Guignardia leaf spot

Guignardia leaf spot is a significant fungal disease caused by the pathogen Guignardia mangiferae. It is widely recognized as a major problem for mango (Mangifera indica) growers worldwide, impacting both the health of the tree and the quality of the marketable harvest.

The disease primarily affects leaves and fruits, though it can also cause dieback of young shoots. In many cases, Guignardia mangiferae survives as an endophyte within the host tissue, becoming pathogenic only when environmental conditions become favorable or the plant undergoes stress.

Symptomatically, the infection starts as small, angular, or irregular spots on the leaves. These spots eventually enlarge and develop dark brown centers with lighter margins. On infected mango fruits, the disease presents as dark brown or black lesions that can cause premature fruit drop and significant yield loss.

The development of this fungal disease is highly correlated with wet, humid weather conditions. Rain splashes and wind serve as the primary modes of spore dissemination. Consequently, orchards located in areas with high seasonal rainfall are at the greatest risk of severe infection and rapid spread of the fungus.

Management strategies focus on sanitation and chemical intervention. Growers are advised to prune affected foliage to improve canopy aeration and apply appropriate fungicides during susceptible growth stages. A consistent integrated pest management (IPM) program remains the most reliable way to mitigate the harmful effects of the pathogen.