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Application Equipment

Proper Equipment Selection and Application

The best application equipment for a particular situation is that which provides thorough coverage within a reasonable amount of time and with reasonable effort.

High-volume foliar sprays
. Most ornamental plant growers apply pesticides with high-volume hydraulic applicators. These devices provide good coverage, particularly if care is taken to direct the nozzle(s) properly. Most pesticides are applied to the point of runoff to both the under- and upper-surfaces of foliage. However, some products (Bacillus thuringiensis, insect growth regulators and others) are applied to wet foliage only and instructions say to avoid runoff.

Low-volume applications. Low-volume application methods use higher pesticide concentrations and are generally used to apply insecticides of short residual life. Some pesticide labels offer specific rate recommendations for use with mist blower applicators. Low-volume applications need to be repeated frequently, and coverage on the lower leaf surface may be poor. Thermal fogging devices and controlled-droplet applicators require that special carriers (diluents) be used with pesticides. Contact the manufacturers for specific information.

Coverage. When making applications, make every effort to determine if target surfaces are being reached. For less toxic contact materials such as horticultural oils, insecticidal soaps, microbial insecticides and insect growth regulators, applying sprays directly to the pests or pest-infested surfaces is essential for good control. Coverage is relatively less important when using systemic pesticides. There are several dye products available that can be mixed with the sprayer contents to reveal areas where pesticides have been applied.

Granular systemic insecticides. The use of granular systemic insecticides before pest infestations occur is often referred to as a "preventive" treatment. Although these applications are convenient, they may or may not be justifiable either economically or environmentally. Making such applications unnecessarily can be a costly mistake. But if early pest outbreaks have occurred frequently in past production cycles, this approach could be justifiable.

It has been claimed that systemic insecticides are less harmful to natural enemies, since these organisms do not contact or directly ingest the pesticide. However, the period of protection offered by granular systemics varies. After application, continue to monitor for outbreaks of secondary pests, and determine the length of the product's activity.


Manual sprayers. Manual sprayers such as compressed air and knapsack sprayers are designed for spot treatment and for restricted areas unsuitable for larger units. For pressurizing the supply tank, most manual sprayers use compressed air or carbon dioxide, which forces the spray liquid through a nozzle. Several types of small power sprayers that deliver one to three gallons per minute (GPM) at pressures up to 300 pounds per square inch (psi) are available. Adjustable handguns are usually used with these units, but spray booms are available on some models. These sprayers are relatively inexpensive, simple to operate, maneuverable, and easy to clean and store.

Small motorized sprayers. Some small sprayers have all the components of larger field sprayers but usually are not self-propelled. They may be mounted on wheels so they can be pulled manually, mounted on a small trailer for pulling behind a small tractor, or skid-mounted for carrying on a small truck. They may be low-pressure or high-pressure, according to the pump and other components with which they are equipped.

Standard equipment includes a hose and an adjustable nozzle on a handgun. Some models have multi-nozzle booms. These sprayers are suitable for relatively small outdoor areas. Advantages include: larger capacity than manual sprayers, low- and high-pressure capability, built-in hydraulic agitation, small enough for limited spaces.

Another type of small motorized sprayer is the power backpack sprayer which has a small gasoline-powered engine. The engine drives the pump, which forces the liquid pesticide from the tank through a hose and one or more nozzles. The engine also drives air blowers, which help propel the spray droplets. This model can generate high pressure and is best suited for low-volume applications of dilute or concentrated pesticide.

Other Sprayers

Controlled droplet applicators (CDA). These applicators use a spinning disk (or cup) that breaks the liquid into uniform-sized droplets by centrifugal force. The droplets may be carried to the target by gravity or by an airstream created by a fan. Power to spin the disk or cup is provided by a small electric or hydraulic motor. Atomization is produced by the spinning disk rather than by pump pressure and nozzle. CDAs range in size from a small hand-held type to large tractor-mounted and trailer-mounted units. They require a low volume of water, produce a narrower range of droplet sizes than conventional nozzles and so reduce drift, and droplet size can be adjusted by the speed of rotation.

Electrostatic sprayers. Electrostatic sprayer systems give the pesticide a positive electric charge as it leaves the nozzles. Plants naturally have a negative charge, so the positively charged pesticide is attracted to the plants. The spray is directed horizontally through or above the crop, depending on the pesticide being applied. Because the pesticide adheres to the foliage so well, less pesticide is needed per area, coverage is more even than with other types of equipment, and drift is minimized.

Aerosol Generators and Foggers

Aerosol generators and foggers convert special formulations into very small, fine droplets (aerosols). Single droplets cannot be seen, but large numbers of droplets are visible as a fog or mist. Aerosol generators and foggers usually are used to completely fill a space with a pesticidal fog. Some insects in the treated area are killed when they come in contract with the poison. Other insects are simple repelled by the mist and return after it has settled.

Most hand-operated or permanently mounted automatic machines are for use indoors, such as in greenhouses where they penetrate dense foliage, cracks and crevices. Aerosols and fogs drift easily from target areas, and they have no residual control‹pests may return to the area as soon as the fog dissipates.

In general, use and care for an aerosol generator as you would a sprayer. They do require several special precautions, however:

Be sure that the pesticides used in the aerosol and fog generators are registered for that use.
Keep the pesticides on the target.
Because aerosol and fog formulations are easily affected by weather conditions during application, follow special use instructions.
The operator, other people and animals should stay out of the fog or smoke cloud.

Duster Applicators

Hand dusters. Hand dusters may consist of a squeeze bulb, bellows, tube, shaker, sliding tube or a fan powered by a hand crank. They are lightweight, do not require water and provide good penetration in confined spaces. However, drift potential is high, the dust may not stick to foliage and is difficult to direct.

Power dusters. Power dusters use a powered fan or blower to propel the dust to the target. They include backpack types, units mounted on or pulled by tractors, and specialized equipment for treating seeds. Their capacity in area treated per hour compares favorably with some sprayers. Because no water is required, they are lightweight, are simply built and easy to maintain.

Granule Applicators

Granule applicators distribute granular pesticides by several different methods, including:
forced air, spinning or whirling disks, multiple gravity-feed outlets, soil injectors and agricultural aircraft.

Granule applicators may be designed to apply the pesticides:

By broadcast:
even distribution over the entire area
By drilling:
soil incorporation or soil injection.
To specific areas:
side-dress, banding, in-furrow.

Granule applicators are simple in design, have minimal drift hazard and low exposure hazard to the applicator. Since no water is needed, mixing is eliminated. Limitations include: the need to calibrate for each different granular formulation; limited use against some pests because granules will not adhere to most foliage; weather and ground conditions can affect the flow rate of granules.

Terms to Know

Abrasive - Capable of wearing away or grinding down another object.
Agitation - The process of stirring or mixing.
Calibrate - Measure and adjust the amount of pesticide the application equipment will release per unit of area.
Concentrate - Pesticide having a high percentage of active ingredient; occasionally applied full strength but usually diluted before application.
Corrosion - Process of being worn away gradually be chemical action.
Diluent - Anything used to dilute a pesticide.
Dilute pesticide - A pesticide that is not concentrated; one that does not have a high percentage of active ingredient.
Drift - Pesticide movement in air, away from the target site.
Foliage - Primarily the leaves; may include stems of a plant.
Formulation - Pesticide product as sold, usually a mixture of active and inert ingredients.
Fumigant - Pesticide that is a vapor or gas or that forms a vapor or gas when applied and whose pesticidal action occurs in the gaseous state.
gpm - Gallons per minute.
Hydraulic - Operated by the pressure created by forcing liquid through a narrow opening.
Hydraulic agitation - Stirring or mixing provided by the high-pressure flow of surplus spray material from the pump.
Mechanical agitation - Stirring or mixing done by rotating paddles or propellers in the sprayer tank.
Nontarget - Any site or organism other than the site or pest at which the pesticide is being directed.
psi - Pounds per square inch.
Solvent - A liquid, such as water, kerosene, xylene or alcohol, that will dissolve a pesticide (or other substance) to form a solution.
Suspension - A substance that consists of undissolved particles mixed throughout a liquid.
Target - The site or pest toward which control measures are being directed.
Volatile - Evaporating rapidly; turning easily into a gas or vapor.