Family Solanaceas 329 



BLACK ROT OR JELLY END ROT 

 Caused by Fusarium radicicola Woll. 



This disease is seldom found in the field at digging 

 but is usually manifested as a storage trouble. It is 

 common in Idaho, Oregon, Washington, California, 

 Nevada, Mississippi, New York, Virginia, District 

 of Columbia, and certain parts of Pennsylvania. 



Symptoms. In the irrigated sections of California, 

 Oregon, and Idaho the trouble is manifested as a soft 

 rot termed " Jelly End Rot." The stem end soft 

 rots, and the affected portion may be easily removed 

 from the remainder of the tuber. The disease pro- 

 gresses inwards until the entire tuber within the skin 

 becomes soft and jelly like in consistency. If not 

 disturbed, the inside tissue will dry, and the skin per- 

 sist as a loose tunic, or it may shrivel and shrink, 

 giving the appearance of a dry rot. 



In the non-irrigated potato districts, the symptoms 

 of the disease are sunken, blackish, leathery areas on 

 any part of the tubers. In Pennsylvania the disease 

 is known as "black rot" or "black head.'* Micro- 

 conidia of the fungus are the dominant type of 

 spores. Chlamydospores are common and pseudo- 

 pionnotes are absent, while sporodochia are usually 

 present. 



Control. This disease does not make any progress 

 in storage at or below fifty degrees F. The trouble 

 is confined mostly to the Idaho, Rural, and Pearl. 

 So far as possible, these should be avoided and re- 



