10 BULLETIN 1178, U. S. DEPARTMENT OF AGRICULTURE. 
oil emulsion. Collections of leaves were made before and after each 
application of spray material and on two occasions considerably after 
the spraying season closed. In cases where the tests were com- 
parable the results were similar for the two years. Those for 1922 are 
shown graphically in Figure 3. 5 
These tests show that there was no marked difference in persistence 
whether the Bordeaux mixture with a great excess of lime was prop- 
erly made by pouring concentrated limewater into diluted bluestone 
solution or was improperly made by pouring the two concentrates 
together, or whether just enough milk of lime was added to precipitate 
all the soluble copper present. In the last case a considerable excess 
of insoluble lime was present. This suggests that the addition of oil 
emulsion to poorly made Bordeaux mixtures may overcome their 
deficiency in sticking properties or possibly may reduce the solubility 
of copper compounds in slightly alkaline Bordeaux mixtures. 
Perhaps, after all, the most dependable indicator of the presence 
of active copper on the sprayed parts is the gross effect of the Bor- 
deaux mixture on the crop of entomogenous fungi. On the plats 
referred to in Figure 3 there was practically no difference in the 
increase of scale insects and the crop of entomogenous fungi even as 
late as November 25. 
FIELD TRIALS. 
During the winter of 1916 and 1917 several orange trees on the 
laboratory grounds at Orlando, Fla., were sprayed with Bordeaux 
mixture plus 1 per cent of oil as emulsion, and several others were 
sprayed with plain Bordeaux mixture in order to determine the 
effects of the combination spray on the mature leaves and fruit. 
The Bordeaux-oil emulsion spread more evenly and apparently 
adhered better than plain Bordeaux mixture. Spray-burn was not 
observed. 
GROVE A, ORLANDO, FLA. 
In the fall of 1917 the combination spray was tested more thor- 
oughly in a bearing orange grove with a mature crop of fruit. Plats 
were sprayed as often as three times with 3-4-50 Bordeaux mixture 
plus one-third to 1 per cent of oil as emulsion, made according to 
Yothers's formula. Plats were also sprayed with plain Bordeaux 
mixture and others with plain oil emulsion. 
The Bordeaux-oil emulsion appeared to spread more evenly, and 
quantitative chemical tests indicated that the residue persisted 
longer than that of plain Bordeaux mixture. No spray injury 
was noted. 
Observations made 30 days after the applications showed that 1 
per cent of oil used either alone or in combination with Bordeaux 
mixture killed scale insects much better than one-third of 1 per cent 
of oil. 
On May 16, 1918, those plats sprayed with 1 per cent of oil were 
reasonably free from scale insects; those sprayed with one-third of 
1 per cent of oil had many more, while those receiving plain Bor- 
deaux mixture had very many more. The difference in the number 
of scale insects became less striking as time went on, and by Sep- 
& The heavy lines in Figure 3 show the readings made for plats receiving three applications of Bordeaux- 
oil emulsion, while the light lines represent the plats receiving a slightly alkaline or decidedly alkaline 
application and two improperly prepared applications of this spray. 
