Poplar scab

Fusicladium subsessile is a pathogenic fungus that causes a condition known as poplar scab or fusicladiosis. This fungal disease primarily affects the foliage and young twigs of poplar species, leading to severe defoliation and weakening of the tree's health and aesthetic value.

The primary hosts for this pathogen are various species of the Populus genus. The disease is frequently identified in nurseries, plantations, and urban landscapes where humidity levels remain high, creating an environment conducive to the successful establishment and rapid colonization of the fungus on host tissues.

Symptoms typically manifest as dark brown or olive-black spots on leaves and petioles. These spots often develop a characteristic velvety appearance, which is the result of abundant sporulation. As the infection progresses, the leaves become twisted, distorted, and necrotic, eventually dropping from the tree well before the normal autumn cycle.

The spread of the disease is heavily dictated by environmental factors, particularly moisture and temperature. Spores are easily disseminated by wind and rain splashes during the growing season. The pathogen survives the winter months primarily in the infected leaf litter that accumulates at the base of the trees, serving as a primary inoculum source for the following season.

Managing Fusicladium subsessile requires an integrated approach to plant protection. Key control measures include the removal and disposal of infected plant debris to reduce the inoculum load, improving air circulation through proper pruning, and the strategic application of fungicides during periods of high vulnerability to prevent infection and protect new growth.