40 U. S. DEPARTMENT OF AGRICULTURE. 



scales as does neck rot, but usually follows certain scales 

 all the way around. 



Slimy soft rot occurs in all onion-growing districts in the 

 United States, and is most common in onions harvested dur- 

 ing warm, rainy seasons, or in onions sun-scalded during the 

 curing process. It is also very common in Spanish onions. 

 It is claimed by growers that yellow varieties are more sus- 

 ceptible than red. Careful handling to avoid sun-scald and 

 bruising during the harvesting operation is of primary im- 

 portance as a preventive measure. 



In badly affected shipments, immediate drying of the 

 stock will check the progress of the rot. This may be done 

 by dumping the sacks at once and spreading the contents. 



Ref. (67). 



ONION: SMUDGE. 



Cause: A fungus (Colletotrichum circinans). 



Smudge or anthracnose is a disease of white onions char- 

 acterized by black blotches or aggregations of minute black 

 dots on the outer scales. Each one of the minute dots is an 

 acervulus (plural, aceryuli). These acervuli are often ar- 

 ranged in concentric rings. In severe cases, the smudgy 

 spots are so extensive that the side of the onion appears 

 smoked. Generally the smudge is on the outside scales, 

 though it may appear on the inner scales as well. It should 

 not be confused with the black powder which is character- 

 istic of black mold. 



It is of widespread geographic distribution, but only white 

 varieties are seriously affected. Infection takes place in 

 the field from the fungus which overwinters in the soil. The 

 disease appears shortly before the harvest, and develops 

 rapidly in the crated onions after the harvest if the weather 

 is moist. It causes very little shrinkage of affected bulbs, 

 the chief damage being due to the appearance and reduced 

 market value of affected bulbs. 



Smudge can be prevented by rapid curing of the crop as 

 soon as it is harvested. If the bulbs are stored in a dry place, 

 the disease makes little progress. In a moist atmosphere, 

 the fungus penetrates from scale to scale, and causes a soft- 

 ening of the tissues. 



Ref. (72). 



ONION: SMUT. 



Cause: A fungus (Urocystis cepulae). 



Onion smut appears as dark-colored, slightly raised 

 streaks or blisters on the bulbs and leaves. The leaves are 

 often recurved and distorted. Sets may be greatly shrunken 

 with the whole exterior covered with the blisters. When cut 

 open, these ridges or pustules are found to be filled with a 

 greenish black powdery mass. Smut differs from black mold 

 in that the black powder is within the tissues of the scale, 

 not upon or between the scales. 



