314 DISEASES OF CROP-PLANTS 



The Iliau Disease. 



The name Iliau, from an expression meaning " hide-bound " 

 is given to a disease endemic in Hawaii and regarded by H. L. 

 Lyon, who investigated it there, as having caused more loss than 

 all other cane diseases combined. The affection is also common 

 in the more northern parts of Louisiana. The effects are liable 

 to be confused with a common symptom of root disease, and the 

 fungus with Melanconium Sacchari, so that very possibly the 

 affection occurs unrecognised in these islands, but the fact that 

 it assumes importance in Hawaii only in periods of continuous 

 cool damp weather would seem to exclude its appearance as a 

 serious trouble in the sugar-cane districts of the West Indies. 



Symptoms. 



Iliau is entirely a disease of young shoots, which are attacked 

 from the soil, and mainly affects the leaf-sheaths, which become 

 very tightly cemented to each other and to the surface of the 

 underlying stalk by the growth of a mat of white mycelium 

 in and between them. The adhesion is much more firm than 

 that produced by Marasmius and the rind is entered to some 

 extent. Further useful growth of the shoot after this condition 

 is attained is entirely prevented, though the stem is often found 

 variously bent or doubled by the elongation of the joints while 

 the tip is firmly held. Sometimes the shoot grows through 

 before the barrier is firmly established. Large numbers of 

 young shoots, both in young and older stools, are killed out in 

 this way. Older shoots are not injured. Much more damage 

 is done to plant canes than to ratoons. 



Causation. 



The disease has been demonstrated by experiment to be due 

 to a fungus which has an ascigerous stage, Gnomonia Iliau, 

 Lyon, and a Melanconium stage, M. Iliau, Lyon. The former 

 is the commoner form in Louisiana, the latter in Hawaii. The 

 perithecia are flask-shaped, immersed in the substance of the 

 leaf-sheath, with long, hard necks which project from the surface. 

 The spores are spindle-shaped, with two cells. The Melan- 

 conium closely resembles M. Sacchari in general appearance, 

 but the spores are larger (7-10x15-28), and are usually filled 

 with large globules which are quite distinctive. 



Control. 



Immune varieties are not known, but the Demerara seedlings 

 grown in Hawaii are the most resistant. Thorough preparation 

 is recommended as a very ef&cient measure for reducing damage. 



