40 
BULLETIN 1474, U. S. DEPARTMENT OF AGRICULTURE 
It will be seen from Figure 7 that very much more copper can be 
recovered from leaves of trees sprayed with 3-3-50 Bordeaux-oil 
emulsion than with a 1-1-50 Bordeaux-oil emulsion. If it is assumed 
that 15 milligrams of copper per 100 grams of fresh leaves is neces- 
sary to afford protection against melanose, it is obvious that the 
1-1-50 Bordeaux-oil does not meet the requirements for any great 
length of time, whereas a single application of Bordeaux-oil emulsion 
in late April carries about enough copper to afford protection 
throughout the entire period of infection. It is also shown that three 
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Fig. 7. — Quantities of copper remaining in spray residue on citrus leaves during 
a 4-nionth period. Four sprayed plots were sampled : A, sprayed three times 
with 1-1-50 Bordeaux plus 1 per cent oil ; A', sprayed once with the same 
material ; B, sprayed three times with 3-3-50 Bordeaux plus 1 per cent oil ; 
B\ sprayed once with the same material. The first spraying was on April 28. 
The first sampling of leaves was on May 3. 
applications of a 1-1-50 Bordeaux-oil emulsion weathers down dur- 
ing the rainy season about to the point of a single application of 
3-3-50 strength. 
Other experiments in 1921. — The Florida Agricultural Experiment 
Station in 1921 conducted spraying experiments based largely on the 
results obtained by this office during 1920 and obtained very satis- 
factory control from single applications made before the heavy in- 
f ection of May took place. These tests, together with experiments in 
1922, were reported by Burger, DeBusk, and Briggs (£). 
erli snim'jo iei/ i 
TOT 8J39J OVJIbJl. . SPRAYING EXPERIMENTS IN 1922 
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] i ^ ^r^in^<ex|}[erim,ents were repeated in 1922 in the same grove that 
.^agfjaped (Ifbej Receding year. The first applications were made be- 
tween April 10 and 14 and the late applications as late as June 10. 
