water from some deep wells required from 4 to 6 pounds of soap to 
50 gallons, while most of them required between 1^ and 3 pounds 
each (i). 
A less expensive method was desirable, and it was found that a 
combination of caustic soda and fishoil soap gave most excellent 
results. Considerable experimental work proved that 8 ounces of 
caustic soda and from 1 to 2 pounds of soap would be sufficient for 
any deep-well water in Florida thus far tested (9). The caustic 
soda was dissolved in a small quantity of water, which was then 
poured into the water to be used for spraying. The soap was like- 
wise dissolved in a small quantity of water, which was then added to 
the water already treated with the caustic soda. After this mixture 
had stood about a minute the emulsion was added. This method has 
never been known to fail. It proved satisfactory even in slightly 
brackish water at Miami Beach. 
VALUE OF COMBINATION SPRAYS. 
In the citrus-growing sections of the southeastern United States 
and the West Indies it is often necessary to spray for rust mites with 
some form of sulphur and at about the same time to spray for white 
flies and scale insects with an emulsion made of lubricating oils. For 
many years soda-sulphur and potash-sulphur solutions have been 
combined with the oil emulsion for this purpose with reasonably 
satisfactory results. The oil emulsion is only partially effective 
against rust mites, while the soda-sulphur has little or no effect on 
white flies and scale insects at the rate of dilution usually employed. 
This mixture is compatible, and the resultant spray material con- 
tains no precipitate when soft waters are used. The soda-sulphur 
solution, according to the experiments, will not render deep-well 
water miscible with oil emulsion. It can, however, be substituted 
for the caustic soda in the formula wherein caustic soda and fishoil 
soap are used. When the mixture is satisfactory, it is unnecessary 
to use an agitator in applying it to citrus trees. The likelihood of 
injury following its use is no greater or little greater than when each 
material is applied separately at about the same strength or perhaps 
a slightly greater strength. Numerous examinations extending over 
more than 10 years have shown that this combination spray is just 
as effective against rust mites, white flies, and scale insects as when 
the materials are applied separately. 
STABILIZED OIL EMULSIONS. 
While this combination has been generally satisfactory, the results 
indicate that the soda-sulphur or potash-sulphur solutions when 
applied alone are not very satisfactory as a spray to control rust 
mites. At any rate, they have never been found to be so satisfactory 
as the lime-sulphur solution. It was therefore thought probable that 
a better combination spray would result if the oil emulsions were 
used with the lime-sulphur solution, and that the combination would 
retain the better properties of each spray. 
Although any good unstabilized oil emulsion will mix with the 
soda-sulphur and potash-sulphur solutions, this is not the case with 
