Isifivv York Agricultural Experiment Station. 71 



ually increases from year to year until finally it becomes so 

 destructive that a profitable crop of onions can no longer be 

 grown. Onion smut seems to be affected but little by weather 

 conditions and is not subject to sudden fluctuations in virulence. 



MODE OF DISSEMINATION. 



Onion smut is chiefly a soil-inhabiting fungus. It rarely gets 

 away from the soil except as it is carried on the bulbs. Unlike 

 many fungi, its spores are not carried by the wind except, per- 

 haps, for very short distances in times of heavy wind when 

 considerable quantities of soil are moved. 



It is not carried on the seed, but on the bulbs it may travel 

 long distances. It is carried short distances, as for example, 

 from one field to another in the same neighborhood or from one 

 part of a field to another part of the same field, on tools used in 

 cultivation, on crates, barrels and bags, on the feet of men and 

 horses, with onion refuse used as fertilizer, and by the washing 

 of the soil during heavy rains. 



Many onion growers are accustomed to dispose of their onioB 

 refuse by spreading it on the land as fertilizer. This practice is 

 to be condemned as it unquestionably serves to spread the smut. 

 Unless it can be used on land not designed for growing onions 

 or on land already thoroughly contaminated with smut (in which 

 case the damage is inappreciable) it had better be allowed to go 

 to waste. Especially is this true since the fertilizing ingredienta 

 in a ton of onions are worth only about 50 to 60 cents and a large 

 part of this is lost by the escape of the nitrogen in decay. 



METHODS OF COMBATING THE DISEASE. 



BY THE USE OF LARGER QUARTITIES OP SEED. 



When much smut is present in the soil the chief difficulty is to 

 secure a " stand " of plants. To overcome this, onion growers 

 are in the habit of using larger and larger quantities of seed oa 

 the smut increases year by year. 



