Vegetable and Field Crops 



249 



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kf.f- 



Soil-rot 301. 303 (Cystospora hatatce (E. & H.) Ell.). — The 

 loss from this rot is sometimes almost total. Due to soil 

 infestation the raising of the crop is pro- 

 hibited for several years. 



The roots are attacked when quite 

 small, sometimes over the whole surface. 

 The part infected ceases to grow, while 

 adjoining parts enlarge. This results in a 

 condition such as that shown in Fig. 136. 

 The smallest rootlets are the points of 

 attack, thence the disease proceeds to 

 the potato and causes the surface spots 

 as seen in the illustration. 



The chief loss is in the cessation of 

 growth. In badly infested fields no po- 

 tatoes of marketable size mature, and 

 the crop is not worth harvesting. 



Long rotation to avoid placing sweet 

 potatoes upon infested soil is advised. 

 Halsted showed that soil-rot, even upon 

 land badly infested with the fungus, can 

 be controlled by sulfur and kainit; 400 

 pounds of each applied to the soil gave 

 the best results. Treated plats gave 60 

 bushels of clean potatoes as contrasted /C"'' '. . ,^^^M 



with 5 bushels for the untreated plat. ^-'f'-^ 



Wilt, stem-rot (Fusarium sps.). — In W"}"*'^^^ 

 this disease, prevalent from the Atlantic L /v\f 

 to Kansas, the leaves turn pale yellow F-^ . 

 and wilt; the stem is blackened within, ^^ 

 and, later, ruptures. The whole vine 

 dies unless supported by roots at some 

 other point. Following the death of the 

 original stem, the portion of the root still 



alive throws out a fresh growth of short ^ ^^ .. 



stems and leaves near the center of the j.^^. ^j ^^^^^ potato. 

 hill. Such efforts at recovery are inef- After Halsted. 



