PLANT DISEASES 



293 



382. Diseases controlled by seed disinfection. The stinking 

 smut of wheat, sometimes called bunt, is caused by a fungus 

 which produces dark-colored kernels in the affected heads. These 

 dark-colored grains are filled with smut spores. 

 When the grain from a smutted crop is 

 threshed and handled in sacks, bins, and ma- 

 chinery, the smutted kernels or smut balls 

 break and the spores are scattered over the 



other grains. When 



this infected seed is 

 planted and germi- 

 nates, the smut spores 

 germinate also and 

 produce smut plants. 

 These are little tubes 

 or filaments which 

 attack the sprouting 

 wheat plants, usually 

 below the ground line, 

 penetrate them, and 

 live and grow inside 

 until the grain is about 

 to mature. The smut 

 then develops its spore 

 masses in place of seed. 

 These spores mature 

 when the grain is ripe 

 and break in thresh- 

 ing and handling, 

 scattering the spores 

 over next year's seed. 

 The smut of oats (Fig. 141), covered 

 smut of barley, kernel smuts of sor- 

 ghums and broom corn, and a smut of millet have somewhat simi- 

 lar life histories. The loose smuts of wheat, as well as other smuts, 

 have their own peculiar life histories and effects upon their hosts. 



FIG. 141. Oat smut 



The smut has occu- 

 pied all the grains, 

 thus completely de- 

 stroying them and 

 at the same time 

 producing a large 

 crop of spores to in- 

 fect next year's crop. 

 (Photograph by E. 

 C. Johnson) 



P'IG. 142. Loose smut of 

 wheat 



At left, a healthy head; at 

 right, two heads with grain 

 completely destroyed by the 

 smut. (Photograph by E. C. 

 Johnson) 



