THE PESTS AND DISEASES OF THE CANE 



157 



x: 130 



Fig. 



after Dickoff and Hein, are bobbin-shaped, from 2 to 3*5 microns wide and 

 from 10 to 50 microns long, and contain from one to seven septa. This 

 disease is reported from Java only. 



Brown Leaf Spof.''^ Cercosporalongipes (Butler). — Maculis elongate, amphygenis, 

 saepe confluentibus, prima sangiiineis, arescendo siramineis brunneo-cinctis ; hyphis in 

 caespitulos gregarios collectis plerumque hypophyllis jiexuosis, brunneis, sur^iim geni- 

 culcUis vel denticulatis , 100-200 x 4, conidiis obclavatis sursum attenuatis, rectis vet 

 curvulis 4-6 septatis 40-80 x 5 hyalinis. 



This disease is described bj^ Butler as very 

 prevalent in North and South Behar. It has 

 albo been reported in Trinidad and Porto 

 Rico. Narrow oval spots about one-eighth of 

 an inch long, and of a reddish brown colour, 

 are the first signs of the disease ; as the 

 spots increase in size a brown centre be- 

 comes evident, and at one stage of the 

 disease three concentric rings, brown, red 

 and yellow, are seen. Eventually the spot 

 becomes a broad oval, deep brown ring, 

 with a straw-coloured centre. The rings 

 are usually from a quarter to a third of an 

 inch long b^' a quarter of an inch or more 

 in breadth. At a late stage the bodies shown in Fig. 50, after Butler, appear 

 on the spots, but it is not certain that they belong to the same fungus. 



Ring SpotJ^ LeptosphcBria sacchari (Van Breda de Haan). — ^The conidia 

 of this fungus are shown in Fig. 51, after Cobb. The appearance of this 

 disease is so similar to that caused by eye spot that confusion is 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 

 yeUow margin observed in Eye Spot is absent, and the 

 centre of the spot is a dull greyish white. The conidia 

 are found chiefly on the under surface of the leaf. 

 The}^ are three-celled, the central cell being larger than 

 the outer ones, the whole cell forming an obtuse-angled 

 body. Recent workers think they have no connection 

 with the disease. At a later stage perithecia appear on 

 the leaf as small black spots. Each ascus contains four 

 bobbin-like spores. This fungus has been reported from 

 Java, Hawaii and British Guiana, where it is the most 

 common leaf disease. Its prevalence depends on climatic 

 conditions, late ripening being accompanied by a heavy 

 incidence. 



Re:^ Spot.^^ Eriosphcsria (Went), Coleroa (Van Breda de 

 Haan), Venturia (Saccardo) sacchari. — Hab. in foliis sacc. offic. 

 Perithecia 70-80 diam. ; asci 25 long., octospori, sporidia 11x16. 



This organism forms dark red spots on 'the leaf, 

 generally roughly circular and about one centimetre in 

 diameter. The connection between the disease and the F:g. 51 



fungus has not been proved by infection experiments. 



Red Rot of the Leaf Sheath.''^ — This disease, originally reported from Java, 

 is probably the same as that due to Sderotium Rolfsii. The disease is char- 



