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Pesticide Safety Education Program (PSEP)
Part of the Pesticide Management Education Program


Pesticide application equipment varies widely from the simple paintbrush, plunger duster, pressurized can or aerosol bomb to the modern agricultural airplane that is fully equipped with liquid spray systems and/or granular spreaders. There are also several types of support equipment filler pumps, tank trucks, nurse or mixing tanks, front-end loaders, etc. that are not used in actual application but that make the spray operation more efficient.

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Goals of This Module

  • Learn the names and uses of the various types of application equipment.
  • Learn how to select the best application equipment for the job.
  • Understand the basic principles of operation for each type of equipment.
  • Know the advantages and disadvantages of each type of application equipment.

Choose Your Equipment Wisely

Most application equipment can be used for several different kinds of problems. By choosing the type of equipment best suited for his type of work, the applicator can save himself and his customers time and money. The aerial applicator's equipment differs greatly from that of the structural pest control operator. The arborist uses machinery suited for arborist needs. Even when he specializes in a specific type of pest control the pesticide applicator will need to make a choice of equipment. The choice will depend on his working conditions, pesticide formulation, type of area treated, possible problems, etc. While large power equipment may be desirable for some problems, other jobs may be best done by using small portable or hand equipment. Most application equipment can be placed into two groups; one group that applies dry pesticide formulations and another for liquid pesticides.

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Dry Formulation Equipment


Dusters blow fine particles of pesticide dusts onto the target surface. They may be very simply constructed. Often the package containing the pesticide dust acts as the duster, such as a plastic squeeze bottle or a telescoping tube with a spout. Even the larger powered models are of simple construction. Dusters are used mostly by home gardeners, pest control operators, and truck gardeners for individual spot treatment of plants or a small area. In some areas dusts are still applied with aerial application equipment.

Advantages.Dusters are lightweight, relatively cheap, and fast acting. They do not require water.

Disadvantages. Dusts are highly visible, drift easily and are difficult to control. Because of this, dusters are less desirable for most crops or large outdoor jobs.

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Granule Spreaders

Granular equipment is designed to apply coarse, dry particles that are uniform in size to soil, water, and in some cases foliage. Spreaders may work in several different ways including pneumatic whirling discs (seeders, fertilizer spreaders), multiple gravity feed outlets (lawn spreaders, grain drills), soil injectors (furrow treatments), and ram-air (agricultural aircraft).

Advantages. Granular equipment, like dusting equipment, is light, relatively simple, easy to calibrate, and no water is needed. Because granules are uniform in size, they flow easily and are relatively heavy. Seeders and fertilizer spreaders can be used to apply pesticide granules, often without modification.

Disadvantages. Granular formulations have a limited number of uses and are known to poison non-target wildlife if left uncovered. Therefore, the applicator will need other machinery for controlling most leaf feeding insects and plant diseases.

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Liquid Formulation Equipment


More pesticides are applied with sprayers than with any other equipment. Consequently, there are many different types and sizes of sprayers varying from hand operated units to machines weighing several tons. Some apply dilute pesticide mixtures while others apply concentrates. Some use low pressure and low gallonage (low volume) and usually have simple roller pumps. Others are high pressure and/or high volume, usually supplied by high pressure piston pumps. Some apply spray through single outlets or nozzles while others use multiple nozzles linked by sections of pipe or tubing to form a boom. The principal types are described below but there may be several variations or combinations of these types.

Hand Operated Sprayers

Hand operated sprayers are most commonly used by individuals for their own relatively small pest problems. However, the commercial applicator will often find it convenient and efficient to have hand sprayers for small jobs that do not require larger powered equipment or that require only a small amount of spray. They are also used for small jobs in hard-to-get-at areas where the spray equipment must be carried in. Hand sprayers use carbon dioxide or compressed air to force the spray liquid through a nozzle. These sprayers may be available for use with single or multiple nozzle systems. The capacity of hand sprayers generally ranges from one-half to five gallons.

Advantages.Hand sprayers are economical, uncomplicated, light-weight, yet will do a surprising amount of work and adapt to many different problems. The spray is easily controlled when it comes to direction, drift, etc., because relatively little spray is used at low pressure.

Disadvantages. Hand sprayers are efficient and practical for small jobs only. Wettable powders tend to clog regular nozzles and agitation is frequently poor.

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Low Pressure Boom Sprayers

These sprayers are usually mounted on tractors, trucks, or trailers. They are designed to be driven over field crops or large areas of turf, applying the pesticide in swaths. Low pressure sprayers generally use a relatively low volume of dilute spray ranging from 10-40 gallons per acre and applied at 30-60 psi. Typical low pressure sprayer components consist of a pump, tank, agitation system, flow control valves and the boom. Low pressure sprayers use roller or centrifugal pumps.

Advantages. Low pressure sprayers are relatively inexpensive, lightweight, adapted to many uses and can cover large areas rapidly. They are usually low volume, so one tankful will cover a large area.

Disadvantages. They will not adequately penetrate and cover dense foliage because of their low capacity (pressure and gallonage). Because most use hydraulic agitators, wettable powder formulations often settle out. However, if mechanical agitators are used the problem is solved.

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High Pressure Sprayers

High pressure sprayers are often called "hydraulic sprayers." They operate with dilute mixtures and different pressures from two hundred and fifty up to several hundred psi. The design of high pressure sprayers is similar to that of low pressure sprayers, the only difference being that the components have to withstand high pressures. When fitted with booms they can do any work done by a low pressure boom sprayer. They may also be fitted with handguns. The handguns are used for spraying shade trees and ornamentals, livestock, orchards, buildings, unwanted brush, rights-of-way, commercial crops, etc.

Advantages. High pressure sprayers are useful for many different pest control jobs. They have enough pressure to drive spray through heavy brush, thick cow hair, or to the tops of tall shade trees. Because they are strongly built, they are long lasting and dependable. Piston pumps are standard and resist wear from gritty or abrasive materials. Mechanical agitators are also standard and keep wettable powders well mixed in the tank. With a long hose, targets in hard-to-get-at places such as trees, shrubs, etc., can be treated. If label directions for mixing are followed the applicator is not likely to overdose.

Disadvantages. High pressure hydraulic sprayers have to be strongly built and can be heavy and costly. They usually use large amounts of water and thus require frequent filling. The pesticide can easily be misdirected, causing drift and off-target contamination.

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Air Blast Sprayers

Air blast sprayers use air and water to deliver the pesticide to the target surface. The pesticide mixture is pumped through a nozzle or a series of nozzles. A high performance fan (blower) creates an air blast that blows the pesticide away from the spraying nozzle. The rushing air shatters the liquid into tiny droplets that are carried to the target by the air blast. The high speed air aids in breaking up larger droplets and transporting the smaller droplets for thorough coverage. The droplets may be carried 10 to 40 feet effectively depending on the need and the fan speed. Air blast sprayers are typically used in operations involving tree spraying, but are also used in field crop situations where the air blast provides a more effective means of penetrating foliage and providing coverage on all parts of plants.

Advantages. A small amount of pesticide mixture covers a large area and little operating time is lost in refilling. They are usually less tiring to operate than hydraulic sprayers and are particularly adapted to applying sprays over a large area in a relatively short time. They provide an effective means of delivering pesticide to hard-to-reach areas and through dense foliage.

Disadvantages. Air blast sprayers are relatively expensive machines. Since the pesticide is carried by an air blast, they must operate under calm conditions. Windy conditions interfere with the normal pattern of application of the blower. Wind can also cause the small, fine particles of concentrate to drift into surrounding areas where they may do damage. The visible mist that is blown into the air gives the perception that pesticides are missing the target. Larger models may not be able to treat hard-to-get-at areas.

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Low, Ultra-low Volume Sprayers, and Volume Air Sprayers

ULVs and mist blowers

Mist blowers use a fan or whirling disk to break up and blow spray droplets toward a target. Both units apply low volumes of pesticide on target in the form of a mist. The mist consists of small droplets and is often hard to see. These sprayers depend on a metering device, which may or may not be a conventional nozzle. Low volume mist blowers use a diluted pesticide mixture, but ULV mist blowers use undiluted concentrate.

Advantages. Saving time and labor is the main advantage of low and ultra-low volume sprayers. This is accomplished by limiting the amount of liquid carried. These devices are light weight and easy to use. Effective pest control is achieved with a minimum of liquid applied, thus eliminating the problems with wet, dripping walls, animals or plants.

Disadvantages. Calibration is critical and overdosing is a potential problem because the applicator is applying a concentrate or nearly concentrated pesticide. Applying pesticides in favorable weather becomes more critical with this equipment than with air blast sprayers. A more concentrated mixture is being applied and drift could have devastating effects. Coverage with very low volumes on some crops may be less effective and thus less control is achieved. The use of concentrated pesticides increases the risk to the applicator. There are only a limited number of pesticides labeled for ULV application at the present time.

Aerosol Generators


Aerosol generators break certain pesticide formulations into very small, fine droplets (aerosols). An individual droplet cannot be seen with the naked eye. When large numbers of droplets are formed, they can be seen as a fog or smoke. This is why the machines are commonly called "foggers." In some foggers, heat is used to break up the pesticide. These are called thermal aerosol generators. Other foggers break the pesticide into very fine particles with rapidly whirling discs, air blast breakup, or extremely fine nozzles. Aerosol generators are usually used to completely fill an area with a pesticidal fog, whether it be a greenhouse, warehouse, or open recreational grounds. Insects and other pests in the treated area can be controlled when they come in contact with the aerosol fog.

Advantages. The droplets produced by foggers are so fine they do not stick to surfaces within an area. Therefore, foggers can be used in the home for flying insects, in commercial buildings for a variety of pests, or outside in populated areas for blackflies and mosquitoes without leaving unsightly residues. The droplets float in the area and penetrate tiny cracks and crevices in furniture or through heavy vegetation to reach pests in hard-to-get-at places. Because they blanket an area, it is difficult for pests to escape exposure.

Disadvantages. Since most of the droplets produced by aerosol generators do not stick, little residual control of a pest is possible. As soon as the aerosol moves out of an area other pests can move back in. Also, the droplets produced are so fine that they drift for long distances and may cause unwanted contamination or injury. Most aerosol generators require special pesticide formulations. A general purpose formulation usually is not suitable. When foggers are used outside, the weather conditions must be just right. For example, if an area is being treated for mosquitoes, rising air currents could carry the aerosol harmlessly over the pests and out of the area. There must be little or no wind, otherwise the pesticide may be flushed from an area before it can be effective. When a building or an area is treated, it should be ventilated before it can be reoccupied to avoid harmful exposure to the pesticide.

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Flexible-Impeller pumps. Flexible-impeller pumps have a series of rubber "paddles" attached to a rotating hub. The pump housing is eccentric in shape and squeezes the paddles as the rotor turns. This pump has an automatic pressure relief characteristic. The paddles will not return to the radial position if the pressure is to high. The pump is limited to low pressures (less than 50 psi) and can handle all except highly abrasive materials.

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Roller pump. Roller pumps are probably the most widely used pump because they are effective, flexible and inexpensive. The "rollers" of a roller pump fit into slots of a rotating hub. The slots allow the rollers to follow the eccentric shape of the housing. As the rollers pass the inlet port, they push the liquid around the housing and toward the outlet port. As the rollers near the outlet port, the spaces become smaller and fluid is pushed out. The output from a roller pump decreases as the pressure increases because the rollers leak back fluid between rollers. Roller pumps are easily and economically rebuilt when worn.

Centrifugal pumps. Centrifugal pumps have become increasingly popular in recent years. They handle abrasive materials well and their high capacity provides plenty of hydraulic agitation. This pump has an automatic pressure relief characteristic. One of the limitations is that they must be driven at high speed to develop pressure. Belt, gear, or hydraulic drives are used to gear up the pump to high speed. This pump requires priming unless it is located below the level of the supply tank. Pump output falls off rapidly at 30 to 40 psi. The steep performance curve is an advantage as it permits controlling pump output with a relief valve. However, it also produces uneven pump output under some conditions.

Piston pumps. Pistons are "positive displacement" pumps, which means that every time the piston moves the liquid must move. There is no leakage inside the pump chamber or automatic pressure relief characteristic like the roller pumps have. The piston pump output is virtually unaffected by pressure. Pump output is usually low and may not be sufficient for hydraulic agitation. It is the most expensive pump, but good for wettable powders and other abrasive mixtures.

Gear pumps. The gear pump is a semi-positive displacement type of pump and was used on many early sprayers. Gear pumps are rarely used today because of the high wear rate that occurs when pumping abrasive fluids. It is well suited to pumping oil suspensions or emulsions at high volumes and pressures. The internal parts (housing and gears) are generally made of bronze and the shaft is made of stainless steel. The pump cannot be rebuilt and must be thrown away when it is worn.

Diaphragm pumps. The pumping action in a diaphragm pump is produced by moving a flexible diaphragm. Liquid is drawn into one chamber on the downstroke and forced out of another on the upstroke. These pumps may be constructed with either one or two diaphragms. The diaphragm is resistant to wear from abrasives, but may be worn by certain chemicals. Diaphragm pumps are moderately priced and servicing is easy and economical.

Ground driven pumps. Ground driven pumps, or metering pumps, are powered by a ground wheel. When speed changes, the rate of pumping changes accordingly. The major advantage of these pumps is that the application rate is held constant as the speed changes, compensating for changes in terrain and surface conditions. There are two types of pumps normally used on sprayers with ground drives.

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The variable-stroke piston pump is designed to change the length of the piston stroke to adjust the application rate. Increasing piston stroke increases flow; reducing stroke cuts flow. When driven by a ground wheel, the applicator selects a flow rate by setting the piston stroke. Once the flow rate is selected it will stay the same whether the sprayer is traveling one mph or five mph.

The hose pump consists of a series of rollers on a reel with a flexible hose stretched over the reel. As the ground wheel drives the reel, the rollers push a fixed amount of fluid around the hose, thus pumping the fluid. Flow from this pump cannot be changed.

Sprayer Nozzles

Nozzles for sprayers are very important to proper pesticide application. Even experienced applicators often overlook the proper selection and maintenance of nozzles, perhaps the most important component of liquid pesticide application equipment. You as a new candidate for applicator certification must realize from this point on that with improper or worn nozzles, accurate application can never be utilized.

Nozzles (often called "spray tips") serve three functions:

  • Meter or regulate the flow of the liquid
  • Atomize the liquid stream into droplets
  • Spread droplets in a specific pattern

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Regulate flow. A nozzle regulates the flow of liquid with the size of it's orifice. The pressure of the liquid is also a factor. With most nozzles, flow rate increases as pressure increases. However, doubling the pressure does not double the flow rate. Pressure must be increased four times to double the flow rate.

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Atomize stream. Atomization of a liquid into droplets is caused by the tearing action of air. The nozzle spreads the liquid into a thin unstable sheet which breaks up into droplets as it hits the air. Each nozzle produces a range of droplet sizes from very small to large. Droplet size is measured in microns one micron is equal to one millionth of a meter. An increase in the pressure causes an increase in tearing action, thus the droplets become smaller. If the droplets are too small drift will become a problem. If droplets are to large they will not stick to the surface and will roll off. Droplet size is an important consideration when selecting nozzles. Most nozzle manufacturers give droplet size information in their catalogues.

Spray nozzle tip wear. Worn nozzles have poor spray patterns and higher flow rates than new nozzles. Determine spray tip wear by comparing the flow rate of the used tip to the flow rate of a new one. Check the flow of each used tip by using an accurate graduated container and collecting liquid for a measured time. If the flow rate of the used tip is five percent greater than a new one, it should be replaced.

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Maintain the nozzle. Nozzles must be protected from grit and dirt by adequate screens. Finely machined edges that control spray pattern can be damaged by the sanding action of dirt and abrasive spray mixtures. Clogged tips should be cleaned with a soft bristled brush only, never use a metal object. Use extreme care with soft tip materials such as plastic and brass. Remember!! Never put a dirty, clogged nozzle to your mouth to clean it.

Nozzle materials. Materials used to construct spray nozzles are chosen for their cost and durability. Although other materials are in use today, the following list gives the most common types.

  • Brass - probably the most commonly used, least resistant to wear and relatively inexpensive.
  • Nylon - used for non-abrasive formulations, inexpensive and corrosion-resistant. Not recommended for high pressure.
  • Plastic (polymer) - can be used for corrosive chemicals. Different grades of plastic available with the more expensive grades show-ing good wear resistance.
  • Stainless steel - non-corrosive, excellent wear resistance and relatively expensive.
  • Hardened stainless steel - very durable and useful for highly abrasive formulations.
  • Ceramic - most durable tip for highly abrasive and/or corrosive chemicals.

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Nozzle Spray Patterns

Hollow cone and solid cone nozzles produce a circular pattern. Hollow cone nozzles generally make finer, smaller particles than the solid cone. These nozzles are used on handgun sprayers and row crop sprayers. They generally penetrate foliage well and are used to apply fungicides, insecticides and sometimes herbicides.

Flat spray nozzles are used to broadcast most types of pesticides. The pattern is fan shaped with gradually tapered edges. Uniform coverage across the sprayer width is achieved by overlapping the tapered portion of the pattern. This is also a common spray pattern used for applying structural pesticides to floor or wall surfaces.

Even spray nozzles produce a narrow rectangular pattern with a sharp cut of edges. They are used for band applications of chemicals and are frequently used with planting equipment.

Flooding nozzles are often used for broadcast application of fertilizers, herbicides and defoliants. They deliver a wide flat spray pattern consisting of large droplets. They can be mounted on a boom in a variety of positions and are sometimes used alone for boomless broadcast spraying.

Multi-pattern spray nozzles are used on professional hand held sprayers and usually provide the applicator with a choice of different patterns built into one nozzle. Usually two flat fan patterns are availabl e; one that produces fine particles and low volume patterns and a large volume fan with large particles. Another pattern will be the pin stream, used to apply the pesticide into a hole or crevice. There may also be a "crack and crevice" accessory tool attached as well. The applicator selects these patterns by loosening the nozzle collar and turning the nozzle body so that the desired pattern is used.

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Care of Equipment

Whether equipment is very simple or very complex, it must be properly cared for so it will be both dependable and safe. Cleaning equipment including hoses, nozzles, pumps, tanks and hoppers is very important. Pumps and other equipment that will be stored in below freezing weather should be thoroughly drained, or better yet alcohol or antifreeze should be circulated through the equipment. Nozzles should be removed, cleaned, and stored.

Cleaning Sprayers

Clean the sprayer after each days use. appropriate protective clothing when cleaning any piece of application equipment. Flush with clean water inside and out to prevent corrosion and accumulation of chemicals. When finished for the season or when changing chemicals, clean the sprayer thoroughly with a cleaning agent. Be careful to avoid contaminating water supplies and avoid injury to plants or animals when washing.

These steps are suggested:

  1. Wash off the inside of the tank and partially fill it with water. Flush this water through the nozzles. When the tank is empty repeat these steps so that two complete rinses are done.
  2. Take off the nozzle tips and screens. Clean them in a strong detergent solution or kerosene using a soft brush.
  3. Fill the tank a third time, this time adding a cleaning agent. Refer to the following table for information on the type and amount of cleaning agent.

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Cleaning Agents and Rates for Cleaning Sprayers

Pesticide used 2.5 Gallons Cleaning Solution Instructions
Insecticides (1) and/or fungicides.  1 Tbsp. powder detergent (2) Agitate, flush, and rinse.
Hormone herbicides, salt or amine formulations (2,4-D, Dicamba, MCPA, etc) (3) 1/2 cup household ammonia Thoroughly agitate, flush small amount through system, and let remainder stand in sprayer overnight. Flush and rinse.


3 Tbsp. washing soad (sal soda)

Same as above except let stand for at least 2 hours.


1/4 lb. trisodium phosphate

Same as above except let stand for at least 2 hours.


2 Tbsp. fin activated charcoal and 1-2 oz. powder detergent (2)

Agitate, operate sprayer for 2 minutes, let remainder stand for 10 minutes, then flush through sprayer. Rinse.
Hormone herbicides, ester formulations (2,4-D,brush killers, MCPQA, etc.) (1) 4 oz. washing soda (sal soda) + 1-1/2 cup kerosene + 1 Tbsp. powder detergent (2) Rinse inside of tank and flush small amount through system. Let stand at least 2 hours. Flush and rinse.
Other herbicides (atrazine, simazine,alachlor, etc.) 1 Tbsp. powder detergent (2) Rinse with clean water before and after using sudsy solution.

(1)Organophosphate and carbamate insecticides may be detoxified by adding household ammonia to the cleaning solution (half cup per 2.5 gallons).

(2)Liquid detergent may be substituted for powder detergent; mix at a rate to make a sudsy solution.

(3)Caution: Since only a trace of 2,4-D herbicide can damage sensitive plants, it may be risky to use an insecticide or fungicide in a sprayer that has been used to apply 2,4-D.

Cleaning Granular and Dust Application Equipment

These devices must also be cleaned following use. Here are some recommended steps:

  1. Remove all pesticide from the device. This may require taking it apart to be thorough.
  2. Clean the inside of the hopper.
  3. Use sand paper or a wire brush to clean rusted parts. Paint the cleaned parts.
  4. Coat the inside with oil. Oil or grease the bearings.
  5. Thoroughly clean and oil the flow control slides or valves.
  6. Excess oil should be wiped off if it will contact the chemical upon
  7. the next use.

If a pesticide applicator uses common sense, chooses the right formulation, the right pesticide, and the right machine to apply it, he can expect a good pest control job.

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