THE PESTS AND DISEASES OF THE CANE. 



then this fungus stands ever ready to take advantage of the accident, and in a 

 few weeks' time makes such an inroad as to send the whole cane well on its 

 way to decay. . . . The amount of damage done by spume is difficult to 

 estimate. There is no doubt that through its agency much cane, which 

 though injured would be saleable, is soon rendered worthless." 



As a result of further study in Hawaii, Cobb treats this fungus as strictly 

 parasitic, and mentions that it is a frequent cause of the non- germination of 

 cuttings used for seed. 



Lewton-Brain 52 also treats the fungus as parasitic ; his studies have 

 indicated that the Melanconium is unable to penetrate the hard outer rind of 

 the cane, but that when introduced through a wound, in a susceptible cane, it 

 can enter the thin- walled cells, and bring about the death of the cane. He 

 does not, however, regard it as markedly parasitic on varieties at present 

 widely cultivated. 



The literature of ' rind fungus ' is very confused, but may be thus briefly 

 summarized. 



Howard treats rind disease as synonymous with the red smut of Java, 

 caused by Colletotrichum falcatum. 



Cobb and Lewton-Brain treat rind fungus as a disease caused by Melan- 

 conium sacchari, and Howard does not regard this organism as parasitic. 



The planter, when speaking of rind fungus, refers to the appearance of 

 black hairs growing out from a diseased cane ; this appearance may be caused 

 by the Melanconium sacchari, by Diplodia cacaoicola, or by Cytospora sacchari, 

 and most often follows on attacks of other diseases. 



Lewton-Brain calls the disease caused by Colletotrichum falcatum ' red rot 

 of the stem,' thus distinguishing the disease from the red rot (rood rod) applied 

 by Went and Wakker to a disease of the leaf sheath. 



The organisms associated with the well-known appearance of rind fungus 

 have been described under different names, and we have Trichosphceria sacchari 

 Melanconium sacchari Strumella sacchari and Darluca melasporum Conio- 

 thryrium melasporum Diplodia cacaoicola. 



In the writer's opinion, the etiology of ' rind diseases ' still remains 

 obscure ; those who have been unfortunate enough to have seen ' rind disease ' 

 at its worst in Demerara, the West Indies, or Mauritius will require much 

 convincing that this appearance is not connected with an aggressive parasite ; 

 experiments with the Melanconium seem to prove that this form is not parasitic. 

 On the other hand Howard has shown the parasitic nature of Diplodia cacaoi- 

 cola on cane in the West Indies ; an outbreak of ' rind disease ' was observed 

 by Harrison 53 in the experimental plots at Georgetown, British Guiana ; on 

 the affected canes Howard found the Diplodia ; on Mauritius canes examined 

 by Prilleux and Delacroix the same organism was found. All this seems to 

 point to the Diplodia as being the aggressive parasite, and the cause of rind 

 fungus, to the exclusion of the Melanconium. 



153 



