CARBON DISULFIDE EMULSION 5 



Preparation of Bei^s. — The larger infested roots of the old crop were removed 

 when the plants were cleaned out, but in one instance (Table 8) these were left 

 in the ground for comparison (Fig. 1). In most of the experiments three to 

 four weeks elapsed after the removal of the previous crop to permit decay of the 

 roots, but shorter intervals were used in some cases in order to determine to what 

 extent the decay of the roots influenced the effectiveness of the chemical. If 

 the soil was dry, it was wetted well with water a day before treatment. 



Application of the Chemical. — Some of the beds were dug over and left rough 

 and then drenched. Others were dug as the chemical was applied. The usual 

 application was at the rate of 1 gallon of diluted emulsion to each square foot of 

 bed, but in some instances more was applied for comparison. The thoroughness 

 of application and penetration in the subsoil are important factorsjnfluencing the 

 efficiency of steam or hot water methods of sterilization, and this fact was fully 

 appreciated in the use of chemicals. Walls adjacent to the beds were also drenched. 

 After the beds were treated they were wetted further with water. 



Experiments in a Commercial Greenhouse 



Spring of 1930. — Four beds were treated with carbon disulfide emulsion, to 

 determine the effect of different concentrations of carbon disulfide emulsion on 

 the control of the root-knot nematode and the consequent yield and income 

 cf tomatoes. The stock emulsion was used at concentrations of 1-25, 1-50, 1-75, 

 and 1-100 gallons of water, and applied at the rate of 1 gallon to each square foot 

 of bed. The treatments were made February 21. The roots were well decayed 

 when the plots were spaded in preparation for the treatments. 



Potted tomato plants which were grown in steam sterilized soil were set in 

 the beds five days after the treatment. A control plot adjoined each treated plot. 

 Careful yield records were kept. No records of root infestation were made, but 

 examination of the roots when the plants were pulled on July 17, 1930, revealed 

 some root infection in all the treated plots. The plants in all of the treated 

 plots maintained a healthy, turgid growth, produced a good set, and the tomatoes 

 were practically all of first grade. In the control plots the plants produced a 

 poor set, and wilting, which is characteristic of a severe infestation of nematode, 

 was very pronounced. One-half of the yield of the controls was of second grade 

 fruit. The results clearly show the merit of carbon disulfide emulsion in eliminat- 

 ing the nematode as a factor in crop loss (Table 2). 



TABLE 2. — Effect of Different Concentrations of Carbon Disulfide 



Emulsion on the Control of the Root-Knot Nematode and the 



Consequent Yield and Income of Tomatoes 



(Spring Crop, 1930. Commercial Greenhouse) 



Dilution of 

 Carbon Disulfide Emulsion No 



-Treatment 



1-25 1-50 1-75 1-100 



Cost of chemical for 100 square feet $ 1.88 $ 0.94 $ 0.59 $ 0.47 



Yield of 100 plants pounds 695 719 720 672 403 



Increase in yield pounds 292 316 317 269 



Gross income from 100 plants at 23 cents per pound $159.85 $165.37 $165.60 $154.56 $64.48* 



Increase in gross income $ 95.37 $100.89 $101.12 $ 90.08 



Since approximately 50 per cent of the crop from the control plot was of second grade, the 

 income from that plot is calculated on the basis of an average of 16 cents per pound. 



