SUGAR-CANE 95 



Some workers have expressed doubt as to whether 

 these fungi are the causes of the diseases attributed to 

 them. A more thorough knowledge of this group of 

 fungi will doubtless reveal a much larger number of 

 species, and extend the range of those already known. 



The disease may be held in check by careful cultiva- 

 tion and drainage, by the selection of healthy plants, by 

 developing immune varieties, by destroying the waste 

 material left on the fields, and by rotation of crops, or 

 resting the lands. The success of any method, however, 

 will depend in a great measure on the methods of 

 cultivation followed in the locality. 



Root Galls. The nematode root - galls have been 

 reported in the sugar-cane from various parts of the 

 world, and they are frequently the cause of very great 

 losses (page 71). 



CORN, ETC. 



While corn is not strictly a tropical plant, and in 

 fact does not reach its highest development in the 

 tropics, it is grown for local consumption, and its 

 diseases must be taken into consideration. 



Smut. One of the most common and widespread 

 diseases of corn is the smut ( Ustilago zeae or U. maydis). 

 This disease may occur as swellings on any part of the 

 plant above ground, but is most common on ears and 

 tassel. The affected parts become transformed into an 

 unsightly mass of moist, spongy fungus tissue (Fig. 44), 

 which eventually becomes dry and extremely light and 

 fragile. This condition is well known to every one 

 familiar with growing corn. The fungus contains an 

 enormous number of spores which are readily distributed 

 by the wind. It can also maintain itself in old stalks 

 left in the fields, and produce spores which pass directly 

 to the young and growing crops the following season. 



It cannot be prevented by any known treatment of 

 the seed as in the case with some other smuts. Where 

 very troublesome, the diseased stalks should be cut and 



