272 PLANT DISEASES 



the easy place to attack this smut is when the spore 

 is clinging to the seed. It is therefore possible to kill 

 the smut by washing off or killing the spores on the 

 outside of the grain. Hence, seed treatment as de- 

 scribed below will cure this disease. In all cases the 

 life story of the disease-causing fungus is an important 

 thing. It is the main object of this chapter to bring 

 before the student the relationship between these life 

 histories and combative measures which will give a 

 basis for the intelligent handling of plant diseases in 

 general. With this in view four types of diseases will 

 be described, each type demanding a different kind of 

 treatment. The reason for the treatment in each case 

 will be shown to depend on the life story of the disease. 



SOME COMMON DISEASES OF PLANTS 



Smuts Seed Treatment. Smuts constitute one 

 of the most common and destructive groups of fun- 

 gous diseases. The damage in the United States to 

 cereals alone reaches many millions of dollars, and 

 other crops may also be attacked. Every farmer is 

 familiar with smut in wheat and oats, and everybody 

 is familiar with the large smut mass which is produced 

 in corn. Not all the smuts of cereals are caused by the 

 same fungous plant. That is, the smut of corn is not 

 the same smut that attacks wheat, nor is the smut of wheat 

 the same as the smut of oats. Each smut is a separate 

 disease and has its own life story, although two or more 

 smuts may have a similar life history. For instance, the 

 oat smut and the stinking smut of wheat are similar 

 in their life stories, but oat smut cannot be transferred 

 to wheat, neither can wheat smut be transferred to 

 oats. In order to illustrate the different life histories 



