THE PESTS AND DISEASES OF THE CANE 155 



elimination of the Cana blanca, or Otaheite cane. An extant account 

 of the disease by Stahl describes what appears to be top rot as a dominant 

 symptom. 



In 1876 an epidemic described as "rust' did great damage in Australia 

 and Natal in the 'eighties also suffered severely from some undescribed disease. 

 The two epidemics most often referred to are the sereh disease of Java^ 

 which appeared about 1890, and resulted in the nearly complete disappear- 

 ance of the Cheribon cane ; and the rind fungus of the British West Indies, 

 prevalent at the same time, and which, as in many other cases, selected for 

 attack the Otaheite (Bourbon) cane. These last two epidemics had some 

 good effect, as they afforded great stimulus to the propagation of seedling 

 canes. 



Yet another instance of the susceptibility of the Otaheite cane to disease 

 may be found in its early disappearance from the Island of Hawaii, and to 

 its present sickness in the other islands of that archipelago. 



The latest instance of an epidemic is to be found in Porto Rico, where in 

 1916 the YeUow Stripe disease but recently imported there assimied a 

 fulminant form. J 



Degenerescence is often given as a cause of these epidemics, but the 

 writer in the position of a layman regards the explanation as unrational. 

 What is in all probability one and the same cane (Otaheite) has been the 

 subject of most of the epidemics referred to above. During the time 1848-51 

 that the first Mauritius epidemic occurred, this cane was flourishing in the 

 West Indies, and a few years later was introduced to the Hawaiian Islands 

 with remarkable success. Excepting the possible presence of adventitious 

 seedling descendants, each and every cane then growing must have been the 

 progeny in unbroken asexual descent of one cane, which probably originated 

 as a seedling in some island of Polynesia, probably Otaheite, and, to go 

 further, all the then existing canes may be regarded strictly as one and the 

 same individual. Looked at in this light, degeneration as the result of age, 

 or as the result of continued propagation from cuttings, appears ill-founded, 

 and the epidemics were more likely to have been due to improper agriculture 

 leading to harmful soil conditions, combined possibly with the development 

 of an organism or organisms of a virulent strain due to long-continued 

 access when the cane once formed the sole crop of a locality. 



Leaf and Leat-Sheath Diseases. — No one of the fungi that attack the 

 leaf is to be considered as a major disease. Notwithstanding, the sum total 

 of the damage done by the immobilization of some portion of leaf surface 

 must annually reach a very large sum. Most of the diseases that have been 

 described in the literature are referred to below. 



Yellow Spot. ' — Cercospora Kopkei {Kriiger) ; Maculis amphigenis, sinuosis, 

 confluentibus, purpurea brunneis, infra pallidioribits, margine concolori ; hyphis plerum- 

 que hypophyllis fasciculatis, septatis, apice nodulosis, denticulatisque fumoso brunneis, 

 40—50 X 7 / conidiis fusoideis, sulrectis, 20—30 x 5—8 medie 40 x 6 utrinque obiusiusculis, 

 3-4 septatis, non constrictis, passim guttulatis, subhyalinis. 



The disease appears as dirty yeUow spots, often meeting to form one 

 irregular blotch. A brown mycelium is found on the leaf, the branches of 

 which, sometimes isolated, sometimes united in bundles, carry colourless 

 spores {Fig. 46) ; the appearance of the underside of the leaf is as if covered 

 with a white dust. It is only reported from Java. 



