260 APPLIED BIOLOGY 



the smut plants appear first as white masses ; but soon these 

 burst open and expose masses of spores. These have the 

 blackness of lamp-black or soot; hence the name " smut." 

 These spores may infect other corn plants in the same season. 

 Examination of a smutty ear of corn shows that the grains 

 have been destroyed wherever the mycelium of the smut 

 has penetrated them. 



The blights, rots, and scabs are numerous and destructive. 

 Common examples are potato blight of the leaves and rot 

 of the tubers (caused by mycelium growing from leaves 

 through stem to tubers) ; the blight which causes leaves of 

 many orchard trees and vegetables to wither and dry up 

 in part or whole ; peach-leaf curl ; the black rots of grape and 

 tomato ; the scabs of apple, grape, and potato ; the leaf- 

 spot of pear and other trees ; and black knots of plum and 

 cherry branches. 



The above-mentioned examples are but a small fraction 

 of the plants affected injuriously by fungous diseases. Most 

 of the enemies of cultivated plants are either these diseases 

 or insects. One who attempts to grow any special kind of 

 crop should become familiar with the known diseases and 

 the remedies. For such information consult the bulletins of 

 the United States Department of Agriculture and of state 

 experiment stations. Farmers' Bulletins 91, 219, 243, 250, 

 284 (all free) describe some important fungous diseases. 



Remedies. In general, the remedies against fungous 

 diseases consist in (1) destroying all infected materials, such as 

 leaves and stems which may carry spores ; (2) in destroying 

 spores on seeds before planting (e.g., soaking wheat and rye 

 in formalin solution to kill smut spores, and potato tubers 

 to kill potato rot or blight) ; and (3) spraying the stems 

 and foliage with solutions containing lime, copper sulphate, 

 copper carbonate, or iron sulphate. The spraying method 

 has within the past two decades come into extensive use, and 

 hundreds of special machines have been invented for spreading 



