February, '22] DE long: GRAPE leaf hopper control 89 



At first seven disk nozzles were used. One was placed so as to point 

 downward from the horizontal pipe, midway between the vertical pipes, 

 and directly over the grape row. Three nozzles were placed on each 

 vertical pipe, one at the extreme lower end pointed upward at an angle 

 of about 45 degrees, another about a foot and one-half above directed 

 upward and slightly backward, and a third about three feet from the 

 bottom directed upward and slightly forward. The nozzles were fitted 

 to the vertical pipe by means of "T's", and an "Ell", which sufficed 

 in the case of the extreme lower one. The principal disadvantage en- 

 countered at the start was the spreading of the vertical pipes on the 

 application of pressure from the pimip, preventing a thorough applica- 

 tion to the foliage. This was readily overcome by a weight at the end 

 of each vertical pipe, and fully as good results were finally obtained in 

 spraying by removing the upper nozzle on each vertical pipe, leaving 

 only five nozzles arranged as described above. 



Three things are important in the construction. First, the lower 

 nozzle should be as close to the surface of the ground as possible, as 

 the lower portions are frequently most heavily infested by the nymphs; 

 second, the nozzles should be upturned at an angle of approximately 

 45°, but this will vary with the vineyard and a difference of 5° will 

 often cause a 15 to 20% difference in the killing; third, the lateral noz- 

 zles should be alternated slightly forward and backward. 



The driving spray from the up-turned nozzles raises the leaves and 

 covers the under surface thoroughly, while the nozzle above the vine 

 covers the upper surface. Under sufficient pressure a perfect mist was 

 obtained by this arrangem.ent of nozzles, and observations of the leaves 

 just after spraying proved that the greater percentage of immature 

 hoppers had been hit and killed by the spray. 



In the vineyard where this experiment was carried on, the undersides 

 of the leaves were almost covered with hopper nymphs, and an ex- 

 cellent chance was afforded to try out this apparatus on a large acreage. 



Comparing the two types of "set nozzle grape sprayers" the boom 

 system has certain advantages over the old type; first, the thorough 

 treatment of one row at a time, enveloping both sides of the vine in a 

 fine driving mist offering little opportunity for either nymphs or adults 

 to escape to safety; second, the up-turned nozzles lift the leaves and 

 thoroughly cover the under surfaces. As compared with the trailer 

 system the economic factors of time and expense are important. It 

 requires more than twice as long to spray with trailer nozzles than to 

 cover the same area twice with the boom system and an extra man is 

 necessary to operate the trailer nozzles. In other words the extra 5 

 to 10% killed by the trailer system costs as much as the first 80 or 85% 

 which can be obtained by the boom system and is an economic control. 



