What Are Biocontrol Agents? Definition, Types & Applications
Biocontrol can be defined as the control of the type of living organisms with the application of another. The use of Biocontrol agents are also called biological control and are mainly used for the reduction of pest population and produce yields that are free of any pests. The biocontrol methods are a long-term method and most importantly, a self-sustaining one that helps in the control of invasive species of plants. Weed infestation and pests are controlled with the help of insects, pathogens, and grazing animals. The natural animals in the form of parasitism, predation along with other similar mechanisms perform the role of biocontrol agents which help in maintaining the balance.
Types Of Biocontrol Agents
Natural biological control can be done using two primary methods. Inundative Biocontrol makes use of pathogens. This approach makes use of pathogens that help to control the growth of weeds and is as effective as herbicides. Nematodes and nuts are most commonly used in inundative biological control and prevent invasive plants from implementation. Classical Biocontrol is another process that helps in the organic method of pest control. This method of Biocontrol makes use of the natural prey-predator relationship. In classical Biocontrol, an eternal relationship is formed between plants and biological control animals.
Different Biological Control Agents
Biological control agents' examples are given below:
Fungi
Fungus, as a biocontrol method, forms a biological method of pest control. Fungi as a biocontrol method are considered a rapidly developing method and do not cause any harm to the environment. Fungi as a biocontrol method have proved to be a very effective alternative to chemical pesticides. Fungi as a biocontrol method are gaining widespread popularity in recent times. Entomophaga is a form of fungi that is effective against green peach aphids that forms a biological method of pest control.
Predators
Predators are mainly free-living organisms that consume other animals in a large number of prey in the span of their lives. Considering insects are majorly consumed crops, the ideal predators to act as a biological method of pest control are spiders, dragonflies, lacewings, etc.
Bacteria
The bacteria which belong to the genus coccobacillus are comparatively more pathogenic to insects and hence used for biological control. The bacteria infect insect's digestive tracts which limit the options for insects that have sucking mouthparts. Bacteria form a biological method of pest control.
Virus
The creation of a virus which would selectively target pests and act as biological control is still under scientific research. These viruses would be specific regarding their hosts and would hence be effective biocontrol agents.
Parasitoids
The parasitoids lay eggs in the body of their hosts which ultimately leads to the death of the host. The dead host is then used by the larvae as a food source as is one of the most prevalent methods of biological control.
Advantages and Disadvantages Of Biological Control
The advantages of biological control ecology and applications are plenty. The biological control agents are environmentally friendly and do not have any side effects for humans. These methods are also comparatively cheaper than other Agrochemicals like pesticides and insecticides. These methods are also easy to use, readily available, and can be used in any season throughout the year. The most crucial use of biocontrol agents is perhaps they help in reducing the use of chemicals and pesticides which have harmful effects for human beings. There are several other demerits of the use of biocontrol methods too. The use of biocontrol agents causes a significant and noticeable deterioration in the quality of produce. The biocontrol agents do not eradicate all the pests and are a useful and economical tool for pest control only when used on a large scale.
List of Biological Control Agents
Insect-eating animals such as spiders, flies, ladybugs, wasps, beetles, and dragonflies.
Pathogenic microorganisms such as viruses, bacteria, fungi, etc. Coccobacillus bacteria are very dangerous to insects. They affect the digestive system and are used by insects and aphids. Entomophaga fungi are used against the green peach aphid.
Parasitoids lay eggs in the animal's body and kill it. It is later used as a food source for the young caterpillar. It is commonly used as a biocontrol agent.
Microbial Biocontrol Agents
Ladybird and dragonfly are two common insects that are used to eradicate aphids and mosquitoes in succession. Besides insects, microbes are also used as biocontrol agents. These viruses include viruses, fungi, viruses, and protozoans. Bacteria act as a biocontrol in three ways, causing pathogens or competing with or killing themselves.
Biotechnology has greatly expanded and improved many biocontrols. For example, Bacillus thuringiensis commonly referred to as Bt is a biological control agent. Spraying Bt solution made from seeds on plants will kill butterfly caterpillars. The dried seeds expel toxins from the intestines of worms and kill them.
Biotechnology has developed disease-resistant and insect-resistant plants by injecting B toxic B genes. thuringiensis in plants. For example, cotton. Trichoderma-like fungus and baculoviruses of the genus Nucleopolyhedrovirus are other microbial biocontrol agents. These agents are naturally straightforward; this and costs reduce their use.
What is ‘biological control’ and why do we need it?
Many farmers use chemical methods to control their pest problems, there are a few disadvantages to this method:
Chemicals may not clear and kill beneficial insects.
Insects may be resistant to pesticides.
Pesticides can enter food chains, accumulate and harm other organisms.
Chemical residues may harm people, especially farmers.
This has led to the development of Biological control methods. This is an insect control method that uses other predators or insect pests to reduce the number of pests to lower levels where there is minimal economic damage.
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Solved Examples
Why is A Fungus Used As A Biocontrol Agent?
Ans: Fungal biocontrol agents do not harm the environment and have proven themselves to be a cheap alternative to harmful chemical pesticides, and they also do not need to be ingested by the host but can invade them directly. They are an effective biological method of pest control.
Did You Know?
Aphiline refers to a braconid wasp that is used in controlling the aphid species from damaging crops. Aphiline works with the use of stinging and parasitizing the comparatively small aphid species such as the peach aphid and the cotton aphid. The female wasp also lays eggs within the aphid, and the larvae that come out from the hatched eggs feed on the female wasp's body causing the aphid to be nothing more than a mummy on the crop.
FAQs on Biocontrol Agents: Types, Examples, Uses & Benefits
1. What are biocontrol agents as per the Class 12 syllabus?
Biocontrol agents, also known as biological control agents, are living organisms used to suppress or control the populations of pest organisms like insects, mites, weeds, and plant pathogens. This method relies on natural mechanisms like predation, parasitism, or herbivory, offering an ecological alternative to synthetic chemical pesticides. The core principle is to use a pest's natural enemy to keep its population in check, thus protecting crops and maintaining biodiversity.
2. What are some key examples of biocontrol agents used in agriculture?
Several organisms are used as effective biocontrol agents in agriculture. Common examples mentioned in the NCERT syllabus include:
- Insects: The ladybird beetle (Ladybug) is used to control aphids, and Dragonflies are used to prey on mosquitoes.
- Bacteria: Bacillus thuringiensis (Bt) is a bacterium used to control butterfly caterpillars.
- Fungi: The fungus Trichoderma is a free-living fungus in root ecosystems that controls several plant pathogens.
- Viruses: Baculoviruses, particularly those from the genus Nucleopolyhedrovirus (NPV), are pathogens that attack specific insects and other arthropods.
3. What are the main categories or types of organisms used for biocontrol?
Biocontrol agents are broadly categorised based on the type of organism and its mode of action. The primary types are:
- Predators: These are free-living species that consume a large number of prey during their lifetime. A classic example is the ladybird beetle feeding on aphids.
- Parasitoids: These are organisms, typically insects like wasps, that lay their eggs in or on a host organism. The developing larvae then consume the host, eventually killing it.
- Pathogens: These are disease-causing microorganisms, including bacteria, fungi, and viruses, that are specifically toxic to certain pests. For example, Bacillus thuringiensis is a pathogen for certain insect larvae.
- Herbivores: These are insects or other animals that feed on and control the population of undesirable weeds.
4. Why is biological control considered a better alternative to using chemical pesticides?
Biological control is considered superior to chemical pesticides for several key reasons. Firstly, biocontrol agents are often highly specific to their target pest, meaning they do not harm non-target organisms like pollinators, other beneficial insects, or the crop itself. In contrast, chemical pesticides are broad-spectrum and can kill beneficial species, disrupting the ecosystem. Secondly, pests are less likely to develop resistance to a natural predator compared to a chemical. Lastly, biocontrol avoids the problem of chemical residue on food products and prevents pollution of soil and water sources, making it an environmentally sustainable approach.
5. How does the fungus Trichoderma function as a biocontrol agent against plant diseases?
Trichoderma species are highly effective biocontrol agents commonly found in root ecosystems. They work by controlling soil-borne and foliar plant pathogens through several mechanisms:
- Mycoparasitism: Trichoderma can directly attack and feed on other pathogenic fungi, coiling around them and secreting enzymes that break down their cell walls.
- Competition: It grows rapidly and aggressively colonises the root zone (rhizosphere), outcompeting harmful pathogens for space and essential nutrients.
- Inducing Plant Resistance: Its presence can trigger the plant's own defence mechanisms, making the plant more resistant to future pathogen attacks.
6. What is the specific mechanism by which Bacillus thuringiensis (Bt) kills insect pests?
Bacillus thuringiensis (Bt) works through a highly specific and effective mechanism. The bacterium produces a protein crystal (cry protein) during its growth. When an insect larva (like a caterpillar) ingests the Bt spores containing this crystal, the following occurs:
- The alkaline pH of the insect's midgut dissolves the crystal, activating the inactive protoxin into a toxic form.
- This active toxin binds to the surface of the midgut epithelial cells, creating pores.
- These pores cause cell swelling and lysis, leading to the breakdown of the gut wall.
- The insect stops feeding, becomes paralysed, and dies. This mechanism is specific to certain insects because the toxin requires an alkaline gut pH for activation, which is absent in most other animals, including humans.
7. How are Baculoviruses used as biocontrol agents, and what makes them ideal for Integrated Pest Management (IPM)?
Baculoviruses, especially Nucleopolyhedrovirus (NPV), are excellent biocontrol agents used to target specific insects and arthropods. They are considered ideal for Integrated Pest Management (IPM) programs because of their narrow-spectrum insecticidal action. This means they are highly specific to a particular host pest and have no negative impact on non-target organisms such as plants, birds, fish, or even other beneficial insects like bees. This specificity ensures that the ecological balance is maintained while controlling the target pest, which is a fundamental goal of any successful IPM strategy.
8. What is the fundamental difference between biocontrol and the use of biofertilisers?
While both involve using living organisms in agriculture, their purposes are entirely different. Biocontrol agents are used for pest management; their function is to control, kill, or suppress harmful insects, weeds, or pathogens to protect the crop. In contrast, biofertilisers are used for nutrient enrichment. They are microorganisms that enhance soil fertility by fixing atmospheric nitrogen, solubilising phosphorus, or promoting plant growth through the synthesis of growth-promoting substances. Essentially, biocontrol agents are for plant protection, while biofertilisers are for plant nutrition.
