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not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
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site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
POWER PESTICIDE SPRAY EQUIPMENT
FOR THE HOMEOWNER
Larry M. Curtis
Richard P. Cromwell
FLORIDA COOPERATIVE EXTENSION SERVICE
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA, GAINESVILLE
JOHN T. WOESTE, DEAN
TABLE OF CONTENTS
Application Techniques ------.... ----- -............. ............................ 1
Sprayers ---- --------.....-..... .......... .................... 1
Sprayer Components -------------------------.................... 4
Sprayer Operating Characteristics -.....................-------.--- 8
Mistblowers .....--------.... ---..---------------.........-------. 9
Mistblower Components ------------..-----.........-...-........... .... 11
Mistblower Operating Characteristics .--...--...--............. --12
Foggers ----------------------..--------.-------.........-........-.... 12
Fogger Components .....-.........--...-.......... ......._..-..... 12
Fogger Operating Characteristics ---...-.--...-...................-- 15
Calibration ........--------..--- ..-- ...--.. --..................... .................-. 15
Care and Maintenance -------------- ---------............................ ... 19
Safety ----------------.----------.- ----.-....... .................................... 20
POWER PESTICIDE SPRAY
EQUIPMENT FOR THE HOMEOWNER
A large number of small pesticide application devices are
available for control of insects, weeds and plant diseases in the
home, in the yard and garden, and on the farm. USDA Home
and Garden Bulletin No. 63 describes basic hand-powered spray-
ers and dusters. The purpose of this publication is to discuss
small engine powered spray machinery available to the home-
Power machinery for control of pests and for care of gardens,
lawns, ornamental plants and other jobs around the home was
once considered practical only for large estate owners. However,
the growing interest in personal care of dooryard plants along
with the increased availability of relatively inexpensive mobile
power equipment has made this equipment attractive to the
Power spray equipment has certain advantages over manually
operated machines. These advantages include speed of operation,
ease of operation and job versatility. Disadvantages include
greater cost, increased maintenance requirements and noise.
Chemicals may be applied in the form of a spray, mist, fog,
dust or granule. This bulletin will discuss components, opera-
tional characteristics, calibration and care and maintenance of
sprayers, mistblowers and foggers.
Sprays, mists, and fogs differ in the size of chemical particle
generated by the applicator. These particle sizes are determined
by the technique used to achieve chemical breakup. The relative
sizes of spray, mist and fog particles are illustrated in Figure 1.
Spraying has become one of the most popular techniques for
applying pesticides. Typical examples of power sprayers may be
seen in Figure 2. These sprayers are normally equipped with
wheels and may be pulled by hand or with a garden tractor.
Sprayers use water as a transport medium for the active chem-
ical. A large volume of water is used to dilute the active chemical
and pest control is obtained by thoroughly wetting the treated
area with this solution.
10 to 50 MICRONS
50 to 350 MICRONS
150 to 3000 MICRONS
Range of Diameters in Microns*
THIS ILLUSTRATION REPRESENTS RELATIVE AND NOT ACTUAL
PARTICLE SIZES. 1 INCH c 25,400 MICRONS
FIG.1 RELATIVE DIAMETERS OF SPRAY,
MIST AND FOG PARTICLES
FIG. 2. TYPICAL POWER SPRAYERS
The basic components of all sprayers are illustrated in Figure
3. These components are the engine, pump, spray tank, pressure
regulator, agitator, pressure gauge, filtration system and dis-
charge gun or nozzle. For the small units discussed in this publi-
cation certain components may be omitted or combined with
The power source of a typical sprayer is 11/2 to 3-horsepower
single cylinder gasoline engine or electric motor. This engine
drives the pump and, where mechanical agitation is used, drives
The pump is the most critical item on any sprayer. The type of
pump determines the gallons per minute and pressure the sprayer
will develop. Several pumps are available for use on garden
sprayers. Piston, centrifugal, roller and gear pumps are the most
widely used with the piston and centrifugal being most popular.
These four pumps are illustrated in Figure 4.
The piston pump on small sprayers is a high pressure unit
which develops pressures between 250 and 400 pounds per square
inch (p.s.i.) and delivers a volume of from one to three gallons
per minute. These pumps are generally one cylinder units which
deliver a rapid pulsating discharge. Several manufacturers in-
clude a dampening device to minimize this pulsation.
The centrifugal pump develops lower pressure but is capable
of greater volume and constant, nonpulsating flow. It develops
up to 70 p.s.i. pressure and delivers around three gallons per
minute on the typical garden sprayer. Centrifugal pumps may be
mounted inside the liquid tank and thus are not visible on many
FIG. 3. BASIC SPRAYER COMPONENTS
- PRESSURE GAUGE
(50 MESH OR
FIG. 4. PISTON, CENTRIFUGAL,
ROLLER 8 GEAR PUMPS
Roller and gear pumps also operate at higher volume and lower
pressure than do piston pumps. Gear and roller pumps are more
subject to wear if abrasive materials are used than are piston
and centrifugal pumps.
When selecting a sprayer one should consider the maximum
pressure needed. If tall trees are to be sprayed, a pump develop-
ing high pressure would be necessary, whereas for low shrubbery
or lawn work a lower pressure pump would be satisfactory.
Chemical resistant materials are used in the construction of
pumps to protect them from corrosive and abrasive action of
chemicals. Nylon, brass, stainless steel, fiberglass and ceramic
materials are used to increase their wear resistance. However,
after a spray job is complete, it should be remembered that the
use of these materials is not a substitute for thoroughly cleaning
The sprayer tank is another important component of the
sprayer system. Tank capacities are normally between 10 and
25 gallons although larger tanks are available. The tanks may be
constructed from a wide variety of materials, but should be cor-
rosion resistant. Common corrosion resistant materials include
galvanized steel, stainless steel, porcelainized steel, fiberglass,
plastic materials and various epoxy coating compounds. For con-
venient filling, emptying and cleaning, tanks should have large
filling spouts and a drain plug in the bottom.
The pressure regulator on a sprayer controls the pressure of
the chemical that flows to the spray gun or nozzle. This regulator
is an adjustable valve that divides the pumped chemical, sending
part to the discharge nozzle and returning the remainder to the
tank. Some sprayers have pressure regulators as individual com-
ponents; some combine the regulator with the pump while others
do not have pressure regulators but rely upon engine speed to
regulate pressure and volume.
Agitation in sprayers keeps the active chemical suspended in
solution. There are two types of agitators available-mechanical
and hydraulic-as illustrated in Figure 5. Mechanical agitation
is accomplished by a mechanically driven propeller or baffle in-
side the tank. Hydraulic agitation is accomplished by return of
fluid from the pump, either through a pressure regulator line or
a separate agitation line. Separate agitation lines are not nor-
mally installed on small sprayers. Mechanical agitation is prefer-
able to hydraulic agitation where wettable powders are used.
FIG.5. MECHANICAL AND HYDRAULIC AGITATION
A pressure gauge is available on small sprayers. This gauge
indicates the pressure of the liquid in the fluid line and is useful
for calibrating the sprayer.
The filtration system of any sprayer is important. This mini-
mizes pump and nozzle wear and prevents clogging of sprayer
nozzles, lines and valves. A minimum of one strainer should be
located on the intake end of the pump or suction line. Additional
strainers in the spray lines and nozzles are beneficial in reduction
of clogged nozzle tips.
Practically all small power sprayers are equipped with a hand
gun adjustable for long range or mist spraying. Accessories in-
clude sprayer mounted boom, multi-nozzle hand booms and root
feeders. These devices are illustrated in Figure 6.
Nozzles for boom spraying are designed for specific purposes.
Nozzles commonly used are the flat spray nozzle for uniformly
applying spray on a flat surface and cone nozzles for applying
material to trees, shrubbery, and plants where coverage is de-
sired on the underside of the leaves. Figure 7 illustrates the
spray pattern obtained with flat and cone nozzles.
FIG. 6. SPRAYER ACCESSORIES
Sprayer Operating Characteristics
The typical sprayer operates in the following manner. The
sprayer engine drives the pump which draws chemical from
the chemical tank, forces it through the chemical line and out
through the sprayer gun or nozzle. The pressure regulator con-
trols the pressure of chemical emitted. The volume of spray ma-
terial is controlled by the pump speed, pressure regulator setting
and nozzle type.
FIG. 7. SPRAY PATTERN FOR
FLAT AND CONE NOZZLES
Mistblowers, misters or low volume sprayers offer a different
technique for applying pesticides. These machines, called mist-
blowers in this publication, use air as a transport medium for
the chemical. A low volume of concentrated small particle size
pesticide is introduced into a high velocity air stream which
blows or transports the material to the desired area. Typical ex-
amples of mistblowers may be seen in Figure 8.
The low volume-high concentrate technique offers certain ad-
vantages over conventional spray methods. With this method
the concentration of active chemical per unit volume is increased,
the spray particle size is decreased and the number of spray part-
icles per unit volume of chemical is increased. Thus, a lower vol-
ume of concentrate spray is needed for thorough coverage and a
smaller, lighter, more compact applicator may be used.
Mistblowers are often equipped to apply dust as well as spray.
Conversion from sprayer to duster is usually accomplished by
connecting a dust line between the tank and air outlet line.
Disadvantages of mistblowers include difficulty in visual
checking of spray coverage and drift problems because of small
FIG. 8. TYPICAL MISTBLOWERS
The basic components of a mistblower are illustrated in Figure
9. They are: engine, air blower, chemical tank, discharge hose or
nozzle, chemical flow line, filter and rate control valve.
Mistblowers for home and garden use are available with either
electric or gasoline engine drives. The gasoline engine units are
primarily back pack sprayers for use outside the home. Many
of the electric motor driven units can be adjusted for inside ap-
plication of nonresidual space sprays or for outside application
of residual sprays.
The size and capacity of home and garden mistblowers vary
with different manufacturers. Generally speaking, the compo-
nents of a back pack gasoline driven mistblower or an electric
mistblower would have the characteristics listed in Table 1.
Table 1. Characteristics of home and garden mistblowers
Engine size 11/ to 5 HP 1/2 to 1 HP
Tank capacity / to 3 gal. 1 to 2 gal.
Tank material Chemical resistant material Chemical resistant material
Weight (empty) 16 to 40# 10 to 13#
Constr. material Light weight metal Light weight metal
Running Time 1 hr. (fuel consumption) Chemical exhausted
Fan Type Centrifugal Radial or centrifugal
Hose Flexible Fixed outlet or
FLEXIBLE DISCHARGE HOSE
VT AIR OUTLET
TANK FILTER CHEMICAL FLOW LINE
FIG. 9. MISTBLOWER COMPONENTS
Mistblower Operating Characteristics
The operational characteristics of the mistblower are simple.
The engine drives the blower, usually a centrifugal fan, which
produces a high velocity air stream. The air is directed to the
area being sprayed by means of a flexible hose or fixed nozzle.
The chemical moves from the chemical tank, either by gravity
flow, by pressurizing the tank, by the siphoning action of the air
stream or by a combination of these methods. It then passes
through the chemical flow line to the control valve which regu-
lates the rate the chemical is introduced into the air stream. The
chemical is atomized as it enters the air stream and is then car-
ried to the area being sprayed.
A filter should be located in the intake portion of the chemical
flow line to prevent clogging of the control valve.
Fogging is another chemical application technique used to
control insect pests around the home. Foggers operate by pro-
ducing extremely small chemical particles which resemble a thick
fog when emitted from the applicator.
The applicators are designed to apply nonresidual or short
term residual insecticides which kill when the material contacts
the insect. Fogging is not recommended for application of re-
sidual chemicals to control plant insects and diseases and cannot
be used for application of herbicides.
Foggers for the homeowner are available in a wide variety of
models from small handheld units to larger garden tractor
mounted units. Three types of foggers are illustrated in Figure
The basic components of thermal foggers vary, depending
upon the method used for vaporization. The components of gas,
electric and exhaust foggers are illustrated in Figure 11. These
components may include the chemical tank, chemical feeder line,
control valves, heating chamber, heating coil, fuel tank and fuel
FLOW CONTROL VALVE
/r- HEATING CHAMBER
FUEL CONTROL VALVE
MANUAL PUMP HANDLE
ELECTRIC HEAT BARREL
PLUG FOG OUTLET
FLOW CONTROL CHEMICAL FLOW UNE
VALVE CHEMICAL CONTAINER
FLOW CONTROL VALVE
EXHAUST. FOG OUTLET CHEMICAL FLOW LINE
FIG. II. BASIC FOGGER COMPONENTS
Fogger Operating Characteristics
There are two basic techniques used to generate fog. First,
mistblowers can be used to produce extremely small foglike part-
icles and, second, fog can be produced by vaporizing the chemi-
cal. The first technique uses the same apparatus discussed in the
mistblower section and will not be covered here.
Electric heaters, gas heaters and hot exhaust gases are used to
provide energy to produce fog. Each of these heating methods de-
velops fog by forcing insecticide into a heated chamber where
almost instantaneous vaporization occurs. Upon vaporization
there is a tremendous expansion which forces the fog out the
open end of the heating chamber.
There are several methods for moving the chemical from the
chemical container to the heating chamber or exhaust. Gas fog-
gers may use pressurized chemical containers or hand-actuated
pumps and exhaust foggers may use pressurized containers,
gravity flow or gasoline engine driven pumps. A variable valve
control is normally used to regulate the rate of flow of chemical
from the container.
The heating chamber on gas and electric foggers is heated
either by a burner assembly where the gas is burned or by an
electric heating coil. Replaceable gas cylinders attach to gas
foggers to supply the fuel. The rate of flow of fuel is controlled
by a variable valve and the fuel is ignited with an open flame.
Exhaust foggers use the exhaust pipe of a small engine for a
heating chamber. The insecticide is introduced into the exhaust
line where the hot exhaust gases vaporize the material.
Foggers should be used in the late afternoon or early evening
for the best results. During this time of the day winds are usu-
ally calm and the fog tends to settle to the ground. When oper-
ating a fogger the prevailing wind should be to the operator's
back, allowing the fog to drift into the area being treated.
Calibration of a chemical applicator is the process of adjusting
the sprayer to distribute the recommended quantity of chemical
on the area being treated. The procedure is important because
an excess amount of chemical may be harmful and an insufficient
quantity may fail to achieve the desired results.
The pesticide label recommends the amount of chemical to ap-
ply to a given area of various types of plants. The application
rate of the pesticide must be followed closely in order to achieve
Often the label will also specify how much total spray mixture
should be applied to an area to achieve good coverage. The total
amount of spray mixture to apply is normally just a guide, but
the recommendation is based on experience and should probably
Example: A pesticide label recommends that 1 pint of a chem-
ical in a total spray mix of 20 gallons be applied per acre to con-
trol a pest.
When using manually directed guns or blowers, a great deal
of individual discretion must be used in determining when an
adequate amount of chemical has been applied. Tree and other
plant sizes vary, thus varying quantities will be required for each
The operator should know the rate of application of his ma-
chine in gallons per minute to achieve the best results. The rate
may be determined by filling the sprayer tank with water, oper-
ating the sprayer for a certain length of time and measuring the
amount of water required to refill the tank. The rate can then
be determined by dividing the gallons used by the time (min).
After the rate has been determined the time required to spray a
given area can be determined by dividing the total quantity rec-
ommended for this area by the rate. The formulas for this cali-
bration technique are:
Quantity of Water Applied (gal.)
Time Required to Apply (min.)
for the Area (gal.)
Time for Application (min.) =-- ate (gal./mn.)
Fogger application is often more difficult to control. Manu-
facturer's recommendations should be followed.
Boom sprayers may be pulled by garden tractors to apply
chemicals to a lawn or a garden in the early stages of growth.
The following calibration procedure can be used for such an
1. Calculate the speed at which you intend to operate meas-
uring the distance traveled in one (1) minute.
Measured Distance (ft.)
Speed (ft./min.)=- 1 (m.)
2. Calculate the desired rate.
Recommended Quantity (gal./acre) X
Speed (ft./min.) XBoom Width (ft.)
Rate (gal./min.) --43560
3. Calculate the actual rate by the technique mentioned earlier.
4. Adjust the sprayer to obtain the desired spray rate.
If the rate is too high you may:
a. Reduce the sprayer engine speed.
b. Reduce the pressure with the pressure regulator.
c. Use smaller nozzle tips.
d. Operate the tractor at a greater speed.
If the rate is too low you may:
a. Increase the sprayer engine speed.
b. Increase the pressure with the pressure regulator. Never
exceed 30 psi pressure if applying herbicides in order to
minimize drift of the spray onto non-target plants.
c. Use larger nozzle tips.
d. Operate the tractor at a slower speed.
5. Continue these adjustments until the desired rate is
6. Mix the spray according to the area that will be covered by
the volume of mix in the tank.
Example: A gardener is to apply a pesticide recommended at
1 quart in 20 gallons of spray mixture per acre. A small sprayer
with a 6 feet long boom drawn by a garden tractor will be used
to apply the spray. How would the sprayer be calibrated?
1. Determine the speed of the tractor when traveling at the
speed normally used. Assume that the tractor travels 250
feet in 1 minute or 250 feet per minute.
2. Determine the required flow rate (gal./min.) in order to
apply the recommended 20 gallons per acre.
from pesticide label
X Speed (ft./min.) X
Required Rate (gal./min.) 43560=
20 X 250 X 6
43560 =-.69 gal./min.
3. Determine flow rate from the sprayer by conducting a tank
Assume that the sprayer is operated for 1 minute and it
takes 67 ounces to refill the sprayer tank.
The actual flow rate is 67 ounces per minute.
The required flow rate to be applying the 20 gallons per
acre recommended was 0.69 gallons per minute which is
equal to 0.69 x 128 or 88.5 ounces per minute. It is obvious
that the required rate is more than that delivered by the
4. The sprayer must be adjusted to achieve the recommended
application rate. If the difference between the desired and
actual flow rate is small, the desired amount can usually
be achieved by adjusting the tractor speed or the pressure
regulator as needed. If the difference is large, the nozzle
tips will probably have to be changed.
Assume that the gardener elects to achieve the desired ap-
plication rate in this example by decreasing the tractor
speed. The tractor speed which must be used is found as
Actual Flow Rate
Required Speed= Required Flow RateActual Speed
-8. n.250 ft. /min. = 189 ft./min.
The tractor would be adjusted until it traveled approxi-
mately 189 feet in a 1 minute trial.
5. Determine the correct amount of pesticide to add to the
Assume that the sprayer tank holds 10 gallons. Since the
application rate of the mixture will be 20 gallons per acre,
the 10 gallons will spray 1/2 of an acre. The pesticide was
recommended at 1 quart per acre, so the tank mixture
should be 1/2 of a quart of pesticide and the remainder
The 10 gallon tank in the above example would spray 1/
of an acre when applying 20 gallons per acre. Home owners
quite often would not need a full tank because the area
to be sprayed would be quite small. In a situation like this,
the method used to determine how much spray should be
mixed is shown below:
Example: A gardener calibrates his boom sprayer to apply
20 gallons per acre as in the previous example. The area to be
sprayed is a 50 x 100 feet garden plot. How much spray mixture
should be mixed up and how much pesticide should be added to it.
1. Determine what portion of an acre that the area to be
Square Feet In Area
Portion of an acre =--
50 X 100 5000
43560 -43560 115
Amount of Mixture Needed = (Portion of an acre) (Gal./acre)
= .115 X 20 = 2.3 gallons
Amount of Pesticide _(Portion of an acre) (Rate per acre
To Add To Mixture -recommended)
= .115 X 1 qt. = .115 quarts
or 3.7 ounces
CARE AND MAINTENANCE
Proper care and maintenance of chemical application equip-
ment is essential for satisfactory service and long life. Equip-
ment manufacturers provide recommendations that, when fol-
lowed, should keep their equipment in top condition.
A complete maintenance program is necessary for power spray
equipment. The engine or power source as well as the sprayer
tank, pump and filters must be properly maintained for con-
tinued reliable service. Some power sources require more atten-
tion than others. Gasoline engines require a regular maintenance
program for easy starting and long life; electric motors require
less attention; and butane, propane or other heat producing
sources must simply be refilled or replaced when empty.
The primary fact to remember when cleaning chemical appli-
cation equipment is that all surfaces that contact the chemical
should be cleaned after each use. A standard procedure recom-
mended by USDA Home and Garden Bulletin No. 63 for care of
hand operated equipment may also be used for maintenance of
This procedure is as follows: Drain sprayer tank after each
use and flush with clean water. Where possible, disassemble and
clean thoroughly all parts of the sprayer, especially nozzles and
screens. Apply oil to parts that might rust. Before reassembling
the nozzle, fill the tank partly full with water and force it
through the discharge line.
Specific items of equipment, especially foggers, may have
maintenance procedures different from those listed above. In all
cases the manufacturer's recommendations should be followed.
Safety procedures must be followed when handling or using
pesticides. The following rules are suggested for users of pesti-
cides and application equipment:
1. Read and follow the instructions for use as outlined on the
pesticide package label. Heed all cautions and warnings.
2. Store chemical containers in a safe dry place out of the
reach of children and pets. Store pesticides in their original
3. Dispose of empty containers promptly and safely.
4. When spraying apply the chemical where it is needed;
avoid random dispersion and waste.
5. Treat plants early in the morning or late in the evening
when winds are calm.
Remember power sprays should be used for fast, efficient, well-
planned spraying; not for haphazard applications which may do
more harm than good.
This publication was promulgated at a cost of $658.61, or
11 cents per copy to provide basic information on types of
power pesticide spray equipment especially designed for
the homeowner and landscape operator.
Single copies are free to residents of Florida and may be obtained
from the County Extension Office. Bulk rates are available upon
request. Please submit details of the request to C.M. Hinton. Publi-
cation Distribution Center, IFAS Building 664, University of
Florida, Gainesville, Florida 32611.
Larry M. Curtis is Assistant Professor and Extension Engi-
neer at Auburn University and Richard P. Cromwell is
Assistant Professor and Extension Agricultural Engineer
at the Institute of Food and Agricultural Sciences (IFAS),
University of Florida.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
K. R. Tefertiller, Director