266 FUMIGATION METHODS 



should not be applied either at the flowering or fruit- 

 ing season, as the check would injure the crop most at 

 those seasons. The injury to the vines results' from 

 the killing of the tender, fibrous, feeding roots. It 

 would therefore be better to apply the treatment before 

 these roots have started in early spring, or after they 

 have become hardened in the fall. The condition of 

 the soil usually favors the spring treatment, and the 

 condition of the insect is said to make it more suscep- 

 tible at that time. 



Amount to use per acre. To secure extinction it is 

 usual to apply about 300 grammes, nearly 10 ounces, 

 per vine, using 150 grammes in each of two applica- 

 tions ten or twelve days apart. This will kill ninety- 

 nine out of every hundred vines. In cultural treat- 

 ment the amount of the liquid to be used varies from 

 140 to 265 pounds per acre. 



Instruments for application. One of the principal 

 difficulties in the first use of carbon bisulphid was to 

 force the vapors to the desired depth. When first 

 used below the surface it was poured into holes formed 

 by driving an iron bar with a maul. The demand for 

 a more convenient, accurate, and rapid working in- 

 strument was soon met by the invention of the pal- 

 injector by M. Gastine. This instrument was later 

 improved by M. Vermorel. The carbon bisulphid is 

 placed in a large chamber, from which an outlet leads 

 down through a series of valves, so adjusted that the 

 amount of each discharge can be exactly regulated as 

 desired, and opens near the tip of the pointed bar. 

 The instrument is forced into the ground by the 

 handle and the pressure of the foot upon the spur to a 



