फसलों मे कीट नि‍यंत्रण के लि‍ए जैवि‍क कीटनाशकों का प्रयोग

Pesticides having biological origin i.e., viruses, bacteria, pheromones, plant or animal compounds are known as biopesticides. They are natural in origin derived from animals, plants, bacteria, and certain non-synthetic minerals.

Bio-pesticides are highly specific affecting only the targeted pest or closely related pests. They are safer for living beings. Biopesticides are one of the promising alternatives to manage environmental pollution and subsequently has gained interest in view of the growing demands for organic food.

Biopesticides can successfully be used for specific crops and niche areas as a component of IPM.

Biopesticide in India

 In India, so far only 12 types of biopesticides have been registered under the Insecticide Act, 1968. Neem based pesticides, Bacillus thuringiensis, NPV (Nuclear Polyhedrosis Virus) and Trichoderma are the major biopesticides produced and used in India.

Whereas more than 190 synthetics are registered for use as chemical pesticides. Most of the biopesticides find use in public health, except a few that are used in agriculture.  

Consumption of biopesticides has increased from 219 metric tons in 1996-97 to 683 metric tons in 2000-01, and about 85% of the biopesticides used are neem based products. Consumption of chemical pesticides has significantly fallen from 56,114 MT to 43,584 MT during the same period.

Table 1:   Annual availability of biopesticides in India

Source:  Kalra & Khanuja 2007

The National Farmer Policy 2007 has strongly recommended the promotion of biopesticides for increasing agricultural production, sustaining the health of farmers and environment. It also includes the clause that biopesticides would be treated at par with chemical pesticides in terms of support and promotion. Some success stories about successful utilization of biopesticides and biocontrol agents in our country has been described below:

Bacillus thuringiensis (Bt) is primarily a pathogen of lepidopterous pests like American bollworm in cotton and stem borers in rice. When ingested by pest larvae, Bt releases toxins which damage the mid gut of the pest, eventually killing it.

A study between 2002 and 2008 in the country by Kathage and Qaim (2012) showed that Bt caused 24% increase in cotton yield per acre through reduced pest damage and 50% gain in cotton profit among smallholders. Bt cotton adoption has caused sizeable socio-economic benefits and has raised consumption expenditures, by 18% during the 2006–2008 period.

Complete dependence on chemical control by the farmers of Kothapalli village of Ranga Reddy District of Andhra Pradesh resulted in unsatisfactory pest management, followed by diminishing profits.

Raoet al. (2007) reported that field demonstration of bio-intensive pest management technologies by International Crop Research Institute for the Semi-Arid Tropics (ICRISAT) revealed that neem and Helicoverpa NPV were as effective or more effective than synthetic pesticides or other biopesticides in reducing larval population and pod damage by Helicoverpa in chickpea (2000-2002).

Further, neem-based products were on a par with synthetic chemicals in reducing pest population and boll damage in cotton (2003-2006).

Trichoderma spp. plays a major role as biocontrol agents, owing to their capabilities of ameliorating crop yields by multiple roles, such as biopesticide and plant growth promotion. Among the different biopesticides, Trichoderma is most exploited and have many success stories. India is a leading grape exporter. The main concern in grape export is pesticide residues, sulphur dioxide injury and berry decay.

To overcome these problems, ICAR-National Research Centre for Grapes, Pune has identified a natural strain of Trichoderma harzianum commercially available as ‘Grape-guard’.

Experiments and pack house studies have revealed that the grapes treated with ‘Trichoderma’ retain their freshness for longer duration as compared to fungicide treated grapes. In 2001, the technical guidance for the large-scale production of Trichoderma harzianum was given to “Mahagrapes”, a leading apex grape co-operative society in Maharashtra. Mahagrapes is producing approximately 10 MT of Trichoderma annually and distributing it to the farmers (http://nrcgrapes.nic.in/success_stories.htm).

It has been estimated that there are at least 32 commercial companies which actively produce biopesticides, with an additional 32 IPM centers under the Ministry of Agriculture producing selected bio-control agents (Singhal, 2004).

The state departments of agriculture and horticulture in the states of Tamil Nadu, Kerala, Karnataka, Andhra Pradesh, and Gujarat have established bio-control laboratories for producing selected microbial bio-control agents.

A few state agricultural universities and Indian Council of Agricultural Research (ICAR) institutions also produce small quantities of microbial pesticides (Rabindra, 2005). In total, at least 410 biopesticide production units have been established in India, am among which 130 in the private sector (Singhal, 2004).

Biopesticides are classified into three major classes:

a. Microbial pesticides:

They consist of a micro-organism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides can control different kinds of pests, although each separate active ingredient is relatively specific for its target pest(s).

For example, there are fungi that control certain weeds, and other fungi that kill specific insects. The most widely used microbial pesticides are subspecies and strains of Bacillus thuringiensis, or Bt.

Each strain of this bacterium produces a different mixture of proteins, and specifically kills one or a few related species of insect larvae. While some Bt's control moth larvae found on plants, other Bt's are specific for larvae of flies and mosquitoes.

The target insect species are determined by whether the particular Bt produces a protein that can bind to a larval gut receptor, thereby causing the insect larvae to starve.

b. Plant-Incorporated-Protectants (PIPs):

These are pesticidal substances that plants produce from genetic material that has been added to the plant. For example, scientists can take the gene from the Bt pesticidal protein, and introduce the gene into the plant's own genetic material. Then the plant, instead of the Bt bacterium, manufactures the substance that destroys the pest.

c. Biochemical Pesticides:

They are naturally occurring substances that control pests by non-toxic, mechanisms. Conventional pesticides, by contrast, are generally synthetic materials that directly kill or inactivate the pest.

Biochemical pesticides include substances, such as insect sex pheromones, which interfere with mating, as well as various scented plant extracts that attract insect pests to traps. Because it is sometimes difficult to determine whether a substance meets the criteria for classification as a biochemical pesticide, Environmental Protection Agency (EPA) has established a special committee to make such decisions.

New generation pesticides:

Neonicotinoids, Fiproles, Benzoyl ureas, microbial origin insecticides:

The last decade of twentieth century (1990’s-2003) was marked by introduction of neonicotinoids, the newest major class of insecticides having outstanding potency and systemic action for crop protection against piercing-sucking pests and soil insects.

They are highly effective for flea control on cats and dogs (Imidacloprid, Acetamiprid, Thiacloprid, Thiamethoxam, Clothianidin, Dinotefuran, Nitenpyram). Fipronil (Phenylpyrazole) was introduced in 1990.

It is effective against insects resistant to pyrethroids, OrganoPhosphates and carbamate insecticides. Benzoyl ureas (1978-2001) are an entirely different class of insecticides that act as insect growth regulators (IGR).

They interfere with chitin synthesis and are taken by ingestion. (e.g.Triflumuron, Chlorfluazuron, Teflubenzuron, Diflubenzuron(Dimlin).Avermectins, spinosads are the microbial origin new generation insecticides.

Microbial formulations:

About 680 products of different microbials are currently available worldwide. In India about 16 commercial preparations of Bt (Bacillus thuringiensis), 38 fungal formulations based on Trichoderma, Metarhizium, Beauveria and about 45 baculovirus-based formulations for Helicoverpa and Spodoptera are available. Microbial biopesticides are likely to replace at least 20% of chemical pesticides. Microbial formulations are mainly two types:

Dry formulation: Wettable Powder (WP), Water Dispersible Granules (WDG), Granules(G)

Liquid Formulation: Aqueous Flowable, Aqueous Suspension, Emulsifiable Suspension, non-Emulsifiable Suspension

Neem:

Neem is attracting worldwide attention in recent decades mainly due to its bioactive ingredients that find increasing use in modern crop and grain protection. Azadirachtin, a tetranortritarpinoid, is a major active ingredient isolated from neem, which is known to disrupt the metamorphosis of insects.

It affects the reproductive and digestive process of a number of important pests. Described here are some easy methods by which the neem extracts can be prepared by the farmer himself: 

Neem Seed kernel extract

50 gm neem kernel is required for 1 litre of water. The neem kernel is pounded gently. It should be pounded in such a way that no oil comes out. The outer coat is removed before pounding, this is used as a manure. If pounded with seed coat 1 ½ times (75 gm) seeds is required.

The seeds that are used for preparation of neem kernel extract should be at least 3 months old and should not be used after 8-10 months. Before 3 months or after 8 months, the azadirachtin quantity is quite low in the seed and hence it cannot efficiently be used for pest control.

The pounded neem kernel powder is gathered in a muslin pouch and this is soaked overnight in the water. The pouch is squeezed and the extract is filtered. To the filtrate, an emulsifier like soap oil or soap cake powder is added. One ml of emulsifier is added to one litre of water. The emulsifier helps the extract to stick well to the leaf surface. 

Neem leaf extract

For 5 litres of water, 1 kg of green neem leaf is required. Since the quantity of leaves required for preparation of this extract is quite high (nearly 80 kg are required for 1 hectare) this can be used for nurseries and small gardens.

The leaves are soaked overnight in water. The next day the leaves are ground and the extract is filtered. The extract is beneficial against leaf eating caterpillars, grubs, locusts and grasshoppers. An emulsifier is added to the extract as mentioned in kernel extract. 

Neem cake extract

100 gm of neem cake is required for 1 litre of water. The neem cake is put in a muslin pouch and soaked in water. It is soaked overnight before use in the morning. It is then filtered and emulsifier is added @1 ml/1 water. It can then be used for spraying.

Neem oil spray

For general purpose spraying of 0.5% -1% neem oil is sufficient. Depending on the purpose it may be increased up to 2%. It has a shelf life of 3- 22 days in soil and around 45 minutes to four days in water.

Quality of neem oil depends on the type of extraction.Preparation of neem oil includes the collection of raw materials for the extraction and selection of extraction method. Neem seed is widely used in the extraction process instead of neem leaf. There are three common processes of making neem oil. First one is, the neem oil from seeds, second one, mixing the neem oil and  third one, extracting neem oil by machine.

In first method, ripen seeds are collected from the tree. At first, neem seeds are dried in sun and then put in to a chopper and crashed. After crushing the semi powders are ready to for filtering oil. It is poured into a metal bowl and mixed with water in the ratio of 10:1 (crushed seed: water).

The mixer is squeezed again and again. Finally, 100% organic oil is collected.In second system, depending on uses neem oil is mixed with other oils. But in each case of application, process discussed in first method is repeated.In third one, neem oil extraction is done by modern machines for commercial use.

After selection of the dried seeds, these are directly poured in the mechanical bucket. The highest concentration currently available in the market is 3%.

Thus in food production system, neem based by products as well as Bacillus thuringiensis, NPV and Trichoderma can be safely used by the food growers for the management of agricultural pests. It is assumed that biopesticides will create a new era in the pest management without disturbing global ecosystem of the future. 

Refrences:

• Jonas Kathage and Matin Qaim (2012) Economic impacts and impact dynamics of Bt (Bacillus thuringiensis) cotton in India,retrieved at www.pnas.org/lookup/suppl/doi:10. 1073/pnas.1203647109
• Kalra A.& Khanuja S.P.S.(2007).Research and Development priorities for biopesticide and biofertilizer products for sustainable agriculture in India. In Business Potential for Agricultural Biotechnology (Edited by Teng P.S.).Asian Productivity Organisation.Pp: 96-102.
• Rabindra R J. (2005) Current status of production and use of microbial pesticides in India and the way forward.p1-12, In Rabindra, RJ, SS. Hussaini and B. Ramanujam (ed.), Microbial Biopesticde Formulations and Application. Project Directorate of Biological Control, Technical Document No.55

Authors:

Dr. H.Chowdhury*, Dr. S. Kumar** and Dr. M. L. Roy***

*Principal Scientist, ICAR-CRIJAF, Barrackpore, Kolkata- 700 120 (West Bengal)

**Sr.Scientist, ICAR-CRIJAF, Barrackpore, Kolkata- 700 120 (West Bengal)

***Scientist,ICAR-CRIJAF, Barrackpore, Kolkata- 700 120 (West Bengal)

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