Cercospora leaf spot of grapevine

Cercospora kyotensis is a fungal pathogen responsible for causing Cercospora leaf spot in grapevine. This disease primarily affects the foliage, significantly impairing the photosynthetic capacity of the vines, which can result in reduced vigor and potential yield losses in susceptible grape cultivars.

The disease targets various species and cultivars of grapevines. While the leaves are the primary sites of infection, the pathogen can also colonize petioles and rachises during periods of high humidity. Such infections can weaken the structural integrity of the clusters and indirectly lead to fruit drop or shriveling.

Symptoms typically manifest as small, angular spots on the underside of the leaves, which later turn dark brown. As the disease progresses, a distinct olive-gray velvety growth appears on the necrotic spots, which represents the sporulation of the fungus. Heavily infected leaves eventually become chlorotic and undergo premature abscission.

The development and spread of Cercospora kyotensis are heavily dependent on environmental conditions, particularly high humidity and moderate temperatures. The fungus overwinters in crop debris, such as fallen leaves, which serve as the primary source of inoculum in the spring. Spores are then dispersed by wind and rain splashes.

Effective management of this disease requires a combination of cultural and chemical strategies. Cultural control involves sanitation, such as removing and destroying infected leaves to reduce the pathogen load. In terms of chemical control, the application of fungicides, particularly those used for other leaf spot diseases, can provide adequate protection if timed correctly during the growing season.