cobb's disease of sugar-cane. 69 



The remedies advised by Cobb are: (1) selection of healthy sets; (2) good drainage; (3) 

 burning of the trash; (4) rotation of crops, or bare fallow once every few years; (5) produc- 

 tion of new varieties of cane by raising seedlings; (6) improvement by selection; (7) introduc- 

 tion of new sorts from outside Australia; (8) the fostering of nurseries where (5), (6), and (7) 

 are to be carried out. At the close is the following pertinent paragraph, which, be it remem- 

 bered was written in 1893: 



vSelection of disease resistant sorts. This is a subject that needs an essay by itself. I am con- 

 vinced that one of the greatest improvements destined to be made in agriculture is in the line of secur- 

 ing pest-resisting varieties. We stand as yet but on the threshold, yet we can clearly see the alluring 

 prospect. What we now possess in a few cases, having obtained them almost by accident, show's how 

 on the alert we should be to discover varieties as little subject to disease as possible. 



Cuttings designed for planting should be inspected very critically and those showing 

 any signs of the yellow bacterial ooze on the cut surface must be rejected. Even very care- 

 ful inspection at the time of cutting is not sufficient, however, for the removal of all dis- 

 eased canes. Queensland planters, according to Tryon, are in the habit of covering the 

 piles of cut canes for about three days with trash upon which water is thrown ; this induces 

 a sweating process which greatly facilitates the detection of unsound cane. In this way 

 " tons of bad cuttings have been picked out which otherwise would have spoiled the stand 

 of the cane. " The Fiji method of detecting slightly diseased cane-cuttings is by steaming. 



The poisonous action of sodium salts on the organism suggested to Greig Smith that 

 common salt might be used to check the disease unless the amount necessary to inhibit the 

 growth of the bacterium would injure the sugar-cane. On inquiry, he found that in Fiji 

 healthy crops of cane were grown on soil containing 1 per cent or less of salt, but any greater 

 percentage was more or less injurious. Reports differ as to the comparative amount of this 

 disease among crops raised on the seashore. One instance is given of a man whose farm 

 was on an island in the Lakes, Clarence River, who was able to grow a comparatively sound 

 crop of Mauritius Ribbon cane long after other growers had abandoned it because of its sus- 

 ceptibility to this disease. On the other hand, there is the opinion on the part of some that 

 canes grown on salty soil are more liable to be affected. This, Greig Smith thinks, may be 

 traced to defective drainage. He agrees with Cobb, however, in regard to growing disease- 

 resistant varieties, and mentions one well-known variety, Tanna, which has never been 

 known to develop this disease. The sugar-content is less high than in some of the more sus- 

 ceptible varieties, but Tanna is a stout, heavy cane, and when planted in fields which have 

 yielded badly diseased crops produces perfectly sound canes. 



Table 6. Susceptible and Resistant Varieties of Sugar-Can c. 



SUSCEPTIBLE. RESISTANT. 



Common Green (EFS.) Tanna or Elephant (Tryon, RGS.) 



La Canne Bambou (Boname) Louisiana No. 74 (EFS.) 



Louzier or White Bamboo (Tryon) Common Purple (EFS.) 



Rappoe or Rose Bamboo (Tryon) Malabar or Green Tanna (Tryon) 



Djioenig-Djioenig (Tryon) Daniel Dupont or Bambou Brancheuse Rayee (Tryon) 



Striped Singapore (Tryon) Cheribon or Outamite (Tryon) 



Mauritius or Striped Guingham (Tryon) China (Tryon) 



Meera (Tryon) Moore's Purple (?) 



Lahina (MeGuigan) Green Dupont or Bamboo Brancheuse Blanche (Tryon) 



Kewensis (Knox) Australian Creole, a cane resembling Meera (Tryon) 



According to Tryon, the canes most subject to the gum-disease are just those varieties 

 richest in sugar. "It may be remembered, however," he says, "that the canes that have 

 been found to be free from disease in Queensland are included in both the poor-in-sugar and 

 rich-in-sugar categories," e. g., Daniel Dupont, rich, and Elephant, poor. 



Tryon noted also that the disease was most pronounced in canes grown upon the best 

 lands. Most of the immune varieties have hard canes and the susceptible ones soft canes, 

 but this does not appear to be a rule without exceptions, since the Outamite or Cheribon is 



