330 Diseases of Truck Crops 



placed by the more resistant varieties best adapted to 

 the infected localities. 



Stem End Rot 



Caused by Fusarium eumartii Carp. 



Although a storage trouble, stem end rot may cause 

 a wilt in the field which may not be easily distin- 

 guished from other Fusarium wilts. However, in 

 the laboratory the causative organism may be readily 

 determined by pure culture methods. 



Symptoms. The wilt produced on plants in the 

 field resembles other wilts. On the tubers, decay 

 starts at the stem end. The infected part slowly 

 shrivels and becomes filled with a mass of a dried 

 brown pulp, consisting mainly of dead tissue. In- 

 fection usually takes place through a wound or even 

 through a lenticel in the tuber. The fungus is char- 

 acterized by its production of macroconidia which are 

 4 to 6 septate, pionnotes are present, otherwise the 

 organism resembles F. martii. 



For control, see p. 337. 



Powdery Dry Rot 



Caused by Fusarium trichothecioides Woll. 



Powdery dry rot is a storage trouble which is pre- 

 valent in the arid and semi-arid sections of the 

 western part of the United States. The disease was 



