Factors Affecting the Occurrence of Die-Back and Canker Disease of Tea

Abstract

1. Surveys on method of cultivations, climatic conditions, soil conditions and nutritive conditions of tea plant were carried out on more than twenty Benihomare tea gardens, which had various severities of the die-back and canker disease, to find out factors affecting the occurrence of the disease since 1960 to 1962.Factors which seemed to be associated closely with the disease were as follows.2. From the results of the survey on method of cultivations, the tea gardens which had ill-draining soil, started plucking in too young plant and severely infected with such diseases as Japanese Exobasidium blight (Exobasidium reticulatum) and brown blight (Guignardia camelliae) etc. seemed to be suffered severely from the die-back and canker disease. No disease was seen in tea bushes of less than 5 years old. All severely infected tea bushes were more than 10 years old.3. Winter temperature during 1953 to 1955 was considerably lower than average and low temperature and much rainfall in summer time were recorded in 1955, on the other side, there were many observations that the occurrence of the disease initiated in these three years.Severe climatic conditions were also supposed to closely related to the outbreak of the disease.4. Through the survey on soil conditions, it was found that the disease was severe in such tea gardens which had small air phase or large liquid phase.These results coincided with the previously stated fact that the disease was severe in illdraining gardens. Root systems of severely infected tea bush also were poor or omnipresent near soil surface.5. Results of the chemical analysis of leaves collected from many Benihomare tea gardens showed that the total nitrogen was rich and P2O5, K2O etc. were poor in severely infected tea gardens.Judging from the view point of water balance, also, Benihomare was presumed to have some specific nature comparing with other varieties of tea plant.