THE GBAPE-BERRY MOTH. 



57 



The results of the spraying operations for this season are quite 

 indefinite and serve only to bring out the great irregularity in infesta- 

 tion, its progress throughout the season, and the difficulty in laying 

 out a plat arrangement which will show accurately the effect of spray 

 treatment against this pest. That some benefit did result from the 

 spray application is indicated by the fact that in a comparison of 

 infestation in Plats V, VI, and VII, where the infestation was lighter 

 but more uniform than on the opposite side of the vineyard, there was 

 throughout the season a greater infestation on the unsprayed plat 

 than on the two adjacent sprayed plats. There was not sufficient 

 difference in the weight of fruit from the different plats to indicate a 

 commercial value resulting from the use of arsenate of lead as against 

 arsenite of lime. 



VINEYARD EXPERIMENTS WITH POISON SPRAYS IN 1908. 



The spray work for 1908 was conducted in the same vineyard as in 

 1907. The plat arrangement, however, was changed. The number 



Fig. 21. — Plat arrangement of poison-spraying experiments against the grape-berry moth in the vineyard 

 of Mr. W. S. Wheeler, North East, Pa., 1908 and 1909. (Original.) 



of plats was reduced to four. Plat I consisted of 5 rows, Plat II of 

 12 rows, Plat III of 13 rows, and Plat IV of 5 rows. The position of 

 the check or unsprayed plat was also changed. Checks were left in 

 two places. In the west section 10 vines were left unsprayed on the 

 east end of all the rows of the four plats; in the east section 15 vines 

 were left unsprayed on the east end of all of the rows of the four plats. 

 (See plan of plat arrangement, fig. 21.) The dotted line running 

 across the plats near the east end of both sections indicates the loca- 

 tion of the unsprayed check vines ; these portions thus separated are 

 numbered Plat Ya and Plat Yb, respectively. 



This rearrangement of plats was adopted in the hope that the 

 infestation of the vines in these locations would more nearly represent 

 that existing on the sprayed vines. 



Arsenite of lime was eliminated from the spray formulas used, on 

 account of slight injury to foliage. The spray formula on all four 

 plats was the same. (See Table XXIV.) 



