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very rapidly and much less of it being required to wet the tree than 
of a soap and water spray. Pure kerosene is more apt to be injurious 
to peach and plum than to pear and apple trees, and the treatment of 
the former, as with the soap wash, should be deferred until spring, 
just before the buds swell. With young trees especially it is well to 
mound up about the trunk a few inches of earth to catch the overflow 
of oil, removing the oil-soaked earth immediately after treatment. 
The crude-petroleum treatment.—Crude petroleum is used in exactly 
the same way as is the common illuminating oil referred to above. 
Its advantages over kerosene are that, as it contains a very large per- 
centage of the heavy oils, it does not penetrate the bark so readily, 
and, on the other hand, only the hight oils evaporate, leaving a coat- 
ing of the heavy oils on the bark, which remains in evidence for 
months and prevents any young scale, which may come from the 
chance individuals not reached by the spray, from getting a foothold. 
Crude petroleum comes in a great many different forms, depending 
upon the locality, the grade successfully experimented with in the 
work of this Bureau showing 43° Baumé. Crude oil showing a lower 
Baumé than 43° is unsafe, and more than 45° is unnecessarily high. 
The lower specific gravity indicated (43°) is substantially that of the 
refined product, the removal of the lighter oils in refining practically 
offsetting the removal of the paraffin and vaseline. The same cau- 
tions and warnings apply to the crude as to the refined oil. 
The oil-water treatment.— Various pump manufacturers have now 
placed on the market spraying machines which mechanically mix 
kerosene or crude petroleum with water in the act of spraying. The 
attempt is made to regulate the proportion of kerosene so that any 
desired percentage of oil can be thrown out with the water and be 
broken up by the nozzle into a sort of emulsion. Some of these ma- 
chines, when everything is in good working order, give fairly satis- 
factory results, but absolute reliability is far from assured. The 
best outlook for good apparatus of this sort seems to be in carrying 
the oil and water in separate lines of hose to the nozzle, uniting them 
in the latter, and in maintaining an absolute equality of pressure on 
both the oil and the water tanks by employing compressed air as the 
motive force, kept up by an air pump, the air chamber communicat- 
ing with both of the liquid receptacles. One or more manufacturers 
are now working on apparatus of this general description. A 10-per- 
cent-strength kerosene can be used for a summer spray on trees where 
the San Jose scale is multiplying rapidly and where it is not desirable 
to let it go unchecked until the time for the winter treatment. The 
winter treatment with the water-kerosene sprays may be made at a 
strength of 20 per cent of the oil. Applications of the oil-water 
spray should be attended with the same precautions as with the pure 
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