Vietnam is one of the countries growing tea at top ten position in the
world. Tea has become a high value product and a key economic plant of the
country (Report on Tea Sectors in Vietnam, 2007). Pest and diseases are big
problem in tea production of Vietnam. Among the tea disease, Grey blight
disease causes by Pestalotia spp. occurs commonly in the most tea growing
regions of Vietnam in the raining season. When the disease lesion spread over
1/2 leaf area, the leaf becomes a skeleton and then falls into bits (Van Hung,
Nguyen., 2001). It causes loosing of tea yield and decreases tea quality.