Notes Agricultural pests Chapter 4 to 6

2.4.  Pest Control Practices

2.4 Pest control practices in brief: 2.4.1.Cultural control, 2.4.2.Physical control, 2.4.3.Mechanical control, 2.4.4.Chemical control, 2.4.5.Biological control, 2.4.6.Pheromonal control and 2.4.7.Concept of IPM in brief

Introduction

The control of insect pests can broadly be divided into natural control and applied control measures. The natural control agencies do not depend upon the activities of human beings and cannot be influenced much by man. The success of applied control depends completely upon human beings for their application in the field).

2.4.1. Cultural control

The regular farm operations performed by cultivators in order to reduce the population of insect pests to minimize the level of economic injury are called as cultural control. It differs from the mechanical and physical control in being usually preventive and indirect so that farmers are unable to know that how much successful farming operations are. During the general course of various farming operations a large number of insect pests are being destroyed by farmers unknowingly. Therefore, much effective farming practices can be made by adopting the improved agricultural practices during the specific stage of life cycle which can easily be destroyed. Thus, for an effective cultural control, it is essential to have a clear cut idea about the life history, behaviour, habit and ecological status of the pest concerned.

This is the cheapest of all the control measures, as it requires only the adjustment of ploughing, sowing, irrigation and harvesting time which is being done in the normal course of farming. The cultural control parameters which are effective for one pest may be useless against similar type of other pest species belonging to' the same family having different habits and variation in the biology.

The crop rotation and improved practices of farm management are of great significance. The proper timing of cultural practices is the key point for successful management of pest population. The fanning operations are very useful for the control of tissue borers which are neither damaged by the insecticides nor easily attacked by the predators or parasites.

1. Clean cultivation- The regular removal of all weeds and residues of crops is an important factor in reducing the pest population, since insect pests of crops feed on weeds in the absence of host plants. The decaying fruits of guava, tomato and melon, harbouring maggots of fruit-flies and tissue-borers should be removed from the farm. If they remain in the field, the adults emerging from these infested fruits will rein fest the standing crops. The dead grasses and leaves should be burnt to kill the insects, since they are protected under them.

The complete removal of bare grasses is helpful in reducing the population of sugarcane mites. The moths of red hairy caterpillars deposit their eggs on the weed lahni and just after hatching, caterpillars feed on this weed. The eggs of rhinoceros beetle are deposited in the heaps of manure so it should not be kept open and must be covered with soil. In this way clean cultivation is also helpful in the control of insect pests.

2. Crop rotation and trap crops- Crop rotation plays significant role in reducing the population build up of the insect pests. If a field is occupied every year by the same crop, it will certainly provide most favourable conditions for the multiplication of insect pests associated with that particular crop. The rotation of crops has proved to be most effective control measure against those pests which are monophagous or restricted feeders, slow breeder and having longer duration of feeding phase. Some pests having high power of migration and omnivorous in habit may become an established pest in the very first year of infestation on a new crop. So, in this case crop rotation will not be helpful in checking the multiplication of pests. In case of serious infestation of potato tuber moth it is always advised to discontinue further cultivation of potatoes for 3-4 years in that field. If potato crop is infested by the golden nematode of potato the crop rotation is the only practical means of their control. The main idea behind the crop rotation is to starve the pests so that there should be discontinuity in the regular availability of the same food material to the pest.

The crops of the same group such as wheat, corn and oats grown on the same land regularly for a number of years will give favourable conditions to those insect pests which attack the grass crops. The crop rotation is generally recommended for the control of those insects of which the life histories are not studied in detail, so other cultural practices cannot be applied successfully.

Around the major crop in the field, some early growing other preferred crop is sown in strips which are termed as trap crop. The pests are attracted towards the early grown trap-crop and then can easily be killed by cutting and destroying the trap crop. A good example of trap-crop is bhendi or okra (Lady's finger) which is sown around the cotton field to attract the jassid and spotted bollworm. Sesame is known to be a good trap-crop to attract the red hairy caterpillar from the cotton field.

3. Tilling or cultivating the soil- The insect population is affected by the texture of the soil, its chemical composition, moisture content, temperature and other soil organisms, since these factors are responsible for the growth of host plants. Consequently various methods of soil management have profound effect on the survival of a number of insect’s pests. To obtain good results it is id to have all ideal about the complete life history and habits of the species to be controlled. In some species of insects if we know which phases of their developmental stages are passed in the soil, they can be easily killed by cultivating the soil when they are in the pupal cells e.g., wire worms. The depth of ploughing the soil should also be sometimes varied according to the habit of insects. The exact timing of ploughing during the particular life stage in the soil leads to the destruction of soil infesting white grubs exposed, whereas, ploughing at other time will be of minor importance. So, the depth of cultivation, its frequency and timing will depend on the pest species concerned. The rolling or packing the soil raises the water level which may drive some subterranean insects above the soil surface where they are attacked by birds etc. A number of birds like the king-crow, starlin and the myna are found picking up a number of insects exposed in the field. So, if ploughing is performed in early spring a number of hibernating life stages of insects will be exposed and picked up by these birds. The hibernating insect species found in the soil are Bihar hairy caterpillar), the cutworms cotton semilooper etc. The larvae of pink bollworm and spotted bollworms of cotton, found in the soil in damaged cottonseed, if buried in deep soil by ploughing the farm, are unable to emerge as adult moth in the coming spring.

4. Use of resistant varieties- The use of resistant varieties of crops as a preventive measure for insect control is comparatively new in the field of Applied Entomology. Certain resistant varieties of crops are least infested by particular pest in comparison to other varieties of crops by the same pest. The factors responsible for the plant resistance to insect attack are commonly complex and interrelated with the physical, chemical and physiological status of plants. The acidity, distastefulness of cell-sap, early maturity, vigour and thickness of husk also cause tolerance to the insect attack. Now-a day’s insect resistant plant variety is being produced by hybridization, grafting and pure line selection and is being used widely by progressive farmers of the world.

5. Pruning and thinning- In case -I perennial plant like fruits the pests are normally carried from old crop to new one. In such cases pruning and thinning have been found to be most effective in keeping away the pests from the new crops. The pruning of dead branches, scraping of diseased stem, patching up wounds with clay and tar may keep some insects away which lurk in such places in any of the stages of their life cycle. But if not checked properly they may cause damage to the other healthy portions in due course e.g. bark caterpillars and stem boring beetles. The proper pruning of citrus plants can check the further infestation of citrus leaf miner, citrus red scale and citrus psylla. In the same way the pruning is also useful in other cases like woolly apple aphid and the peach leaf-curl aphid of stone fruits.

6. Fertilizing and stimulating vigorous growth- It has been noticed that healthy and vigorous plants are highly resistant to the attack of insect pests in comparison to those plants which are weak due to deficiency of proper nourishment or any disease. Therefore, the use of fertilizers and manures in the properly cultivated field will provide ample nourishment for development and growth of healthy plants having highly resistant potential to the pest infestation.

The growth of sugarcane can be stimulated by the use of BHC and telodrin in the crop and that will be free from the attack of stem borer and root borer.

The use of Bordeaux mixture stimulates the growth of potato crop which becomes less susceptible to the attack of jassid, blight and other fungal diseases.

The cucurbits sown early in the properly manure fields have very fast growth rate in the early spring so that they develop the power of resistance to the attack of red pumpkin beetle otherwise the beetle completely destroys the late and weak cucurbits.

7. Use of clean seed- Seeds also play important role in carrying the insect pests from one crop to the next so, only tested and certified seeds should be used for growing new crops. The double seeds of cotton carry the hibernating larvae of the pink bollworm. Thus, before sowing seed should be fumigated by methyl bromide, phosphine or carbon bisulphide. Wheat galls should be separated by dipping the wheat seed in 5-10% salt solution. Citrus nursery plants shout also be fumigated before dispatching them for planting otherwise red citrus scale will infest the new plant in the field.

8. Regulating irrigation- A large number of insect pests are drowned if excess of water is retained in the field by flooding. After Lucerne is harvested, a large number of Lucerne caterpillars remain in the field. After harvesting over the field should be irrigated to, kill the pests. The attack of white ants can be avoided by irrigating the fields of wheat and sugarcane. The attack of stalk borer of sugarcane is more damaging in flooded area; therefore, in the infested area crop should be irrigated by controlled water only.

9. Variation in sowing and harvesting time- Careful adjustment in the sowing period of crop influences the attack of insect pests. Most of the insect pests lay maximum number of eggs during certain confined phases if host plants are available. By adjusting the sowing time farmers can avoid the egg laying phase of a particular insect pest and get the young plant well established before the infective stage of pest becomes active. The short duration crops should be managed to attain the maturation stage before the appearance of pests or allow minimum possible time for multiplying the pests. The crops which are attacked at the time of maturation can be saved from pest which might become abundant rather late in season, by adjusting the harvesting time before the normal period of harvesting. The early maturation of crops can be achieved by giving proper fertilizer, irrigation or by choosing the early varieties of crops.

There is no better example of the application of farm management in insect control than the effect on the infestation by the Hessian fly of early and late seeding of wheat. The early sown wheat has been reported to be moderately too heavily infested, whereas, medium late sown wheat are found to be least infested. It is advised that sugarcane should be either harvested before the middle of February or the terminal part be cut and fed to cattle. However, the recommendations for adjusting the sowing and harvesting time must be worked out properly, keeping in view the effect of ecological conditions with regard to the suitability for the growth of host plants and establishing capability of the pest.

10. Mixed cropping- By applying the mixed cropping scheme in the field, one can reduce the intensity of pest infestation by creating hindrance in the normal spread of the pest. If certain crops are sown mixed with others, the insect pest associated with the host crop takes comparatively much time to reach other host plant, due to presence of the non-host plants in between because of the distance e.g., wheat and gram in the same field. In this system of cropping, pests are less dependent on their capacity for migration where the hosts are in the separate fields. Mixed cropping has been the subject of study in relation to the effect of certain combinations of host plants on the population growth of pest insects.

2.4.2. Physical control

It includes the manipulation of physical factors like temperature, moisture, light, electricity and atomic energy to keep the pest population under check. The manipulation of extremes, at higher and lower levels, of both temperature and humidity are found damaging the population build up and serve as effective barriers in the spread of insect pests.

a)         Heat- The high range of temperature is employed to kill the insect pest causing infestation in stored grains, fruits, soil, bulbs, furniture, bedding and clothing and fibres. No insect can survive long if kept under super-heated condition of 140-150' F. Most of the insect pests are killed within 3 hours of exposure at 125-130' F: The exposure of infested stored grains to sun light on pucca floor in the month of June causes high mortality of stored grain pests adult stage. The hibernating larvae of pink bollworm, are killed if cotton seed is exposed to 125* F for 5 minutes. The woolly bear is killed by the stream heating of woollen clothes.

There are varieties of heat treating machines in the market which raise the stored grain to high temperature while passing through machine in grains. It should also be kept in mind that the heat treatment may cause shrinkage loss of water content. The application of heat to bins of grains, bales of goods w piles of clothing requires a long time to penetrate inside so that the temperature  in the surface reach the killing point of insect pests.

b.   Cold- Artificial cooling of stored products or mills where such products are processed is employed for reducing the damage caused by the insect pests. This method is not as effective as super heating to kill the insect pest founds but storage of food products or clothing near or belch/ freezing point is suitable to prevent the damage caused by insects. Most of the insects become inactive at a temperature range of 40-60' F and practically below 40 F insect pests are unable to cause any type of damage. The sudden change in the temperature from higher to lower and lower to higher is found to be more effective in killing the insect pests.

c.     Moisture- The rise and fall in moisture content of food and other products affects the survival of insects. By reducing the moisture content of grains below 8%, the insect pest infestation can be avoided easily. The infestation of boring weevils can be checked by soaking the wood in water for about 15 days. Draining of the unnecessary stagnant water is most effective for the control of mosquitoes because all the immature stages of mosquitoes are found inhabiting the stagnant water.

d.     Light- Among the various extrinsic factors light plays a vital role in water destroying the insect pests, as insects are attracted towards light. Various investigative studies are being made to study the distribution and attraction of insects towards different frequencies of light. It has been investigated that a number of insects are attracted towards blue and ultra-violet portions of-spectrum than the yellow and red light. In this method pests are attracted at one place and killed easily.

f.    Electricity- In this method insect pests are exposed to a higher voltage of electro-static fields' due to which much heat is machines are available for the treatment of insect’s cereal products and grains. In this machine when such material is passed through the high frequency of electro- static and between the electrodes, the insect pests are killed easily.

g.   Atomic energy- Recent advances in the field of nuclear physics have opened new platform for the management of insect pests. The successful eradication programme of screw-worm, a serious pest of cattle in Craco Island, has been operated by sterilizing the male sum-worms by radioactive isotopes. Such type of ionizing radiations is alpha- particles or helium nuclei, beta-particles of high speed electrons, neutrons and electromagnetic gamma-rays or short wave X- rays. For the successful application of the atomic energy for pest control following conditions is preferred.

1. The area of operation should be localized.

2. Good method of mass rearing of pests must be available.

3. The released sterile males must be dispersed adequately.

4. The sterilization by nuclear agencies should not affect the mating frequency of males.

5. The nature of female should be to mate only once.

Studies on the application of radioactive isotopes against house-fly and stored product pests are being carried out at Atomic Energy Establishment, Trombay, Mumbai.

2.4.3. Mechanical control

Operations which are involved in the killing of pests by mechanical actions with or without the aid of specially designed equipment are termed as mechanical methods of insect control. The disadvantage of this method is that they are costly due to manual labour and generally ineffective on a large scale hence cannot be applied commercially. This method includes hand-picking, use of hand-nets and bag-nets, jarring, beating and hooking, sieving and winnowing, mechanical exclusions and mechanical traps etc. These methods are adopted according to the type of pest infestation.

Hand-picking - It is the oldest method being used from ancient times where the cost of labour is cheaper. It involves the destruction of eggs or any of the developmental stages. In the field, pests can be hand-picked if they are easily accessible, large sized, conspicuous, sluggish, present in large number and are found in restricted area. This method is highly recommended to deal with the egg clusters and adults of lemon butterfly, grubs of the mustard sawfly and all the developmental stages of Epilachna sp.

Hand-nets and bag-nets- Netting and bagging is an important method which can be effectively employed during infestation of Pyrilla, migrating from maize to sugarcane. This method can also be used against rice bug, grasshoppers and red pumpkin beetles. The field-bag is made up of strong cloth bag, 2 meters long with its mouth measuring 1 x 1.5 meters which is supported with bamboo sticks having two cords on upper side. At the time of operation, bag is carried with the ground surface by two persons.

Jarring - To control the locust and defoliating beetles, small trees are shacked early in the morning in the cold season and the pests are collected in jars containing kerosenized water.

Beating and hooking- Knocking down the locusts with thorny brushes and the house-flies with fly-flappers is very much effective measure for killing them. The rhinoceros beetle can be picked out from the holes of coconut palms.

Sieving and winnowing- It is employed for the control of stored grain pests. The grubs of Tribolium castaneum and Trogoderma granarium can effectively be removed with the help of such operations.

Mechanical exclusion- By this method, pests is physically prevented from reaching the crops. A number of devices are under practice as

(i) The windows, ventilators and doors of houses should be screened to keep away the mosquitoes, bugs and house-files. (ii) The field should be trenched or 45 cm high barriers erected to save the crops from red hairy caterpillars or attacking phase of locust hoppers. (iii) The fruits of citrus and pomegranate can be saved from the infestation of annar butterfly by wrapping the fruits individually with butter paper. (iv)The sticky bands around the trunks of the trees, a few feet above the ground, are posted against insects that infest trees by climbing up the tree.

Mechanical traps- The various traps are as follows

a. Light traps-They are used against ber beetle and red hairy caterpillars. For this pest a petromax or bulb is kept in the centre of a wide flat vessel having water mixed with kerosene oil. The beetles or moths are attracted towards the light and fall down into the water resulting into death field.

b. Electric trap- Insects are electrocuted on the live metal plates in the grain pests.

c. Air suction trap- This trap is fixed in godowns for the control of stored

d. Cricket trap- It is made up of a deep cylindrical vessel containing liquor prepared from malt as bait and provided within strips of wood to help the crickets to approach the bottom.

2.4.4. Chemical control

The control operations involving the destruction of pests based on the chemicals, their action or properties, is termed as chemical control. Control of insects with chemicals is known is chemical control. The term pesticide is used to those chemicals which kill pests and these pests may include insects, animals, mites, diseases or even weeds. Chemicals which kill insects are called as insecticides.

Insecticide may be defined as a substance or mixture of substances intended to kill, repel or otherwise prevent the insects. Similarly pesticides include nematicides –which kill nematodes, miticides or Acaricides which kill mites, Rodenticides – which kill rats, weedicides- that kill weeds, Fungicides- that kill fungus etc.

Importance of chemical control:

Insecticides are the most powerful tools available for use in pest management. They are highly effective, rapid in curative action, adoptable to most situations, flexible in meeting changing agronomic and ecological conditions and economical. Insecticides are the only tool for pest management that is reliable for emergency action when insect pest populations approach or exceed the economic threshold. A major technique such as the use of pesticides can be the very heart and core of integrated systems. Chemical pesticides will continue to be essential in the pest management programmes.

There are many pest problems for which the use of chemicals provides the only acceptable solution. Contrary to the thinking of some people, the use of pesticides for pest control is not an ecological sin. When their use made on sound ecological principles, chemical pesticides provide dependable and valuable tools for the biologist. Their use is indispensable to modern society. Chemical control methods include the use of the insecticides, attractants, repellents, antifeedants, synergists etc. The control of insect pests by insecticides immediately checks the pest population, therefore, insecticidal control is being considered as essence of applied entomology by the farmers but unfortunately causing heavy pollution in the environment.

Insecticides

The substances which kill the insects due to their properties of having chemical actions are termed as insecticides. The term insecticide is not as old as being used as poison for killing the insects since very early times. As early as 200 BC a boiling mixture of bitumen (mineral pitch or asphalt) and blowing fumes through grape leaves was applied to keep the insects away. Sulphur and arsenic were known to be toxic for insects in 100 BC and about 40 to 90 AD respectively. Pyrethrum is being used widely for insect control since even before 1800 in Persia. Neem leaf is being utilized as an insecticide since ancient times.

The history of modern insecticides starts from 1867 with the use of Paris green for reducing the population of Colorado beetle. With the discovery of insecticidal spectrum of DDT in 1939, insecticidal property of BHC and potentialities of phosphorus chemicals in 1941-42, the real concept of insecticide and insect control was revolutionized, as a result insecticide is being considered as the boon of applied entomology.

Qualities of insecticide-

1. General Properties of Insecticides

1.    Pesticides are generally available in a concentrated from which are to be diluted and used except in ready to use dust and granules.

2.   They are highly toxic and available in different formulations.

Properties of an ideal insecticide or pesticide:

1.       Should be very potent against insect pests even at lower doses.

2.       It should be freely available in the market under different formulations.

3.       It should be toxic and kill the pest required to be controlled.

4.       It should not be phytotoxic to the crops on which it is used.

5.       It should not be toxic to non target species like animals, natural enemies etc.

6.       It should be less harmful to human beings and other animals.

7.       Should not leave residues in crops like vegetables.

8.       It should have wide range of compatibility.

9.       It should not be toxic to bees and fish and other beneficial organisms.

10.   It should have higher tolerance limits.

11.   Should possess quick knock down effect.

12.   Should be stable on application.

13.   Should not possess tainting effects and should be free from offensive odour.

14.   Should be cheaper

Formulations of insecticide - For easy application, insecticides are formulated in various ways like dusts, granules, solutions, wettable powders, emulsifiable concentrates, concentrate liquid, fumigants, aerosols, mists and mixed formulations. The insecticides available for common use are rarely impure form so; they are always marketed in a lower concentration which may be further diluted at the time of applications as per need.

Different Classifications of Insecticides

Insecticides are classified in several ways taking into consideration their origin, mode of entry, mode of action and the chemical nature of the toxicant.

I. Based on the origin and source of supply

A. Inorganic insecticides: comprise compounds of mineral origin and elemental sulphur. This group includes arsenate and fluorine compounds as insecticides. Sulphur as acaricides and zinc phosphide as rodenticides.

B. Organic Insecticides:

1.   Insecticides of animal origin: Nereis toxin isolated from marine annelids, fish oil rosin soap from fishes etc.

2.   Plant Origin insecticides or Botanical insecticides: Nicotinoids, pyrethroids, Rotenoids etc.

3.   Synthetic organic insecticides: Organochlorines, Organophosphorous, Carbamate insecticides etc.

4.   Hydrocarbon oils etc.

II. Classification based on the mode of entry-

a. Stomach poison- These are applied with the food material which on ingestion cause death of insects. The poisoning is caused primarily by the action on or absorption from the digestive system. The stomach poisons are commonly applied to control the insect pests having chewing type of mouth parts. In certain cases they are also used against insects having sponging, siphoning and lapping mouth parts. They may even be used against higher animals.

The Stomach poisons are applied in various ways in accordance with the case of .infestation. Commonly, the food material of insects are spread with insecticide or insecticide mixed with food and an attractant. The other way is to sprinkle the insecticide on the runways of pests where poison is picked up by feet or antennae and while cleaning these parts with mouth, pests ingest the poison. The sucking insects, while feeding on plants, treated by systemic insecticide, suck the cell-sap of plant containing poison and die due to poisoning through the digestive system.

Qualities of stomach poison. The stomach poisons, (i) should be stable, cheap and easily available, (ii) should not be distasteful so as repel the pests, (iii) should not be soluble in water, (iv) should not have residual effect, (v) the concentration applied should not be injurious to plants, (vi) should be potent enough to kill the pest quickly, (vii) should have finer particles to be spread uniformly and having adhering property to the surface of plants.

The stomach poisons are applied in a number of formulations viz., dusts, spray, dips, or baits etc. All the elements (thallium, sulphur, phosphorus, mercury) and inorganic compounds (Paris green, lead arsenate, sodium fluoride, sodium cryolite, and borax) are found to be acting as stomach poisons.

b. Contact poison - The toxic chemical which kills the insects by simple contact or touch is termed as contact poison. The contact poisons are applied as spray or dust either directly on to the insect body or to the places where pest visits frequently. The contact poisons kill the insects either by clogging the spiracles or by penetrating into the insect body through sutures, bases of setae, membranes and directly through the cuticle into the blood acting as general or nerve poison. The contact poisons are highly lipophilic so readily absorbed by the liquid present in the epicuticle of exoskeleton.

The contact poisons are available in a wide range of insecticides as elements and inorganic compounds-sulphur, sodium fluoride and arsenicals; mineral oils-diesel oil and crude oil; animals fat—fish oil and soaps prepared from fish oil; organic compounds obtained from plants-nicotine in sulphate form, pyrethrum, neem extract, anabasine, rotenone etc.; synthetic organic compounds-chlorinated hydro-carbons (BHC, DDT, endrin etc.), carbamates (carbaryl) and organic phosphates (Parathion, metasystox etc.).

C.  Systemic poison- For the control of insect having piercing and sucking type of mouth parts, the stomach poisons can be applied through the plant or animal system. When systemic insecticide is applied to the root, stem, leaves or seeds or plants, it is absorbed and reaches to different parts of plants. The insects feeding on the treated plants, through sucking mechanism, ingest the poison inside the gut along with the cell-sap of plants. Commonly the systemic insecticide may act as contact and stomach poison both.

‘Non systemic insecticides’ are not possessing systemic action is called non systemic insecticides. Some non systemic insecticides, however, have ability to move from one surface leaf to the other. They are called as ‘trans laminar insecticides’. E.g. Malathion, Diazinon, Spinosad etc.

Ideal systemic insecticide qualities are

1.   Should have high intrinsic pesticidal activity.

2.   The toxicant must be adequately liposoluble for it to be absorbed by the plant system and water soluble for it to be translocated in the plant system.

3.   The toxicant or its metabolites should be stable for sufficiently long period to exercise residual effect.

4.   Sufficiently soluble in water for translocation through vascular system

5.   Should degrade to nontoxic form in reasonable time to avoid toxicity to consumer Systemic insecticides are applied as seed dressing, granular formulations, sprays etc. In the leaf, the entry of the toxicant is through stomata and cuticle. On stem the entry is through lenticels and cracks in the cuticle. In the seed it is through seed coat especially through the micropyle. Systemic insecticides are highly useful against sap sucking and vectors such as leafhoppers, whiteflies, thrips, aphids etc.

d. Fumigants- Fumigants are applied as vapour and affect the respiratory stem (tracheae) in gaseous form through spiracles causing death of insect. Fumigants are applied to kill the insect pests of stored grain, warehouse, museum, human dwellings, soil infesting grubs, borers etc. Its application is limited to plants or products in air-tight enclosures, tents or buildings or to the soil. Since all the fumigants are deadly poisons great care should be taken during the course of application. The common fumigants are hydrogen cyanide, sulphur dioxide, carbon bisulphide, naphthalene, ethylene dichloride, phosphine, methyl bromide, nemagon. The ideal fumigant is determined due to its relative effectiveness, safety to human beings, animals and plants, cost, penetrating power, reactivity with house-hold goods, effect on the germination of seed etc.

Commonly used Fumigants and their doses:

1. Aluminium phosphide, marketed as Celphos tablets used against field rats, groundnut bruchids etc

2. Carbon disulphide 8-20 lbs/1000ft3 of food grains

3. EDCT (Ethylene Dichloride Carbon Tetrachloride) 20-30 lbs/1000cft of food grains

4. EDB Ethylene dibromide 1 lb/1000ft3 of food grains.

5. SO2: By burning sulphur in godowns SO2 fumes are released.

III. Classification based on the mode of action-

The way by which chemical acts upon a specific system results the death of the individual is known as mode of action. The toxic chemicals may be grouped as under:

a. Physical poison - It affects the individual by creating physical disorders like exclusion of air or loss of moisture from the body. The exclusion of air may be caused with the use of heavy tar and oil. The loss of moisture may occur due to inert dust like aluminium oxide which causes water loss. Some chemicals absorb water from the insect body which causes dehydration.

b. Protoplasmic poison - The protoplasmic poison causes the precipitation of protein inside the cell. A number of inorganic stomach poison like arsenites, arsenates, fluosilicates, fluoaluminates, borates, fatty acids, mineral acids, formaldehyde and ethylene oxide destroy the cellular protoplasm of the midgut epithelium.

c. Respiratory poison - The respiratory poison is concerned with the checking of oxygen intake by blocking the cellular respiration and inactivation of respiratory enzymes. The fumigants like HCN, H₂S and CO are known to act as respiratory poisons.

d. Nerve poison - The nerve poison is associated with the inhibition of acetyl cholinesterase enzyme. During the normal course of nerve conduction a chemical substance, acetylcholine, is formed which mediates the conduction of nervous impulses at neuro-synaptic junction. Acetylcholine, after conducting the nervous impulses is hydrolyzed into choline and acetate enzyme by the action of acetylcholine esterase present in the tissues. Thus, the end organs i.e., nerves, muscles and glands are returned to their resting state, preparatory to further functioning. If due to any reason acetylcholine 'is not hydrolyzed by acetylcholine esterase, it will continue to conduct impulses resulting in the production of a new coactive substance by the central nervous system which becomes toxic and hampers the normal nerve conduction resulting into tremors, convulsions, muscle paralysis and finally death. The organic insecticides arc inhibitors of acetylcholine esterase in insects and mammals. The nerve poisons are many as botanical insecticides like pyrethrum, nicotine; organochlorine-lindane, carbon tetrachloride, DDT; organic phosphates -parathion etc.

e. Chitin inhibitors - Chitin inhibitors interfere with process of synthesis of chitin due to which normal moulting and development is disrupted. Ex Novaluron, Diflubenzuran, Lufenuron, Buprofezin

f. General Poisons: Compounds which include neurotoxic symptoms after some period and do not belong to the above categories. Eg.Chlordane, Toxaphene, aldrin

IV. Based on toxicity:

Fig.2.4.1. Indication of Toxicity by colour and sign mark

V. Based on stage specificity:

1. Ovicides

2. Larvicides

3. Pupicides

4. Adulticides

VI. Generation wise:

First generation - Inorganic and Botanicals

Second generation - Synthetic organics

Third generation - Recent chemicals for reproductive control,

IGRs like MH & JH mimics

Fourth generation - Synthetic pyrethroids

Fifth generation - -DO-

1. Alfamethrin - Alfaguard/ Fartac 10 Ec

2. Fenpropathrin – Danitol 10 Ec

3. Bifenthrin – Taletar 10 Ec

4. Fluvalinate – Mavrik

5. Ethofenpron – Treban 10 Ec and Neonecotinoids

2.4.5. Biological control

It is a bioeffector-method of controlling pests (including insects, mites, weeds and plant diseases) using other living organisms. It relies on predation, parasitism, herbivore, or other natural mechanisms, but typically also involves an active human management role. The successful management of a pest by means of another living organism (parasitoids, predators and pathogens) that is encouraged and disseminated by man is called biological control. In such programme the natural enemies are introduced, encouraged, multiplied by artificial means and disseminated by man with his own efforts instead of leaving it to nature. It can be an important component of integrated pest management (IPM) programs. There are three basic types of biological pest control strategies: importation (sometimes called classical biological control), augmentation and conservation.

Natural enemies of insect pests, also known as biological control agents, include predators, parasitoids, and pathogens. Biological control agents of plant diseases are most often referred to as antagonists. Biological control agents of weeds include seed predators, herbivores and plant pathogens.

Types of biological pest control

There are three basic types of biological pest control strategies:

1.    Importation

Importation (or "classical biological control") involves the introduction of a pest's natural enemies to a new locale where they do not occur naturally. This is usually done by government authorities. In many instances the complex of natural enemies associated with a pest may be inadequate, a situation that can occur when a pest is accidentally introduced into a new geographic area, without its associated natural enemies. These introduced pests are referred to as exotic pests and comprise about 40% of the insect pests in the United States.

The process of importation involves determining the origin of the introduced pest and then collecting appropriate natural enemies associated with the pest or closely related species. Selected natural enemies are then passed through a rigorous assessment, testing and quarantine process, to ensure that they will work and that no unwanted organisms (such as hyper parasitoids) are introduced. If these procedures are passed, the selected natural enemies are mass-produced and then released. Follow-up studies are conducted to determine if the natural enemy becomes successfully established at the site of release, and to assess the long-term benefit of its presence.

To be most effective at controlling a pest, a biological control agent requires a colonizing ability which will allow it to keep pace with the spatial and temporal disruption of the habitat

Classical biological control is long lasting and inexpensive. Other than the initial costs of collection, importation, and rearing, little expense is incurred.

2.    Augmentation

Augmentation involves the supplemental release of natural enemies, boosting the naturally occurring population. Relatively few natural enemies may be released at a critical time of the season (inoculative release) or millions may be released (inundative release). An example of inoculative release occurs in greenhouse production of several crops. Periodic releases of the parasitoid, Encarsia formosa,  are used to control greenhouse whitefly, and the predatory mite Phytoseiulus persimilis is used for control of the two-spotted spider mite. Lady beetles, lacewings, or parasitoids such as those from the genus Trichogramma spp. are frequently released in large numbers (inundative release). Recommended release rates for Trichogramma in vegetable or field crops range from 5,000 to 200,000 per acre (1 to 50 per square meter) per week depending on level of pest infestation. Similarly, entomopathogenic nematodes are released at rates of millions and even billions per acre for control of certain soil-dwelling insect pests.

3.    Conservation

The conservation of existing natural enemies in an environment is the third method of biological pest control. Natural enemies are already adapted to the habitat and to the target pest, and their conservation can be simple and cost-effective. Lacewings, lady bird beetles, hover fly larvae, and parasitized aphid mummies are always present in aphid colonies.

Important conservation measures are:

• Use selective insecticide which is safe to natural enemies.

• Avoidance of cultural practices which are harmful to natural enemies and use favourable      cultural practices 

• Cultivation of varieties that favour colonization of natural enemies

• Providing alternate hosts for natural enemies. 

• Preservation of inactive stages of natural enemies.   

• Provide pollen and nectar for adult natural enemies

Biological control agents

1.       Predators:-

 Predators are mainly free-living species that directly consume a large number of preys during their whole lifetime. Ladybugs, and in particular their larvae which are active between May and July in the northern hemisphere, are voracious predators of aphids, and will also consume mites, scale insects and small caterpillars. The larvae of many hoverfly species principally feed upon greenfly, one larva devouring up to fifty a day, or 1000 in its lifetime. They also eat fruit tree spider, mites and small caterpillars. Adults feed on nectar and pollen, which they require for egg production.

2.    Parasitoid insects:-

Parasite: A parasite is an organism which is usually much smaller than its host and a single individual usually doesn’t kill the host. Parasite may complete their entire life cycle (e.g. Lice) or may involve several host species. Or Parasite is one, which attaches itself to the body of the other living organism either externally or internally and gets nourishment and shelter at least for a shorter period if not for the entire life cycle. The organism, which is attacked by the parasites, is called hosts. Depending upon the nature of host parasites can be grouped as, 1. Zoophagous - that attack animals (cattle pests)                                2. Phytophagous - that attack plants (crop pests)  3. Entomophagous - that attack insects (parasites)                    4. Entomophagous insects  - parasitoids

Parasitism: Is the phenomena of obtaining nourishment at the expense of the host to which the parasite is attached.

Parasitoid: is an insect parasite of an arthopod, parasitic only in immature stages, destroys its host in the process of development and free living as an adult. E.g.: Tachinid flies Carcelia illota, Exorista fallux, Palexiorista laxa, Braconid wasps etc. Parasitoids lay their eggs on or in the body of an insect host, which is then used as a food for developing larvae. The host is ultimately killed. Parasitoids are one of the most widely used biological control agents. Commercially there are two types of rearing systems: short-term daily output with high production of parasitoids per day, and long-term low daily output with a range in production of 4-1000million female parasitoids per week. Larger production facilities produce on a yearlong basis, whereas some facilities will produce only seasonally.

Rearing facilities are usually a significant distance from where the agents will be used in the field, and transporting the parasitoids from the point of production to the point of use can pose problems. Shipping conditions can be too hot, and even vibrations from planes or trucks can disrupt the parasitoids.

Most insect parasitoids are wasps or flies, and usually have a very narrow host range.

Four of the most important groups are:

a)                                                                   Ichneumonid wasps:             Prey mainly on caterpillars of butterflies and moths.

b)                                                                  Braconid wasps:       Tiny wasps attack caterpillars and a wide range of other insects including greenfly. A common parasite of the cabbage white caterpillar- seen as clusters of sulphur yellow cocoons bursting from collapsed caterpillar skin.

c)                                                                   Chalcid wasps:         Among the smallest of insects Parasitize eggs/larvae of greenfly, whitefly, cabbage caterpillars, scale insects and Strawberry Tortrix Moth.

d)                                                                  Tachinid flies:          Parasitize a wide range of insects including caterpillars, adult and larval beetles, true bugs, and others.

Qualities of a Successful Parasitoid in Biological Control Programme: 

A parasitoid should have the following qualities for its successful performance.

1. Should be adaptable to environmental conditions in the new locally 

2. Should be able to survive in all habitats of the host 

3. Should be specific to a particulars sp. of host or at least a narrowly limited range of hosts.

4. Should be able to multiply faster than the host

5. Should be having more fecundity 

6.  Life cycle must be shorter than that of the host 

7. Should have high sex ratio

8. Should have good searching capacity for host 

9. Should be amendable for mass multiplication in the labs 

10. Should bring down host population within 3 years 

Some successful examples 

·         Control of cottony cushion scale, Icerya purchasi on fruit trees by its predatory vedalia beetle, Rodolia cardinalis in Nilgiris. The predator was imported from California in 1929 and from Egypt in 1930 and multiplied in the laboratory and released. Within one year the pest was effectively checked. 

·         For the biological suppression of Water Fern, Salvinia molesta, the weevil, Cyrtobagous salviniae, was imported from Australia in 1982. Exotic weevil, C. salviniae was released for the control of water fern, S. molesta in a lily pond in Bangalore in 1983-84. Within 11 months of the release of the weevil in the lily pond the salvinia plants collapsed and the lily growth, which was suppressed by competition from salvinia resurrected. Apple woolly aphis, Eriosoma lanigerum  in Coonor area  by Aphelinus mali (parasitoid)

·         Control of shoot borers of sugarcane, cotton bollworms, stem borers of paddy and sorghum with the egg parasitoid, Trichogramma australicum @ 50,000/ha/week for 4-5 weeks from one month after planting 

·         Centrococcus isolitus on brinjal; Pulvinaria psidi on guava and sapota; Meconellicoccus hirsutus on grape and Pseudococcus carymbatus on citrus suppressed by Cryptolaemus montrouzieri.

·         Control of Helicoverpa armigera by using egg parasitoid, Trichogramma spp. And larval expupal parasitoid Tachinid flies Carcelia spp.

Fig. 2.4.2. Female tachinid fly C. illota after mating depositing eggs on

body of host larva H. armigera.

1)   Micro-organisms:-

Pathogenic micro-organisms include and bacteria, fungi and viruses. They kill or debilitate their host and are relatively host-specific. Various microbial insect diseases occur naturally, but may also be used as biological pesticides. When naturally occurring, these outbreaks are density-dependent in that they generally only occur as insect populations become denser.

2)   Bacteria:-

Bacteria used for biological control infect insects via their digestive tracts, so insects with sucking mouth parts like aphids and scale insects are difficult to control with bacterial biological control. Bacillus thuringiensis is the most widely applied species of bacteria used for biological control, with at least four sub-species used to control Lepidopteran (moth, butterfly), Coleopteran (beetle) and Dipteran (true flies) insect pests. The bacteria are available in sachets of dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees. B. thuringiensis has also been incorporated into crops, making them resistant to these pests and thus reducing the use of pesticides.

3)   Fungi:-

Fungi that cause disease in insects are known as entomopathogenic fungi, including at least fourteen species that attack aphids. Beauveria bassiana is used to manage a wide variety of insect pests including: whiteflies, thrips, aphids and weevils. A remarkable additional feature of some fungi is their effect on plant fitness. Trichoderma species may enhance biomass production promoting root development, dissolving insoluble phosphate containing minerals.

4)   Viruses:-

A viral biological control that can be introduced in order to control the overpopulation of European rabbit in Australia is the rabbit haemorrhagic disease virus that causes the rabbit haemorrhagic disease.

2.4.6. Pheromonal control

In 1959 Karlson and Butenandt coined the term pheromone. For a Chemical that is secreted into the external environment by an animal and that elicits a specific response in a receiving individual of the same species. It is also referred to as “ectohormone”. Depending on their mode of action pheromones are divided into two general classes. 

i) One which gives a releaser effect – an immediate and reversible behavioural change is produced in the receiving animal.

ii) One which gives a primer effect - a chain of physiological changes is triggered off in the receiving animal. E.g.: Gustatory stimulation, controlling caste determination and reproductive control in social Hymenoptera (Ants and Bees), Isoptera (Termites). 

Behaviour – releasing pheromones are typically odorous and act directly on the central nervous system of the receiving animal. E.g.: Alarm, trail following, aggregation for mating, feeding (or) oviposition. The pheromones that promote aggregation are sex pheromones and aggregation pheromones.

Thus the chemical which is released externally by an animal and influences the behaviour of receiving individuals belonging to the same species is termed as pheromone. Such chemicals are also called as ectohormones. The pheromonal communications in insects have been reported to be in the individuals belonging to orders Orthoptera, Isoptera, Hemiptera, Homoptera, Coleoptera, Lepidoptera, Diptera and Hymenoptera. It was found in a field study that one female pine sawfly had attracted over 11,000 males.

Pheromones giving releaser effect- This type of pheromone causes immediate and reversible change in the behaviour. They act directly on the central nervous system of the recipient, including trail following alarm as sexual activity, aggregation, dispersal and territoriality.

Pheromones giving prima effect- This type of pheromone triggers a chain of physiological events in receiving individuals. It affects the individual through gustatory stimulus having a control on the caste determination and reproductive potential in social hymenopteran and isopteran.

Sex pheromones- They are released by only one sex and trigger the behaviour of other sex of the same species. They facilitate mating and are called as sex attractants e.g. gyptol.

General aggregation pheromones- They may be released by only one sex but affect the behaviour of the individuals of both sexes of the same species. Among pheromones, sex attractants show the greatest potential for pest control. They are emitted purposely for mating. Hundreds of insects have been known to have sex pheromones and many more would be added to the list as a result of continuing researches in this field.

The sex attractant of gypsy moth is Cis-(Z)-7, 8-epoxy-2methly-octadecane, however, the sex pheromone producing glands of moth also contain 2-methly-(Z)-7-octadecane, possibly a precursor of disparlure. The later chemical is a potent inhibitor of the pheromone.

Besides being used for the evaluation of population density of a pest in a locality, sex attractants are being used for the control of insect pests. The male insects can be trapped, thereby reducing the possibility of mating. If such pheromones are released in the field, they may either confuse the males or so fatigue the receptors that they may fail to find mates. Other method is the use of such chemicals which inhibit the perception of the pheromone by the males.

The sex pheromones are specific in their biological activity, the males responding only to a specific pheromone of the female of the same species, and their reactions are directed towards the air currents carrying the odour. The time of release of the pheromones by the females and response by male to them appears to be specific for each species. Effective distances for sex pheromones depend on the threshold concentration for male stimulation and release rate from the female. 

The following sex pheromones have been isolated and identified.

i)     Bombycol           : Silkworm, Bombyx mori

ii)   Gyplure              : Gypsy moth, Perthetria dispar;

iii) Gossyplure          : Pink bollworm, Pectionophora gossypiella

iv) Trimedlure          :  Meditarrnian fruifly, Ceratitis capitapa

v)   Cuelure                           : Melon fly, Bactroceracucurbitae

vi) Litlure                : Tobacco cutworm, Spodoptera litura

vii)  Helilure               : Red gram pod borer,  Helicoverpa armigera

viii)                        Amlure                : Chaffer beetle,   Amphimallon sp

ix) Looplure                         : Cabbage looper, Trichoplusia ni

x)   Ferrolure                        : Coconut  Red Palm Weevil ,  Rhynchophorus ferrugineus

xi) Leucilure                        : Brinjal Shoot and Fruit Borer Leucinodes orbonalis 

Sex pheromones in insect pest management 

1) Monitoring of insect pests: Traps baited with synthetic sex pheromones is useful in estimating population and detecting early stages of pests. Four pheromone traps per acre is recommended.

2) Mass-trapping: (Male annihilation technique): Large numbers of pheromones baited traps can be used in the fields to capture male moths of newly emerged and reduce the number of males for mating.

3) Control of pest by mating disruption: By permeating the atmosphere with higher concentration of the pheromone the opposite sex is rendered confused and unable to locate their mates.

Merits: 1. The pheromones are species specific.

2. They are safe to natural enemies and environment.

3. They require in small doses.

4. They are economical and compatible with other components of IPM.

Demerits: 1. Synthetic pheromones are available only for a few pest species.

   2. Replacement of pheromone lures at regular interval is required for good catch of moths.

   3. Pheromone traps attracts only target pest even when crop is attracted by many other pests.

  4. Pheromone reception and disperse.

Thus, by employing suitable pheromones, insects aggregated at certain places can be easily killed by any of the physical, chemical or mechanical measures. The interference of sex pheromone may reduce the mating frequency of insects resulting in the reduction of pest population.

2.4.7. Concept of IPM in brief

Integrated Pest Management (IPM)

In recent years, modern concept of pest management is based on ecological principles and integration of different control tactics into a pest management system. Integrated control was defined by Stern et al., (1959) as applied pest control which combines and integrates the biological and chemical control. Later the concept of pest management has gained importance .The idea of managing pest population was proposed by Geier and Clark 1961 who called their concept as protective management which later was shortened as pest management. Later Smith and Van Den Borsch in 1967 mentioned that the determination of the insect numbers is broadly under the influence of total agro ecosystem and the role of the principle element is essential for integrated pest management. In 1972 the term IPM was accepted by CEQ (Council of Environmental Quality)

Where, IPM includes:

I - Integration - is harmonious use of multiple methods to control the impact of single pest as well as multiple pests.

P - Pest- any organism that is detrimental to humans including vertebrates and invertebrate or weed or pathogens.

M - Management refers to a set of decisions or rules based on ecological principles, economic and social consideration. The backbone of management of pest in an agricultural ecosystem is the concept of economic injury level (It is the level of the pest up to which the damage can be tolerable).

According to FAO (1967), IPM was defined as “a pest management system in the context of associated environment and population dynamics in pest species. It utilizes all suitable techniques and methods in as compatible manner as possible and maintains the pest population at levels below those cause economic injury.

IPM is a term that is used loosely with many different definitions and methods of implementation. IPM can mean virtually anything the practitioner wants it to mean. Beware of chemical dependent programs masquerading as IPM.

The Six IPM Program Essentials

Monitoring-This includes regular site inspections and trapping to determine the types and infestation levels of pests at each site.

Record-Keeping- A record-keeping system is essential to establish trends and patterns in pest outbreaks. Information recorded at every inspection or treatment should include pest identification, population size, distribution, recommendations for future prevention, and complete information on the treatment action.

Action Levels- Pests are virtually never eradicated. An action level is the population size which requires remedial action for human health, economic, or aesthetic reasons.

Prevention- Preventive measures must be incorporated into the existing structures and designs for new structures. Prevention is and should be the primary means of pest control in an IPM program.

Tactics Criteria- Under IPM, chemicals should be used only as a last resort only, but when used, the least-toxic materials should be chosen, and applied to minimize exposure to humans and all non-target organisms.

Evaluation- A regular evaluation program is essential to determine the success of the pest management strategies.

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2.5 Plant protection appliances

.

2.5.1 Rotary duster, 2.5.2 Knapsack sprayer,   2.5.3 Cyanogas Pump

2.5.1. DUSTER:-

Duster is a machine used to apply chemicals in dust form. Dusters make use of air stream to carry pesticides in finely divided form on the plants. A duster essentially consists of 1. Hopper, 2. Agitator, 3. Feed control, 4. Fan or blower, 5. Delivery nozzle

Types of dusters

1. Plunger type, 2. Knapsack type, 3. Rotary type, 4. Power operated duster

1. Plunger type - it is a simple duster with a small piston. The piston drives current of air over the dust in the hopper. The dust is carried away through a delivery spout. Small hand pump dusters of this type are available and are suitable only where the area to be dusted is small like vegetable gardens.

2. Knapsack type - It is a duster with the powder container carried on the back of the operator. Knapsack dusters have a hopper through which a current of air is blown to pick up the dust. The air current is produced by a lever operated leather bellows. Shoulder straps are used to carry in the field. These dusters are suitable for small areas.

3. Rotary duster – Hand rotary dusters are useful to apply chemicals which are in powder form. It consists of a hopper, a fan, gear box, handle, delivery hose and a deflector plate. When the handle is rotates the fan rotates at high speed and draws air from outside. The chemical from hopper is fed in to the air stream in the suction side of the fan. The chemical mixes with the air, passes through the delivery line and is applied on the plants. The rate of delivery can be regulated It is used to apply powdery chemicals to vegetables, sorghum crops.

4. Power operated duster- Power operated duster mainly consists of a power driven fan, a hopper and a delivery spout. The fan creates strong air flow which causes the dust to blow off from the hopper to a considerable distance vertically or horizontally. Direction of dust is regulated by a movable spout suitably fitted with the unit. These types of dusters are used for large areas.

5. Arial duster or crop duster - an aircraft is used for dusting or spraying large acreages with pesticides. Aerial spraying and dusting permit prompt coverage of large areas at the moment when application of pesticide is most effective and avoid the need for wheeled vehicles that might damage crops. The technique was greatly improved in the 1960s with the development of ultra-low-volume applicators, in which concentrated pesticides are distributed in amounts as small as 1 ounce per acre (70 grams per hectare).

Fig. 2.5.1. Types of Shoulder rotatory duster

2.5.2. SPRAYERS:-

Sprayer is a machine used to apply liquid chemicals on plants to control pest and diseases. It can also be used to apply herbicides to control weeds and to spray micronutrients to enhance plant growth.

The main functions of a sprayer are

•          Breaking the chemical solution in to fine droplets of effective size.

•          Distributing the droplets uniformly over the plants.

•          Applying the chemicals with sufficient pressure for positive reaching the plants

•          Regulating the amount of liquid applied on plants to avoid excessive application.

Desirable quality of a sprayer

      A good sprayer should posses the following qualities

•          It should produce a steady stream of spray material in desired droplet size so that the plants to be treated may be covered uniformly.

•          It should deliver the liquid at sufficient pressure so that the spray solution reaches all the foliage and spreads uniformly over the plant body.

•          It should be light in weight yet sufficiently strong, easily workable and repairable.

BASIC COMPONENTS OF A SPRAYER

Components of a sprayer are as follows:

i) Pump, ii) Chemical tank, iii) agitator, iv) Air chamber, v) pressure gauge, vi) Pressure regulator,                 vii) valves, viii) Strainer, ix) suction line, x) delivery line, xi) nozzles

i)        Pump: A pump is a device used to move fluids, such as liquids or slurries, or gases from one place to another. A pump displaces a volume by physical or mechanical action. Most hydraulic sprayers are equipped with positive displacement pumps capable of developing pressure, required for many spraying jobs. The discharge capacity of these pumps is approximately proportional to the speed. A pressure relief valve or by-pass valve is required to protect these positive acting pumps from damage when the discharge line is closed and for the convenience of the operator.

ii)      Tank: It is the container to hold the chemical solution. It is made up of PVC, Brass, etc. It is usually made of metal sheet or synthetic rubber or plastic having well resistant quality against corrosion, erosion, and similar actions. The size of the tank varies according to the pump capacity and the requirements.

iii)    Agitator: It is the device which stirs the solution and keeps the contents in homogenous condition. Positive agitation of spray material in the tank is essential to permit using the full range of spray materials including powdery emulsions, fungicides, cold water paints or other spray material. The propeller or paddle type mechanical agitators or hydraulic agitators are very common.

iv)    Air chamber: In a reciprocating type pump, an air chamber is provided on the discharge line of the pump to level out the pulsations of the pump and thus providing a constant nozzle pressure.

v)      Pressure gauge: It is a dial gauge which indicates the pressure at which the liquid is delivered from the pump. A pressure gauge properly calibrated, within the pressure range of the pump is provided on the discharge line to guide the operator for making proper adjustment of the pressure at site.

vi)    Pressure regulator: The pressure regulator serves several important functions. It is the means of adjusting the pressure as required for any spray job within the pressure range of the pump. With the positive displacement type of pump, it also serves as a safety device in automatically unloading the excess pressure by directing the unused discharge flow from pump back to the tank.

vii)  Valves: A valve is a device that regulates the flow of a fluid by opening, closing, or partially obstructing various passageways. Cut-off valve is provided in the delivery line to control the flow from the pump. By-pass valve is provided in the delivery line to by-pass the flow from pump to tank when flow in delivery line is reduced than the pump capacity

viii)Relief valve - It is an automatic device to control the pressure of fluid or gas within a range a predetermined pressure.

ix)    Strainer: It is a small circular plastic ring with nylon wire mesh to filter any dust particle coming with the chemical solution It is included in the suction line between the chemical tank and the check valves. In some sprayers strainers are provided at the mouth of the chemical tank e.g. Knapsack sprayers.

x)      Nozzles: It is the component which breaks the fluid in to fine droplet. Automation of spray fluid is usually achieved by discharging the liquid through an orifice called nozzle under pressure. Atomization is also achieved by breaking up the jet of liquid with a blast of air.

xi)    Spray gun: It is a hand held metallic of PVC pipe to one end of which the nozzle is

    fitted and a flow cut off valve and a handle are fitted at the other end. The delivery hose is connected to the spray gun. It conducts the fluid from the delivery hose to the nozzle. The operator holds the gun and does the spraying job. Area of coverage by a spray gun is less compared to the coverage of a spray boom. Spray guns are used with low power sprayers E.g. Knapsack sprayers, rocker sprayer.

xii)  Spray boom - It is a long metallic or PVC pipe to which several nozzles are fitted with. The delivery hose is connected to the spray gun. High power and high capacity sprayers use spray booms. The coverage is larger compared to spray guns. Booms are usually mounted on suitable structures and used. E.g. Tractor operated sprayers, power tiller operated sprayers.

xiii)Over-flow pipe - It is a conduit pipe through which excess fluid from a pump is bypassed in to chemical tank by the action of a relief valve or pressure regulator.

Salient features of knapsack sprayers:

1. Useful to develop high pressure with less effort.

2. Light in weight and easy to carry on the back of the operator.

3. High work rate and economical.

4. Robust and simple to maintain.

5. Both left and right hand operation

6. Capacity10-15 lit.  Easy to spray chemicals.

Fig.2.5.2. Knapsack Sprayer

2.5.3. Cyanogas pump:-

The cyanogas pump is and a special pest control appliance designed for fumigation of suitable pesticides likes calcium cyanide against subterranean pests. Fumigation is a very effective method of pest control and is employed usually in closed chambers to fumigate stored products.

Cyanogas pump consist of Pump itself with a long foot rest. In between a foot rest and pump, a glass container is suspended which holds the calcium cyanide. A pump is provided at the top handle and is used for pumping the air through the glass into the delivery hose. The glass container is filled with dust or gas of calcium cyanide. It is suited for small scale operations like fumigating the rodents like rat burrows, kitchen, gardens, poultry houses, sheds etc. with calcium cyanide or sodium cyanide. The mask should be used during operation for protection.

Fig.2.5.3. Cyanogas pump

*****

2.6   Hazards of pesticides on human and antidotes

Hazards of pesticides on human:

There is no doubt that pesticides harm human health, domestic animals and other environmental biotic and abiotic components. The World Health Organization estimates that there are 3 million severe acute poisonings worldwide each year and 2, 20,000 deaths attributable to pesticides. It is necessary to bear in mind that all pesticides are biocides, and that at sub - cellular level most organisms are dependent on similar chemical processes. 

There are two categories of harm that must be considered.

I. Acute effects: These covers the immediate effects which appear soon after poisoning. No one seems to know how many people are affected each year by pesticides. Most minor exposures caused relatively minor acute symptoms. These include nausea, dizziness, vomiting, abdominal pain, diarrhoea, headache, sweating and thirst.

II. Chronic effects: The chronic effects of pesticide poisoning are more difficult to attribute to pesticides simply because they appear long after initial exposure to the chemicals, and they can be due to very small amounts of chemical over many years. Exposure may come from food, ordinary household atoms like clothes, pot plants and pets or from household chemicals such as those in garden sprays, rat poisoning and wood preservatives. Other sources include factories which make or use pesticides, and many other places of work where pesticides happen to be present. Following are some of the agents which produce chronic effects in human-

Mutagens- The most feared chronic effects those are produced by mutagens are cancers, and deformities to the embryos in the womb. These defects are due to pesticides and chemicals. The damage can be to a small segment of chromosome or gene, or can affect a larger length of a chromosome.

Carcinogens- Many pesticides are called either potential or presumed carcinogens on the basis of laboratories studies and experience with human populations. These are often classified with the quaint name of suspected carcinogens.

Teratogens- These cause deformities to the new born foetus, producing miscarriages as well as congenital defects. Pesticides by interfering with cellular metabolism in very active growth centres like those in the rapidly growing embryo.

Other Chronic effects- Pesticides may produce reactions like asthma and dermatitis of various types, and they may induce hypersensitivities. Pesticides also cause damage to kidneys, liver, lungs, and heart, as well as range of nervous disorders and allergies. 

Safe use of Insecticides:

1. Mixing and loading operations are the most hazardous because they generally result in possibilities of exposure i.e. spills

2.   Read label carrying out the necessary calculations for the required dilution of the insecticide

3.   Obtain proper equipment, including protective clothing, etc

4.   Never work alone while handling highly hazardous insecticides

5.   Mix insecticides outside or in a well ventilated area. Never position any part of the body directly over the seal while opening .Always stand upwind when mixing or loading the insecticides

6.   Clean up spilled insecticide immediately from skin, clothing etc.

7.   Persons engaged in handling, mixing or applying insecticides should not smoke, eat or drink while working.

8.   Do not use mouth to siphon an insecticide from the container.

9.   Avoid drift.

10. Guard against drift of insecticides on to nearby crops, field, fish pond, stream or livestock

11. Do not spray when it is windy.

12. Do not spray or dust when it is likely to rain.

13. Do not use poor quality or leaky equipment

14. Take the most needed parts/tools to the field (site of application)

15. Never allow the children to apply insecticides

16. Do not blow out the clogged nozzles with the mouth

17. Cleanliness and maintenance of insecticide application equipments and keep separate sprayers for herbicides

18. Do not eat, drink or smoke during application operation and later do these only after washing hands and face thoroughly

19. Never leave insecticides and equipments unattended in the field

20. The insecticides should always be stored in their original containers and kept in a locked cupboard where they are out of reach of the children and the domestic animals

21. These should be kept away from food or feed stuffs and medicines

22. Instructions found on the labels should be carefully read and strictly followed.

23. The empty containers, after the use of the insecticide, should be destroyed and should not be put into some other use.

24. Persons engaged in handling insecticides should undergo regular medicinal check-up.

25. In case of any suspected poisoning due to insecticides, the nearest physician should be called immediately.

INSECTICIDE POISONING AND ANTIDOTES

Symptoms of mild poisoning

1.   Headache

2.   A feeling Of Sickness (nausea)

3.   Dizziness

4.   Fatigue

5.   Irritation of the Skin, Eyes, Nose and Throat,

6.   Perspiration

7.   Loss of Appetite

Symptoms of moderate poisoning

1.  Vomiting,

2.  Blurred vision,

3.  Stomach cramps,

4.  Rapid pulse,

5.  Difficulty in breathing, constricted pupils of the eyes,

6.  Excessive precipitation,

7.  Trembling and twitching of muscles, fatigue and nervous distress headache,

Symptoms of severe poisoning

1.   Convulsions

2.   Respiratory failure

3.   Loss of consciousness

4.   Loss of pulse

Symptoms due to Chlorinated hydrocarbons poisoning

       1.  Uneasiness

Symptoms due to Chlorinated hydrocarbons poisoning

1.  Uneasiness

2.  Headache

3.  Nausea

4.  Vomiting

5.  Dizziness and tremors

6.  Convulsions

7.  Respiratory arrest followed by coma

8.  Leucocytosis and rise in blood pressure.

Symptoms due to organophosphate and carbamate insecticides poisoning

1.   Headache, giddiness, vertigo, weakness, excessive mucous discharge from nose and sense of tightness are symptoms of inhaled exposures.

2.   Nausea followed by vomiting, abdominal contraction, diarrhea and salivations are symptoms of ingestion.

3.   Loss of muscle coordination, speech defects; twitching of muscles; difficulty in breathing; hypertension; jerky movements; convulsions and coma indicate seriousness of poisoning.

4.   Death may occur due to depressions of respiratory centre

5.   Headache, giddiness, vertigo, weakness, excessive mucous discharge from nose and sense of tightness are symptoms of inhaled exposures.

6.   Nausea followed by vomiting, abdominal contraction, diarrhea and salivations are symptoms of ingestion.

7.   Loss of muscle coordination, speech defects; twitching of muscles; difficulty in breathing; hypertension; jerky movements; convulsions and coma indicate seriousness of poisoning.

8.   Death may occur due to depressions of respiratory centre

Zinc phosphide

1.  Nausea

2.  Vomiting

3.  Diarrhea

4.  Severe abdominal pain followed by symptom free period of eight hours or longer

Aluminum phosphide

1.   Headache

2.   Giddiness

3.   Nausea

4.   Diarrhea and mental confusion

5.   If treatment is delayed, coma, loss of reflexes may develop and death may occur from respiratory or circulatory collapse

First Aid Operations:

Many accidental pesticide deaths are caused by eating or drinking the chemical. Some applicators die or are injured when they breathe pesticide vapors or get pesticides on their skin. Repeated exposure to small amounts of some pesticides can cause sudden, severe illness. All pesticide handlers should know and thoroughly understand first aid treatment for pesticide poisoning. Call local emergency response provider and local emergency medical facility immediately and

1.   Move immediately patient to fresh air

2.   Loosen all knots of clothes and change overalls.

3.   Flush eyes with copious cold water till irritation subsides

4.   Wash the patient thoroughly with plenty of soap and water.

5.   Keep the patient calm, comfortable and warm.

6.   In case of accidental ingestion, induce vomiting by administering a glass of warm water mixed with two spoons of common salt or putting the forefinger at the base of plate.

7.   Show label leaflet of pesticide for identification

8.   If breathing is stopped provide artificial breathing.

Swallowed poisoning

1.   Remove poison from the patient’s stomach immediately by inducing vomiting.

2.   Give common salt 15 g in a glass of warm water as an emetic and repeat until vomit fluids is clear.

3.   Gently stroking or touching the throat with the finger or the blunt end of a spoon will aid in inducing vomiting when the stomach is full of fluid.

4.   If the patient is already vomiting, do not give emetic but give large amounts of warm water and then follow the specific directions suggested

Inhaled poisons

1.   Carry the patient to fresh air immediately,

2.   Open all doors and windows.

3.   Loosen all tight clothing.

4.   Apply artificial respiration if breathing has stopped or is irregular and avoid vigorous application of pressure to the chest.

5.   Prevent chilling and wrap the patient in a blanket.

6.   Keep the patient as quiet as possible.

7.   If the patient is convulsing, keep him in bed in some dark room.

8.   Do not give alcohol in any form.

Skin contamination:

1.   Drench the skin with water.

2.   Apply a stream of water on the skin while removing clothing.

3.   Rapid washing is most important for reducing the extent of injury.

Eye contamination:

1.   Hold eye lids open.

2.   Wash the eyes gently with a stream of running water immediately.

3.   Delay of even a few second greatly increases the extent of injury.

4.   Continue washing until physician reaches.

5.   Do not use chemicals as they may increase the extent of injury.

Antidotes:

An antidote is a substance which can counteract a form of poisoning. The term ultimately derives from the Greek antididonai, "given against". Thus antidote is a medicine or a remedy against poisoning, which neutralizes the toxicity of insecticides and their toxic effects.

Antidotes in Case of Pesticide Poisoning-

A. General Antidotes:

a.    Removal of Poison: Remove poisons by including vomiting.

b.   The “Universal Antidote”: A mixture of 7 g of activated charcoal, 3.5 g of magnesium oxide and 3.5 g of tannic acid in half a glass of warm water may be used to absorb or neutralize poisons. This mixture is useful in poisoning by acids, liquid glycosides and heavy metals. Except in cases of poisoning by corrosive substances it should be followed by gastric lavage.

c.    Gastric Lavage (Removal of Stomach Contents): Lavage is the most important method for removing poisons from the stomach.

d.   Demulcents (Substances having Soothing Effect): After the stomach has been emptied as completely as possible, give one of the following:

 i.   Raw egg white mixed with water.

 ii. Gallatin 9 to 18 g dissolved in 570 ml of warm water.

 iii. Butter

 iv. Cream

 v. Milk

 vi. Mashed Potato

 vii. Flour and water

B. Specific Antidotes for Some Pesticides:

The following emergency treatments are prescribed for poisoning by some specific pesticides.

a) BHC, Chlordane, DDT, Toxaphene, Methoxychlor and other Organochlorines:

If swallowed, give 28 g of magnesium sulphate (Epsom salts) in a glass of water, followed by hot tea or coffee. Inject 10 ml of 10% calcium gluconate intravenously. It necessary, inject Phenobarbital 0.1 g intravenously. Feed the patient with rich carbohydrate and calcium diet to prevent liver damage.

b) Organophosphorus Compounds (Parathion, HETP, and TEPP etc):

If the patient has blurred vision, abdominal cramps and tightness in the chest, give two tablets of atropine (each 1/100 g). Administer artificial respiration in case of respiratory failure. Do not give morphine.

c) Zinc Phosphide:

If the patient has taken the poison within 24 hours, proceed as follows: (1) Stir one teaspoonful of mustard powder into a glass of warm water and make the patient drink it: (2) After vomiting from treatment (1) has stopped, give the patient 5 g of potassium permanganate dissolved in a glass of water: (3) Ten minutes after the above treatment (2) have the patient drink a solution made of ½ teaspoonful of copper sulphate in a glass of water; and (4) Fifteen minutes after treatment (3) give the patient a solution made by dissolving one tablespoonful of magnesium sulphate (Epsom salts) in a glass of water. If the poison has been taken earlier than 24 hours, omit treatment (1) above and give the others in order.

Specific antidotes:

1.   Atropine is the usual antidote for organophosphate and carbamate poisoning. It can be given orally and in severe cases, injections are given. Repeated injections may be required.

2.   2 PAM: It is injected intravenously as an antidote in organophosphate poisoning. It should not be used in case of carbamate poisoning.

3.   Calcium gluconate is recommended as an antidote for some organochlorine insecticides

4.   Vitamin K is the preferred antidote for anticoagulant poisoning such as warfarin.

5.   Dimercaprol (BAL) is recommended for arsenic poison