552 INSECTS AFFECTING VEGETATION 



Smudge. This fungus (Vermicularia circmans} develops as a 

 superficial spotting upon the exterior, especially attacking the white 

 varieties; it is really an anthracnose of onions. For some time, be- 

 cause of its coincident development with the black neck or dry-rot, 

 these two troubles have been confused. It is now apparently clear 

 that there is no connection between the two, although this fungus 

 causes dry rotting of sets and bulbs. The smudge fungus is cumula- 

 tively worse on old land where onions are grown consecutively. Ap- 

 parently also in addition to rotation of crops the formalin drip 

 treatment described under smut gives good results in keeping down 

 this fungus. In field experiments made heretofore, the onions have 

 been lost in storage from the dry-rot and the smudge disease has not 

 been studied very fully in storage; apart from this it is believed to 

 have little or no connection with the commoner storage rots, although 

 the disfiguring effects of badly spotted onions reduce their market- 

 value, and rotting does take place as a result of it. The illustrations 

 give characteristic appearances of these compared with healthy 

 onions. (Ohio E. S. B. 214.) 



Onion Smut. The presence of smut in seedling onions is first 

 indicated by one or more dark spots at various points in the leaves 

 of the onion; these spots, especially when viewed by holding them 

 between the observer and the light, exhibit a dark, opaque character 

 in marked contrast with the remainder of the leaf. As growth pro- 

 ceeds these affected leaves die above while the dark spots are exposed 

 as sooty, powdery masses by the decay of the surrounding leaves. All 

 stages of disease from smut may be observed if one studies the seed- 

 ling when in the field. Some die soon after infection, others survive 

 for a longer time, while yet others continue to live despite the at- 

 tack of the smut, and though showing many evidences of smut, sur- 

 vive until the time for harvesting the crop is reached. Doubtless 

 other conditions than the fact of infection, such as lack of sufficient 

 moisture, will cause earlier death and, conversely, abundant moisture 

 may increase the resistance of the onion plant, largely by increasing 

 its vigor and power of resistance. When onion seedlings survive 

 for some time the smut will be found upon or within the bulb ; either 

 affecting the external layers, or attacking the inner layers, where its 

 presence is scarcely obvious from without. The tendency of such 

 smutted onions is to rot or dry up so that they are readily separated 

 from the healthy ones. This is particularly true in the handling of 

 onion sets and this fact greatly facilitates the separation of diseased 

 sets. (Ohio E. S. B. 122.) 



Suggestions for Preventing Onion Smut. The suggestions aris- 

 ing from the brief study made of this subject relate to general field 

 handling of sets and to the treatment of seed ; in both cases the ob- 

 ject is to reduce and prevent smut. Under the first heading every 

 method should be employed to reduce or destroy smut spores. To 

 this end it would appear practicable to collect all refuse from the 

 screening of the sets, either in shallow boxes or upon canvas and give 

 these a baptisrn of fire sufficient to destroy the spores. This material, 



