CONTROL OF THE GRAPE-BERRY MOTH. 



31 



applied safely. However, the combination of arsenate of lead and 

 soap alone produced slight burning of foliage in 1916. (Bartlett 

 vineyard, Plat VII.) 



No serious staining of fruit occurred except when the second- 

 brood spray was applied in August in 1916. This was much reduced 

 by using the arsenate of lead and soap with lime instead of with 



Bordeaux mixture. 



Method of Application. 



The first season's experiments clearly demonstrated the difficulty 

 in covering grape clusters by the " set-nozzles " applications. This 

 was particularly inadequate at the last application, at which time 

 the foliage is very heavy, and pressure up to 250 pounds was not 

 effective. The use of " trailers" on a few plats for the last appli- 

 cation suggested the complete change of method which followed the 

 next season. 



A specific demonstration of the inadvisability of depending on 

 "set nozzles" as a means of applying spray was shown in 1915 by 

 the contrast between Plats I and X in the Miller and Carlburg vine- 

 yard. 



The necessity of using " trailers " was so satisfactorily established 

 in the first two seasons that during 1916 "set nozzles" were not used 

 in both applications in any plats. However, in the Moorhead vine- 

 yard, Plat IV, and in the Southwick vineyard, Plat IV, "set nozzles" 

 were tried for the first application. In the former, at the time of 

 the first application, the results were reasonably satisfactory, 

 although not the best. In the latter vineyard the foliage was very 

 heavy when "set nozzles" were used, and the failure to cover the 

 clusters with spray was obvious. The reduction of infestation that 

 resulted should be credited largely to the last application, which 

 was made with "trailers." 



The relative efficiency of "set nozzle" and "trailer" methods of 

 application and a combination of these methods is shown in Table 22. 



Table 22. — Relative efficiency of "trailer" and "set nozzle" methods of application. 



(Treatments common to all plats: Arsenate of lead, 3 pounds paste or 1J pounds powder; laundry- 

 soap, 1 pound; Bordeaux mixture (3-3-50) applied after falling of blossoms and when grape berries 

 were just touching.) 



Method of application. 



Years 

 tried. 



Num- 

 ber of 

 vine- 

 yards. 



Num- 

 ber of 

 plats. 



Infested grape berries. 



Best 

 plat. 



Adja- 

 cent 

 check. 



Poor- 

 est 

 plat. 



Adja- 

 cent 

 check. 



Aver- 

 age of 



all 

 plats. 



Aver- 

 age of 



all 

 checks. 



'Trailers/' 2 applica- 

 tions 



'Set nozzles," 1 appli- 

 cation; "trailers," 1 

 application 



'Set nozzles," 2 applica- 

 tions 



1915, 1916 



1916 

 1915 



Perct. 

 0.89 



6.61 



20.41 



Per ct. 

 50.43 



38.43 



Perct. 

 8.43 



19.13 

 20.41 



Per ct. 

 75.16 



65.65 



Per ct. 

 4.12 



12.87 

 20.41 



Per ct. 

 50.03 



52.04 

 28.80 



