MARKET DISEASES OF VEGETABLES. 41 



Onion smut is common in northern growing regions, espe- 

 cially in Wisconsin, Illinois, New York, Ohio, Iowa, and 

 Massachusetts. 



The fungus persists in the soil, and infection occurs when 

 the plants are seedlings. Badly infected plants are usually 

 killed and large losses are thus caused in the field. There 

 is no progress of the disease in storage or transit. Smut is 

 uncommon in the market except on onion sets. 



Control measures are planting in clean soil or the use of a 

 formaldehyde drip on the seed drill. 



Ref. (71). 



ONION: MISCELLANEOUS DISEASES. 



BLOTCH. 



Cause: A fungus (Macrosporium). 



The name "blotch" has been temporarily adopted for this 

 blemish on the outer scales of red and yellow varieties of 

 onions. The symptoms are large bleached or greenish dis- 

 colored areas on the bulbs, bearing numerous fine black 

 linear marks or ridges parallel to the veins. 



BLUE MOLD. 



Cause: A fungus (Penicillium). 



Under certain conditions in storage or transit, blue mold 

 occurs on the outside of the bulbs, and is usually associated 

 with insufficient ventilation and some predisposing injury to 

 the tissues, such as wounds, freezing, or sun-scald. 



While most fruits are subject to attack by species of Peni- 

 cillium, among vegetables, only onions, sweet potatoes and 

 sweet corn are commonly attacked. 



FUSARIUM ROT. 



Cause: A fungus (Fusarium). 



This rot usually but not always proceeds from the base 

 of the bulb. The affected region is soft and flabby and be- 

 comes shrunken and shriveled in appearance. The surface 

 may be studded with small white pads, the fruiting bodies 

 of the causal fungus. There is no development of gray mold 

 or black sclerotia as in neck rot. 



GRAY MOLD SPOT. 



Cause: A fungus (Botrytis). 



This disease causes a bright red lesion on the neck at the 

 ground line, which results in the death of the outer leaf. At 

 times a slight outgrowth of gray mold may be formed in the 

 lighter colored center of the lesion. Gray mold spot is found 

 only on winter-grown green onions in the spring, and has 

 been noted in the Kansas City market gardens. 



SUN-SCALD. 

 (See Sim-Scald). 



