🌬Plant Protection Equipment — Sprayers and Dusters

As multiple cropping intensifies across Indian farms, fields remain under crop cover for longer periods — providing a continuous habitat for pests and diseases. Timely and effective application of pesticides through the right sprayer or duster can mean the difference between a bumper harvest and devastating crop loss. This chapter covers the full range of plant protection equipment, from the humble hand atomiser to engine-powered sprayers.

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Need for Plant protection equipment

• These days more fields remain covered under crops for longer duration of time due to multiple cropping and various methods employed for increasing the efficiency of crop production. Multiple cropping means growing two or more crops on the same land in a single year, which keeps the field occupied continuously and provides a constant habitat for pests.

• Because of these reasons, it has become necessary to use pesticides and fungicides for controlling pests and diseases. As cropping intensity increases, so does the risk of pest and disease buildup, making timely and effective application of chemicals more important than ever.

• These chemicals are applied in the form of spray and dust. Spraying involves applying liquid formulations, while dusting uses finely powdered chemicals. The choice between spraying and dusting depends on the type of chemical, target pest, crop canopy, and available equipment.

• There are many types of dusters and sprayers that are available for plant’s protection. Choosing the right equipment depends on the crop, field size, type of pest, and available resources.

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Sprayers

• It is a machine to apply fluids in the form of droplets. Sprayers break the liquid into fine droplets and distribute them uniformly over the target surface. The finer the droplets, the better the coverage on plant surfaces.

• Now, the sprayers are used for multiple purposes beyond just pest control.

Purposes of sprayers

• Application of fungicides to avoid/minimize fungal diseases
• Application of herbicides to remove weeds
• Application of insecticides to control insect pests
• Application of micro-nutrients on the plants — foliar feeding of essential nutrients for better crop growth when soil application is insufficient or slow.

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Types of Spray

• Based upon the volume of liquid handled, sprayers may be classified into:

  • High volume spray (more than 400 liters/ha) ^{IBPS AFO} — used when thorough coverage of foliage is required, especially in orchards and plantations where trees have dense canopies.

  • Low volume spray (5 to 400 liters/hectare) — uses less water, making it more practical for field crops and areas where water availability is limited.

  • For aerial dose: 15-75 liters/ha (used in fruit crops). Aerial spraying covers large areas quickly but requires specialized aircraft and skilled operators.

• For ground dose: 100-120 liters/ha (used in field crops).

• Ultra-low volume sprayer (ULV) spray (less than 5 liters/ha). One hectare of crop can be treated in around 2.5 hours. ULV spraying uses highly concentrated formulations with very little or no dilution.

• ULV spraying can be defined as plant protection in which total volume of liquid applied amounts to a few milli liters per acre. It is mainly used in aircraft. The advantage is that very little water is needed, making it suitable for areas with water scarcity and for rapid coverage of large areas.

• Most commonly used sprayers are low volume and ultra-low volume sprayer.

• Nozzles on field sprayers have angle ranges of 60 to 90 degrees but pressure nozzles have smaller angles. The nozzle angle determines the spray pattern width — wider angles cover more area per nozzle but produce larger droplets with less penetration.

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Commercial Sprayer

• Sprayers are of three types:

  • Manually operated — powered by hand or foot effort, suitable for small farms.
  • Engine operated — powered by IC engines, for medium to large operations.
  • Airplane operated — for very large-scale aerial spraying operations covering hundreds of hectares.

• Manually operated sprayers are classified as follows:

  • Hand atomizer type
  • Stirrup pump type
  • Knapsack type
  • Bucket type
  • Hand compression sprayer
  • Rocket sprayer
  • Foot sprayer

• Engine operated sprayer is classified as follows:

  • Knapsack mist sprayer duster
  • Power sprayer

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Hand Atomizer

• This sprayer is also ideally suited for home gardens and small fields. It is the simplest type of sprayer and requires the least investment.

• It consists of a container of 0.5 to 3.5 lit capacity, a built-in air pump, pressure gauge, nozzle and flow cut-off lever. The tank is to be filled with 3/4th volume to leave space for pressurized air above the liquid.

• The pump is operated to build pressure in the tank of 0.15-0.3 kg/cm2.

• When the flow cut-off lever is pressed, the fluid passes through the nozzle and spraying is done.

• The application rate ranges from 45 to 100 litres/ha.

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Hand compression sprayer

• It is suitable for applying chemicals for field crops and lawns.

• The pump is operated to pump air into the tank to build pressure up to 2.0-3.5 kg/cm2. The higher pressure compared to the hand atomizer allows for greater throw distance and finer droplet formation, enabling better coverage on taller crops.

• When the flow cut-off lever is pressed, the fluid passes through the nozzle and spraying is done. The sprayer is carried on the shoulder of the operator.

• The application rate ranges from 45 to 100 liters/ha.

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Knapsack sprayer (hand operated)

• This sprayer is suitable for applying chemicals to several field crops. It is one of the most widely used sprayer types in Indian agriculture due to its portability and ease of use.

• It has a flat or bean-shaped tank of 10-15 liters capacity.

• A hydraulic pump fitted inside the tank, a handle to operate the pump, agitator, filter, delivery hose, and spray gun with nozzle and flow control lever. The agitator keeps the spray solution well-mixed during operation to maintain uniform chemical concentration.

• The tank is made of either brass or PVC material. PVC tanks are lighter and more affordable, while brass tanks are more durable.

• The pressure developed in these sprayers depends on the pump and varies from 3 to 12 kg/cm2. The application rate is 500 lit/ha.

• The coverage is 0.5-1.0 ha/day.

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Rocker sprayer

• Rocker sprayer is mainly used for spraying fruit trees in orchards, coconut and areca nut trees, flower gardens, and cotton and tapioca fields. Its high-pressure capability makes it particularly effective for reaching tall tree canopies where knapsack sprayers cannot reach.

• The pump builds up a pressure up to 14-18 kg/cm2 which facilitates the use of the sprayer for tree spraying. This is significantly higher than knapsack sprayers, enabling a powerful jet that can reach heights of several meters.

• The output of the sprayer is 70-90 lit/hr with one nozzle.

• Coverage is about 1.5 ha/day.

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Foot or pedal operated sprayer

• The foot or pedal sprayers, as they are commonly called, consist of a plunger assembly, stand, suction hose, delivery hose, spray gun with a nozzle etc. The operator uses foot action to pump, freeing both hands for directing the spray precisely.

• Constant pedaling is required for continuous spray.

• It develops a pressure of 17-21 kg/cm2. This is among the highest pressure achievable with manually operated sprayers, making it suitable for spraying tall trees and achieving fine droplets.

• The discharge rate with one nozzle is 110-135 L/hr and coverage is 1.0 ha/day.

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Power Sprayer

• Power sprayers are operated usually with internal combustion engines. They eliminate the need for manual pumping effort, allowing the operator to focus entirely on directing the spray for maximum coverage.

• It can be powered by a 3 HP engine or electric motor.

• The pressure pump is operated by a small power unit ensuring a constant steady pressure throughout the spraying operation, unlike manual sprayers where pressure fluctuates.

• They are operated at pressure from 20 to 55 kg/cm2. This high pressure produces very fine droplets and a powerful throw, suitable for orchards and large field operations.

• These machines are usually portable type and can be mounted on trolleys or tractor linkages.

• A power sprayer consists of the following parts:

  • Prime mover — the engine or motor that drives the pump.
  • Tank — holds the spray liquid.
  • Agitator — keeps the solution mixed.
  • Air chamber — dampens pressure pulsations for steady flow.
  • Pressure gauge — displays operating pressure.
  • Pressure regulator — controls and maintains the desired pressure.
  • Strainer — filters out debris that could clog the nozzle.
  • Boom — a horizontal pipe that holds multiple nozzles for wide coverage.
  • Nozzles — break the liquid into fine droplets and distribute them.

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Pumps for Spraying

There are three types of pumps that are used for spraying:

• Piston or plunger pump — well suited for high pressure spraying. The volumetric efficiency of this pump is as high as 90%. These pumps deliver a precise volume of liquid per stroke, making them reliable for consistent spray output. They are used in most power sprayers.

• Rotary pump — used for low pressure sprayers. They provide a smooth, continuous flow and are simpler in construction with fewer moving parts, resulting in lower maintenance.

• Centrifugal pump — pump working on high speed having high volume discharge. Centrifugal pumps are preferred when large quantities of liquid need to be moved quickly at moderate pressures, such as in boom sprayers covering wide swaths.

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Duster

• Duster is a machine to apply chemical in dust form. Unlike sprayers that use liquid, dusters distribute finely powdered pesticides directly onto the crop canopy. Dusting is often preferred when water is scarce or when quick application is needed.

• Dusters make use of air streams to carry pesticides in finely divided dry form on the plants. The air stream generated by the duster blows the dust onto the plant surfaces where it adheres due to dew or plant surface moisture.

• Types of duster:

  • Plunger type — a simple hand-operated duster where the operator pushes a plunger to create a blast of air that carries the dust. Suitable for small gardens and kitchen gardens.

• Knapsack type: capacity 2.5 to 5 kg. Carried on the operator’s back, it uses a bellows mechanism or fan to distribute dust while walking through the field. It provides wider coverage than the plunger type.

• Rotary type — uses a hand-cranked fan to generate a strong air stream for dust distribution. It provides more uniform coverage than plunger type and can cover larger areas.

• Power operated duster — driven by an engine, capable of covering large areas quickly with uniform dust application. These are used in commercial farming operations and plantation crops.

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Summary Cheat Sheet