Family Liliaceae 285 



covered by the host epidermis. Chive rust is dis- 

 tinct from the onion rust. 



DISEASES OF THE ONION (Allium cepa) 



The onion is commonly attacked by numerous dis- 

 eases. Fortunately most of them may be controlled, 

 by proper care, and timely preventive methods. 



Soft Rot 



Caused by Bacillus caratovorus Jones. 



The disease was first studied by Stewart, * who how- 

 ever did not determine the causative organism, but 

 merely referred it to a species of Bacillus. The writer, 

 however, was able to prove that soft rot of onions is 

 caused by the same organism which causes a similar 

 rot on carrots and other vegetables. 



The rot on the onion often starts at the neck of the 

 bulb which is spoken of as " weak in the neck." Sound 

 bulbs are hard at the neck, but when rot sets in, the 

 outer layer remains sound while the interior tissue 

 soft rots (fig. 53 a) . Sometimes a single scale is found 

 rotted within the bulb, and the others apparently 

 remain healthy. At other times a sound scale may 

 be found between two rotted ones. Occasionally 

 the rot is confined to the outer fleshy scale, in which 

 case it is spoken of as "slippery onion. " In storage, 



1 Stewart, F. C, New York (Geneva) Agr. Expt. Sta. Bui. 164: 

 209-212, 1899. 



