Sprayer should be well
maintained during the spraying season.
Checking and preparation
should commence well before the beginning of the season.
It is of paramount importance
to clean both inside and outside of sprayer after each days
work, even if the same chemical is being used the next day.
- Sprayer should be lubricated thoroughly and regularly,
especially all moving parts, before starting the work.
- No matter how well the sprayer is designed and
equipped, even if it is new, all sprayers wear out and deteriorate.
- All parts should be inspected. Worn out, broken
and damaged parts should be replaced.
- These costs are nominal, compared with the value
of the chemicals to be used. The nozzle is the most neglected,
precision component of sprayer.
- If nozzle is worn out and delivers a 10 % overdose,
chemical wastage in a couple of hours would cover the cost of
a new one.
- A detailed instruction book giving simple advice
and illustrated drawing of component and assemblies are provided
with each new sprayer.
- To avoid guess work and waste of time, it is
necessary to specify correct name and code number of the part
specified in the manual. Parts that are likely to be needed should
be kept in stock.
- Extra time should be devoted to the sprayer at
the end of the spraying season, before it is kept in the store.
- Sprayer should be cleaned thoroughly, since residual
chemical if left over for several months will corrode parts of
sprayer. Filters and Nozzles should also be cleaned thoroughly.
- Corroded parts should be painted. The pump should
be greased and operating / moving parts should be well oiled.
Rotary dusters are provided
with an agitator, which stirs the powder and releases it evenly
through the discharge vent.
The blower sucks the dust
or powder from the hopper through the connecting pipe, and pushes
it out forcefully to achieve efficient dispersal.
The operator carries the duster
by means of one or two shoulder straps, and holds the lance
in his left hand cranking the handle with his right.
Plunger type duster
This operates on the piston
principle, by generating an air blast, which passes through
the dust chamber and expels the dust through the discharge outlet
Bellows type dusters
- This type of duster also creates a blast of air
through the dust chamber to discharge the powder, the significant
difference being that the force is generated by means of bellow
- This variety of duster is not popular in
Power operated dusters
Manually operated sprayers
in the foot sprayer consists of a pump barrel and a pressure
with a suction cup or piston drives into the pump barrel, thus
sucking the liquid into the pressure chamber and expelling it
through the discharge line.
stroke of the plunger pulls the liquid in through the suction
hose for the next discharge.
develops a pressure of 60 80 psi and has a provision
for attaching two discharge lines.
Rocker type sprayers
Operating on the same principle
as the foot operated sprayer, this model is different only in
as much as the plunger is operated by means of a lever that
is pushed by hand.
The pressure vessel is
detachable. The options of two lines are available.
The Rocker Sprayer develops
60 80 psi pressure.
Pressure retaining knapsack sprayers
Also known as the Battery Sprayer, this model
permits the use of more than one tank depending upon the number
of operators employed.
A separate charge pump with an inlet and an
outlet device is used to fill the tank with air and liquid.
The tank is first pumped with air upto a pressure of 40
50 psi and then charged with liquid, boosting the pressure to
100 110 psi.
- As soon as the liquid is completely discharged
from the tank, a check valve designed like a float seals the outlet
vent, preventing the air from escaping.
- The tank is a pressure vessel in which
the liquid is filled to two third capacity.
- It is then pressurized to 60 psi by means
of the air charge pump.
- A pressure gauge or safety valve may optionally
be fitted to the tank.
- A pressure regulator may also be used when
the discharge pressure needs to be strictly controlled.
- The tank is non-pressurised and made of
brass, or galvanized steel. The pump may be fitted into or outside
the tank, and sucks the liquid from the tank and expels it through
the discharge line.
- A spray boom or rig may be attached when
wider areas have to be covered. The knapsack sprayer develops
30 40 psi pressure.
- In the single barrel type the plunger is
hollow and acts as a pressure chamber.
- In the double barrel variety, one barrel
is of smaller diameter than the other and acts as a pump, while
the bigger barrel serves as a pressure chamber, to produce more
continuous spraying. A pressure of 30 40 psi is generated.
These are small, simple sprayers, generally
recommended for use in a nursery or private garden.
They produce a fine mist spray and can
be effortlessly operated.
Varieties with a small compressor-type
or plunger-type sprayer are also available.
Power Operated Sprayers
Hydraulic sprayers may be engine or electric
motor driven, and are available with single, double, and the
triple piston pumps.
The single piston pump develops a maximum
pressure of 150 psi, whereas the double and triple piston type
develops 300 400 psi. Only two discharge lines can be
used with the single piston pump, whereas the double and triple
piston pumps can accommodate 4 6 discharge lines.
Operation is by means of 1 2 HP
electric motor, or 2 3 HP petrol, petrol-kerosene or
- These sprayers can also be driven by a
power tiller or tractor.
Motorised Knapsack Mistblower cum duster
- This sprayer cum duster is fitted with
a two-stroke air cooled engine of 35 or 70 cc capacity, connected
to a centrifugal fan by a direct drive.
- The spray liquid is first pressurized by
air generated by the blower. This air current achieves a velocity
of over 275 kmph at the nozzle, and sprays the chemical in fine
particles than can be measured in microns.
The nozzle design enables even spraying
at maximum efficiency.
When dusting, the air blast enters the
tank from an air inlet, which is connected, to a tube with several
holes on its surface.
- This agitates the powder which is then
thrust out by the velocity of the air coming out of the blower,
through the pleated hose and out through the nozzle.
Tractor mount sprayers
As the name indicates, this sprayer is
attached to a tractor for use.
The pump is driven by the PTO shaft of
the tractor, and the sprayer unit sucks the chemical and discharges
it through the spray boom, or through the discharge line consisting
of a delivery hose and spray guns.
- The boom has a swivel arm to direct the
spray correctly. The main frame allows the spray boom to be adjusted
according to the height of the crops being sprayed.
Spinning disc sprayers
Liquid is fed from the tank on to the
spinning disc by the force of gravity. The spinning disc, which
has 180 channels onthe wall and
180 teeth on its periphery, operates at 4000 5000 rpm
to stir the liquid and create very fine, even particles for
low volume spraying.
- A smooth flow of liquid with highly controlled
droplet (100 165 microns) application is thus achieved.
The stainless steel disc is interchangeable.
This sprayer consists of a battery operated
motor with a spinning disc, a liquid tank, a handle and a set
This is a fairly new technique, which
has greatly enhanced uniformity of spraying throughout the plant
In this process, a free charge flows to the plant in response
to the presence of an electrical field, which is created by
a charged cloud. The surface charge is of the opposite polarity
to the charged cloud, and has a magnitude and distribution that
maintains the plant at ground potential (Zero Volts) in the
presence of the charged cloud.
The most commonly used version of this
new system is the hand-held Electrodyn Sprayer, which atomises
and propels charged droplets, by means of electrical forces
set up between a high voltage, positively charged nozzle, the
droplets and the earthed crop.
The formulation is fed by gravity to the
bozzle (bottle plus nozzle) where it picks up a
high voltage charge.
The formulation then forms a number of
uniform ligaments, which in turn are broken up into electrically
These droplets are of uniform size and
mutually repellent and form a tenacious, even coating all over
the crop, including stems and undersides of leaves.
- No mechanical energy is required at the
nozzle to induce droplet formation; neither are compressors or
centrifugal energy employed, so the whole system works without
Type of appliances
- Most suitable for spraying targets which are
not within the reach of a man.
- Gives a wide angle hollow cone to a straight
solid stream that is, it gives a jet to a cone type of spray pattern.
- Difficult to calibrate as the flow and droplet
sizes vary widely with the nozzle angle.
Double swirl spray nozzle
- Used for spraying in two different directions
- Nozzles can be fitted with different types of
tips like hollow cone, solid cone or flat fan.
- Suitable for high volume applications
- The shape and size of Nozzle Tip orifice controls
the spray angel, discharge rate and spray pattern. Spray angle
influences the swath of a spray.
- And also:-Droplet size increases as orifice size
increases (for any given pressure). Droplet size decreases with
an increase in fan angle (for any given nozzle size and pressure).
When it is desired to spray with more than one nozzle with the
help of a spray rig or a spray boom, care should be taken in mounting
to avoid overlapping or gapping.Overlap causes double dose Higher
dose is harmful to crop Gap leaves untreated area Poor biological
Selection of appliance
- Purchase of pesticide appliance is a long
term investment. One needs to keep in mind the type of job one
wants to handle and check the appliance for the following
- Suitability for the job
- Ease of operation and maintenance
- Good performance
- Good serviceability
- Easy availability of spare parts
- Reasonable cost
- Spray Volume : Depending upon the volume of spray
required per hectare the application is categorized
HV : High Volume = More than 150 l/ha.
- Suitable for insecticides, fungicides,
- Can be done woth knapsack sprayers, tractor
LV : Low Volume = Approx. 10-150 l/ha.
- Pesticide is applied on the leaves of plant
covering it thoroughly at a time.
Target and application method
A pesticide needs to be applied to a particular
Target area occupied by pests and insect,
disease or weed.
If pesticides are to be used more efficiently,
the actual target needs to be defined judiciously.
Selection of the target requires knowledge of the biology of
pests in order to determine at which stage it is most vulnerable
The selected target may not be the most
obvious site or the site where the damage is caused. The spray
application method essentially requires
Thorough knowledge of the target
Where, when and what amount of pesticide
to be applied
Correct droplet size, density and distribution.
Pesticide is directed on the weeds in
the vicinity of plant.
Band Soil Application
- Application of pesticide to a band or strip
of soil where the crop will be grown.
- Application of pesticide on a particular
portion of the plant.
Working principle of spray equipment
- Conversion of spray liquid into droplets
is achieved using some form of energies.
- Various forms of kinetic energies such
as hydraulic, gaseous and centrifugal are utilized in this process.
- The type of sprayer and nozzles or atomizers
can be classified according to the energy used.
A reciprocrating pump operated mechanically
by a lever. Pressurised by compression.
This pressure forces the liquid out of
nozzle in the form of spray particles.
- A blower generates high wind velocity
air. A liquid or dust is fed into air stream to be carried to
A high speed spinning disc (flat, concave
or cage or perforated cylinder atomizes the spray liquid to
- Theoretically speaking if ideal droplet
diameter and the desirable droplet density are known, the minimum
volume of pesticide spray per unit area can be calculated. Such
a calculation of optimum droplet density is difficult because
the effectiveness of the droplet is dependent on many other factors.
However, the following broad indications can
serve a general guideline:
5-10 droplets/cm2 for translocated
20 droplets/cm2 for most insecticides
and systemic fungi-cides.
50-70 droplets/cm2 for non systemic
In case of insecticides, to achieve satisfactory
biological efficacy atleast 20 droplets are required per square
centimeter irrespective of their size.
To achieve effifient deposition a narrower
droplet spectrum is needed to minimize losses caused by the
droplets which are larger than 300 microns and also which are
smaller than 100 microns.
Most wastage of pesticide is undoubtedly
due to the largest droplets which have high terminal velocity
and fall rapidly.
Even if large droplets fall on target
they are liable to bounce off.
- A 400 micron droplet will contain 1000
times the dose to a 40 micron droplet. If this is not retained
on the target there will be considerable wastage.
- In actual practice, spray volume applied
is always more than the value obtained from the theoretical calculation,
the reasons being the loss of spray volume due to drip and drift,
the deposition of spray on non-target areas and also due to erratic
distribution of droplets on target surfaces.
Spraying efficiency can be represented
Spraying efficiency (%) = Minimum spray volume
required X 100%
Actual spray volume applied
Spray Application Area
- The target infested by an insect, pest,
disease or weed needs to be sprayed.
- Generally the spray application area differs
from the land area except in the case where pre-sowing treatment
is required on soil where land area equals the area to be sprayed.
- The area required to be sprayed varies
with the distance between the rows of plants, distance between
the plants in the same row and growth of the crop.
- This is being illustrated diagrammatically.
- Pesticides are mostly applied on the target
in the form of spray droplets. Droplets produced by hydraulic
nozzle are not uniform in size.
- Sprays contain both fine and coarse droplets.
They are defined in term of their diameter and density on the
Less under leaf coverage
More spray volume is required
Particles coalesce and run off
Poor penetration into the crop
Less loss due to wind, thermal current.
Poor biological efficacy
Spray pattern like rain.
- Wider swath
- More under leaf coverage
- Less spray volume is required
- Particles do not coalesce and run off
- Good penetration into the crop
- More loss due to wind, thermal current
- Good biological efficacy
- Spray pattern like mist
- To understand how spray application equipment
delivers pesticides to a target, it is necessary to know a little
about thephysical properties and behaviour
- Droplet size and density (number of droplets
per unit area of target) are two important factors for effective
- Knowledge of droplet diameter and density
is important for efficient use of pesticides.
- The droplets diameter of a given spray
can be measured as the median of either the volume or number of
The Volume Median Diameter
- The Volume Median Diameter (VMD) is defined
as that droplet diameter which divides the volume of spray into
two equal parts i.e. the volume of spray with droplets of a diameter
less then VMD equals the volume of droplets with a diameter greater
than the VMD.
The Number Median Diameter (NMD)
The Number Median Diameter (NMD) is the droplet
diameter where the number of droplets above the NMD is equal
to the number of droplets below the NMD.
The NMD is usually smaller than the VMD because
most pesticide sprays usually contain a large number of very
The VMD is affected by relatively few large
droplets whereas the NMD is more influenced by small droplets.
The more uniform the size of droplets, the closer
the ratio of VMD and NMD approaches.
In a normal course, the spray droplets are in
a spherical shape.
To understand the mathematical logic and for
simplicity in calculations the droplets may be considered in
the shape of a cube and not a sphere.
Imagine that the ideal spraying has been carried
out which has produced all droplets of same size in cube shape
having all sides of equal dimensions say 2 mm.
The volume of a droplet is the sum arrived at
after multiplication of length, breadth and height i.e. a cubic
If the droplet size is reduced from 2 mm to
1 mm, number of droplets produced will increase by 8 times from
the same volume.
The area occupied by the droplets is the sum
arrived at after multiplying length and breadth i.e. a square
Similarly when the size of a droplet is reduced the contact
area of droplets on the target increases.
Thus by reducing the droplet size from 2 mm3
to 1 mm3, double contact area can be achieved from the same
amount of spray volume.
Conclusively, if the droplet size is reduced
from 2 mm3 to 1 mm3 in other words by a factor of two, from
the same volume of pesticide:
Eight times more droplets can be produced. This
means number of droplets increase by the cube of the factor
of size reduction.
Double contact area of droplets on targets can
be achieved. This means the contact area increases by the same
factor of size reduction.
- Spray droplets density will be eight, time more,
in other words, it increases by the cube of the factor of size
Optimum Droplet Size
Optimum droplet size for application of
pesticide are generally specified within a range of droplet
More precise definition of optimum droplet
size in application of pesticide on Agricultural Pests may not
be possible, due to biological complexity of target.
Besides this, the fate of droplets from
the time of their formation by a nozzle until their deposition
onto a target is influenced by several factors such as:
Velocity of droplet ejection
Air Turbulence caused by thermal movement
Volatility of the spray liquid and
Characteristics of target surface
Droplet size is most important for efficient
application with minimum contamination of environment. A 500
micron droplet will contain 1000 times the Lethal dose of a
50 micron droplet. To reduce wastage, narrow range of droplet
spectrum is essential.
Coarse droplets are largely influenced
by gravitational force and relatively unaffected by turbulence.
Fine droplets will be influenced by wind and turbulence and
have a tendency to drift.
Different spraying techniques like High
Volume (HV), Low Volume (LV) and Ultra Low Volume (ULV) are
most commonly used.
In these spraying techniques a range of
droplets is produced as shown in the diagram.
Droplet sizes more than 300 microns are
lost by drip whereas the droplet sizes less than 100 microns
are lost by drift.
Loss of spray by drip and drift are more
prominent in HV and ULV spraying technique respectively.
Leaf Area Index (LAI)
- The target leaf area requiring treatment
may be much greater than the ground area. The Leaf Area Index
(LAI) is the ratio of Leaf Area to Ground Area.
Leaf Area Index (LAI) = Leaf Area
* If both upper and lower surfaces are considered,
the droplet density per cm2 dhould be halved.
- To demonstrate the relationships between
droplet diameter, droplet density, LAI and spray volume it is
assumed that all droplets are of one size, distribution on the
target is uniform and that no loss of pesticide occurs on non-target
surface. In practice, of course, this is never achieved.
Selecting a spray nozzle
- The proper selection and use of spray nozzle
is the most important part of pesticide application.
- The nozzle determines the amount of spray
that is generated over a given area, the uniformity of the spray
produced, the coverage obtained and the amount of drift that occurs.
- The nozzle selected must optimize coverage
application rate and pressure and minimize loss through drift.
For each kind of application, dependent upto the physical conditions
prevailing, a different nozzle design is available.
- Nozzle tips are usually available in brass,
stainless steel, and engineering plastic. Steel tips are most
resistant to corrosion and abrasion.
- Brass tips are very commonly used, but
ear out more easily and can be corroded by some chemicals. Engineering
plastic is likely to become the most serviceable material for
spray nozzles, being highly resistant to wear-and-tear and corrosion.
Hollow cone nozzles-Disc and core type
- Operating flood-jet nozzles at 5-25 psi
minimizes drift, but pressure changes critically affect the width
of the spray pattern.
- Generally, the spray generated by the floodjet
is not as uniform as the flat-fan type.
- This model is capable of producing a cone spray
in various angles, and also a solid or broken jet spray.
Single swivel nozzles
- Here the joint of the nozzle and extension
rod is capable of swiveling without leakage, it can be locked
for use at any angle between 0 180 degrees.
Double swivel nozzles
- This has two swivel nozzles instead of
one, capable of independent movement.
Double fixed nozzles
- Double fixed nozzles are fixed on the U
bend, which is, in turn, coupled with the end of a straight extension
- NOTE: Single swivel, double swivel and
double fixed nozzles come in both cones-spray and flat fan varieties.
- This design consists of several nozzles
mounted on a rod, ideally suited to row crops, and can be operated
with foot / rocker / knapsack / power operated sprayers.
Spray guns consist of cut-of-value extension
rod and nozzle and can be trigger or hand-operated.
- The spray pattern is adjustable from solid
jet to hollow cone, and are most widely used for tall trees.
These can be spring-activated (trigger
control) or operated by means of a simple knob or trap.
A strainer can be built into the control
valve handle, and in the trigger type a pressure regulating
device can also be incorporated
Every sprayer should have
- A discharge Line consisting of a delivery hose
with couplings and a spray lance.
Every Spray Lance must have
- A cut-off valve
- An extension rod-straight or goose-neck
- An appropriate nozzle
Comes in varying lengths, according to
customer requirements but lengths longer than 90 cms are difficult
For tree spraying, bamboo lances i.e.
brass tubes inserted into a hollow bamboo are recommended.
The larger diameter of the bamboo helps
to off-set the length of the lance (up to 2.5 meters, making
it easier to handle).
Plant protection equipment classification
Plant Protection equipment falls into two major
- Dusting equipment, which is used for the
dispersal of insecticide in powder form.
- Spraying equipment, which is used for the
dispersal of insecticide in liquid form.
- Both dusters and sprayers are available
in manually operated and power operated varieties.
- Identify the pest and asvertain the damage done.
- Use pesticide only if it has exceeded the Economical
- Use only the recommended pesticide which is the
- Read instructions manual of the pesticide and
- Check the spraying equipment and accessories
which are to be used.
- Ascertain that all components are clean, especially
filling and suction strainer, sprayer tank, cut off device and
- Replace worn out parts such as O
ring, seal, gasket, worn out nozzle tip, hose clamps and valves.
- Test the sprayer and ascertain whether
it pumps the required output at rated pressure. Check the nozzle
spray pattern and discharge rate.
- Calibrate the sprayer. Set spraying spped and
nozzle swath by adjusting spray height and nozzle spacing.
Make sure that appropriate protective clothing
is available and is used.
Train all concerned with the application and
also understand the recommendations. Ensure that soap, towel
and plenty of water is available.
Pesticides should be kept in a dry, locked
Take only sufficient pesticide
for the days application from the store to the site.
DO NOT transfer pesticides
from original container and packing into the containers.
Recheck the use instructions
of pesticide and equipment.
Make sure pesticides are mixed
in the correct quantities.
Wear appropriate clothing.
Avoid contamination of
the skin especially eyes and mouth.
Liquid formulation should
be poured carefully to avoid splashing.
Do not spray in high wind,
high temperature and rain.
Avoid drift by selecting
proper direction of spraying and also holding nozzle and boom
at a proper height.
Start spraying near the
down wind edge of the field and proceed upwind so that operator
moves into unsprayed area.
Never eat, drink or smoke
when mixing or applying pesticides. NEVER blow out clogged nozzles
or hoses with your mouth.
Follow correct spray technique.
Spray plant crop thoroughly by operating sprayer at correct
speed and correct pressure.
Never allow children or
other unauthorized persons to be nearby during mixing. NEVER
leave pesticides unattended in the field. Never spray if the
wind is blowing towards grazing livestock or pastures regularly
Remaining pesticides left in
the tank after spraying should be emptied and disposed off in
pits dug on wasteland.
Never empty the tank into irrigation
canals or ponds.
Never leave unused pesticides
in sprayers. Always clean equipment properly. After use, oil
it and then keep away in store room.
Do not use empty pesticide containers
for any purpose.
Crush and bury the containers
preferably in a land filled dump.
Clean buckets, sticks, measuring
jars, etc. used in preparing the spray solution.
Remove and wash protective clothing
and footwear. Wash yourself well and put on clean clothing.
Keep an accurate record of pesticide
Prevent persons from entering
treated areas until it is safe to do so.
Mark the sprayed plots
with a flag.