204 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



any particular point ; but the air is blown out of the machine in a very 

 definite column and with much force. With our experimental fan, 

 objects that could be drawn in only when within a range of a few 

 inches, could be blown out many feet. This induced us to try blowing 

 the hoppers into a funnel-shaped receptacle. For this purpose a large 

 blacksmith's rotary bellows was used, with a large galvanized iron 

 funnel three or four feet in diameter for the receptacle. The black- 

 smith's bellows did not produce an air current of sufficient diameter; 

 for this to work successfully the diameter of the current of air 

 should be at least three or four feet, and this again would require 

 bulky machinery. The hoppers also held on very tenaciously to the 

 opposite side of the leaves when the air current was turned on them, 

 and thus it was impossible to get them all off the vine. While this 

 method of fighting the hoppers gave more promise of working success- 

 fully than the suction method, it would necessitate the use of rather 

 expensive and cumbersome machinery that would not appeal to the 

 practical vineyardist. 



Torches. On account of the difficulty of killing adult hoppers with 

 any spray while they are in the air, we tried the torch as a means of 

 overcoming this difficulty. The torch, which was tried, consisted of 

 burning the kerosene as it left a/i ordinary spray nozzle which would 

 throw a very fine mist spray. This was tried during the dormant 

 season on the hoppers as they would fly up from the vegetation growing 

 in the vineyards. Even with this many hoppers would escape around 

 the edges of the flame, and this, together with danger of scorching the 

 vine when in foliage, led us to put this method in the negative list of 

 remedies. 



Dry Powders. It has been very positively maintained by certain 

 growers that they could kill the nymphs of the vine hopper very 

 successfully by the use of air-slaked lime. In order to determine this 

 we made a number of experiments by keeping nymphs in all stages 

 in a vial and thoroughly dusting them and filling the air in the vial 

 with lime, but many did not appear to be inconvenienced by this 

 treatment. This method was carried out on a practical scale by thor- 

 oughly dusting a row of vines through a vineyard by means of the 

 French vermorel machine used in applying sulfur for the Oidium 

 (Fig. 16). The air-slaked lime had no effect whatever, so far as could 

 be observed, on the number of nymphs. 



Pyrethrum was used with better success in the laboratory experiments 

 where the hoppers were confined, but the results in the vineyard were 

 not at all satisfactory in controlling the nymphs. The expense, more- 

 over, of pyrethrum if used on such a large scale would be too great 

 to make this a practical remedy. 



