With the advent of rapid modernization and the advancement of tremendous industrialization, simultaneously arrives the invincible phenomenon of increase in population. And in the present day earth, this is one of the most alarming problems which require long term solutions, that too, with immediate effect.
This problem of population is invariably linked with the problem of environmental hazards, because higher the number of individuals inhabiting this land, greater is the probability of polluting the earth and the atmosphere. It must be kept in mind that the amount of cultivable land is shrinking day by day due to increasing urbanization and growth of civilization and at the same time, population is increasing at an alarming rate. As a result, there is an inevitable conflict between the supply and demand of agricultural land. The only way out in solving this problem is to INCREASE the yield of all the food crops per unit area.
But, increasing the yield per unit area can only be done by proper scientific methods like application of chemical fertilizer, use of high yielding variety seeds, use of hybrid crops with disease resistance, use of chemical pesticides for protection of the crops and so on. But in this case also, indiscriminate use of chemical fertilizers and pesticides should be prohibited since they provide potential threats and hazards to the environment which are irreversible in nature. With the invention of chemical pesticides, individuals came out with totally uncontrolled and indiscriminate use of these chemicals in the fields which resulted in pollution of the major water sources, development of chemical resistant pests and insects which are not only harmful for the plants and crops but are also possess insane damaging potentials for human beings.
Due to this careless application of chemical pesticides for over four long decades, nowadays even an application of minimal quantities of these may pose long term hazardous effects and threats to the whole environment.
For keeping the world incredibly beautiful, and if not, at least conveniently habitable for the future generation, scientists came out with the concept of biological control of pests instead of the use of harmful chemical pesticides. Because at this phase of utmost degraded environmental condition, sustainable agriculture is the only way out or the solution to this burning problem of contamination, pollution and chemical resistant pests.
Why not chemical pesticides?
There are many reasons for discarding the use of chemical pesticides and fertilizers in the present day world. The most important ones can be listed as –
1) Pollution of water bodies due to surface runoff.
2) Non-biodegradable nature of the pesticides leading to environmental pollution.
3) Gradual imbalance in the nutrient content of the soil.
4) Appearance of pesticide resistant insects and pests due to prolonged and indiscriminate use.
Then, what is the solution?
The single option that is left with us in these circumstances is to shift our attention from chemical to biological methods which are environment friendly as well as sustainable at the same time.
Biological Methods of pest control –
It is a method of controlling pests and insects by means of OTHER ORGANISMS, that is, by biological means only.
Types of Biological Pest Control -
The types of biological control of pests can be broadly divided into –
1) Importation – It involves the natural enemies of a pest to be introduced into a new habitat where they are not present naturally. Early phenomena were often unofficial and absolutely not based on research, thus some introduced species became serious pests themselves on adaptation.
Successful incident - Rodolia cardinalis, the vedalia beetle, was taken from Australia to California in the 19th century, which successfully controlled the Cottony Cushion Scale.
2) Augmentation - Augmentation involves the supplemental natural enemies to be released that occur in a particular place, accelerating the naturally occurring populations there.
Successful incident – Bacillus thuringiensis has come out victorious in almost all cases where genetically engineered plants were used.
3) Conservation – It involves the conservation of the naturally existing enemies of the pests and insects in the environment.
For example - Earwigs are natural predators which can be brought in gardens by hanging upside-down flower pots filled with straw or wood wool. Green lacewings can be encouraged by using plastic bottles with an open bottom and a roll of cardboard inside. Birdhouses allow insectivorous birds to nest; the most useful birds can be attracted by choosing an opening just large enough for the desired species.
Agents of Biological Pest Control –
The agents of biological pest control may be listed as follows -
1) Predators – The natural enemies of a particular species in the ecosystem are called predators of that species and the species concerned is designated as prey and the process of the predator catching the prey is called predation. After extensive research and field works it is now well known to us the pests and insects specific for particular crops. The concept is to induce the pest’s natural predators into the crop fields so that it can control the pests by the process of predation without imposing any potential harm to the environment as such.
For example – Polistes wasp is a natural predator for cotton bollworms.
2) Parasites – Organisms which depend on food source and nutrition from a specific host and impose life threats on the host are known as parasites and the process of obtaining food from hosts and sustaining life is called parasitism. In fields, natural parasites of the identified insects and pests should be introduced for controlling their growth and ultimately death and decay of the pests eventually.
For example - The parasitoid wasp Aleiodes indiscretus parasitizing a gypsy moth caterpillar, a serious pest of forestry
3) Pathogens – The pathogenic microorganisms include specimens of bacteria, fungi and viruses. They are mostly host specific and have a high rate of success in the fields as a biological pest control agent.
For example – In BACTERIA, the species Bacillus thuringiensis is widely used as a biological pest control agent. With the help of cry genes, it induces holes in the gut walls of insects and pests like cotton bollworm. Being host specific and highly successful, it is widely used nowadays. Even in crops like cotton, brinjal, tomato, genetic engineering is taking place for the introduction of genes of Bacillus thuringiensis.
In FUNGI, Green peach aphid, a pest in its own right and a vector of plant viruses, is readily killed by the fungus Pandora neoaphidis.
In OOMYCOTA, Lagenidium giganteum is a water borne mold that acts as a parasite for the larval stage of mosquitoes. After their release in water, the motile spores get rid of unsuitable host species and search out suitable mosquito larva for acting as a host. Unfortunately, it is highly susceptible to the chemicals which are often released in the water bodies as a part of mosquito killing programs.
4) Competitors – According to the Darwinian theories of evolution, interspecific and intraspecific competitions are a part and parcel of the ecosystem. Similarly, in this case, the concept of inter specific struggle and competition is made to play the lead role where a natural competitor of a particular pest or insect is chosen and released into the crop fields resulting in incredible controlling of pests without any forms of chemical means or mechanization.
For example - The Australian bush fly, Musca vetustissim, is a major nuisance pest in Australia, but native decomposers found in Australia are not adapted to feeding on cow dung, which is where bush flies breed. Therefore, the Australian Dung Beetle Project (1965–1985), led by George Bornemissza of the Commonwealth Scientific and Industrial Research Organisation, released forty-nine species of dung beetle, to reduce the amount of dung and therefore also the potential breeding sites of the fly.
Disadvantages, Difficulties and limitations of biological methods of pest control –
1) Being a natural and biological phenomenon and for abiding by the laws of nature, the methods of biological pest control takes a very long time to be effective. Presently, the extent of agricultural land is constantly shrinking but the population of the world is increasing, thus there is an urgent need for higher yield per unit area in the shortest time span possible. So, in the dimension of time it is somewhat disadvantageous.
2) The introduction of foreign and exotic species as competitors, predators, etc. in different crop fields greatly hampers the natural balance of the ecosystem and sometimes has side effects. Sometimes, due to the introduction of predators, the pest also faces “co-evolution” and new pesticide resistant varieties come into being which are very difficult to get rid of.
3) The biological control of pests is still mostly in research level and should be brought at once “From LAB to LAND.” But the limitation of education of the farmers as well as the high expenditure for the biological means of pest control, it is still somewhat impractical to use fully biological means of pest control without the use of chemical pesticides.
The present era can be undoubtedly called the era of modernization, but with its positive effects, modernization on the other hand has so many negative and detrimental effects that it should be avoided at most for a sustainable development, otherwise, our future generations will have nothing to relish on except the dreams of the graceful past that used to stay in this beautiful world. For the sake of the environment, for the sake of us and our future generations to come, the only single option available nowadays is only the shifting from “Chemical era” to “Biological era” and transforming it from the “The age of hazards” to “The age of sustainability.”