VEGETABLE AND FIELD CROPS 275 



Early blight {Alternaria solani (E. & M.) J. & G.)- — 

 This is one of the very serious potato diseases that pre- 

 vail throughout the country. In 1906 the loss in Wiscon- 

 sin was placed at about 5,000,000 bushels, and a 50 per cent 

 loss was reported from Wyoming. 



The grayish brown leaf spots, which are brittle, irregularly 

 circular, and are concentrically marked, appear about the 

 time the tubers begin to form. The coalescence of the spots 

 involves large areas of leaf tissue and results in browned, 

 withered leaves, the stems remaining green. The effect 

 is often so complete as to lead the grower to think the vines 

 have died a natural death. The progress of the disease is slow, 

 covering three or four weeks before all the leaves are dead. 

 The loss of efficient leaf tissue so diminishes the vigor of the 

 plant that the yield is largely reduced. Though the tubers 

 are not directly attacked and never rot from this disease, 

 their growth is usually stopped at the attack of the disease. 

 This is a disease characteristic of dry soils and seasons, and 

 is liable to be associated with tip-burn. 



The general spraying (p. 281) will hold this blight in check. 



Wilt, fusariose {Fusarium oxysporum Schlecht.). — This 

 wilt is definitely known in Michigan, Virginia, North 

 Carolina, Ohio, Kansas, Nebraska, District of Columbia, 

 New York, Florida, California, Colorado, Wisconsin, Oregon, 

 Washington, Massachusetts, Iowa, West Virginia, and Ver- 

 mont, and is probabh' identical with a very destructive 

 potato disease of England, Germany, France, and Belgium. 



When the plants are about a foot high, or in mild cases a 

 little later, the first trace of the wilt is noticeable.' The 



1 Smith, E. F., and Swingle, D. B., U.S. Dept. Agr. Bur. Plant Indue. 

 Bui. 55, February, 1904. 



