24 



BULLETIN 550, U. S. DEPARTMENT OF AGRICULTURE. 



Table 15. — Percentage of infestation in experimental jrtais, Southwich vineyard, North 



East, Pa., 1916. 





Number 



of 



vines. 



Number 

 of 



clusters. 



Total 

 berries. 



First brood. 



Second brood. 



Plat No. 



Infested 

 berries. 



Infesta- 

 tion. 



Infested 

 berries. 



Infesta- 

 tion. 



Check A 



20 

 20 

 20 

 20 

 20 

 20 

 20 



609 

 570 

 638 

 623 

 585 

 584 

 608 



16,443 

 15,960 

 19, 778 

 15, 575 

 14, 625 

 16, 936 

 15, 200 



2,866 

 565 

 597 



2,129 



1,364 

 995 



1,073 



Per cent. 



17.43 

 3.41 

 3.02 



13.61 

 9.32 

 5.87 

 7.06 



11,635 



1,339 



835 



11, 706 

 4,966 

 3, 242 

 9,963 



Per cent. 

 70.76 



I 



8.43 



II.. 



4.22 



Check B 



75.16 



Ill 



33.95 



IV 



19.13 



Check C 



65.65 







A/o/?r/y 



tvtrsr 



zr 



zzz 



Cf>>£-CA 



U7 



jzr 



&4ST 



The final counts in this vineyard showed that the grape-berry moth 

 had been controlled in the plat where two applications with "trailers " 

 had been made, using arsenate of lead (powder) at the rate of 2\ 



pounds to 50 gallons with an 

 adhesive (Plat II). This was 

 in the face of a very heavy in- 

 festation in the checks. In 

 contrast to the results in all 

 other vineyards, in the plat 

 in which 1 \ pounds of arsen- 

 ate of lead (powder) was used 

 the final count was distinctly 

 less satisfactory (Plat I). 

 This difference was conspic- 

 uous only at the north end of 

 the vineyard, where the in- 

 festation hi the checks was practically total and where several eggs 

 had been deposited on a majority of the berries. It should be noted 

 that the contrast was not apparent until the second-brood counts 

 were made, and the first-brood infestation was about the same in 

 both plats. An unusually large percentage of second-brood larvae 

 found in Plat I were very late, indicating that the early second 

 brood had failed to enter the berries. This would indicate that the 

 two amounts of poison were equally effective for some time, but that 

 the higher amount withstood the weathering better. 



Two applications (1) with "set nozzles" and (2) with "trailers" 

 (Plat IV) were partially effective, though not satisfactory. A single 

 application with "trailers" when the berries were just touching 

 (Plat III) was entirely unsatisfactory. 



Fig. 8. — Diagram showing arrangement of experimental 

 plats in the vineyard of Mr. J. M. Moorhead, Moorhead- 

 ville, Pa., 1916. (Original.) 



