14 



H. H. Whetzel and John M. Arthur 



some experimental work on the control of the disease by means of soil 

 disinfection. The junior author undertook the work of carrying out 

 these experiments in the fall of 1922. The bed in which the experiments 

 were conducted was 66 feet long and 5 feet wide (figure 5). It was bounded 

 on one side by a cement walk and on the other by upright boards about 



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r- - Check - *i 7% lbs. formalin | — Check - -\ Ijlbs formalin i- - Check - -! 10 lbs. formalin < 

 Figure 5. plan of the plots in the 1022-1923 control experiments 



6 inches wide. This area was divided into six plots. The first five plots 

 were each 10 feet long, and the sixth was 11 feet long. An isolation strip 

 about 1 foot wide was left between adjoining plots. These isolation strips 

 were set off from the adjacent plots by upright board partitions sunk 

 some inches into the soil. Each plot thus contained 50 square feet of 

 planted space, but, since every other plot (nos. 2, 4, and 6) and its adjoin- 

 ing isolation strips were treated with formalin, the treated areas each con- 

 tained approximately 60 square feet. 



Although the disease had appeared only in certain parts of this bed, 

 in preparing the bed in the spring of 1921 an attempt was made to thor- 

 oughly distribute the pathogene before dividing the bed into plots The 

 diseased bulbs had not been removed in any numbers but had been allowed 

 to rot down, and presumably an abundance of sclerotia were formed. 



Plots 1, 3, and 5 (figure 5) were left untreated as checks. To plot 2 

 with its adjoining isolation strips A and B, and to plot 4 with its adjoining 

 isolation strips C and D, was applied 7 5 pounds of 40-per-cent formalin 

 each, diluted with water at the rate of 1 to 50. Plot 6 with its adjoining 

 isolation strip E received 10 pounds of formalin diluted with water at 

 the rate of 1 to 50. The solution was applied as evenly as possible in each 

 case, and the lied was then covered with tarred paper. The soil had been 

 wet by a rain the day before treating. 



The formalin was applied on October 11, 1922. The tarred paper was 

 removed on October 23. The bulbs purchased from importers were first 

 peeled, that is, the dry brown scales were removed. All cankers or 

 diseased spots in the fleshy outer scales were carefully cut out, and the 

 bulbs were then disinfected hy soaking for one hour in a l-to-120 solution 

 of formalin, after which they were rinsed through three changes of tap 

 water and spread out to dry. 



The bulbs were planted in four rows lengthwise of the plots, none being 

 set in the isolation strips. There were approximately fifty bulbs in each 

 plot. The check plots 1, 3, and 5 were planted first, the treated plots 



