CONTROL OF THE GRAPE-BERRY MOTH. 



27 



Results in this vineyard showed that spraying will control the 

 grape-berry moth fully as well in the very compact clusters of the 

 Niagara grapes as in the less compact Concord. The test was thor- 

 ough, as shown by the heavy infestation in the checks. Arsenate 

 of lead used at the rate of 5 pounds (paste) to 50 gallons of liquid 

 (Plat I) did not appear to have any advantage over 3 pounds to 50 

 gallons (Plat II). 



The Spray Mixture. 



arsenate op lead, amount necessary. 



Arsenate of lead, either as paste or as powder, was the insecticide 

 used in all field experiments. In all instances but one, when used 

 at the rate of 3 pounds, paste, or 1£ pounds, powder, to 50 gallons 

 of liquid, the amount was sufficient to reduce the grape-berry moth 

 satisfactorily. During the seasons of 1915 and 1916 at least one plat 

 was sprayed with poison at the above rate, and one other plat was 

 sprayed under conditions as nearly the same as possible except that 

 the amount of poison was increased to 5 pounds of paste or 2\ pounds 

 of powder to 50 gallons of liquid. In all instances except the one 

 referred to no distinct advantage was shown in favor of the higher 

 amount, while in two of the vineyards the plats sprayed with the 

 higher amount were actually the more heavily infested. The differ- 

 ences in results that did appear were usually slight and could be 

 accounted for largely by variation of infestation. The comparative 

 value of the two amounts of poison as it appeared in the different 

 vineyards is summarized in Table 20. 



Table 20. — Relative efficiency of arsenate of lead at the rate of 

 (paste) to 50 gallons of liquid. 



pounds and 5 pounds 





Treatments 



common to all 



plats. 



Years 

 tried. 



Num- 

 ber of 

 vine- 

 yards. 



Num- 

 ber of 

 plats. 



Infested grape berries. 



Amount of arse- 

 nate of lead. 



Best 

 plat. 



Adja- 

 cent 

 check. 



Poor- 

 est 

 plat. 



Adja- 

 cent 

 check. 



Aver- 

 age 

 of all 

 plats. 



Aver- 

 age of 

 all ad- 

 jacent 

 checks 



3 pounds paste 

 or 1J pounds 

 powder to 50 

 gallons of water. 



Laundry soap, 

 1 pound, 

 B o r deaux 

 mixture (3-3 

 formula). 



50 gallons ap- 

 plied twice 

 with "trail- 

 ers." 



1915, 1916 



1915, 1916 

 1915, 1916 



7 



6 

 6 



7 



6 

 i 6 



Per ct. 

 0.89 



Per ct. 

 50.43 



Per ct. 

 8.43 



Per ct. 

 75. 16 - 



Per ct. 

 4.12 



3.41 

 3.34 



Per ct. 

 50.03 



49.17 



above. Poor- 

 est plat elimi- 

 nated. 

 5 pounds paste or 

 2-J pounds pow- 

 der to 50 gal- 

 lons of water. 



3.15 



75.16 



5.06 



94.83 



54.90 







i Plat II, Miller and Carlburg vinevard, is not included in this average because the results were prejudiced 

 by rain. 



Table 20 indicates that as a rule there is practically no difference 

 in effectiveness between the two amounts of poison. However, in 



