RED ROT OF THE LEAP-SHEATH {ScleroHum Bolfsu). 



This is again one of the diseases of cane which, though very com- 

 mon everywhere, has not been considered of economic importance. 

 In fact there have been no observed cases of serious loss in cane fields 

 attributable to this fungus in Porto Rico, although such instances 

 have been reported from St, Croix and Georgia. 



The fungnis favors the more moist situations and apparently heavier 

 soils. In cane fields it does not appear to any extent until the cane 

 has closed in creating a moist situation. Upland fields show but little 

 of the fungus, except in wet weather. It is not uncommon to find 

 fields practically every stool of which shows an abundance of infection. 

 It has not been possible even in such cases to observe that any damage 

 was being done, the stand apparently being entirely normal. Young 

 shoots will be commonly found dead and covered with the sclerotia. 

 but the death of these young shoots occurs under all conditions and 

 is considered a natural phenomenon due to smothering or lack of light 

 or food. The lower leaf sheaths are undoubtedly prematurely killed, 

 but since the fungus rarely attains to any height on the stalk the 

 leaves so destroyed are those already shaded and hence rendered 

 more or less useless, so that the injury due to reduction of leaf surface 

 is considered negligible. Whether the fungus attacks the roots as 

 it does those of other hosts is not known. This is a point which must 

 be taken up along with a detailed study of the root disease fungi. 



The fungus appears as a white, more or less feathery mycelium 

 growing up the lower leaf-sheaths binding them together and pro- 

 ducing a red rot of the infected tissues. The color of the rot is a 

 bright orange-red quite distinct from that of Cercospora vagitme or 

 of any other disease attacking at this point. The areas ni-e very 

 irregular, Avith indistinct margins, seldom extending over a foot oi- 

 a foot and a half above the ground level. The only fruiting stage 

 known consists of the sclerotia produced particularly along the edges 

 of the leaf-sheaths, in the folds, or between two diseased sheaths and 

 to a less extent on the reddened areas of the outer surface. They 

 are first noticed as white, very small, masses of hyphae forming on 

 the strands of mycelium. They finally become from one thirty-second 

 to a sixteenth of an inch in diameter, more or less spherical, flattened 

 at the poles. The color varies from white through yellow-brown to 

 a very deep red-brown or brown, when mature. The sclerotia when 

 mature are quite firm and but loosely attached to the substratum. 



This fungus has been observed (76) as the cause of a serious wilt 

 disease of various vegetable crops, particularly the egg-plant, pepper. 



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