The principal pests and diseases of tea all occur in the Far East, the most important being blister blight disease. Pests in other parts of the world are mainly local ones, and the plantations in East Africa are relatively disease free.
The two most damaging pests are tea mosquito bug and the red spider mite. In severe attacks, the feeding of the bugs may entirely suppress development of new growth and whole areas of planted tea may go out of production. The most dangerous tea disease is blister blight, a fungal disease which quickly spreads until practically all the young foliage is diseased. Although it was first recorded in 1868, it was relatively unimportant until 1946 when it suddenly spread to Southern India and Sri Lanka, where it would have wiped out the tea industry had fungicides not been available. From it spread to Sumatra in 1949, Malaya in 1950 and Java in 1951. Root diseases of tea are also a serious problem in most of the tea growing areas of the world. At least nine different causal fungi have been recognized as being lethal to the plant.