CEREALS 331 



per cent of infected stalks. Infection can occur only upon 

 very young plants. Between the times of infection and 

 the appearance of the smut masses in the panicle no signs 

 of the disease are seen without the aid of the microscope. 



The smut can be prevented by the use of clean seed, 

 obtained either from clean fields or by disinfecting the 

 seed by the hot water (135° F. for 10 to 15 minutes) or 

 formalin methods, as given for oats. 



Head smut. See sorghum. 



CORN 



Smut {Ustilago Zeoe (Beckm.) Ung.). — Corn smut is 

 well known to every farmer, occurring everywhere the 

 corn plant is grown, as black, pulverulent masses most 

 conspicuous upon the ear and tassel. The damage done 

 by it is estunated at 1 per cent of the ears. To this should 

 be added perhaps 1 per cent more to cover the loss in vigor 

 that is sustained by the plant. Under exceptional con- 

 ditions the damage may exceed these figures. Thus in 

 Iowa a loss of two thirds of the crop was at one time re- 

 ported. 



Corn smut is first mentioned in literature in 1754, and 

 the first American record is that of its collection in North 

 Carolina in 1822. Experiments looking to its prevention 

 were made as early as 1760. The disease may attack any 

 part of the plant at any age, — leaves, stalks, aerial roots, 

 ears, tassels, — provided only that they be still in tender 

 growing condition, not mature and hard. 



The first symptom is a pale, glistening, swollen area 

 covered with a white membrane, which soon appears black 

 owing to the maturation of the spores within. The mem- 



