FUMIGATION WITH CARBON BISULPHID 265 



varies considerably with the amount of the dose, the 

 temperature and humidity of the soil, and other con- 

 ditions. It has been found more satisfactory to employ 

 smaller and more frequent doses rather than a few 

 large ones. A dose of 5 or 6 grammes, */ 6 to '/ 4 ounce, 

 is believed to be thoroughly effective through a radius 

 of from 1 2 to 20 inches, though it may penetrate much 

 farther than that. The general rule is to make three 

 injections per square meter, nearly i'/ 6 square yards, 

 in light soils, and four injections in heavy soil. The 

 holes should be at regular intervals, so as to cover the 

 ground evenly, and never nearer than one foot to the 

 base of the vine. To be effective all the ground must 

 be treated. 



On account of the liability of injuring the vines it 

 has been found best to make the treatment in two small 

 applications, separated by an interval of from six to ten 

 days. This decreases the density of the vapor, but 

 continues its action for a much longer time. It 

 removes the danger of injuring the vines, and gives 

 even better results upon the insects than would be 

 obtained by one large dose. The total amount of car- 

 bon bisulphid to be used should be divided into as 

 many equal parts as there are injections to be made. 

 The holes for the second treatment should be inter- 

 mediate between those for the first. The depth of the 

 holes will depend somewhat upon the depth and per- 

 meability of the soil. The average depth is about one 

 foot. Holes 1 6 inches deep are desirable on very 

 permeable soil. 



Treatment may be applied at any season of the year; 

 but, as it is followed by a slight check in growth, it 



