Biological control of insect pests is one of the methods of controlling insect pests by use of living organisms. Biological control is an eco friendly method and eliminates the unnecessary use of chemical pesticides thereby reducing the environmental pollution. The introduction of natural enemies to control the unwanted insects in the field has many positive effects. The natural enemies may be classified as predators, parasites, and pathogens. Predators are the free living natural enemies which attack the adult insects, larvae or eggs of the pests. Parasites are the natural enemy that live within the pest body and slowly kills the pest individual as it develops within the host body. Pathogens are the naturally occurring microbial enemies of the pest which when released in the field, infect the adult, larvae or eggs, rapidly multiplies in the body and kill the pest due to high infection. The pathogens are very effective in the larval stages of the pest, which multiplies in the larval body and affects the moulting phase or pupal phase which results in non emergence of adults.

Biological control method is an alternative method of controlling insect pest in the agricultural field and is not an additional method, which cannot be used with combination of other insect control programs especially the chemical control method. The natural enemies are also affected with pesticides and chemicals hence for the successful of Biological control program, the field should be devoid of pesticides. Biological control is very effective in closed environment agricultural field like green houses.

Biological control method involves selection of correct natural enemies for the pest in question. For all pest, there may or may not be effective Biological control method available. Depending on the kind of usage of natural enemies, the Biological control method is classified into three types as classical Biological control (importation), conservation, and augmentation. The type Importation involves use of natural enemies that are non native and imported from different places to suppress the pests. The importation method is little expensive in the initial phase as it requires collecting the predators, colonization and transportation. It gives a long lasting effect and once successfully established, there is no further cost incurred in the classical Biological method. The conservation method involves making favorable conditions for the natural enemies occurring in the field which increases the population of the predators to control the pests. The conservation method involves providing shelter or food for the natural enemies for their multiplications or resting. It also involves sometimes providing artificial nectar or growing nectar plants those flowers around the year for the adult flies as many of the insect larvae are predators, while the adults are only nectar feeder. The augmentation method of Biological control involves constant release of natural enemies into the field thereby making the enemies population level in optimum threshold to reduce the pest population. In some conditions the natural predator's population varies seasonally and to have the optimum ratio of predators, constant release of them is required, which is called augmentation kind of Biological control.

Involvement of natural enemies either exotic or local to control pest population requires careful research for the success of the Biological control. Some instances are present where the released predator instead of eliminating a particular pest species targets other harmless insects in the field. In Biological control method, care should be taken to have the complete information on the biology of the natural enemies so that it will not later change the biodiversity of the place. Biological control method is not a quick method to eliminate the pest population. Sufficient time is required for the released enemy to colonize in the field and to increase in numbers to control the pest species. Hence Biological control method should be initiated from the initial stage of pest management.

Biological control method application in the field results in many beneficiaries to human as well as nature. The foods grown using Biological control methods are free from any harmful pesticides, which makes the food safe for consumption. Due to the species specific nature of natural enemies, other beneficiary insects are not affected thereby making the balanced biodiversity of ecology. The drawback of Biological control method is that it is a slow process of controlling the pests and successful natural enemies are identified for handful of insect pests and for many species of insect pest, there is not effective solution in Biological control.

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An enthuiastic author from India