BULLETIN 198. 



THE GRAPE LEAF-HOPPER. 



209 



One pound of soap was used to fifteen gallons of water. In the case 

 of the resin one pound was used with fifteen gallons of water and enough 

 lye or potash to completely dissolve the resin. This is at the rate of 

 one pound of lye to about eight pounds of resin. 



The time to spray for the nymphs is when they first reach their 

 maximum numbers in the spring, just before the first of them change 

 into the adult winged hoppers. This was during the last of May and 

 the first of June during the past two years at Lodi. 



The spray should be applied from below and the under side of 

 every leaf thoroughly wetted with the solution, since the spray will 

 kill no more nymphs than it hits. This is not very difficult to do in 



Fig. 20. An apparatus designed by a vineyardist at Madera for use against 

 both the leaf-hopper and grasshoppers. The trough at the bottom con- 

 tains crude oil, into which the hoppers are supposed to fall upon hitting 

 the upright screen. 



May or early June, while the shoots are still comparatively short. The 

 best type of nozzle to use is the cyclone, with the spray emerging at 

 right angles with the long axis of the rod, shown in figure 19. This 

 will allow the operator to poke the rod anywhere among the vines with- 

 out its being caught. 



The spray is intended to kill the nymphs only. There are adults 

 always present which will escape, and the spray will not prevent what- 

 ever eggs may be present from hatching later. In bad cases of vine 

 hopper injury, however, it will pay well to do this spraying for the 

 nymphs, if the screen method, described below, has not been used or 

 the work not effectually done. 



