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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
once dried, are factors which doubtless have an important bearing on the 
efficacy of spraying in controlling insect and fungous enemies of plants. 
Spray spreaders and adhesives have been studied and used in a limited 
way in various countries, but they have not come prominently to the 
attention of students of pest control in America until the past two or 
three years. Efforts to increase spraying efficiency have been directed 
chiefly toward the improvement of spray machinery and equipment 
rather than toward improvement of the physical properties of spray 
solutions and mixtures. In order to secure a more even distribution 
of spray material as well as to get a more complete coverage on fruit 
and foliage, a great deal of emphasis has been placed upon the use of 
high powered sprayers and the mist or fog type of spray. 
The “fog theory” of spraying requires that the spray carry out a short 
distance from the nozzle, then break into very fine mist particles which, 
like the particles of moisture in a fog, would suspend in the atmosphere 
and come to rest so thickly and evenly on the surface of an apple, for 
example, that the result would be tantamount to an unbroken film of 
spray. Much may be said in favor of high-powered sprayers but fog 
spraying, on the whole, works out very poorly in actual practice. 
Probably not less than seventy-five per cent of spraying, the country 
over, is done with sprayers which do not give sufficient pressure for 
effective fog spraying. Furthermore, the technique of ideal fog spraying 
is exacting and requires decidedly more thoughtful manipulations than 
the average sprayman will give. Finally, satisfactory fog spraying is 
very difficult, if not impossible, where any considerable wind may be 
blowing. Even under optimum conditions one finds that in order to 
reach all parts of the tree some parts will become oversprayed, with 
the result that the spray collects in drops, leaving the surfaces unevenly 
covered and less effectively protected. 
The film spray, such as is obtained by use of a spreader, is well appli¬ 
cable to practical spraying conditions. Spreader enables one to secure 
the same uniform covering of spray with low pressure as with high 
pressure sprayers, although it should be stated that high pressure, 
giving a fine, driving mist, is most efficient and economical. By using 
a suitable spreader and spraying equipment that is reasonably efficient, 
it is within the bounds of practicability for the orchardist to effect a 
fairly uniform, continuous and complete covering of spray material 
over the fruit, leaves or bark of his trees. Contrary to popular con¬ 
ception, spreaders do not cause the spray to spread or creep, at least to 
any material extent, from the sprayed side of an apple, for example, to 
