686 Journal of Agricultural Research voi.xx, N0.9 



has been much used up to the present time. However, since the symp- 

 toms have little in common with those of the more common anthrac- 

 noses, and since it is believed that as simple and as descriptive a 

 name as possible should be chosen, the name "onion smudge" is used in 

 this paper to designate the disease, and this name is recommended 

 for general usage. 



HOST PLANTS 



White varieties of the onion (Allium cepa) are the chief ones affected 

 by smudge, but all varieties thoroughly tested have been found sus- 

 ceptible to at least a slight degree. The disease also occurs on shallots 

 (A . ascalonicum) and on leek (A . porrum) . It has never been found on 

 garlic (A. sativum). 



HISTORY AND GEOGRAPHICAL DISTRIBUTION 



Onion smudge was first described in 1851 by Berkeley (4) in England, 

 where it was found on the outer scales of a white variety. Subsequent 

 reports of its occurrence in Europe have been made by Massee (77) in 

 England, Bubak (8) in Bo 1 ^ emia, and Voglino (35) and Allescher (1) in Italy. 



The first collection of this disease in America, made by Michener, was 

 reported by Berkeley (5) in 1874. Since that time it has been re- 

 corded in literature as occurring in Rhode Island (3), Connecticut 

 (10, 19, 33), New York (20, 22), New Jersey (13, 25), Ohio (26), In- 

 diana (21, 34), Illinois (30), Wisconsin (23), and Alabama (2). Addi- 

 tional data furnished by the Plant Disease Survey show that it has 

 been present also in Massachusetts, Pennsylvania, Delaware, Mary- 

 land, Virginia, Georgia, Louisiana, Texas, Minnesota, and Iowa. 



It is thus a disease of widespread occurrence; and, indeed, when one 

 considers the fact that thousands of bushels of infected "bottom "sets 

 are being shipped annually to all parts of the country and abroad, it is 

 reasonable to suppose that its distribution is even more general than 

 this summary indicates. 



DESCRIPTION OP SMUDGE (PL. 80, 8l) 



The disease is confined entirely to the scales and the lower portions of 

 the unthickened leaves which constitute the neck of the bulb. It first 

 becomes manifest upon the appearance of minute stromata which form 

 just beneath the cuticle of the host. These are dark green at first, be- 

 coming black with age. Depending on conditions of infection, the indi- 

 vidual stromata may be scattered miscellaneously over the surface of 

 the bulb, or, as is more commonly the case, they may be congregated in 

 smudgy spots around a few centers of infection. These spots are usually 

 roughly circular and variable in size. They often coalesce and occa- 

 sionally contain stromata arranged in concentric rings. Under moist 

 conditions the stromata bear acervuli which contain prominent setae 

 readily distinguished with a lens of low magnification. Cream-colored 

 spore masses frequently form on these fruiting bodies. 



