138 DISEASES AND INSECT ENEMIES 



In both cases the smut begins to grow when germination of the 

 wheat begins and at once infects the plant, living inside the tissues. 

 The infected plants are not noticed until heading time when the 

 heads turn into smut. The infected plants are usually shorter and 

 not so noticeable, so that the damage by smut from a casual observa- 

 tion is usually underestimated. 



Treatment of Seed. Since the disease is carried over from year 

 to year on the seed, treatment consists in using some disinfectant that 

 will destroy the smut but not injure the wheat germ. 



(1) Bunt spores are on the outside of the grain and are easily 

 killed by treating the seed with a solution of formalin. Use one pint 

 or pound of 40 per cent formalin solution in 40 to 45 gallons of 

 water. The wheat may be put in loose sacks and placed in the 

 solution to soak for 5 minutes. A simpler way is to pile the wheat on 

 a floor or in a wagon box, and apply the solution with a sprinkling 

 can, shoveling the grains over until all are thoroughly wet. While 

 the spores should be killed by contact with the solution, the treatment 

 is considered much more effective if the grain is piled up and covered 

 with wet blankets or sacks for 12 to 24 hours. The formaldehyde 

 gas will then have time to penetrate all crevices of the grain and 

 to destroy the spores. 



Loose smut, having infected the seed in the field while very 

 young, is found inside the seed in the form of a small filament. No 

 treatment for the outside of the grain will kill it. The only effective 

 method is known as the hot-water treatment, which rests on the 

 principle that the smut filament is killed by a temperature of 130 F. 

 while the wheat germ will stand four to five degrees higher tempera- 

 ture. First soak the seed for four to six hours in cold water. Have 

 ready two tubs of water heated to 133 F. and place the grain in a 

 loose sack in the first tub, to bring up the temperature. Then place 

 in the second tub, keeping the temperature not lower than 129 F. 

 or higher than 133 F. Five minutes at 133 or 10 minutes at 129 

 will kill the smut. Germination of the seed is also likely to be injured 

 and more should be sown. As the treatment is slow it is best to treat 

 only enough for a seed plat. With clean seed and care, another 

 treatment may not be necessary for several years. The smut is often 

 spread by itinerant threshing machines. 



