Cercospora leaf spot of false acacia

The disease is caused by the fungus Cercospora traversoana, an ascomycete pathogen that specifically targets leaf tissues. It is widely recognized as one of the primary foliar pathogens affecting the genus Robinia, particularly the common false acacia tree in its natural and cultivated environments.

The primary host for this fungus is Robinia pseudoacacia. The infection reduces the photosynthetic capacity of the tree, leading to stunted growth, reduced vigor, and in severe cases, dieback of young twigs. The pathogen is particularly problematic in dense forestry stands and ornamental plantings.

Symptoms are identified by the development of numerous discrete spots on the leaves. These spots often start as pale discolorations and eventually turn brown or necrotic as the fungal colonies grow. In high humidity, a greyish, velvety fungal growth often appears on the underside of the leaves, which constitutes the mycelium and spores of the pathogen.

The development and spread of Cercospora traversoana are highly dependent on environmental conditions. A warm, humid climate with frequent rainfall provides an ideal environment for spore germination and colonization. The fungus overwinters on fallen leaves, serving as the primary inoculum for the next growing season.

Effective management requires a combination of sanitation and chemical strategies. Sanitation, including the removal and destruction of infected leaf litter, is the most crucial step to reduce the initial inoculum level. For ornamental and high-value nursery stocks, the application of appropriate fungicides during the growing season can significantly mitigate the progression of the disease.