2S6 Diseases of Economic Plants 



planted earlier, chiefly because it was exposed to contagion | 



only about half as long. Moisture and richness of soil , 

 predispose to disease by increasing growth and giving a J 

 greater number of susceptible points of attack. Corn thickly j 

 planted is more liable to infection because ventilation is j 

 restricted, and thus a more humid atmosphere is maintained 

 around the plants. I 



It has been shown that corn smut can be reduced by j 

 spraying with Bordeaux mixture, but the saving does not ] 

 warrant the expense. To go through the field several times ■ 

 during the season and cut out and burn all the developing 

 smut masses that can be seen, thus to destroy the spores and : 

 prevent the continued spread of the disease, is recommended, j 

 but the actual utility of such practice has not been demon- 

 strated, though it is probable that this practice continued 

 yearly would result in continued diminution of smut. The 

 use of the silo in which the smut spores are rendered non- 

 viable tends to lessen the amount of smut. The smut fungus 

 can live and even increase in manure. Therefore live smut 

 spores may infest the manure pile and thereby increase the 

 disease in fields to which such manure is applied. The smut 

 itself, contrary to popular belief, is poisonous to stock only 

 under very rare and exceptional conditions, so rare as to be j 

 practically negligible. Fresh smut balls that have not yet 

 turned dark are edible, and, prepared as mushrooms, are , 

 delicious. I 



Head-smut (Sphacelotheca reiliana (Kuehn.) Clint.). — 

 This smut, identical with that of sorghum, occasionally 

 occurs upon corn and is somewhat more injurious though less j 

 common than the usual corn snuit. It cannot be controlled | 

 by seed treatment. ' 



Corn Ear Rots ^^^ ] 



Four types of ear rot, due to four distinct diseases, are I 



described below. In the aggregate the loss from these is | 



enormous, constituting as it does 10 per cent or more of a \ 



crop annually. Infection comes from definite species of i 



