290 Diseases of Truck Crops 



It causes the greatest damage under poor storage 

 conditions. For methods of control, see p. 292. 



Botrytis Rot (fig. 52 b) is a storage trouble 

 usually of little importance. 



Black Mold 



Caused by Macrosporium parasiticum Thuem. ; 

 Macrosporium porri Ell. 



Black mold frequently follows injury from downy 

 mildews or any other causes which weaken the plant. 

 Spraying to control downy mildew will also prevent 

 this disease. 



Bulb Rot 



Caused by Fusarium sp. 



This disease is usually a storage trouble; but the 

 injury starts in the field and is favored by a wet sum- 

 mer season. The rot is prevalent in Ohio and Con- 

 necticut and possibly also elsewhere where onions are 

 stored in bulk. It works inward, attacking the heart 

 of the bulb so that the interior easily slips out. For 

 methods of control, see p. 292. 



Sclerotium Rot or Black Neck 



Caused by Sclerotium cepivorum Berk. 



Sclerotium rot is a serious storage trouble of white 

 onions in Ohio. The disease seems to be favored by 



