5 



SUGAR CANE DISEASE. 



In the May number of the Bulletin, was published a letter from the Director of the Royal Gar- 

 dens, Kew, respecting a disease in Sugar Cane, which had bjen investigated by Mr. Q-eorge Massee. 

 Mr. Massee's report and the extract from Mr. Bovell's letter therein referred to, are given below . 



Extract from letter from Superintendent Botanical Station, Barbados, dated February 11th, 1893. 



As the question of a fungus attacking canes which have not been first injured by the moth borer 

 is still a very debatable point with those over your way who take an interest in the matter, I am 

 sending you per Mail Steamer to-day, c/o Messrs Obree & Company, Southampton, a box containing 

 (1) canes which have been just attacked by the fungus, and in which no shot or moth borers are pre- 

 sent as jet, as far as I can see, without cutting up the cane. (2) Canes which have been attacked 

 with the fungus a little longer and in which shot borers have entered but no moth borer. (3) Canes 

 with fungi, shot borer and moth borer. (4) Canes killed by moth borer only. 



Preliminary Report on the Sugar Cane Disease. 



The abundant supply of living material, consisting of 18 large canes, illustrating every stage of 

 the disease, sent to Kew for investigation by Mr. Bovell from Barbados, has enabled the vexed ques- 

 tion as to the part played by fungi in connection with the sugar cane disease, to be conclusively 

 settled. 



Each cane was accompanied by a description of the supposed cause of disease, as, killed by " shot- 

 borer", " moth-borer", " fungus", and in some cases two or all the above were described as being 

 present on the same cane. 



Microscopic examination showed the presence of the fungus in every cane, but in some instances, 

 owing to the absence of fruit, its presence could not be detected by the naked eye. 



Only one fungus, an undescribed species of Irichosphceria was found on the canes. The idea en- 

 tertained by some planters that more than one fungus is connected with the disease, probably arises 

 from the fact that the Trichosphaeria has at least three distinct forms of fruit, very different in general 

 appearance, and whose development depends on the relative vitality of the canes. 



Stage I. Conidial condition, for the rapid reproduction of the species ; appearing on the surface 

 of wounded parts as a very delicate, dark-coloured velvety mass, or when old and very abundant, 

 penetrating the internal tissue of the cane and producing a black charred appearance, due to the 

 numerous chains of large olive-brown conidia. 



Stage II. Melanconium form, bursting through the cuticle of old canes in the form of minute black 

 pustules, often following the ravages of the "moth-borer" or "shot-borer" in dying or dead caaes. 



Stage III. The ascigerous form. Minute, black, hairy perithecia, present oaly on dead and more 

 or less decayed portions of the cane. 



The conidia from Stage I. ^obtained from a pure culture, were placed on the unbroken surface of 

 very young leaves of lateral shoots of a healthy sugar cane plant growing in the Lily House, Kew 

 Gardens ; in five days the infected areas showed deep red blotches, and in fourteen days the conidial 

 form of the fungus was perfectly developed, the mycelium in the meantime having passed into the 

 shoot and adjoining leaves. Soon afterwards the young infected shoots decayed and dropped off, 

 microscopic examination showing that the mycelium had passed into the tissues ot the parent stem. 



Further experiments showed that fully developed leaves and stems cannot be infected on an un- 

 broken surface, nevertheless when the surface is broken infection is readily effected. A cane about 1^ 

 inches in diameter was inoculated by cutting a deep slit and introducing mycelium from a pure culture 

 of the conidia; in 16 days the cane was split at this point, and the central portion was found to be 

 coloured red for a distance of 3 inches, and the mycelium had extended even bayond that distance ; 

 the microscope showed the presence of the dark olive conidia formed in tissues away from the light. 

 Infection also readily takes place at points where lateral branches have been broken off. 



Summary. 



1. The experiments described above prove that the young leaves of the sugar cane can be infected 

 by the spores of Trichosphmria falling on an unbroken surface, and further, that the fungus acts as a 

 true parasite, eventually killing the plant. 



2. In older plants inoculation can only take place when the surface is wounded, but when an 

 entrance through a wound is once effected the fungus acts as a destructive parasite. 



3. The frequent pre ence of both fungus and moth-borer or shot-borer in the same cane is explained 

 by the above statement. Assuming the insect to first pierce the cane, the spores of the fungus would 

 fi.nd a suitable place for development in the wound ; hence the presence of one parasite prepares the 

 way for another, and the combined action of the two soon ends in the destruction of the plant. J^ever- 

 theless the fungus is not entirely dependant on the previous presence of the iasect, but readily finds 

 entrance at broken points, and can alone kill the cane. 



Protective Measures. 



The conidia of the fungus will not germinate, neither will the mycelium grow in a 1 per cent 

 solution of cupric sulphate, but spraying with the ordinary Bordeaux solution is in all probability not 

 practicable other than in the case of an experimental plot, and would certainly have no beneficial 

 effect on an infected area. 



Remembering that the mycelium of the fungus extends, as a rule, far beyond the range indicated 

 by its presence to the naked eye in a given cane ; and further, that almost every cane — judging from 

 the material examined — attacked by the " moth-borer" or " shot-borer," is also infested with the 

 fungus, it would be unwise to use appearently sound portions of such canes for propagation. It was 

 observed in those canes killed by the fungus alone, that the disease was oldest and most mature near 

 the root, and this suggests the question — Was the cane, even if taken from a healthy stock, inoculated 



