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 CuS0 4 
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. 
B, 
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 
3.0 
B 2 
B 3 
do 
do 
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 
4 5 
A 3 
do 
Bi... 
6.7 
7.7 
7.5 
B, 
B 3 
1918. 
A 
do 
do 
Pickering (C) 
B 
Barium water 
C 
Bordeaux, 4-4-50 
Check 
A 
Pickering (C) 
.58 
.60 
1.00 
250 
400 
415 
B 
Barium water 
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 1 1 . 
