236 Journal of Agricultural Research voi. xxii. no. s 



survey which he made some two years ago of the chief onion-growing 

 centers of the entire country, as a representative of the Office of Cotton, 

 Truck, and Forage Crop Disease Investigations of the United States 

 Department of Agriculture. In connection with this, he personally 

 inspected the leading onion-growing sections of Texas and Louisiana 

 and conferred with the plant pathologists of these two States, Drs. C. W. 

 Edgerton and J. J. Taubenhaus. No evidence of the disease was found, 

 and it had not been reported to the Experiment Station of either State.^ 



In comparing the distribution and occurrence of onion smut in differ- 

 ent sections of the country, it is necessary to keep in mind that two 

 distinct types of onion culture are practiced in the United States. The 

 first is followed in practically all of the northern sections, the second is 

 the rule in the southern commercial growing regions, and in one or more 

 sections in the Pacific coast States. In the first, or northern, type the 

 seed is sown directly in the field as early in the spring as the soil can be 

 properly prepared — that is, in March, April, or May, according to local 

 climatic conditions. The bulk of the crop is harvested in these northern 

 districts in August and September. The Globe varieties predominate, 

 including the red, yellow, and some white. In the second, or southern, 

 type of culture the seed is sown in special beds in late summer. The 

 seedlings are tlien transplanted to the main field during the early winter 

 months and the crop is harvested during the period from April to July. 

 Here the Bermuda, Italian, and Spanish varieties predominate. The 

 survey previously referred to brought out the fact that onion smut has 

 become established in essentially all of the older onion-growing sections, 

 which practice the first type — with spring sowing of seed — while smut 

 is either entirely unknown or of no economic importance in those locali- 

 ties where the seed is sown in summer followed by transplantation. 

 Wherein lies the explanation? As already suggested, it can not be due 

 to the matter of chance introduction of the organism. This is certainly 

 being distributed frequently and widely throughout the South. It would 

 seem rather to be associated with some of the factors incident to the 

 southern type of culture. The conspicuously different factors as out- 

 lined above are three: (i) The varieties used, (2) transplantation vs. 

 direct seeding, (3) climatic differences associated with season of culture. 



Greenhouse experiments, in which we have tested the different types, 

 have shown that the Bermuda and Spanish varieties which are used in 

 the South are as susceptible to smut infection as are the Globe varieties 

 of the northern sections. Hence varietal resistance does not furnish the 

 explanation. Turning to cultural methods, we find that in the South the 

 seed beds in which the onions are grown preliminary to transplantation 

 are usually of considerable size and are located as a rule in a portion of 



1 The authors are indebted to Doctors Edgerton and Taubenhaus for continued cooperation in the search 

 for the smut in their respective States. They each reported again early in the current year that not a 

 single specimen had as yet been found. 



