In this article we will discuss about the methods and techniques used for controlling pests.
Legislative Control:
Legislative control involves enactment of laws to regulate the entry, establishment and spread of pests. Man has often realized that when insects and other animals appear as pests in epidemic form, they become formidable enemies and in most cases, cannot be controlled with individual effort.
When a pest like the desert locust appears in a country, it becomes a national calamity. The entire population and the government of the country have to make a united effort to meet the threat. The massive operations required have to have the sanction of the society through legislation and resources have to be mobilized for financial backing.
Legislation is also imperative to stop the accidental entry, from outside the country, of certain pests, which may not be present in that country. Discipline must be enforced among citizens not to bring in certain prohibited material which they might attempt because of ignorance of the danger involved or because of sheer temptation.
The legislation is of following four kinds:
(i) Legislation for foreign quarantine to prevent the introduction of new pests from abroad.
(ii) Legislation for domestic quarantine to prevent the spread of established pests within the country or within a particular state.
(iii) Legislation for notified campaigns of control against pests.
(iv) Legislation to prevent the adulteration and mishandling of insecticides or other devices used for the control of pests.
The history of pest-control legislation in India is very interesting. The first Act in this country was passed in 1906 under the Sea Customs Act of 1878 to stop the entry of the Mexican cotton boll weevil, it was followed by the present Destructive Insects and Pests Act No.II passed on 3rd February 1914 at the instigation of Bombay Chamber of Commerce.
Thus, provisions were made for preventing the entry of foreign insect pests, like the American cotton boll weevil, Anthonomus grandis Boheman, and others that might be harboured in agricultural products. The entry of such plant material as sugarcane and unginned cotton was banned totally.
Plants and seeds, in general, could be imported under certificates of health through notified ports where they could be inspected by qualified staff, fumigated properly and kept in quarantine before being released. There, they could be examined for the presence of eggs of pests or for the presence of bacteria, fungi and other pathogens, which are normally not killed by fumigation. The import of useful insects such as parasites was permitted only to scientific institutions.
According to various amendments of the Government of India Act, 1914, provisions were made for adopting control measures against local and exotic pests in centrally administered territories and states after first obtaining sanction from the President of India or from the Governor.
Before control measures could be adopted by the state, it was considered necessary to- (i) declare the organism to be injurious, (ii) place the infested area under quarantine, and (iii) ensure that preventive and remedial measures were prescribed. In this Act, provisions were also made for the state governments to pass their own legislation for adopting remedial measures. Thus, the East Punjab Agricultural Pests, Diseases and Noxious Weeds Act were passed in 1949. Other states have passed similar legislation.
According to notification No. 1581, dated 1st October, 1931, under the Destructive Insects and Pests Act, 1914, provisions were made to restrict the imports of cotton from America and the West Indies, and to bring air freight within the scope of the Act. The import of cotton was allowed, provided it was fumigated and disinfected at the port of entry. The import of plant material by air was prohibited except under strict quarantine for scientific purposes, with prior permission of the Government of India.
Similarly, fruits and vegetables from Afghanistan were allowed to be imported, provided they were accompanied with certificates of health issued by a competent authority. The import of seeds by air was exempted, but the entry of some of the seeds, namely cotton, Egyptian clover, flax, rubber, coffee and sunflower was banned. The import of potato seed from areas infested with golden nematode and wart disease was prohibited.
Under this Act, notifications were also issued from time to time for the inspection, disinfection or destruction of plant material to be transported by road or by rail within the country. This checked the further spread of pests and diseases that might be present in certain plant parts.
A number of such plants and plant material harbouring various pests were listed and the station masters of railway stations and other inspection authorities were given legal powers. The owners causing hindrance to the inspection of material at the destination were liable to be prosecuted and punished with fine up to Rs. 1000.
These provisions were made to restrict the spread of San Jose scale, Quadraspidiotus pemiciosus (Comstock); cottony cushion scale, Icerya purchasi Maskell, the potato- wart disease, water hyacinth, lantana, spike disease of the sandal tree and the bunchy-top disease of banana.
According to the provision of the East Punjab Agricultural Pests, Diseases and Noxious Weeds Act 1949 (and other similar State Acts), the state government could enforce, when necessary, control measures for the eradication of pests, diseases or weeds, such as locust and grasshoppers, hairy caterpillars, rats, pyrilla and the Gurdaspur borer of sugarcane, Acigona steniellus (Hampson), ergot of pearl-millet, pohli (Carthamus oxycantha), water hyacinth (Eichhornia crassipes) and other weeds.
The Government would issue a notification, declaring the pest or weed to be noxious, specifying the area and the period for which it would remain in force, giving proper directions for carrying out control measures, and for adopting other practices against the introduction, reappearance or spread of the pest, disease or the weed concerned.
The sowing of a particular crop for a given period could also be prohibited. The farmers of the notified area would be bound to carry out the preventive or remedial measures. If, on inspection, it was found that a given farmer did not carry out these instructions and the pest was still present, the Inspector Would issue a notice that the operations must be carried out within a specified period, failing which the Inspector with his staff would perform this job at the expense of the farmer.
The amount involved would be recoverable as arrears of land revenue. It would appear that the procedures laid down were lengthy and it would be rarely possible to enforce, in case of default, the measures recommended during a crop season. For that reason, the implementation of the Act has not been very effective and pohli, for example, remained in the fields after the harvest of wheat fields throughout North India. It was only because of double cropping and intensive agriculture since 1965 that this weeds gradually disappeared in Punjab and other states.
In other cases where free pesticides were supplied for the control of pests, the success was greater. Anti-rat campaigns have been carried out by the Department of Agriculture and the Community Development Organization, and the cutting of sugarcane tops for the control of the Gurdaspur borer has been adopted in the factory zones (10 km of sugar factory) of Punjab and Haryana with considerable success.
It has been noticed that when the entire government machinery and the public were mobilized and the effective instruments, such as the dusting machines and insecticides, were made available to combat locust swarms, the operations were very successful. It is to the credit of the Governments of Punjab and Haryana, and to the rural farmers that, since 1963-64, the locust has not been allowed to breed and not a single swarm originated from these areas, although conditions have been favourable for its breeding.
It is only natural to believe that in spite of best quarantine measures to restrict the import of new pests from abroad or to restrict the spread of an organism from one part of the country to another, new problems will continue to appear and, therefore, notifications or amendments to the 1914 Act will be needed from time to time. The East Punjab Act 1949 and other similar Acts of various states also need amendments to make the Governments effective in their implementation.
The unadulterated sale of pesticides under proper labels, giving instructions for their safe usage, also needs the attention of the Government. In the absence of any legislation, certain pesticides were brought under the purview of the Poisons Act 1919, and the Drugs Act 1940.
However, in view of the fast expanding pesticide industry and the widespread use of these highly poisonous chemicals, more specific provisions were needed to safeguard public interests and even human life. Consequently, a special legislation to regulate the manufacture, transport, handling, sale and use of pesticides was envisaged and a new Bill, namely the Insecticide Bill was passed by the Indian Parliament in September 1968.
Under this Act, provisions have been made for the compulsory registration of pesticides and for the establishment of pesticide laboratories to carry out various functions under the legislation. Earlier, the Prevention of Food Adulteration (PFA) Act, 1954 was enacted on September 1954, for prevention of adulteration of food. Also, Pesticides Management Bill, 2008 is currently under active consideration of the Government of India.
Cultural Control:
The cultural methods of insect control comprise regular farm operations, which are so performed as to destroy the insects or to prevent them from causing injury. A large number of insects are normally killed by farmers unconsciously when they expose them to adverse climatic or biological conditions through agricultural operations like ploughing, hoeing, weeding, etc.
A still more effective kill can be obtained by following improved agricultural practices or so synchronizing the existing practices with the life cycles of the pests, that the weakest links in the life cycle of pests are subjected to adverse environmental conditions. Moreover, many cultural practices enhance the functional biodiversity of the natural enemies whereas some others negatively affect it.
By adopting various cultural practices such as preventive measures, the pests may either be killed directly or indirectly. Since these methods must be employed far in advance of the actual appearance of the pest and the consequent damage, the control achieved is not so spectacular and thus has not a strong appeal to the farmers. These methods cost hardly anything because all that is required is to adjust the time of ploughing, sowing, irrigating, harvesting, etc. Crop rotation and improved management of the farm are also important.
The effective cultural practices can be further improved or new ones devised if the life-history, behaviour, habitat and ecology of the pest concerned are fully understood. A method, effective against one species, might not be effective against another owing to variation in its biology. Proper timing of the practices is the keynote of success.
It is not useful to try to destroy the shelters of hibernating insects after they have emerged from them and reached the host plants. Cultural methods of control are particularly important for the destruction of tissue-borers which are not hit by insecticides or easily attacked by natural predators and parasites.
The following are the main characteristics of cultural practices which should be viewed in the context of IPM:
(i) Cultural practices are simple modifications or adaptations of regular farm operations. The extra cost of their incorporation into pest management system is minimal in most cases. These are often the only control options economically feasible for low-value crops.
(ii) Cultural practices generally produce no or negligible undesirable ecological consequences.
(iii) Cultural control is primarily aimed at prevention and reduction of pest outbreaks.
(iv) The results of cultural practices are often difficult to quantify primarily because ecological relationships within crop systems are poorly understood.
(v) Cultural control tactics are an effective means of pest control. These do not result in total elimination of the pest thus allowing for conservation of beneficial insects.
(vi) Most cultural practices indirectly affect the pests and these are relatively slow acting and thus cannot resolve a pest outbreak. These are, however, important in minimizing pest damage by preventing pest build-up, rather than relieving an already existing pest problem.
(vii) Cultural practices make cropping systems less friendly to the establishment and proliferation of pest populations.
(viii) Cultural practices are designed to have positive effects on farm ecology and pest management; however, negative impacts may also result due to variations in weather, changes in crop management or perturbations in agro-ecosystems.
(ix) Timing is critical to the success of most cultural practices; accordingly, the implementation of cultural control tactics requires thorough knowledge of pest ecology and its interaction with the cropping system.
(x) An area-wide deployment of cultural practices is essential for the effectiveness of the practice in IPM.
(xi) Cultural practices are often pest-, crop and region-specific. Care should be exercised in transferring tactics to a region with markedly different agro-ecological conditions.
Mechanical and Physical Control:
Mechanical and physical control measures involve the use of force or physical factors of the environment with or without the aid of special equipment. The physical control measures give immediate tangible results and are generally popular and convincing to the farmers, even though they are time-consuming, laborious and are often applied when much damage has already been done. These control measures are generally ineffective on a large scale and cannot be applied commercially.
Manual Labour:
It means working with hands, sometimes with the aid of some simple equipment, like bags, nets, etc.
(i) Hand-Picking:
This is the most ancient method employed by man and is still being used for picking out lice from human hair.
In the field, insects can be hand-picked if they are:
(a) Easily accessible to the picker,
(b) Large and conspicuous, and
(c) Present in large numbers.
This method is recommended for dealing with adults and egg-clusters of the lemon butterfly, grubs of the mustard sawfly, Athalia lugens (Klug) and all the developmental stages of Epilachna spp.
(ii) Handnets and Bagnets:
The collection of adults with hand-nets is recommended for pyrilla, Pyrilla spp., when these insects are migrating in April-May from maize to sugarcane. The field-bag is a strong cloth bag, 2 metres long with its mouth measuring 1 × 1.5 metres and supported with bamboo sticks and two strings on the upper side.
It is scraped on the surface of the ground by two men and is recommended against surface grasshoppers, rice grasshopper, crickets, etc. Six men can cover one hectare in six hours. A one-man field bag can also be devised by reducing the size of its mouth.
(iii) Beating and Hooking:
Killing houseflies with fly-flappers and locusts with brooms or thorny bushes is effective. On coconut palms, the rhinoceros beetle can be picked out of the holes with the help of crooked hooks made of iron.
(iv) Shaking or Jarring:
Shaking small trees or shrubs, particularly early in the morning in the cold season when the insects are benumbed, and collecting them in open tubs containing kerosenized water or simply burying them in pits is effective against locust and the defoliating beetles, Adoretus spp.
(v) Sieving and Winnowing:
These are commonly employed against insect pests of stored grains. A good number are removed with these operations, particularly the grubs of Tribolium castaneum (Herbst) and Trogoderma granarium Everts, which infest wheat.
(vi) Clipping:
Clipping off the top of rice seedlings containing egg masses of yellow stem borer and grubs of hispa would reduce carry-over of infestation from seed bed to field.
(vii) Mechanical Exclusion:
Mechanical exclusion consists of the use of devices by which insects are physically prevented from reaching crops and agricultural produce.
The various mechanical methods include:
a. The application of a fluffy cotton band 15 cm wide or a band of a sticky material like ‘Ostico’ or a band of folded slippery sheets like alkathene around the trunk of a mango tree to prevent the upward movement of the mango mealybug, Drosicha mangiferae (Green).
b. Screening windows, doors and venltilators of houses to keep away house flies, mosquitoes, bugs, etc., is quite helpful. In the morning and at dusk when mosquitoes gather on the screen they can be squashed with a piece of cloth.
c. Wrapping individual fruits of pomegranate and citrus with butter paper envelopes to save them from attack of the pomegranate butterfly, Deudarix isocrates (Fabricius) and fruit- sucking moths, Ophideres spp., respectively. Maize cobs can be protected from the attack of crows if the nearest leaf is wrapped around the exposed portion of the cob.
d. Trenching fields or erecting barriers, 30 cm high, in order to save crops from the invading bands of locust hoppers or the red hairy caterpillars, is quite helpful.
e. Placing four legs of a meat-safe in vessels containing water to prevent ants from ascending, is also useful.
f. Using red light in the monsoons to keep away most of insects, and to keep the fields well lit with white light at night to protect against certain insects has been quite effective. Light reflection by aluminium foil is effective against aphids. Similarly, light reflected by plastic ribbon bands or plastic flags hung in the ripening rice fields will protect the crop from bird attack.
g. Scaring birds by creating noise with explosives is quite effective; an automatic device is available in which an explosive gas catches fire intermittently and a loud noise is produced.
(viii) Mechanical Traps:
Various types of traps have been devised for collecting and killing different types of insects:
a. Cricket Trap:
This is a deep cylindrical vessel containing beer as bait and having wooden splinters to aid crickets to reach the bottom.
b. House-Fly Trap:
The house-fly trap is a box containing a piece of stale cake, with a side opening for the insects to get in only to be trapped in a wire-gauze cage on the top.
c. Light Traps:
Light traps against the red hairy caterpillar, Amsacta moorei (Butler) and the ber beetle, Adoretus spp. have given good results. An electric bulb or a petromax lamp is placed in the centre of a wide flat vessel containing kerosenized water in which the moths or the beetles get drowned. Trapping adults through light traps has proved useful in controlling plassey borer, root borer and white grub damage in sugarcane.
d. Air Suction Traps:
These may be fixed in godowns against stored grain pests.
e. Electric Traps:
These are live metal screens on which birds or insects are electrocuted.
(ix) Burning:
The burning of locust adults or hoppers with the help of flame torches and flamethrowers, although costly, has a good psychological effect in mobilizing the public for locust control operations.
Manipulation of Physical Factors of Environment:
(i) Application of Heat:
(a) Superheating of empty godowns to a temperature above 50°C for 10-12 hours will kill the hibernating stored-grain pests.
(b) Exposing infested grain to the sun on a pucca floor in June also kills stored grain insects in the adult stage.
(c) If cotton seed is exposed to 52°C for 5 minutes, the hibernating larvae of the pink bollworm, Pectinophora gossypiella (Saunders), are killed.
(d) By steaming woollen clothes, the woolly bear, Antherenus vorax (Waterhouse), is killed
(ii) Application of Cold:
(a) Refrigeration at 5-10°C of all eatables, including dry fruits and woollen clothes, will kill insects.
(b) When stored grains are exposed to subzero temperatures by opening doors and windows of godowns, the insects are killed.
(iii) Manipulation of Moisture:
By raising or lowering the moisture content of food and other materials, unfavourable conditions are created for insect pests:
(a) Draining stagnant water kills the breeding mosquitoes.
(b) Reducing moisture content of grains below 8 per cent will make these unfit for the consumption of stored grain pests.
(c) Soaking logs in water over extended periods (15 days) drowns the boring weevils and larvae of the wood wasps.
Biological Control:
A large number of predators, parasitoids, bacteria, fungi and viruses regulate the populations of insect pests under natural conditions. This regulation has been termed as ‘biological control’, and has been defined as the action of parasitoids, predators or pathogens in maintaining another organism’s population density at a lower average than would occur in their absence.
In the applied sense, it may be defined as the utilization of natural enemies to reduce the damage caused by noxious organisms to tolerable levels. Success in biological control is measured as complete, substantial or partial according to the extent of population regulation achieved.
Complete success is achieved when the populations of the target pest are maintained below economic threshold levels in an extensive area so that pesticide treatments become rare, if ever necessary. Substantial success is achieved if only occasional pesticide treatments are required to maintain pest populations below economically damaging levels. Partial success refers to cases in which pesticide application remains necessary but less frequent or where complete success is achieved in only a major portion of the pest-infested area.
A parasite is an organism which at one time or other lives on the body of the host which may or may not be killed after it has completed development. A parasitoid is an organism which completes its life on one host only and kills it. A predator, on the other hand, is a free living animal and kills the host immediately.
Superparasitism is a type of parasitism where more individuals of the same species are present in a single host than can complete development in a normal way. Multiple parasitisms are a type of parasitism where the host is attacked by two or more species of parasitoids. Hyperparasitism is a type of parasitism in which a parasitoid attacks another parasitoid.
In 1949, E.A. Steinhaus coined another term ‘microbial control’ in which pathogens are employed to control insect pests. Since then some scientists feel that the scope of biological control should be further widened by including host plant resistance, control by agricultural practices, and genetic control by the use of lethal genes, control by causing sterility in the pest either by radiation or by chemicals. These methods, including the destruction and control of weeds by insects, are also termed by some as para-biological control methods or bio-ecological methods. The control of pests by chemicals is quite distinct from others.