Here is a list of hand operated and power sprayers commonly used for controlling pests.
Hand Operated Sprayers:
(A) Hydraulic (Energy) Sprayers:
Here the sizes of droplets are mostly 300 – 400 µ. Such sprays are high volume – High pressure sprayers and are suitable for complete coverage of both ground and field crops.
Under this heading, followings are the sprayers:
i. Syringes:
It is the simplest hydraulic sprayer and very tiresome to operate. The rate of spraying is difficult to control. Therefore it is used only for small areas and Kitchen gardens and laboratories.
ii. Bucket Pump Sprayer:
Suction hose is placed in the bucket. Spraying is done in both suction and delivery stroke, therefore spraying is continuous.
Although the rate of application is difficult to control. Its application requires only one person (operator). It is suitable for spraying shrubs, low crops (Vegetables) and nurseries.
iii. Stirrup Pump Sprayer:
Its application requires two operators i.e., one for pumping and agitating the suspension (if necessary) and another for spraying (application). It gives satisfactory performance and generates a pressure upto 4 kg/cm2.
To cover bigger areas for spraying, a bigger sized double action pump is fitted permanently in a large container and is mounted on wheels: which is commonly called wheel barrow type of Sprayers.
iv. Knapsack/Backpack Sprayer:
The name of sprayer itself shows that it is used by carrying on Back of the operator. Spraying is done by right hand of the operator. It has double action lever. Here only one operator is required. Normally coarse nozzle is used to spray any type of material. Presently low volume nozzle is used to achieve low volume spraying. It is simple and durable therefore it is useful for diverse use i.e. spraying the bush of tea and Coffee. It is suitable for hilly and muddy terrains where the use of large or power sprayers is not possible.
v. Rocking Sprayer:
The word ‘Rocking’ means forward and backward movement of handle. It gives the pressure of 14-18 kg/cm2. It requires two operators one for pumping system and another for spraying. It is used for spraying tall plants like arecanut, coconut and sugarcane etc. It gives uniform spraying at sufficient pressure.
vi. Foot/Pedal Pump Sprayer:
It is based on the same principle of Rocker but here foot (Pedal) is used for rocking instead of hand. It means it may be used by only one operator. It may be used to spray tall trees with the help of extension rod. The plant up to of 6m height is easily sprayed. Therefore it is suitable for spraying the trees in orchards and also for crops on medium sized farms. It generates a pressure of 14 kg/cm2.
(B) Compression/Pneumatic/Air Sprayers:
(i) Air is compressed into the container by the compression air pump.
(ii) Tank is usually filled to 3/4th of its capacity and 1/4th (one-fourth) volume is left for the compressed air.
(iii) Such sprayers are not provided with agitators. Hence those spray materials which require continuous agitation for keeping them in suspension, normally can’t be effectively sprayed.
(iv) Such sprayers can’t be used for diverse purposes like hydraulic types.
(v) Flame Thrower is certainly a Pneumatic Sprayer.
(vi) It is of two types depending on the size viz., compression hand sprayers and Pneumatic Knapsack sprayer.
a. Pneumatic/Compression Hand Sprayer:
The capacity of the tank of this sprayer is 0.5 to 3.5 litre and tank itself acts as pressure chamber. There is a provision of fine nozzles in these sprayers and due to this provision, solutions and emulsions can be effectively applied. Such sprayer is suitable for household and Kitchen gardens.
b. Pneumatic/Compression Knapsack Sprayer:
It works on the same principle as of Hand Sprayer. Its tank is cylindrical and capacity is 10 to 20 litres. It is used by fixing on back of the operator. Pressure is developed 4-5 kg/cm2. It is good for large areas.
(C) Gaseous Energy/Air Blast Sprayer:
The example of such sprayer is Hand Atomiser or Flint Pump which is the simplest air blast sprayer. The chamber capacity is 0.5 to 1 litre. It is suitable for experimental work on individual plants. The long time spray by this sprayer is tedious.
The working principle of such sprayer:
When plunger is pushed forward (down-stroke) a gust (or blast) of air is come out from the nozzle which creates a momentary vacuum in the tube. Due to vacuum, spray liquid of the container rises out into the tube. When the plunger is drawn backward (upstroke) fresh air enters into the barrel through its nozzle and the spray liquid (i.e. pesticide + air) is only to be expelled out by the next down stroke.
Power Sprayers:
Such sprayers are used for large areas and on the basis of mechanism of action, these are of four types:
(A) Hydraulic energy sprayer.
(B) Air Pump/Compressor or Pneumatic energy sprayer.
(C) Gaseous Energy Sprayer or Blow applicator.
(D) Centrifugal Energy Sprayer.
(A) Hydraulic Energy Sprayer:
It is a High Volume – High pressure sprayer. Tank capacity is 160-200 litres and developed pressure is up to 40-50 kg/cm2. High volume spraying is also called Full coverage spraying. It needs more water and obviously more labour is required. It is suitable for partially soluble or low dispersible chemicals (like Bordeaux mixture) or highly soluble products (i.e. nicotine sulphate).
Here phytotoxicity injury is minimized due to high degree of dilution. Clogging of nozzle is also avoided due to large aperture. Such sprayer requires 500- 1000 litres of spray liquid for one hectare of field crop. Therefore it is not suitable for arid areas.
Low Volume Spraying needs 8-25 times lesser amount of water and chemicals as compared to High Volume spraying. Therefore Low volume spraying is also called concentrate spraying. A water miscible liquid pesticide like Malathion is more suitable for low volume spraying since it can be atomized without the danger of sedimentation. It needs 10-125 litres of spray liquid per hectare, i.e., 10-125 l/ha.
Semi-low volume/semi-concentrate spraying requires 0.5 – 6.25 litres of spray liquid/ha.
Recently ultra-low volume spraying i.e. ULVs is more prevalent where less than 6 litres of spray liquid is needed for one hectare i.e. < 6 l/ha. Low volume, low pressure with the use of a.i. in more concentrated form is the main principle of ULVs. Efficiency of low volume spraying depends on the droplet size and its spreading power. Therefore here more emphasis is given on to control droplet size to cover large area per unit time even with reduced consumption of pesticide.
Hydraulic energy sprayers are of two type’s viz.:
i. Small portable Hydraulic sprayer.
ii. Large Hydraulic Sprayer.
i. Small Portable Hydraulic Sprayer:
Generally it has two delivery haze and it is operated by 1-3 hp air-cooled engine. It is suitable for spraying ground crops and orchards in plantation for smaller areas. It is available in the market in two forms-stretcher type and wheel-barrow type. Stretcher type is light i.e., 20 kg in weight whereas wheel-barrow type is heavy that’s why it requires one or more wheels.
Its tank capacity is 200-2000 litres or more. The developed pressure is upto 28 kg./cm2. Such sprayer is mounted on jeep or another vehicle. It is suitable for such field crops which has long rows and regular spacing with larger area. It is also used for orchards and plantations. It is unsuitable for tall field crops like jute, sugarcane at latter stage and wet rice field.
(B) Pneumatic/compression/Air Energy Sprayer:
There is no use of pump but a layer of compressed air is produced by Engine power over the spray liquid in the tank and the developed pressure is upto 14 kg/cm2. Since there is no pumping action, such sprayer may be used for the spraying of corrosive materials provided the inner surface of the tank has an anti-corrosive lining.
It is of two types:
i. Portable and Small Mounted Sprayer:
The tank capacity is upto 50 litres. Single cylinder compressor is used to produce compressed air which is operated by V-belt air-cooled engine. There is no system of agitation hence is not suitable for spraying of materials which starts to sediment quickly.
ii. Large Mounted Sprayer:
Here the tank capacity is upto 2000 litres. Here there is an arrangement for agitation, therefore it is suitable for spraying of all types of formulations. It is expensive and difficult to use on small undulating lands. Its use is limited to level lands only.
(C) Gaseous Energy Sprayer:
It is a low volume – low pressure sprayer. When a strong current of air is thrown on the spray liquid coming out of the sprayer, the air current atomises the spray liquid in the fine droplets. To throw air current at high velocity, a fan/Blower of 1.2 – 3 hp air-cooled engine is required. Such sprayer is suitable for spraying concentrates but difficult to regulate the uniformity of spray deposits at different distances. It is known as Blow applicator.
Some machines are so designed that both dusting and spraying may be done.
The droplet’s size produced by such sprayer is 100-400 µ VMD (Volume Median Diameter)
Motorised knapsack sprayer is a blow applicator. Presently it is most common because of only one person is capable to treat more than 2 ha areas conveniently. The hopper attached with it is made up of polythene of high density whose tank capacity is 7-12 litres. One more tank is attached which is fuel tank and its capacity is 0.75 – 2.25 litres.
It is operated by 1.2 – 3 hp air-cooled engine. Its weight when empty is 7-15 kg. Therefore it is easily kept on back of the operator. The spray liquid is sprayed by strong air current having velocity of 175-320 km/h at which the discharge rate of air current is 2.7 – 9.1 cubic metre (m3). The discharge of spray liquid is 0.5 – 5 l/minute and the fuel consumption is 0.6 – 1.86 l/hour.
The heavy Knapsack is not taken on the back of the operator. In such condition, it is of two types’ viz., stretcher type and wheel barrow type. Such sprayer is used for greater areas and for spraying on orchards and bushes. Motorised Knaksack sprayer is used for both dusting and ultra-low volume spraying.
[D] Centrifugal Energy Sprayer:
Such sprayers are designed to produce fine drops (50 – 150 µ VMD) in the form of mist hence called Mist blowers/ Mist Sprayers. The centrifugal or axial flow of air at high velocity carries small droplets to the target. It is used to spray large area with small quantity of the spray liquid.
It is suitable for spraying shade or Orchard trees with droplet size 80- 100µ. For mosquitoes control the droplet size is 50-70 µ. Such sprayer is High Concentration, Low Volume and Low Pressure. The centrifugal force of rotor determines the size of the droplets. Here pressure is kept constant at 0.7 kg/cm2.
Mist sprayer is used for Blast spraying and Drift spraying. In case of blast spraying, a blast of air produced by machine carries fine droplets of the spray liquid to the target. But in case of Drift spraying, the fine droplets of spray liquid are carried to the target by using the blow and direction of the wind. Large sized mist blower is grouped into stretcher or wheel barrow or vehicle mounted.
In India, an aircraft was first used to control mosquitoes in Delhi in 1944-45 and to control desert locust in 1951.