CONTROL OF GRAPE-BERRY MOTH. 



17 



The differences in the control effected by the various strengths of 

 arsenate of lead were slight, as shown in Table VI. When compar- 

 ing the averages the differences in the infestation of the adjoining 

 checks should be kept in mind. The tests of 1 pound to 50 gallons 

 have not been sufficient to justify one in drawing conclusions, but 1| 

 pounds to 50 gallons has proved adequate for control. 



ARSENATE OF CALCIUM, COMMERCIAL POWDEE. 



Much interest has centered in the comparative merits of arsenate 

 of calcium and arsenate of lead as insecticides. Arsenate of cal- 

 cium has the advantage of being much cheaper than arsenate of lead, 

 but doubt has prevailed as to its adhesive qualities and its effect on 

 foliage. Since an extra spreader and adhesive in the form of resin 

 soap is necessary even with arsenate of lead for spraying grape 

 clusters, and since grape foliage is comparatively hardy to arsenicals, 

 it was thought that arsenate of calcium should have a wide use in 

 grape spraying. 



Table VII. — Relative efficiency of commercial arsenate of calcium and arsenate 

 of lead for control of the grape-berry moth, Sandusky, Ohio, 1917, 1918. 

 Both arsenicals applied in Bordeaux 2-3-50 with 1 pound of resin soap to 

 each 50 gallons. 





Spray appli- 

 cations. 



M 

 03 

 >-> 



.3 

 



CD 



■n 

 S3 



ft 





 u 



d 



V 



03 

 >i 



CD 



a 



Percentage of infested grape berries. 



Arsenical, pounds to 50 

 gallons. 



© 



03 



u 

 ho 



u 



cd 



*3 a 



a 



10 







CO 



a 

 



M 



CD +J 



p. a 



o3 3 

 bD a 



a 



Catawba va- 

 riety. 



Concord va- 

 riety. 



Ives variety. 



03 

 ft 



c3 



ft 

 W. 



CD 

 CD 



a- 



CD 





 _c3 



-J? 



< 



03 

 ft 



>> 



03 

 M 

 ft 

 02 



M 

 cd 

 o> 



"3 



CD 

 O 



03 



ft 

 •d 



CD 

 >> 



03 



tH 



ft 



02 



M 







CD 



fi 



CD 



a 



CD 

 CD 

 c3 



< 





1- 



X 







1917. 

 1 

 4 

 5 

 6 



1918. 

 1 

 2 



9.46 

 13-78 



64.09 

 79.63 





















Arsenate of calcium 



0.58 

 .66 



32.11 

 40.60 







commercial powder, 42 







1.28 

 1.04 



39.67 



per cent AS2O5, 1 pound 















6.23 





7.22 



87.06 





















6 



7 





10.15 



76.93 



.62 



36.35 



1.16 



22.95 





I- 



X 











1917. 

 1 

 4 



5 

 6 



1918. 



1 

 2 



2.03 

 5.84 



64.09 

 63. 03 























.84 

 .18 



32.11 

 20.60 







mercial powder, 30 per 







2.94 



.86 



19.59 















7.85 





4.78 



68.02 





















6 



7 





4.22 



65.05 



.51 



26.35 



1.90 



13.72 











Table VII shows the comparison of arsenate of calcium with 

 arsenate of lead in six vineyards and seven plats. Control was 



