8 BULLETIN 837, IT. S. DEPARTMENT OF AGRICULTURE. 



was applied when the grapes touched in the clusters, but before the 

 clusters were tight enough to prevent the spray material from being 

 driven between the grapes. This stage of grape growth usually oc- 

 curs from 3 to 4 weeks after bloom. This second spraying was 

 designed to kill the late hatching first-brood larvae and to remain 

 on the grapes to be effective- when the second-brood larvae hatched. 

 The third spraying was timed in each case to precede immediately the 

 hatching period of the majority of second-brood larvae. 



METHOD OP APPLICATION. 



All spraying was done by the hand or trailer method in which 2 

 hose lines of from 20 to 50 feet trail behind the sprayer, and the 

 spray material is delivered through short spray rods and angle noz- 

 zles, directed by hand as in tree spraying. Variations in this method 

 will be discussed later. Sufficient pressure was maintained to drive 

 the spra} T well into the clusters, but the amount of pressure varied 

 from 125 to 225 pounds in different vineyards. The best pressure to 

 maintain will vary somewhat with the vineyards, but the writers 

 believe that from 175 to 225 pounds usualty will be found most 

 efficient. Nozzles set at an angle are absolutely necessary for efficient 

 work, and it was found that nozzles set at angles of 45° allowed 

 more freedom of handling than those set at 90°. A nozzle aperture 

 of T Vinch was most commonly used, but the most efficient size was 

 found to vary with the vineyard and other local conditions. 



WEATHER CONDITIONS 1 AFFECTING SPRAY RESULTS. 



The season of 191G was about normal in all respects except for an 

 unusually dry period during July and August which was favorable 

 for spraying and for spray material adhering. These same condi- 

 tions were likewise favorable for the development of an unusually 

 large second brood of worms. September and October were warm 

 and dry, conditions also favorable to extensive berry moth injury 

 as shown in the uniformly heavy infestation in the checks (Table IV). 



In 1917 conditions were decidedly unfavorable for spraying opera- 

 tions. Both the first and second applications were interfered with 

 by rain and closely followed by showers of varying intensities. In 

 July the total rainfall was but 0.46 inch, but this came between the 

 first and second spray applications. The maturing of first-brood 

 larvae was favored by an exceedingly hot and dry period from July 28 

 to August 6 and a subsequent heavy hatching of second-brood 

 larvae followed. September was 3.3° below normal in temperature 

 and slightly below in precipitation, while October was 8.3° below 

 normal with 3.79 inches of rainfall above normal. These unfavorable 



1 Weather records from the U. S. Weather Bureau Station at Sandusky, Ohio. 



