CARBON DISULFIDE EMULSION 9 



Spring of 1932. — In this set of experiments the influence of different rates of 

 application of carbon disulfide emulsion and the effect of removing the roots on 

 the control of the root-knot nematode were studied. The old tomato vines with 

 attached root clumps of the previous planting were removed on January 20. In 

 two of the three beds the smaller roots were carefully removed as the beds were 

 spaded, and in the third they were allowed to remain. 



The beds were treated on January 21, 1932, with carbon disulfide emulsion 

 of a 1-50 strength to which formaldehyde was added at the rate of 2/3 gallon to 

 each 50 gallons of diluted emulsion. Treatments were at the rate of two and 

 one gallons per square foot. The beds were set to tomatoes on January 29. 

 The roots were examined for root-knot on June 24 (Table 8). 



No yield records were taken, but none of the plants showed evidence of weakness 

 or failure to set during the growing period nor was the grade of tomatoes affected. 

 Infestation was not severe enough to affect the growth or yield. Two gallons of 

 carbon disulfide emulsion per square foot gave better control than one gallon; 

 but like the previous experiment one gallon per square foot removed the nematode 

 as a crop loss factor even when the smaller infested roots were left in the beds 

 (Table 8). 



TABLE 8. — Influence of the Rate of Application of Carbon Disulfide 



Emulsion and the Effect of Root Removal on the Control of 



THE Root-Knot Nematode. 



(Spring Crop of Tomatoes, 1932. Field Station) 



Roots Removed on Si'adint, Roots Not Removed 



2 gallons per 1 gallon per 1 gallon per 



square foot square foot square foot 



Root infestation. per cent 



Apparently none 92.0 31.6 16.9 



Slight 4.8 36.6 70.7 



Moderate 3.2- 26.6 12.3 



Severe 5.0 



Total infestation 8.0 68.2 83.0 



Discussion 



The experimental results show that carbon disulfide emulsion is an effective 

 nemacide and if used properly can be relied upon to eliminate nematode as a 

 serious factor in crop losses. Tomato plants were used exclusively in these 

 experiments and this fact strengthens the case for carbon disulfide emulsion, 

 since according to Jones (5) the nematode gall of the tomato plant offers greater 

 protection to its nematode population than that of the cucumber or lettuce plant, 

 and in addition bears the resistant "cyst" stage. It is logical to believe, therefore, 

 that carbon disulfide would offer better control when following crops of lettuce 

 or cucumbers than when tomatoes have preceded treatment. 



In the experiments reported, the root clump of each plant was dug out of the 

 soil when the old vines were removed from the greenhouse as a means of assisting 

 or rendering more effective the action of the chemical and of reducing the potential 

 nematode population of the soil (Fig. 11. Observations and experiments show, 

 however, that this practice alone offers no control of nematode. Naturally, the 

 smaller infested roots were left behind, but judging from the results in Table 1, 

 carbon disulfide emulsion is apparently nemacidal to small, fresh galls. Soil heating 

 with steam or hot water would appear to be superior to chemicals in its nemacidal 

 effect, especially if the galls possess much root covering tissue. Obviously, the 

 removal of such galls before sterilization should assist materially in the control 



