DISEASES OF CULTIVATED PLANTS 581 



be collected and burned. They should not be thrown on the manure- 

 heap or refuse-pile, thence to be carried back to the land. 



Rotation of crops is valuable in preventing corn-smut. The 

 reason for this is plain. The corn-smut in the soil will not live 

 many years, and that which is in the soil will not damage any other 

 farm crop. After several years, corn may again be planted, with 

 less danger, since the smut in the soil will have at least partly died 

 out. Seed-treatment has not been found to be of any use. The 

 smut does not get into the seedling plant, as in the stinking smut 

 of wheat, and hence seed treatment does not seem necessary. 



As to the treatment, since an infected seed has no spores on 

 the outside, but has the smut inside of the seed, some methods have 

 to be devised other than those used for smut of wheat and barley. 

 Such are described below. They are, briefly, built upon this principle : 

 The seed is soaked in cold water for several hours. In its water- 

 soaked condition, heat can be carried through the seed more uni- 

 formly and quickly than when it is dry. The soaked seed is then 

 treated in hot water, and then the smut-plant inside of the seed is 

 killed; while the seed is not at all, or only slightly, injured by 

 the treatment. For further details see below. 



Since the treatment for one group of smuts may have no effect 

 on the other, it is absolutely necessary for a farmer to know which 

 smut he is dealing with. It then becomes an easy matter to apply 

 the proper remedy. For instance, in treating smut in barley, a 

 farmer who treats his barley with the formalin method will get rid 

 of the covered smut of barley, but will not get rid' of the loose smut 

 of barley. The same holds true of wheat. In order to get rid of the 

 loose smuts of these crops, the modified hot water treatment must be 

 used. 



There is another smut, not described above, which is found on 

 sorghum plants, but this smut has not yet appeared, at least in any 

 quantity, in Minnesota. It is known as head-smut of sorghum. 

 The life story of this smut is not yet known ; but it is undoubtedly 

 different from grain-smut of sorghum, described above, since the 

 ordinary formalin treatments have no effect on it. (Minn. E. S. B. 

 122.) 



BARLEY. 



Closed Smut. The grain is turned a dark color by the forma- 

 tion of the fungus spores in its substance. This remains firm rather 

 than flying out in a dusty mass, as in the next form. 



Loose Smut. Differs from the last in that the smutty sub- 

 stance of the grain scatters out in the form of black dust, leaving 

 the heads empty. Barley is not often affected with smut in Cali- 

 fornia, so that we can not distinguish as to the occurrence of these 

 two different species. It is advisable, however, to treat the seed as 

 follows : Soak for 10 minutes in one of the following solutions : 



1. Bluestone, 1 pound to 5 gallons of water. 



2. Formalin, 1 pint to 30 gallons of water. 



The seed should be soaked long enough to get every grain thor- 

 oughly wet and then immediately taken out. If not planted at 



