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Promoting use of microbial biopesticides
By M. Saleem, S. Hussain, M. Arshad & Ziaulhasan

THE current use of pesticides in Pakistan is about 1,30,000 metric tons of which approximately 90 per cent is applied on cotton, rice, fruits and vegetables. The wide use of pesticides in agriculture has contaminated the highly value-added commodities like rice, cotton, vegetables and fruits.

Due to contamination and low quality, prices in international markets have shrunken. The Indian and Chinese are reaping bonanza from this situation due to their relatively good quality products. The WTO regime demands contamination-free commodities to compete in local and international markets.

Recently biopesticides have received much attention as an alternate to chemical pesticides. These comprise living microorganisms (viruses, bacteria, fungi, protozoa, or nematodes) or the metabolites produced by them. These are applied as pesticides in the form of sprays, dusts, liquid drenches, liquid concentrates, wettable powders, or granules.

The investigation of microbes and their bio-products/metabolites as pesticides dates back to the discovery of Bacillus thuringiensis (BT) in 1902. In 1950, its toxic effect to insects was known to the scientists. Since then, work on formulation of microbial pesticides has witnessed many ups and downs. This was the time when the use of chemical pesticides was gaining popularity among the farming communities due to their immediate and positive results. This factor visibly influenced the commercial use of microbial biopesticides in agriculture.

In the few last decades due to socio-economic, environmental, and public concerns over the use of anthropogenic pesticides, the importance of microbial derived biopesticides has received currency among food producers. Few examples of the microbes used for insect pest control are listed in table 1.

Major advantages of microbial biopesticides are; (1) the microbes used in preparation of these bio-pesticides are non-toxic and non-pathogenic to wildlife, humans, and other non-organisms; (2) these are highly specific to a single group of insect pests and thus have no adverse impact on other beneficial living organism; (3) these could be employed where necessary with synthetic pesticides; (4) their residues are harmless and these could be used at the time of harvest and (5) applied microbes may establish in pest population and could be helpful in maintenance of their population below the threshold level.

Their commercial scale production involves several but relatively simple and environment-friendly steps. Firstly, it involves the investigation of target pests and its habitat and all those biotic and abiotic factors which may influence its population. During this step, it is important to identify microbial pathogens. Isolation of microbes is carried out from its habitat and from the body of diseased insects which undergoes the purification of cultures under highly sophisticated laboratory conditions. Efficient strains are screened for their potentials to inhibit pestís growth. Tests of these isolated microbes are carried out to assess their adverse impacts on other living organisms i.e., plants, non-target insect pests and human beings. It is investigated that the isolated strains must only be the pathogens of target insect pests and it must not have any harmful impact on other non-target organisms.

Pilot trials are conducted to determine their potential to control pest population under field conditions. Meanwhile different formulations, i.e., liquid, granular and dust, etc., are also tested to find better and comfortable ones. Recently, production of microbial metabolites like cyanides is also used for pest control in addition to the introduction of BT genes in plants.

Several kinds of metabolites have been characterized for control of specific pests. Microbial biopesticides are being used successfully on large scales in India, China, the US, Australia and many other countries of the world to break the momentum of synthetic pesticidesí use in agriculture. But in Pakistan, no efforts have been made to encourage their use in agriculture.

Commercial production of such kinds of biopesticides may prove a good step toward organic agriculture and help in the production of pesticide-contamination free agri-products. To promote the use of microbial derived biopesticides in agriculture following strategies could be helpful. * Legitimate efforts should be made to introduce this trend among relevant scientific domains via assigning projects to relevant institutes to conduct market-oriented research for the production of microbially derived biopesticides. * Use of chemical pesticides should be discouraged and regulatory measures should be taken to divert private sectorís mindset towards the commercial scale production of biopesticides. Ď * Research institutes should assist private sector in this direction to remove any bottleneck in this direction. * Production of biopesticides should be subsidized to promote its production and use on large scale. * Joint research projects assisted by both private and public sectors should be launched for development of problem solving and market-oriented products. * Organically produced agri-commodities should be given weightage in terms of their value in markets to encourage the production of crops grown under applications of biopesticides.

Coutesy: The DAWN

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