|1 Crore+ students have signed up on EduRev. Have you?|
Chari Committee Report
The Chari Committee has submitted its report to the central government on the reforms needed in the coal sector. The recommendations include :
- Phased deregulation of coal prices
- Offering of blocks on a competitive bidding basis
- Setting up a separate explorative agency under the coal ministry
- Setting up of a regulatory agency to arbitrate over disputes relating to coal pricing
- Introduction of free mining
- Reduction in coal import duty
- Setting up of new power projects at the coal mine pit head
- Development of lignite fired plants in south and west India
- Improvement of breathing facilities by the surface transport ministry, and
- Steps to ease the linkage problem faced due to inadequate rail infrastructure
Based on the above recommendations, the Central Cabinet has approved the new Integrated Coal Policy (NICP) on February 11, 1997.
Integrated Pest Management
Today Air, Land and Water are alarmingly polluted to the extent that sensitive species around the world are becoming extinct at a rate never experienced before. There are about 60,000 chemicals that have become inextricably associated with us from fabric to food; these ubiquitous pesticides on land and in air and water pose a major threat by affecting all the components of life. The advent of DDT in 1940's revolutionized global agriculture and it was thought that the war with the insects was over once for all. But today the pests have become more resistant and we need more pesticides, for instance in 1995-1996, 1.4 lakh metric tonnes of pesticides required for control of pests of crops. Every year the requirement increases by 20 to 25 per cent.
An ideal pesticide is highly toxic to the concerned insect pest but, harmless to others. The first synthetic broad spectrum insecticides like DDT belonging the organochlorines revolutionized the control of pests especially like mosquitoes and other vectors of mankind. Any progress always involves risk. The wide scale application of these organochlorine compounds, with the then prized characteristics of long term persistence, produced certain damaging side effects not sparing even the humans. Now we have fixed permissible levels for these chemicals in our foods. Despite such regulations, the pesticides levels are going up even in breast milk, not sparing infants too. For instance in Punjab, bottled milk contains 9.5 times more than the permissible amount of DDT and 21 times the allowable limits of various other pesticides. In this regard Rachel Carson, in her pioneering work “The Silent Spring” urges humanity to abandon pesticides and seek ‘The Other Road,’ particularly via biological pest control.
History and Definition
Biological pest control is probably as old as agriculture. Chinese cave paintings depict ducks being used to consume pests of crops, a technique still in vogue in China. The first well documented case of biological pest control occurred in 1762, when a mynah bird was taken from India to Mauritius to control locusts. However, the first real landmark in modern biological control was achieved in 1880s, when ladybird beetles were used to control scale insects in citrus plantations in California.
Biological control can be defined as “Reduction in the density of pests by the action of predators, parasites and pathogens.” This is also referred to as ‘natural control’ because it involves interaction between indigenous predators and pests without human intervention. But stretches this definition further as, — the use of natural enemies like parasites, predators, fungi, bacteria, viruses, etc. which are induced to multiply in the field by artificial means and disorientated by human efforts, instead of leaving it to nature. Thus it differs from natural control since some of the processes are expedited by men.
With the advent and application of bio-engineered organisms for pest control, the concept of biological control got redefined as, “—the use of natural and/or modified organisms, genes or gene products to reduce the effect of undesirable organism in favour of desirable organisms such as crops, trees, animals and beneficial insects and micro-organisms.”.
Success of biocontrol programmes primarily depends upon identification, conservation and enhancement of population of natural enemies, which are commonly found along with the pest population in the ago-ecosystems, for example in natural conditions the Cocinelliid predator, Chiloconus pharocyumnus and Menochilus predate on mealybugs, coccid, scale and mite which attack citrus, grapevine and guava. The mealybug is also effectively checked by its natural Cacodenus perppicax, a common predator found in mango trees; indeed each of these predators has the ability to control more than 300 adult bugs and 500 nymphs during larval development.
Assassin bug, Rhynocoris marginatus is another excellent predator that can efficiently control a wide range of pests. A number of works on this potential peredator with different kinds of insect pests shows the possibility of wielding a high percentage of prey reduction under the field conditions. Assassin bugs are polyphagous insect predators commonly found in semi-arid zones and scrub jungles bordering agricultural lands and tropical and wet forests. They live in groups or pairs under loose barks of trees or heaps of stones. More than 20 sub-families and 6000 species of Redivides have been identified as predators. Prey capturing mechanism of this predator is unique. The bug injects noxious saliva into the prey swiftly succeeding the capture with the help of its rostrum. The paralysed prey is then consumed. Like other organisms these bugs mimic and camouflage for prey capture. These mechanisms serve them from being predated by the same species. Offensive behaviour like stinging and hissing is also found in Redivides which is wanting in other insect predators. Successful mass culture of this insect predator in laboratory is possible by using stored grain pest, Corcyra caphalonica Staintion.
Preying mantids are also yet another group of natural predators commonly found among a wide range of crops; they prey upon a wide variety of insect pests. As biocontrol agents, spiders are also one of the sominant communities of polyphagous predators. For instance Lyssomanes sikkimensis Thikader, a spider species occurring abundantly in mango orchards, controls mango hoppoer. Similarly the wolf spider Lycosa sp., is an important predator commonly found in the rice ecosystem. Aquatic larvae of vectors of human being are controlled by a variety of natural predators like aquatic insects, insect larvae and fishes. As biocontrol agents these have yielded encouraging results in field trials also. Predatory aquatic bugs and other aquatic insects, play a major role in mosquito abatement. The organisms of lower phyla like the planarian, Dugesia tortocepthala; and flat worm, Mesostoma spp. are also known to predate on mosquito larvae. However, the major disadvantages of predators as biocontrol agents are : a) they affect each other directly or indirectly, for instance one predator may feed upon the other b) prey reduction to the desired level is always not possible.
Biological control of mosquito is an effective, economic and eco-friendly way when compared to the other methods and disease treatment. Mosquito larvae control with other predatory mosquito larvae is an interesting fact of biocontrol, because both prey and predator share a common habitat and interestingly the predator species seldom bite human beings. Thus carnivorous mosquito larvae predate upon the other co-inhabiting larvae. Just killing of prey without consumption is one of the desirable features of Toxorhynchites spp. which reduce the number of vector larvae. Culex fuscanus also breeds the ground water habitat. Other organisms used for larval control are larvivorous fishes like Gambusia affinis (mosquito fish), Poecilia reticu lata, tilapia mossambicus, and Cyprinus carpio. Of these G. affinis ranks first and shows an 100 per cent larval reduction.
Microbes in the Array
Recent advances in biological control have led to the inclusion of certain biochemical substances like pheromones, insect growth regulators, chemosterilants etc., in the array of biocontrol agents. In this regard the classical case of control of screw worm fly Oochtimyiahomnivorax through release of males sterilized by radiation is a biocontrol method. Viruses are also used as microbial agents in biocontrol of pests. Nuclear Poly hedrosis Virus (NPV) play a major role in pest control. NPV, a stomach poisoning agent is used against tobacco caterpillar and American bollworm, being a stomach poison, it is effective during the larval stages only and it must be used during egg hatching to get good results.
After the year 1950 bacteria were used to control the insect pest population. Over 90 species of bacteria have the ability to kill insect pests. The microbiological method of control means, culture of pathogen i.e. bacteria under controlled conditions for release in the fields. The debts endotoxin crystals of Bacillus thuringiensis var israelensis (B.t.i.) is a typical microbial insecticide which is widely publicized and used world over to control the larvae of mosquitoes, black flies and other insect pests. Another group of bacteria used as biocontrol agent differs from B.t.i. due to their antigenic serological property and spectrum of action. B. papillae and B. lentimorbus are such spore forming bacteria which are successfully used to control the Japanese beetle. Usually the non-spore forming bacteria are less efficient than spore forming bacteria.
A considerable success was achieved in pest management by using the microbial agent B.t.i. It differs from other groups in possessing of antigenic properties and a broad spectrum of action B.t.i. formulations consist five spores and toxic protein crys- tals. These endotoxins have low toxicity to human beings and warm blooded animals and also seldom harm plants and beneficial insects. B.t.i. is commercially available by the trade names like Dipel, Thuricide, Biotrol and Bactur. When applied along with other insecticides, acaricides and fungicides the B.t.i. endobactericin shows high action even with minimum doses. It is a contact poison, ingested through food. The impact on the target species directly depends upon the amount of toxin ingested. Low toxicity leads to paralysis and affects the food consumption. Besides, the ingested toxic spores in pest intestine multiplies and fill the gut, leading to the host mortality. The toxicity also reduces the micro flora of the intestine of pests leading to low absorption of food. The amount of indoctrination used against pests depends on the temperature pest species and crops on which the indoctrination is used.
Repellents and Attractive Chemicals.
For a long time various ‘folk remedies’ have been used to repel pests with extracts from plants. Citronella has been claimed to be particularly effective. The most widely used repellents are those against mosquitoes and other biting flies that attack human beings. Application of other kinds of repellents particularly like sound have also been explored. When pursued by insectivorous bats, prey moths avoid them. This has led to the use of simulated amplified. Ultrasonic sound mimicking bat calls, to drive away moths from orchards and cereal crop fields.
Communication between individuals is an important social behaviour. Mating is such a kind of fundamental behaviour in a population which is initiated by signals both physical and chemical between the individuals. For chemical communication sex pheromones play a major role. In sexual courtship pheromones are released by the male and female. The amount and composition of the pheromone varies in different species. Any alteration in the composition and concentration results in disturbance in communication which ultimately results in reproductive failure. This is an important point in Integrated pest management, in which the communication between the individuals is altered or interrupted by synthetic pheromones or pheromone analogs.
The insect attractants have been used more effectively than the repellents. These are chemical substances whose vapour inveigles insects into a trap. They are broadly classified as food and sex attractants. Among these, the latter has proved to be of particular value due to its high spectificity. Indeed the most used pheromones in pest control are sex attractants, produced by female pest species to attract males. These affractants were first identified in moth. The isolated attractants are fixed in a simple trap which consists of polythene bag attached to a funnel or small metal of card board roof with sticky floor on which the arriving insects get stuck. This method has been successfully employed in several countries to check Petinophera gosypiella which is a cotton pest. Kairomone a food attractant, extracted from plants are also used to attract pests to non-agricultural areas at appropriate times. It has long been known that light also attracts many insect pests especially those flying at night. This technique is still in use in India for controlling some insect pests in paddy fields.
Parasites and Parasitoids
Parasites and parasitoids also play a major role in the reduction of the insect pest population. A parashite is an organism that is usually much smaller than the pest on which it feeds. In small numbers the mortality effect due to the parasite is insignificant on host population; at the most they render the pests weak. However in large attacks the host usually faces death. Parasitoids, a special group of predators, are of the same size as the host, but kill the host per se for their development. Some of the widely used parasitoids to control agricultural pests are Trichogramma spp., Bracon spp., Telenomus spp. In recent years large scale release of T.chilonies in certain pockets of subtropical India has reduced the incidence of stalk borer, shoot borer and gurdaspur borer infestation. The abundance of mealybug, R. iceryoides in mango ecosystem is effectively checked by the parasitoids Anagyrous sp. and Coccophagus sexvittlatus.
Genetic control is another efficient biocontrol method which interferes with the ability of pests to reproduce without killing them. Thus the release of ‘treated’ individuals in the field can field a greater influence on subsequent generations than merely killing it outright; this is aptly known as ‘one to many’ principle. The control of cattle screw worm by release of sterilized males is a landmark in the history of pest control. Sterilization can be achieved by exposing individuals to gamma rays (Cobalt-60), X rays and neutrons or calcium arsenate, follicle acid etc. For instance oriental fruit flies, Decays cucurbitae and D. dorsals are sterilized by using collocation. ConsoCono-trachelus nenuphar are sterilized by feeding with folic acid. The chemical used in such genetic control is administered through food which prevents the egg and sperm production or destroys them.