse of the entire canopy.

Biology and life cycle. The pathogen survives between seasons as sclerotia in the soil or as mycelium in crop debris. During the growing season, conidia are produced and dispersed by wind, rain splash, or insects. The fungus requires a layer of free moisture on the leaf surface to germinate and penetrate the host tissue, initiating the infectious cycle that can repeat multiple times during a single growing season.

Conditions for development and damage. Disease outbreaks are highly correlated with cool to moderate temperatures (15–22°C) and high relative humidity (above 85%). Dense, lush crop canopies create a microclimate that promotes disease spread. The economic damage is severe, as the infection reduces photosynthetic efficiency, causes flower and pod abortion, and significantly lowers the yield and market quality of the harvested beans.

Protection and control measures. Management strategies should focus on an integrated approach. Essential practices include using certified disease-free seeds, ensuring adequate crop rotation to break the pathogen's cycle, and selecting resistant or tolerant varieties. In high-risk areas, the application of protectant or systemic fungicides (such as strobilurins or triazoles) during the early stages of infection is crucial to prevent the progression of the disease.