Exobasidium vexans Massee is a parasitic fungus that causes tea blister blight. Tea blister blight is characterized by
swelling of infected spots on tea leaves. To date, there is limited information on the cellular alterations that occur during E.
vexans infection. This study aimed to observe the histological changes on tea leaves infected by E. vexans. Diseased and healthy
leaves were thin-sliced by a cryostat microtome and examined by light microscopy. Observations on the thin sections revealed
the mode of hymenium development in E. vexans in which the basidia protruded between the epidermal cells. The infection
caused hypertrophy as the size of the cells at the infected spots became double the size of the healthy cells. We also report the
first description of venous infections of E. vexans. The proliferation of the fungus on the vein resulted in the formation of
hymenium on both the lower and upper sides of the leaves and there was complete disruption of the vascular bundle in the leaf
veins. Blister blight disease was found to be moderately severe at the tea plantation in this study. Morphological and molecular
identification confirmed that the fungus isolated from the symptomatic leaves was E. vexans