6 
BULLETIN 1178, U. S. DEPARTMENT OF AGRICULTURE. 
Figure 2 shows the averages of three tests. While the rate of settling 
is not entirely uniform, the principal point determined is that Bor- 
deaux-oil emulsion settles appreciably more slowly than plain Bor- 
deaux mixture. 
In order to determine the effect of adding oil emulsion to Bordeaux 
mixtures made from certain widely used commercial Bordeaux 
pastes and powders, tests were made with these materials along the 
lines described above. The procedure was as follows: A definite 
quantity of the Bordeaux preparation is weighed, enough water 
added to make approximately a 4-4-50 dilution, which is agitated 
thoroughly; then sufficient oil emulsion and water are added, if neces- 
sary, to bring the combination to a 3-3-50 Bordeaux and 1 per cent 
oil dilution. The subsequent manipulation is the same as for the 
homemade Bordeaux mixture described on page 5. 
2-4-50 
,BORD. M/X. 
3-4-50 4-4-50 
BORD. M/X. BORD. M/X. 
4-3-50 
BORD. M/X. 
4-2-50 4-/SO 
BORD. M/X. BORD. M/X. 
«P$| 
^ ^ < 
Fig. 2— Diagram showing the average of three tests made to determine the rate of settling of Bordeaux- 
oil emulsion as compared with plain Bordeaux mixture. 
As shown in Table 1, it is evident that these commercial prepara- 
tions, even with the addition of oil, settle about as much in 30 minutes 
as plain homemade Bordeaux mixture does in 24 hours. If the rapid- 
ity with which copper precipitates settle is to be considered the 
criterion upon which the effectiveness of Bordeaux mixtures contain- 
ing the same quantity of copper is based, then the commercially 
prepared products are as a rule not as good as homemade Bordeaux 
mixtures. But under orchard conditions in Florida the commer- 
cially prepared Bordeaux mixtures with the addition of oil emulsion 
thus far tested have given essentially the same results against citrus 
scab and melanose as the homemade mixture when containing 
approximately the same proportion of copper. Therefore it is 
questionable whether the rate of settling of the copper precipitate is 
a correct standard for comparing the fungicidal properties of Bordeaux 
mixtures when used with oil emulsion. 
