Hawthorn scab

Hawthorn scab is a fungal disease caused by the ascomycete fungus Venturia crataegi. This pathogen specifically targets plants of the Crataegus genus. As a host-specific parasite, it thrives by colonizing the tissues of hawthorn trees and shrubs, often leading to severe foliage damage in favorable environments.

The fungus affects various parts of the host plant, including leaves, young shoots, blossoms, and fruits. The economic and aesthetic impact is significant, as the infection can lead to early defoliation and a decline in the overall vigor of the plant, making it particularly troublesome for nurseries and ornamental gardens.

Symptoms initially appear as olive-green or dark brown spots on the leaf blades. As the infection progresses, these spots expand, and the leaf tissue may become necrotic and brittle. On fruits and shoots, the fungus creates dark, scab-like lesions, which serve as characteristic visual markers for diagnostic identification in the field.

Development of the disease is strictly correlated with environmental conditions. High humidity and prolonged leaf wetness during the spring are critical for spore germination and infection. The pathogen overwinters primarily in fallen leaves and on infected twigs, where it survives as pseudothecia, releasing airborne ascospores at the onset of the next growing season.

Management strategies focus on sanitation and chemical intervention. Removing and burning all infected leaf litter in the autumn is essential to reduce the primary inoculum load. During the growing season, preventive fungicide applications can protect new growth. Additionally, pruning to ensure proper air circulation throughout the canopy helps to create an environment less conducive to fungal infection.