BULLETIN 198. 



THE GRAPE LEAF-HOPPER. 



207 



and labor. The accurate weighing of such small quantities of cyanide 

 and the liability of injuring the vine or not killing the insects, if this 

 is not carefully done, make the method too complicated for the 

 practical vineyardists, besides being more expensive than other methods 

 of control discussed farther on. 



Some experiments were tried by a vineyardist near Lodi with burning 

 sulfur and liberating the gas in a drum enclosing the vine, as shown in 

 figure 18. A fire was made in a small cylinder on the side of the drum 

 and sulfur blown over this by means of an ordinary sulfur bellows, 



Fig. 18. An apparatus for fumigating with the fumes of sulfur, designed 

 by a vineyardist at Lodi. The tent in the background is for hydro- 

 cyanic acid gas. 



thus converting the sulfur into a gas which was conducted through a 

 tube entering the drum near the bottom. It was diificult to regulate 

 the amount of gas with this apparatus, so that the vines generally were 

 badly scorched. Some modification of this apparatus might be made 

 to work successfully; but sulfur fumes S0 2 , at least when used alone, 

 is not, apparently, a good insecticide, and on the other hand, plants are 

 very susceptible to injury ^by this gas. There is, therefore, a very 

 small margin, if any, between a dose that will kill the insects and not 

 injure the plant. A grower at Madera thought he could kill the 

 hoppers by burning sulfur between the vines. A handful or two of 



