Diseases of tea bush are mainly caused by any of the following five agencies viz.,
(a) Vegetable organisms like fungi, algae and bacteria
(b) Animal parasites
(c) Adverse conditions of soil and climate, leading to physiological disorder
(d) Mechanical damage and
However, the bacterial and viral diseases and those caused by animal parasites are not so serious in tea crop and have no commercial importance. The physiological disorders and mechanical damage caused by some external agents are also found to cause diseased condition in tea plants.