226 



Diseases of Economic Plants 



are present on the seed. Liming the soil, clean culture 

 methods, and crop rotation are palliative. Infested refuse 



should be destroyed 

 by fire. Soil badly 

 infested should not 

 be planted to pota- 

 toes. In general, the 

 remarks made under 

 soil diseases apply 

 here. 



While this disease 

 has long been recog- 

 nized in Europe, 

 especially in Ger- 

 many, no record of it 

 was made in America 

 until 1891. Since 

 that date it has been 

 noted upon many 

 hosts in many states. 

 Sec p. 21. 



Early-blight 27" (AZ- 

 teryiaria solani (E. & 

 M.) J.&G.).— This 

 is one of the very 

 serious potato dis- 

 eases. In 1906 the 

 loss in Wisconsin was 

 placed at about 

 5,000,000 bushels, 

 and a 50 per cent loss 

 was reported from 

 Wyoming. The average loss in Michigan is estimated as 25 

 per cent of the crop. It is known throughout the United 

 States, in Europe, Africa, and Asia. 



The grayish-l)r()vvn leaf-spots, which are brittle, irregularly 

 circular, and concentrically marked, appear about the time 



Fig. 124. 



Little potatoes and aerial pota- 

 toes. After Rolfs. 



