THE PESTS AND DISEASES OF THE CANE. 



250 



FIG. 61. 



3. Leaf Spot Disease. Pestalozzia fusescens var. sacchari. Wakker. 

 This fungus forms irregular spots on the leaves with a withered centre and 

 brown border ; it is a rare and unimportant disease. 



4. Cane Rust.' 2 ' 1 Uredo kuhnii. Wakker and Went. Narrow orange 

 coloured stripes appear on the leaf, especially on the underside, and from these 



stripes an orange coloured rust can be 

 scraped ; this serves to distinguish 

 the fungus from other leaf fungi of the 

 cane. The rust is composed of the 

 spores of the fungus. Kriiger des- 

 cribes this fungus as Uromyces kuhnii. 

 In Java the disease is everywhere 

 present in damp districts, but the 

 damage done is small. The technical 

 description is: Uredo Icuhnii. Soris 

 uredo aporiferis hypophyllis linearibus; 

 uredo-sporis e globoso ellipsoidiis v 

 pyriformilu*, contentu aurantiaco exosporio copiose aculeate hyalino 18 34-' 5 X 

 28- '5 57' 5 ; pedicellio hyalino clavato suffultis. Various forms (after Kriiger) 

 of the spores of this fungus are shown in Fig. 61. 



5. Eye Spot Disease. Cercospora sacchari. Yan Breda de Haan. 

 The presence of the disease is indicated by small red dots, which grow into 

 long elliptical dark red spots, with 



a light yellow margin; at a later 



stage the centre becomes a dull dead 



yellow, surrounded by a dark red 



area, and this is circumscribed by a 



bright yellow border ; the elongated 



elliptical shape of the spots, which 



may grow up to 1^ to 2 inches in 



length, is retained ; the appearance 



of the spots is not dissimilar to the 



eye on a peacock's wing. With a 



pocket lens hairs (conidiospores) may 



be seen growing from the leaf. The disease has been observed in Java and 



in Hawaii ; in Java it does not appear on Cheribon cane or in mountain 



plantations, and in Hawaii it only makes much progress in wet weather ; 



varieties differ much in susceptibility. The technical description of this 



fungus is: Cercospora sacchari. Hob. in foliis, qua maculantur, sacchari 



oficinarum. Hypha pluriseptatce, brunece, 120 60 ; conidia 60 80x9 12 ; 



vermicularia 5 8 septata Irunea. Forms of the spores of this fungus (after 



Cobb) are shown in Fig 62. 



139 



