322 DISEASES OF CROP-PLANTS 



The affection begins on young leaves and develops thickly 

 sown irregular spots, bright yellow on the upper surface of the 

 leaf, covered on the under side in moist weather with a dirty- 

 white web of hyphae. Later the spots show red dots or stripes, 

 and in individual instances may become dull red. 



On the under surface bundles of short conidiophores project 

 from the stomata and bear elongated hyaline conidia of varying 

 length and with i-6 cells. 



Brown Leaf-Spot. 



Brown leaf-spot is recorded by Gough in Trinidad and as one 

 of the rarer leaf-spots in Porto Rico by Johnston and Stevenson. 



Fig. 136 Cercospora Longipes 



From Memoirs, Dept. Agri., India 



It is reported to be by far the commonest leaf disease on the 

 thin canes of India, to which it is practically confined. The 

 spots appear on the blade of the immature leaf and continue 

 during maturity. At first they are narrow, oval, about ^ inch 

 in length, and reddish in colour. A browTi centre early becomes 

 evident, and a yellow border is formed, so that the spot is tri- 

 coloured. When fully developed the spots consist of a broad 

 oval deep-brown ring, with a straw-coloured centre, the whole 

 reaching to half an inch in length. 



The causative fungus is Cercospora longipes, Butler. Long 

 brown unbranched conidiophores, abruptly bent, form a velvety 



