THE SMUT DISEASE OF ONIONS 



By P. J. Anderson and A. V. Osmun 



INTRODUCTION 



Commercial onion growing in Massachusetts sixty years ago was confined to the 

 eastern part of the state, centering especially in Essex county about the Danvers 

 section. But continuous cropping brought diminishing yields year by year until 

 the growers found that they could no longer produce a profitable return on onions 

 even in that fertile section. New land must be found, and the industry shifted 

 gradually to the west until now practically all of the Massachusetts domestic supply 

 of surplus onions is produced in the Connecticut Valley. The fertile acres of the 

 Danvers section, famous onion center since colonial days, are no longer planted to 

 onions. 



When we inquire into the reasons for the diminishing crops and the westward 

 shifting of the industry we find that the most important contributing factor was the 

 increase in the prevalence and desti-uctiveness of smut until the toll which it took 

 wiped out the profits. A field once thorouglil}- infested with smut was permanently 

 eliminated from profitable onion growing, and since no method of checking the 

 disease had been discovered at that time, the ine^^table result was the migration of 

 the industry from a section so largely planted to onions. 



The Connecticut Valley region, however, did not long escape. Year by year, 

 smut became more prevalent; fields were being planted to other crops and the his- 

 tory of Danvers was in a fair way to be repeated along the Connecticut, when the 

 formaldehyde method of controlling smut was discovered and the industry saved 

 for the Valley. 



But the formaldehyde method as worked out by the pathologists of twenty years 

 ago was far from satisfactory. The formulas of application which they recom- 

 mended were cumbersome and the machinery inadequate. The writers were unable 

 to find a single grower in the Connecticut Valley who was applying the formaldehyde 

 according to the rates of dilution and distribution which were recommended by the 

 pathologists. Finding these inconvenient, the practical growers modified them in 

 various ways to suit themselves. The results obtained were more various than the 

 rates of application. Some were successful; many had partial control; others ruined 

 the crop. Lack of uniformly successful results caused many to condemn the method 

 and either to plant the fields to less profitable crops or to omit the formaldehyde and 

 tend the onion crop at a reduced profit or an actual loss. 



Such was the situation when the writers began their investigation of onion smut 

 in 1918. The whole field of control seemed ripe for a reworking. 



It was necessary that a formula of applying the formaldehyde be determined and 

 standardized for Connecticut Valley conditions, a formula which should be practical 

 for the grower and at the same time could be depended on to control the disease and 

 not cause serious injury to the onions. The machine for appUcation must be im- 

 proved. The behavior and hfe-history of the smut fungus throughout the whole 

 year must be carefully studied with the special object of finding a better method of 

 combating the disease. Many other minor problems were yet unsolved. 



During the last six years the investigation has been prosecuted in the laboratory 

 and greenhouse during the winter and in the fields of the onion growers of Sunder- 

 land, Amherst and Leverett and on the Experiment Station farm during the growing 

 season. It was essential that the field control experiments be continued through a 

 series of years on different farms because it was found that the season and other 



