8 



MASS. EXPERIMENT STATION BULLETIN 292 



(Table 6). The single treatment with carbon disulfide emulsion proved very effec- 

 tive and the double treatment gave complete control of the root-knot nematode. 



TABLE 6. — Comparison of One and Two Applications of Carbon Disulfide 

 Emulsion for Controlling the Root-Knot Nematode. 



(Spring Crop of Tomatoes, 1931. Field Station) 



Carbon Disulfide Emulsion 

 1 — 50 



I — One 



Application 



II — Two 



Applications 



No Treatment 



Root infestation per cent 



Apparently none 95.71 



Slight 



Severe 4.29 



Yield of 100 plants pounds 



Ones 735 



Seconds 293 



Total 1028 



100 

 

 



863 

 329 

 1192 





 67.30 

 32.39 





 62.50 

 37.50 



654 360 

 301 265 

 955 625 



Fall of 1931. — The purpose of this test was to determine whether successful 

 control of nematode on one crop, resulting from the use of carbon disulfide emul- 

 sion (Table 6), could be relied upon to provide control for the succeeding crop. The 

 plots of the previous experiment were again planted to tomatoes on August 24. 

 The plots were not sterilized, but the roots of the previous crop were cleaned out 

 well, and the top soil to a depth of 6 inches was removed. Records of root infesta- 

 tion were taken on January 19, 1932. In spite of the removal of the roots and 

 the soil, and the fact that excellent control of nematode was obtained on the 

 previous spring crop, a severe infestation developed in the fall planting (Plot B, 

 Table 7). The results show that the eradication of nematode in greenhouse 

 soils cannot be obtained with this chemical and that soil treatments must be 

 repeated previous to each crop in order to realize a profitable yield. Steam or 

 hot water methods of sterilization are no exception. Eradication has never 

 succeeded in commercial practice with the most efficient methods of steaming, 

 and there is no reason to expect better results from chemicals. 



TABLE 7. — Relation of the Degree of Control of Root-Knot with 



Carbon Disulfide Emulsion on One Crop to Infestation of the 



Succeeding Crop 



(Spring and Fall Crops of Tomatoes, 1931. Field Station) 



Spring Crop 



Plot A Plot B 



No Carbon Disulfide 

 Treatment Emulsion 



Fall Crop 

 Plot A Plot B 



No Treatment 



Root infestation per cent 



Apparently none 



Slight 67.60 



Severe 32.39 



Apparently none 



Slight 62.50 



Severe 37.50 



1 application 



95.71 







4.29 





 25.0 

 75.0 



2 applications 



100 



16.85 



83.14 





 10.93 

 89.06 



34.83 

 24.72 

 40.44 



