THE PESTS AND DISEASES OF THE CANE. 



The localization of the disease to Java, or its presence elsewhere, is of 

 great importance ; in the literature references may be found to its appearance 

 in Australia, Mauritius, and Reunion ; the only authoritative statement I have 

 come across is due to Went, who saw Black Java canes in Surinam with the 

 symptoms of the disease. The writer himself has not infrequently in Mauritius 

 and Demerara seen canes presenting the symptoms of sereh, including the red 

 stripe ; it is admitted that such symptoms may be present in sereh-free canes, 

 and these symptoms appearing in other than sereh canes may account for the 

 great diversity of opinion as to the cause of the disease. 



6. Red Rot of the Stem." Colletotrichum falcatum. "Went.- The Red 

 Smut has been carefully investigated by Went. He says that diseased 

 plants do not show any outward sign of disease so long as they are not 

 seriously affected. At a later stage the plant dies away, the leaves becoming 

 prematurely withered and yellow. On cutting the cane longitudinally the 

 joints are found to be affected, but two consecutive joints are seldom diseased. 

 The disease shows itself in the shape of a red colouration in the interior of the 

 joint, which is unequally distributed and darker in one place than another ; 

 peculiar white spots are also to be seen. This appearance serves to distinguish 

 the disease from Sereh, which is marked by a red stripe. The rind is un- 

 aftected, and since the fibrovascular bundles are chiefly congregated near the 

 rind, the leaves are still able to obtain their food. 



In the white blotches a mould is always present, a few threads of mycelium 

 being found in the red patches. In the vascular bundles brownish-black 

 patches also occur, connected with which is a mycelium flourishing in the cells 

 and walls of the bundles. 



If a piece of diseased stem be allowed to dry, black streaks appear, due to 

 stromata, from each of which spring a number of brownish-black straight 

 hairs measuring from 100 /A to 200 u in length and 4 JLL wide. Among these 

 hairs arise a number of sickle-shaped conidia, measuring 25 p, by 5 /*. If the 

 diseased cane be kept in a damp place a white mycelium turning to grey 

 appears, forming, in a few days, chlamydospores or resting spores. Went never 

 obtained any form of spores other than conidia or chlamydospores. To the 

 organism described above he gives the name Colletotrichum falca'um, and states 

 that it is a wound parasite, only attacking canes already injured by insects. 

 The organism has also a selective power for different varieties of cane. The 

 complete description by W r ent of this is : Colletotrichum falcatum. Setis num 

 seriatis, nunc in pseudo-conceptaculum congregatis cuspidatis, 100200x4., 

 fulgineis, sursum pattidioribus, conidiis falcatis 25=4, hyalinis, ad hasim setul- 

 orum, lasidiis ovoideis 20 x 8, hyalinis vel fuscts, suffultis. Habitat in culmis 

 vivis. This organism is cosmopolitan. More recently the fungus has been 

 studied by Lewton-Brain, 46 who has shown the existence of an enzyme 

 secreted by the fungus, to which the loss of sugar is due. 



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