PICKERING SPRAYS. 33 



Table 11. — Adherence of copper from various sprays to apple leaves ( Virginia) — Contd. 





Spray used. 



Copper 



sulphate 



in spray 



used." 



Time 

 between 

 spraying 



and 

 gathering 

 of leaves. 



Copper adhering to leaves. 



Plat No. 



Parts per 



million 



(dry 



basis). 



Parts per 

 million 

 per 0.1 

 per cent 

 of CuSCu 

 in spray. 



Mg. per 

 square 

 meter of 



leaf 

 surface. 



Mg. per 

 square 



meter of 



leaf 

 surface 

 per 0.1 



per cent 

 CuSC-4 



in spray. 



1917. 

 Bi 





Per cent. 



0.50 



.25 



.125 



1.00 



Days. 

 15 

 15 

 15 

 25 

 25 

 25 

 25 

 25 

 25 

 25 

 25 

 25 

 25 









 

 



28 

 28 

 28 

 28 



362 

 136 



52 

 955.9 



3.2 

 374.8 

 595.2 

 800.9 

 445.8 

 126.0 

 683.3 

 390.0 

 172.3 



2,250 

 3,250 

 4,350 

 6 

 1,450 

 2,400 

 4,150 

 20 



72.4 

 54.4 

 41.6 

 95.6 



16.5 



7.5 



3.0 



46.8 



0.15 



21.1 



32.3 



37.4 



22.2 



5.6 



33.6 



19.3 



9.4 



3.3 



B 2 





3 



B 3 



do 



2.4 





Bordeaux, 4-4-50 



4.7 



Check 







Bordeaux, 2-1-50 



Bordeaux, 2-2-50 



.5 



.5 



.50 



.25 



.125 



.50 



.25 



.125 



.58 



.60 



1.00 



75.0 

 119.0 

 160.2 

 178.0 

 101.0 

 136.7 

 156.0 

 138.0 



390 



542 

 435 



4.2 





6.5 



Ai 



7.5 



A 2 



do 



8.9 



A 3 



do 



4.5 



Bj 





6.7 



B 2 



do 



7.7 



B 3 . 



do 



7.5 



1918. 

 A 







B 









C 



Bordeaux, 4-4-50 







Check 







A 





.58 



.60 



1.00 



250 

 400 

 415 







B 









C 



Bordeaux, 4-4-50 







Check 



















The figures for the copper found on the leaves picked July 26 (13 

 days after spraying) show that the leaves sprayed with standard Bor- 

 deaux held the most actual copper. Calculated per 0.1 per cent of 

 copper sulphate present in the sprays used, however, the leaves 

 sprayed with the Pickering sprays held twice as much copper when 

 calculated by weight and three times as much when calculated by 

 area as did the leaves sprayed with Bordeaux. The figures for the 

 copper found on the leaves picked on July 27 (three hours after the 

 third spraying) are highest in the case of Bordeaux-sprayed trees. 

 The results are much higher for the Bordeaux- than for the Pickering- 

 sprayed leaves when expressed by area and slightly higher when 

 expressed by weight. Evidently, in proportion to the copper sulphate 

 content, the Bordeaux sprays adhered better to the leaves directly 

 after application, although the copper of the Pickering sprays ad- 

 hered to the leaves in a higher ratio than Bordeaux for the 13-day 

 period tested. 



IN 1917. 



Two sets of 50 leaves were collected in duplicate from the trees 

 receiving the different sprays, the first on July 7, two weeks after 

 the second spraying, and the second on August 3, nearly four weeks 

 after spraying. The leaves were analyzed for copper, the results of 

 which appear in Table 11. 



