Since ancient time agriculture has been facing devastating harm caused by weeds, virus, nematodes, fungi, insect pests, animals and birds which has led to the decline in crop produce. It has been evaluated there is loss of 30% crop yield due to insects, diseases and weeds which corresponds to 30 million tons of food grains loss (Koul.O, 2011). To overcome this problem various strategies were employed. One of the way is to eliminate the pests is by using chemical/synthetic pesticides (for example: chlorinated hydrocarbons, carbamates, organophosphates etc.
). In spite of the success gained by using these chemical pesticides, there are prospective health and environmental hazards/risks related with them. These chemical pesticides have long persistence period. Undiscerning and continuous application of these chemical products resulted in escalated residual problems, resistance among the pests and loss of some beneficial species.
To overcome the hazards related with chemical pesticides, there is a need to adopt a coherent and eco-friendly method. One such improvement in pest control strategy is to develop biopesticides which are derived from naturally occurring material such as plants, , animals, microorganisms or their products.
These are effective, biodegradable and poses less impact on the environment. The term ‘biopesticide’ is misleading in the sense it is not necessary that microbial agent for pest control completely eradicate the pest, but rather it suppresses and allow the crop to adequately develop some deleterious effect in the pest so that crop produce is not affected. A decline in the rate of novel insecticide, occurrence of resistance to traditional synthetic pesticide, increased public awareness about impact of synthetic pesticide on environment and humans led to increased interest in microbial pesticides.
Today biopesticides are gaining popularity because of there low environmental impact and as a possible substitute to conventional synthetic pesticides. Some popular integrated pest management strategies employs a combination of chemical and biological crop protection strategies. Use of biological product at an appropriate time can reduce the total need for synthetic pesticides. New biorational pesticides are also developed which comprises pest control agents, chemical analogues of biochemicals such as pheromones, insect growth regulators, etc. These are more environment friendly than synthetic chemical pesticide. Use of Microbial control agents offers more realistic approach compared to chemical pesticides when used as ecologically based integrated pest management.
Biopesticides are broadly classified into three classes: microbial pesticides consisting of entomopathogenic bacteria (e.g. Bacillus thuringiensis), fungi (e.g. Trichoderma spp.), or viruses (e.g. Baculovirus) including their metabolites; entomopathogenic nematodes and protozoa. Herbal pesticides (are unique and diverse array of chemical complex structures in different plant species) provides coherent protection from the pests, microbial diseases and can be used as plant incorporated protectants (i.e., genetically modified crops like transgenic Bt cotton) though their use as food items is debatable.Improvement has been made in the production and formulation technology of microbial pesticides. But at the same time the use of biopesticides has been restricted due to various constraints at developmental, registration and production level. Although there are many developments in terms of novel discoveries of microbial i solates and increase ability of genetic manipulation but, concerns remains for pest resistance, environmental and human welfare. In the present chapter, the classification, mechanism of there action and biopesticides in commercial practice is been discussed.