In this article we will discuss about:- 1. Meaning of Biopesticides 2. Need for Biopesticides 3. Advantages of Using Biopesticides 4. Botanical Pesticides 5. Mode of Action of Biopesticides.
Contents:
- Meaning of Biopesticides
- Need for Biopesticides
- Advantages of Using Biopesticides
- Botanical Pesticides
- Mode of Action of Biopesticides
1. Meaning of Biopesticides:
Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides. At the end of 2001, there were approximately 195 registered biopesticide active ingredients and 780 products.
Biopesticides fall into three major classes:
1. Microbial Pesticides:
Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides can control many 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 mix 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
2. Plant-Incorporated-Protectants (PIPs):
Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant. For example, scientists can take the gene for 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. The protein and its genetic material, but not the plant itself, are regulated by EPA.
3. Biochemical Pesticides:
Biochemical Pesticides 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 that 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, EPA has established a special committee to make such decisions.
2. Need
for Biopesticides:
Farmers are making indiscriminate use of pesticides (chemicals) for the pest control since long to overcome the problem of plant diseases. It has been estimated that the cost of chemical pesticides has multiplied 2500- 3000 times during the period of 1950 to 2000. It is, therefore, beyond the reach of resource poor farmers in India, particularly those who raise rainfed crops under high risk and who can ill afford to invest on costly chemical pesticides.
On the other hand, the cost of biological control agents will be well within their reach, and the cost would be further minimized due to the fact that these agents perpetuate in nature and keep subsequent broods of the pest under check. The hazardous petroleum based pesticides are expensive and a few are now losing their effectiveness because of development of resistant strains. Some of the pesticides are non-degradable and cause environmental pollution.
Awareness has increased in farmers about the uses of biopesticides and possible deleterious effects of fungicides, herbicides, insecticides, nematicides etc. on ecosystem. The export oriented farmers are now interested in pesticide free agricultural products, therefore, the biological control of plant pathogens have received considerable attention. Biological control of pests can solve pest problems in agricultural crops and can improve environmental situations. Bio intensive integrated pest management is now need of Indian farmers.
Predators:
Predators are biocontrol agents those hunt/eat the insect pests e.g. Frogs, lizards, ducks, spiders, dragon fly, coccinellid beetles, meadow grass hoppers, mirid bugs, crickets, ants, sparrows and other birds and their species.
Parasitoides are friendly species which complete their life cycle on different stages of insect pests. There are several types of parasitoids including egg parasitoids, larval parasitoids, pupal parasitoids, adult’s parasitoids, egg-larval parasitoids, larval-pupal parasitoids etc. Some of the parasitoids species are: Trichogramma sp., Bracon sp., Apntales sp., Chelonus sp., Brachymeria sp. etc.
3. Advantages of Using Biopesticides
:
1. Biopesticides are usually inherently less toxic than conventional pesticides.
2. Biopesticides generally affect only the target pest and closely related organisms, in contrast to broad spectrum, conventional pesticides that may affect organisms as different as birds, insects, and mammals.
3. Biopesticides often are effective in very small quantities and often decompose quickly, thereby resulting in lower exposures and largely avoiding the pollution problems caused by conventional pesticides.
4. When used as a component of Integrated Pest Management (IPM) programs, biopesticides can greatly decrease the use of conventional pesticides, while crop yields remain high.
5. To use biopesticides effectively, however, users need to know a great deal about managing pests.
4. Botanical Pesticides
:
These are naturally occurring plant materials. In their simplest form, botanical pesticides may be crude preparation of plant parts ground to produce a dust or powder which can be used in full-strength or dilute form in a carrier such as clay, talc or diatomaceous earth. Such preparations includes dust from Pyrethrum daisy flower, cube roots (rotenone), Sabadilla seeds, Ryania stems, or neem leaves, fruit or bark and slightly more sophisticated are water extracts or organic solvent extracts of insecticidal component of plants.
Several plant base insecticides such as nicotinoids, natural pyrethrins, rotenoids, neem products etc. are being used for suppress in of pest species. Other botanical pesticides include Annona squamosa, Ryania specicosa, Pongamia glabra, Acorus calmus, Anethora sowa etc. are important.
Among all botanical pesticides, Azadirachta indica (neem) is most effective biopesticide as it contains several chemicals, including “azadirachtin”, which affects the reproductive and digestive process of a number of important pests.
Botanical pesticides are derived from plants which have been shown to have insecticidal properties. Used widely until the 1940’s, these natural pesticides were displaced by modern synthetic pesticides that at the time seemed cheaper, easier and longer lasting. As awareness of the health and environmental hazards of chemical pesticides increases, however, and as pests become more resistant to synthetic compounds, the popularity of botanical insecticides is once again increasing.
Natural pest controls like the botanicals are safer to the user and the environment because they break down into harmless compounds within hours or days in the presence of sunlight. They are also very close chemically to those plants from which they are derived, so they are easily decomposed by a variety of microbes common in most soils.
While many situations may require the use of botanical pesticides, they are the heavy hitters.
The potassium soaps (soft soaps) of neem and pongamia oils at 1 per cent are effective against diamond back moth, leafhopper, aphids, leaf miner etc. Field and laboratory studies have shown that the aqueous neem seed kernel extract (NSKE at 4-5%) is more effective and economical to use compared to commercial neem based products.
Preparation of Neem Seed Kernel Suspension (NSKS):
1. Collect the ripe neem fruits and dry them under shade in the season.
2. Separate the neem seed from the fruits by soaking them in water.
3. Dry the neem seed under shade and separate the kernel.
4. Grind the kernel thoroughly to form a paste and soak the paste tied in a cloth bag in water for about 2-3 hours.
5. Squeeze the bag thoroughly for 15 to 20 minutes to extract the NSKE solution which is very essential for good results.
6. Filter the solution using a thin cloth.
7. Add soap @ 2-3 g/1 of solution.
8. Dilute the solution prepared from 7.5 kg of kernel to 200-250 litres and spray in an area of one hectare.
9. Repeat spraying if rain occurs on the same day.
Preparation of Tobacco Decoction:
1. Collect the cheaply available beedi or natu tobacco dust.
2. Boil 2.5 kg of tobacco dust in 25 litres of water for 30 minutes.
3. Add water to the boiling solution to compensate evaporation losses.
4. Cool the decoction after it turns coffee red in colour while stirring.
5. Filter the decoction using a thick cloth. Add soap @ 2-3 g/1 of the solution.
6. Dilute the solution to 200-250 litres and spray in one hectare.
7. Wear cloths and also tie a cloth to nose while spraying to avoid inhalation toxicity.
1. Pyrethrum:
It is important botanical pesticide, obtained from Chrysanthemum. Pyrethrum has been used on many agricultural crops for control of aphids, beetles, mealy bugs, leaf hoppers, trips and many others. Formulation of pyrethrums and synergized pyrethrums has been found useful in the control of insect pests associated with households and food commodity storage and processing facilities. They are used extensively as protectants against the ravages of insect pests of stored products, and against insects attacking dried fruits, nuts and cereal products.
2. Rotenone:
There are a group of compounds in the roots of Derris and other plants of the family Leguminosae which are similar to rotenone in chemical structure such as degnelin, toxicarol, sumatrol, elliptone, malaccol, dalpanol, pachyrrhizone, dolincone, amorphin, munduserone and erosone, collectively called rotenoids, commonly used for beetles, aphids, weevils and many other insect pests of truck crops, and against animal parasites such as fleas, lice and ticks.
5. Mode of Action of Biopesticides
:
The two main factors in controlling the disease are by invasiveness and initiation of disease. The site of entry of bio inoculants may be broken or bruised integuments or by feeding habits of the insects or other openings. When attacking any insect the quantity and quality of inoculum is important. In essence the control of the disease depends on the capacity of the microbial inoculum to rapidly establish itself and multiply in large numbers, resulting in severe infection of the pathogen concerned.
The time lag between the entrance of microorganisms into the body of the insect and the incubation period within varies from pathogen to pathogen and insect to insect. Proliferation and disease control are controlled by environmental factors to a large extent and internal host characteristics to a small extent. The mode of action may be due to the production of endotoxins or exotoxins.
Broadly bioagents which attack insect pests can be classified as follows:
i. Obligate Bioagents:
These bio agents in nature are associated with a specific insect disease and are difficult to culture in artificial media. E.g. Bacillus popilliae causing milky diseases of white grubs and Bacillus larvae causing American foulbrood of bees.
ii. Spore Forming Bio Agents:
The protein crystals formed by these sporulating bio inoculants are highly toxic to the target agent. E.g. Bacillus cereus produces such toxins.
iii. Determinative Bioagents:
The bio agents get activated; once inside the host. They multiply in the haemocoele of insect and produce lethal septicemia.
iv. Facultative Bioagents:
The host tissue is damaged by the invasion of the bio agent but they are not obligate parasites.
v. Predaceous Bioagents:
The bio agent either secretes a sticky substance or builds up.