to other crops for four years, it would then raise a smut-free crop of onions. He did 

 not think that the spores were carried by wind and in order to prevent tlie carrying 

 of spores to uninfested fields, he recommended thorough cleaning of all tools which 

 had been used on smut-infested land. Thaxter (44:138) on the other hand, finds 

 that a badly infested crop of onions was grown on a field which had not been planted 

 to onions for twelve years. Sirrine and Stewart (37:149) find in regard to the value 

 of crop rotation: "it is the common experience of onion growers that even an occa- 

 sional change of the crops for one or two years gives appreciable rehef ; and it is our 

 belief that a systematic rotation of crops would very considerably reduce the amount 

 of loss from smut." Farlow was also the first to recommend that all smutted onions 

 be pulled during the growing season while the crop is being weeded, and that they 

 be removed from the field and burned. It is not recorded in hterature that this 

 method was tried by any grower. 



The first accurate experiments of any value on control are those of Thaxter 

 (44:146) who was at that time mycologist of the Connecticut Agricultural Experi- 

 ment Station. He apphed various dry chemicals to the soil in the drills to see 

 whether anj^ of them would prevent infection of the seedhngs by the fungus. The 

 chemicals used were copper sulfate, iron sulfate, sodium sulfide, potassium sulfide, 

 potassium chloride, calcium chloride, socUum hyposulfite and flowers of sulfur. Air 

 slaked lime was tried also in combination with some of them. The mixture of air 

 slaked lime and flowers of sulfiu" gave a fair percentage of control. The others 

 injured the germinating seeds, or were of little or no value in preventing smut, or 

 their use was impracticable. He repeated the experiments the following year 

 (45:103) and again was able to increase by a ratio of about 5:1 the number of onions 

 which could be raised on badly infested land, by the use of flowers of sulfur. Thax- 

 ter, himself, however, was not very enthusiastic in his recommendation of the 

 method and two years later his successor, Sturgis (41:14) WTites concerning it: "It 

 seems probable now that the measure of success attending tliis treatment will 

 hardly warrant its extended adoption." 



The sulfur-hme treatment was thoroughly tested by Sirrine and Stewart (37 : 152), 

 their field experiments extending over a period of five years. As a result of all their 

 experiments they conclude (37:145) "that the yield of onions on smutty land may 

 be greatly increased by the apphcation of 100 pounds of sulphur and 50 pounds of 

 air-slaked lime per acre in the drills at the time of sowing the seed. In several 

 instances the yield has been increased at the rate of more than 15,000 pounds per 

 acre as compared with untreated plats. Sulphur alone has considerable value as a 

 preventive of smut, but seems more efficient when mixed with lime. The sulphur 

 and lime should not be apphed broadcast as they appear to have no effect on the 

 smut when apphed in that way. The sulphur-hme treatment is recommended 

 whenever the loss from smut is as much as one-third of the crop." 



Thaxter (44:146) found that infection occurred only in the very young seedling 

 stage. Thus, when the plants were started in sterile soil and then transplanted to 

 the field, they never suffered from smut. Sturgis (42:176) made extensive field 

 tests of this method and demonstrated that it was an absolute preventive of smut. 

 It was also recommended by Sirrine and Stewart (37:145). This most effective of 

 all methods of control has not been adopted bj^ onion growers in general because the 

 amount of labor and time required for transplanting is so great as to render it im- 

 practicable where onions are grown on a large scale. 



Burying of the surface soil has been tried with some success, but the labor in- 

 volved is excessive (37:149). 



The use of larger quantities of seed on smut infested land has been tried (37:149) 

 but as pointed out by Sirrine and Stewart "there comes a time when it is impossible 

 to obtain a stand no matter how much seed is used." Such a method is also imprac- 

 tical on a field which is unevenly infested, because the onions are too thick on 

 lightly infested parts of the field and laborious thinning is necessitated. 



In 1900 Selby (35:76) began experiments in Oliio, using the hme and sulfur 

 treatment as recommended by Thaxter, various other chemicals, quick hme and for- 

 maldehyde. After the first year's experiments (1900) he abandoned all but the 

 formaldehyde and the quick lime since they alone gave promising results. All the 

 experiments were on seed sowed very thickly (about 40 pounds per acre) for the 

 production of sets. During the second year he used only the quick Hme and the 



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