1911 Pressure controls and air chamber pressure smoothing 
1916 Adjustable sprayer 
1922 Aerial dusting 
1925 Air blast sprayer for orchards 
1930 Aerial spraying 
1935 All-steel equipment 
1937 High air volume, medium velocity air blast sprayer 
1938 First study of air blast field sprayers 
1944 Introduction of low volume hydraulic sprayer 
1948 Self-propelled high clearance sprayers 
1954 Granular applicators 
PRESENT STATE OF ART AND SCIENCE 
Comparison of application methods. It would be helpful to be able to compare the 
biological effectiveness of different application methods and the physical performance of 
the various machines. Biological differences might then be identified with the physical 
differences which in turn might be common to a number of methods and/or machines. 
If an important effect is found to be general, a principle could be established which could 
be utilized in other situations. 
Some indication of the avaiiability of an insecticide may be obtained by measuring 
the spray-deposit or its distribution on a target area. 
However, the biological effect of an insecticide, for example, is dependent upon the 
distribution of the insecticide on or in the insects, and this is rarely measured. We only 
infer that the insecticide is available whenever the insects die and vice versa. 
Deposit measurement. Progress in measurement of spray deposits has been steady, 
but our present knowledge is by no means adequate. Most progress has been made in 
mass distribution in chemicals. In 1909 Riley developed equipment in which a nozzle being 
tested sprayed dye solution at a sheet of paper through a slot in a moving curtain. This 
sheet of paper then presented a 2 dimensional picture of the mass distributionof spray 
from the nozzle. The next major step was not made until 1947 when Barger, etal., 
described a corrugated device to divide spray from a nozzle into narrow bands and 
measured the amount intercepted in each band. This method has had widespread use 
ever since. However, it is a laboratory device and such tests do not necessarily indicate 
with any reliability the distribution of spray material that may occur in the field. Gen- 
erally there is not sufficient volume in the spray material used to enable one to use 
these devices in the field. Weick developed a system using sensitive balances in the field 
to weigh the deposit directly. This equipment was adversely affected by dew deposit and 
wind. Davis and Eliott devised a method for making quick visual estimates from deposits 
which were caught on dyecards. This methodis widely used in forest spraying. Miller and 
Isler developed a technique in which slides are laid out in an array in the field. The 
sprayer being tested deposits a dye solution which is washed off each individual slide and 
the optical density of the wash wateris measured photoelectrically to provide data on 
general mass distribution in the field. Akkeson and Yates refined this technique by sub- 
stituting a flamespectrophotometer in place of photoelectric dye measurements. Accurate 
measurements can be made with this equipmentfroma variety of salts. Hansen developed 
a method for the use of fluorescent chemicals to detect the presence of spray drift great 
distances from spraying operations. Liljedahl and Strait then developed a technique for 
using fluorescent chemicals for quantitative measurements of spray distribution which 
is fast and moderately accurate. 
Less work has been done on means of measuring chemical distribution on the plant 
or in the soil. Asanimprovement over the usual direct titration, Ban and Carleton showed 
that polarographic techniques could beconveniently used with trace chemicals added to the 
spray, to greatly increase speedofmeasurements. Autoradiographs ofthe plants or leaves 
us 
