DISEASES OF CULTIVATED PLANTS 613 



when the seed is planted they grow at the same time that the seed 

 sprouts. The smut plant penetrates the stalk of the young seedling 

 plant and grows inside of the latter until the heads are formed, when 

 the fungus forms its spores inside of the grains, replacing the latter. 



As in the bunt of wheat, careful seed treatment will kill the 

 smut spores, because the latter cling to the outside of the seeds, and 

 after such treatment the crop will be free from smut. 



It is therefore very important that any farmer who is not sure 

 that his seed is free from smut should treat his seed in one of the 

 ways suggested in this circular. When his seed is once clean he can 

 keep his farm free from smut by raising his own seed, provided he 

 does not allow it to become smutted again in a smutty thrashing 

 machine or in the subsequent handling of the grain. 



Treatment of Grain Smut. Seed that is smutty may be treated 

 in the following ways : Formalin treatment : Mix 1 pound of full- 

 strength formalin with 30 gallons of water. Put the seed in sacks 

 and immerse the sacks in this solution for one hour, stirring it occa- 

 sionally. Then take the sacks out and set them to drain. Spread 

 the seed out on a clean floor or canvas. Be sure that all of the 

 sacks, the barn floor, and the canvas used in handling the grain 

 after treatment are cleaned either with boiling water or with a strong 

 formalin solution. The seed will be infected again if any untreated 

 smut spores touch it. When the seed is sufficiently dry after treat- 

 ment it may be sown. 



The same solution may also be used as a spray, in which case 

 the seed to be treated should be spread out on a clean floor or canvas 

 and sprinkled with the solution. It must be shoveled over fre- 

 quently until all of the seeds are wet. It may then be shoveled into 

 a pile and left over night, covered with a clean canvas or sacking to 

 keep in the fumes, and then spread out to dry in the morning. 

 Seed treated in this way will be free from smut. The immersion 

 method is more thorough, but is not as convenient as the sprinkling 

 method. 



Hot-Water Treatment. Hot water is a most cheap and efficient 

 means of treating sorghum seed. The treatment is more easily ap- 

 plied to sorghum than to wheat and barley, because sorghum seeds 

 (at least those of kafirs and sorgos, or sweet sorghums) will stand 

 much higher temperatures than wheat and barley seeds. The 

 smaller quantity of seed used to the acre in the sorghum crops is 

 an additional advantage, making it possible to treat easily all the 

 seed required for a large area. In the hot-water treatments of sorgo 

 and kafir a fairly wide range of temperature is permissible, and the 

 operation is therefore easily performed on the farm. 



In brief, the process is as follows : Heat two large vats or tubs 

 of water to about 135 and 140 F., respectively. Place the seed to 

 be treated in a clean sack or wire basket and plunge it into the tub 

 of water heated to 135 F. for a moment. Then transfer the j*ack 

 to the second tub or vat for ten to twelve minutes. Keep the tem- 

 perature of the water in the second tub between 134 and 140 F. 

 It should not be allowed to go above 142 or below 134 F. The 



