172 DISEASES OF TROPICAL PLANTS on. 



polished, and glistening, as if coated with honey-dew. On the 

 under side of the leaf there is a corresponding swelling which 

 is pure white, woolly, and soft, but quite dry. As it advances, 

 numerous blisters appear on the same leaf and even coalesce 

 into large patches. They also occur on the young shoots, and 

 cause much destruction of the stalk. In time the blisters 

 change colour, become brown, and ultimately black. The 

 shoots next wither, and the entire block of tea may then look, 

 in May or June, as if the blast from a furnace had passed over 

 it and killed every shoot and leaf. 



The disease is caused by Exobasidium vexans, Massee, 

 a fungus whose delicate mycelium penetrates the cells 

 of the diseased parts, and after growing for some time, 

 concentrates at the points where the blisters are formed, 

 breaks through the surface and produces the abundance 

 of two-celled conidia spores, thus causing the white, 

 woolly, and soft character previously mentioned. The 

 minute oval basidiospores are produced later and in 

 pairs. It spreads from the leaves to the young stems, 

 which it frequently girdles and kills. It is said to be 

 most abundant on the unpruned plants. All plants 

 should be carefully pruned, and the prunings and 

 diseased parts burned. Spraying with Bordeaux mix- 

 ture will undoubtedly prove helpful, but since it dis- 

 colours the foliage it cannot be used near picking time. 

 In spraying, great care should be used to spray the 

 under surface of the leaves. 



Shot Hole. This disease is due to Cercospora, sp., 

 and has been reported from India. It appears on the 

 older leaves, causing small, -brown, circular spots which 

 resemble the injuries of the mosquito blight. It has 

 not proved serious. 



Black Fungi, and Soot Blight. Black masses of fungi 

 are frequently found on the surface of the leaves, 

 especially those near citrus groves, or near the jungles. 

 The most common of these soot blights is Capnodium 

 footii, Berkeley and Desmaz., which lives on the 

 secretions of certain scale insects. It is purely sapro- 

 phytic, and its only injuries are due to interference with 

 the physiological activities of the plant. 



