CHAPTER XXIII. 



CORN MILDEW SUMMER RUST AND MILDEW. 



Puccinia graminis, Pers. 



THE summer rust and mildew of corn, as caused by the 

 fungus known as Puccinia graminis, Pers., is of greater 

 importance from an economical point than the spring 

 rust and mildew already described. The losses entailed 

 on farmers by attacks from Puccinia graminis, Pers., have 

 sometimes reached 50 or even 75 per cent on the whole 

 crop ; where there should have been 40 or 50 bushels 

 only 20 have been harvested, and in some instances only 

 12 have been recorded. 



The first parasite may be found in its early or Uredo 

 state in March, April, and May, whilst the summer rust 

 is seldom seen till June or July. 



As in the last, the early condition of summer mildew 

 is the rust stage, termed in this case Uredo linearis, 

 Pers. The generic name has already been explained ; 

 linearis refers to the elongated form of each dot or 

 disease pustule. The black condition of the fungus, as 

 found in autumn and winter, is the one termed Puccinia 

 graminis, Pers. The name Puccinia has been explained ; 

 graminis needs no explanation. 



Botanists in former times believed the red and black 

 spots of rust and mildew to be caused by two distinct 

 fungi ; it is, however, very common to see both Uredo 

 and Puccinia spores in the same pustule. 



Part of a wheat leaf suffering from summer rust, Uredo 

 linearis, Pers., is shown at Fig. 72, enlarged three 

 diameters. The Puccinia or mildew is replacing the 



