54 ROOT-KNOT AND ITS CONTROL. 



2 gallons per square yard, would be about $150 exclusive of labor, 

 which would include the hauling of 5,000 to 10,000 gallons of water. 



Calcium carhid. — At Monetta, S. C, experiments were made vnth 

 calcium carbid. It was strewn in furrows which were then covered 

 over so that the resulting acetylene gas should penetrate throughout 

 the soil, or it was applied as a solution in water. The amount of root- 

 knot was reduced, but in all cases where the reduction was great the 

 injury to the crops, especially to tomatoes, was also great. Better 

 results were obtained from the dry apphcation in 2-inch furrows than 

 from the solution. Planting was not undertaken for a week or two, 

 but still the results were such that in spite of replanting a second and 

 even a third time the test crops — okra, beans, tomatoes, and cowpeas — 

 were badly killed out. The odor of acetylene was perceptible for sev- 

 eral days. The fairly effective amounts were 1,500 pounds per acre, 

 dry, in shallow furrows or a solution of 5 pounds per 100 gallons of 

 water applied in deep furrows, 1 to 2 gallons per square yard. In 

 view of the high cost of the treatment (at 10 cents a pound this would 

 be $150 per acre exclusive of labor for the dry application and $25 to 

 $50 for the solution) this method can not be recommended. The 

 injury to vegetation is also against it. 



Potassium sulpTiocarhonate. — This salt is obtained commercially as 

 a concentrated dark-brown solution, smelling strongly of sulphureted 

 hydrogen. Gandara ^ states that it has been tried against phylloxera 

 in France and recommends it for root-knot, at a rate of 1 part 

 of potassium sulphocarbonate to 5 parts of water. Accordingly, the 

 following experiments were outlined. Plats of land were laid off as 

 follows: (1) Check, no treatment; (2) 10 parts of the chemical to 

 90 parts of water, 2 quarts per square yard in holes which were quickly 

 filled; (3) 1 part to 99 of water poured on the surface at a rate of 

 2 gallons per square yard, that being the quantity necessary to wet 

 the surface thoroughly; (4) a similar quantity of a solution of 1 part 

 to 199 of water; (5) check. After a few days beans, tomatoes, okra, 

 and cowpeas (New Era) were planted. In all cases where the 

 chemical was used, both weak and strong, the tomatoes, okra, and 

 beans were to a large extent killed, but the cowpeas were not hurt. 

 Root-knot was present, however, even where the solution was the 

 strongest. As a fungicide, too, this chemical had little value, for 

 Rhizoctonia was very abundant at the crowns of all the plants. 



For field use, then, this chemical is not to be recommended as a 

 means of combating the root-knot nematode. 



Ammonium sulphate. — Van Breda de Haan^ recommended against 

 the nematode on tobacco in the Dutch East Indies the use of am- 

 monium sulphate followed by quicklime. The latter sets free the 



> Q&ndara, 1906. > Breda de Haan, 1905. 



217 



