12 MASS. EXPERIMENT STATION BULLETIN 292 



growers have used carbon disulfide emulsion on a commercial scale. Their 

 results have been very satisfactory in some instances and very disappointing in 

 others. The most important factors contributing to the poor results have been 

 lack cf thoroughness of application and failure to remove the larger infested roots 

 of the old planting when cleaning out the beds, and subsequently to allow time 

 enough for the smaller roots to decay before treatment. The results of the writer's 

 experiments show that the success of carbon disulfide emulsion as a nemacide 

 depends chiefly upon the removal of the old roots and the thoroughness of applica- 

 tion. Unless these requirements can be complied with in commercial practice, 

 the use of chemicals is a futile and wasteful expense. 



RECOMMENDATIONS 



If the grower desires, or is obliged to resort to, chemical soil treatments he 

 should first decide on the choice of materials. If nematode is the only crop loss 

 factor, carbon disulfide emulsion should be used at a concentration of 1 gallon of 

 stock to 50 gallons of water. If fungous diseases alone are responsible, formalde- 

 hyde should be used at a concentration of 2/3 gallon to 50 gallons of water. If 

 both fungous diseases and nematode root-knot are factors contributing to the fail- 

 ure of the crop, formaldehyde (2/3 gallon) and carbon disulfide emulsion (1 gallon) 

 should be used in 50 gallons of water. Application should be at the rate of 1 gallon 

 of diluted chemical to each square foot of bed. At this rate of dilution and 

 application, the expense for chemicals used to sterilize 10,000 square feet would 

 be about as follows: 



Carbon disulfide emulsion, alone ... $90.00 



Formaldehyde, alone 70.00 



Carbon disulfide emulsion and for- 

 maldehyde combined 160.00 



To calculate the number of gallons of carbon disulfide emulsion needed, the 

 area to be sterilized is divided by 50. This quotient is multiplied by .68 and the 

 product obtained is the number of galbns of carbon disulfide required. To con- 

 vert gallons to pounds, multiply by 10. The quotient obtained by dividing the 

 area by 50 is multiplied by .06, and the result obtained is the number of gallons 

 of rosin fish oil soap required. This result is multiplied by 9, representing the 

 weight in pounds of each gallon of soap, to obtain the number of pounds of soap 

 needed. To calculate the number of gallons of formaldehyde needed, the area 

 to be sterilized is divided by 75 and the result is multiplied by 8, representing 

 the weight in pounds of each gallon of formaldehyde. Since the chemicals are 

 sold by weight only, it is necessary to know the number of pounds of each required 

 when giving the order. 



Preparation of the Beds for Treatment 



The roots of the previous planting should be carefully cleaned out and des- 

 troyed, and the beds should be kept moist by frequent watering for at least two 

 weeks to assist in the decay of the smaller roots in the soil. Since fresh roots are 

 likely to offer protection to the nematodes against the action of chemical, some 

 decay of the roots is considered desirable before the soil is treated. It is a rather 

 common practice in Massachusetts greenhouses to grow crops of lettuce or radish 

 in the fall and early winter months. The low growing-temperatures for these 

 crops inhibit the activity of the nematode, and root infestation is usually either 

 lacking or not important enough to warrant soil sterilization. In such a rotation 

 of crops, it would be best to delay the use of chemical until 7 to 10 days before 

 planting the spring crop of cucumbers or tomatoes. 



