Abstract
The processes of dieback in tea garden affected with gray blight caused by Pestalotia longiseta were investigated. Tea bushes (variety “Yabukita”) were sprayed with suspension of conidia of P. longiseta and plucked by a plucking machine for inoculation. At 3, 10, 20, 30 and 37 days after inoculation, the affected stems were collected and examined mycologicaly. During the examination period, detection ratio of P. longiseta had been changing decreasingly, conversely, that of Glomerella cingulata increasingly, namely the former was detected in ratios of 85.2, 78.1, 40.6, 47.6, and 6.6%, and the latter was in 7.4, 15.6, 47.5, 42.2 and 86.2%, respectively. In addition, G. cingulata showed a tendency to be detected more frequently from lower part of the tested stem. By microscopic observation, it was found that masses of conidia of G. cingulata were formed abundantly on the browned upper part of the stem, and numerous conidia and appressoria of the fungus were adhering to the apparently healthy lower part, in which some of epidermal cells were infected by the hyphae. These phenomena suggested that G. cingulata existing latently on tea bushes in common got vigorous at the cut end of the stem killed by P. longiseta and produced a great many conidia very quickly, and the healthy lower part of the stem would be heavily infected getting those conidia in plenty. Consequently, G. cingulata might become the most dominant fungus on the dieback stem.
