ABSTRACT
Global reduction in agricultural produce with burgeoning human population is beginning to unleash an era of food shortage where any loss of food during storage may lead to heavy socio-economic burden on any country. Though natural calamities that affect food crop production and their loss 88during storage are beyond human control, conservative estimates of loss exclusively by pests amount to almost 30% in present times. This is of utmost relevance especially when we are discovering that the use of traditional chemo-pesticides has led to resistance amongst target pests. Any more increase in the dose of the presently used pesticides can be associated with dramatic ecological derangements and off-site actions. This necessitates the development of eco-friendly alternatives in the present times. Biopesticides represent an interesting class of interventions wherein living organisms or their products (phytochemicals, microbial toxins) that are biocidal towards the target insect are used. This concept is being extensively applied in the bio-intensive integrated pest management systems (IPM) for protection of crops. A subcategory, microbial pesticide, is particularly interesting due to the fundamental reason that invertebrate pathogens cause epizootic on a specific pest population being noninfective to humans and hence potentially non-damaging to the ecosystem. The typical examples of live microbes used as biopesticides are biofungicides (Trichoderma), bioherbicides (Phytophthora) and bioinsecticides (Bacillus thuringiensis [Bt]) apart from bacteriophage, bacteria, yeast and fungi that are being studied worldwide. The most popular bacterial insecticides are derived from different species of Bacillus, most notably the Bt. Bt-based microbial insecticides are the formulations of either spores or/ and metabolites produced during fermentation culture—known as crystal (Cry) toxins. Cry toxicity results in damage to the insect midgut, followed by bacterial septicemia and death. The limitations such as special formulations, storage, toxicity to only a specific species and end-user availability do pose some challenges but do not limit the acceptance of microbial insecticides. Fungi such as Beauveria bassiana, Nomuraea rileyi, Verticillium lecanii and Lagenidium giganteum are also used as broad-spectrum pesticides. Virus-based biopesticides are mostly composed of nuclear polyhedrosis viruses (NPVs), a package of numerous virus particles or granulosis viruses (GVs), in which one or two virus particles are embedded in a protein capsule. A truly efficacious product could compete effectively in the current scenario if improvements to efficacy can be achieved through better formulation and application methods and reductions in the production expenditure. In order to improve efficacy while retaining the desired host range, there is also a need to investigate additional strains and species of pathogens.
