CANE SUGAR. 



1200 



6. Ring Spot Disease. Leptospharia tacchari. Van Breda de Haan. 

 The appearance of a leaf of the cane attacked by this disease is so similar to 

 that caused by eye spot disease that confusion is easily possible. The 

 differences are that in Ring Spot the spots are seldom more than half an inch 



long, and are nearly as broad as long. The 

 bright yellow margin observed in eye spot is 

 absent, and the centre of the spot is a dull 

 greyish white. The conidia are formed chiefly 

 on the under surface of the leaf ; they are three- 

 celled, the central cell being larger than the 

 outer ones, the whole spore forming an obtuse- 

 angled body ; at a later stage perithecia appear 

 on the leaf as small black spots. Each ascus 

 contains eight four-celled bobbin-like spores. 

 The spores of this fungus are shown (after 

 Cobb) in Fig. 63. 



7. Red Spot Diseased Eriosphceria (Went.) 

 Coleroa (Van Breda de Haan.) Venturia (Sac- 

 chardo) sacchari. This organism forms dark red 

 spots on the leaf, generally roughly circular, 

 and about 1 cm. in diameter. The connection 

 between the disease and the fungus has not been 



proved by infection experiments. In Hawaii, it is said, spots exactly similar 

 to those described have been noted without any indication of the Erispharia 

 being present. The technical description of this fungus is : Venturia sacchari. 

 Hal. in foliis sacc. offic. Perittecia 70 80 diam., asci 25 long; octospori, 

 sporidia 11x16. 



8. Slack Spot of the Leaf Base. 

 A blackening of the leaf base has been 

 observed in Java to be due to an organ- 

 ism, Cercospora acerosum. The spores 

 are bobbin-shaped, from 2 3*5 microns 

 wide and from 1050 microns long; 

 they contain from one to as many as 

 seven cells. These spores (after Dickoff 

 and Hein) are shown in Fig. 64' 



9. Leaf Splitting Disease. 26 This 

 disease, which is perhaps confined to 

 one district in Hawaii, is characterized 



by a number of yellow stripes appearing in the leaf, which afterwards splits 

 and withers. Cobb considered this disease due to an organism, Mycosphcerella 

 striatiformam, but did not prove the connection by inoculation experiments. 

 Similar, and perhaps, identical diseases are known in Fiji and the Argentine. 



FIG. 64. 



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