3i6 



DISEASES OF CROP-PLANTS 

 Cytospora Rot. 



The fungus Cytospora Sacchari Butl., originally described 

 from sugar-cane in India, has been found by J. R. Johnston 

 on certain susceptible Barbados seedlings in Porto Rico, causing 

 an affection of young shoots very similar in its nature and effects 

 to the Hawaiian Iliau disease, but producing also nodal infections 

 on older canes. The fungus occurs in Barbados, but is not known 

 to be injurious. The leaf-sheaths of young shoots are firmly 

 bound together by the mycelium : their exposed portions take 

 on a very dark, dull red colour, and are profusely covered with 

 the pycnidia, the comparatively long pointed necks of which 



Fig. 129 

 Cytospora Sacchari : Surface and Sectional Views of Pycnidia 

 Spore and Sporophore 

 From Memoirs, Dept. Agri., India 



project beyond the surface sufficiently to be readily seen, and to 

 give a rough sensation when the linger is passed over them. 

 During wet weather a minute yellowish globule of conidia exudes 

 from the tip of the beak. The spores are cylindrical and slightly 

 curved, obtuse at both ends, 3.5x1-1.5 microns. 



With the elimination of the susceptible varieties in Porto 

 Rico no further evidence of parasitic activity on the part of this 

 fungus has been seen. 



Leaf Sheath Rot 



Under the name of " rood rot " (red-rot) this disease has 

 been known from Java since 1890 It is generally distributed 



