Biological Control of Pests | Agriculture Optional Notes for UPSC PDF Download

Introduction

In the realm of pest management, the regulation of pest abundance below the level of economic injury is a vital objective. This is where biological control steps in, a subject of significant importance in the field of Zoology, especially for competitive exams like IAS and IFoS. Biological control involves a multifaceted approach, encompassing the study, importation, augmentation, and conservation of beneficial organisms to effectively control harmful animal populations.

Most agricultural pests are insects, and interestingly, most of their natural enemies are also insects. As a result, the majority of examples in the field of biological control revolve around insects. To delve deeper, biological control can be defined as the strategic utilization of natural enemies, such as parasites, predators, and pathogens, to maintain the population density of a specific organism at a lower level than it would reach in the absence of these natural checks.

The Growing Relevance of Biological Control

The significance of biological control has seen a surge in recent years, primarily due to the excessive use of insecticides. This overreliance on chemical solutions has not only led to the resurgence of pests but has also caused pest resistance to insecticides, particularly in the cases of notorious troublemakers like mosquitoes, houseflies, and stored grain pests. Biological control is deeply rooted in ecological principles, earning it the moniker "Applied Ecology." A fundamental aspect of this discipline is the preservation of the balance of nature.

Different Facets of Biological Control

Biological control can be broadly categorized into two facets:

• Natural Biological Control: This aspect involves the role of natural enemies in restraining pest populations in their undisturbed, native environment.
• Applied Biological Control: In this case, humans intervene to manipulate biotic factors (natural enemies) to reduce the population of a pest species. It is a more proactive approach that requires careful planning and execution.

Tackling Pests of Foreign Origin

Pests that originate in foreign lands usually do not wreak havoc in their native habitats because they are kept in check by natural enemies. However, when these pests are inadvertently introduced into a new country, they often multiply unchecked and become formidable adversaries for local agriculture. This is where the role of biological control becomes paramount. The task involves identifying natural enemies of these foreign pests and introducing them to the affected areas. Even for pests of domestic origin, exotic natural enemies of species closely related to the indigenous pest are imported and released, with the aim of mitigating the pest problem.

Success Stories in Biological Control

Several notable successes in biological control stand as testaments to its efficacy. For instance, the control of the cottony cushion scale (Icerya purchasi) in California in 1988 is a remarkable success story. The introduction of the vedalia beetle (Rodolia cardinalis) proved to be an outstanding solution. When the citrus industry in California was devastated by the cottony cushion scale in 1887, chemical control methods had failed. Albert Koebele, a German scholar, was tasked with finding natural enemies of the pest in its native habitat in Australia and New Zealand. His efforts led to the discovery of the ladybird beetle, Rodolia cardinalis, and a dipteran fly, Chryptochaetum, both of which fed on the pest stages. These natural enemies were subsequently dispatched to the USA, with Rodolia successfully establishing itself and drastically reducing the scale population.

Another noteworthy example is the control of cactus, Opuntia stricta, by the Argentine moth, Cactoblastis cactorum, in Australian grasslands during 1927-30. Additionally, the pathogen Bacillus thuringiensis has found widespread use in controlling caterpillars of various pest species in commercial agriculture.

Global Contributions to Biological Control

Biological control has been a subject of intensive research and application in various countries, including Australia, Canada, Chile, Fiji, Hawaii, Japan, New Zealand, and India. Success stories have been reported in over 60 countries. The Commonwealth Institute of Biological Control, headquartered in London with an Indian station in Bangalore, has made significant contributions to the field.

Understanding Key Terms and Methodologies

Key Terms

To grasp the intricacies of biological control, it's essential to understand key terms, including:

• Parasite: An organism that derives its nutritional requirements from another organism, either slowly or without causing death.
• Predator: An organism that kills another organism instantly for food.
• Ectoparasite: Parasites that feed on the host from outside their bodies.
• Endoparasite: Parasites that live inside the host's body and derive nutrition from it.
• Parasitoid: Larvae of certain insects that live as parasites in early stages and behave like predators when nearing maturity.
• Protelian Parasites: Insects in which only the immature stage is parasitic, not the adult.
• Superparasitism: When a parasite lays eggs in a host already parasitized by the same species.
• Hyperparasitism: When one parasite develops on another parasite that is on the host.
• Multiple Parasitism: When two or more species of parasites lay eggs in the same host, with only one typically reaching maturity.

Methodologies

Applied biological control is put into practice through the following methods:

• Importation and Colonization of Exotic Natural Enemies: When dealing with a pest of foreign origin, seeking its natural enemies in its home country is advantageous. It's generally recommended to introduce the predominant natural enemy found at low host densities in the pest's native environment. This method often involves shipping dormant stages of the parasite or the parasitized host. Timing the release with the availability of host stages to be parasitized is crucial. The effectiveness of the introduced natural enemy is evaluated through regular data collection and analysis.
• Conservation and Inundative Releases of Indigenous Natural Enemies: Conserving natural enemies requires minimal use of insecticides to avoid unnecessary harm to parasites and predators. Selective insecticides that are safe for natural enemies are utilized. Various application techniques, such as soil application of systemic insecticides, seed treatment, and bait use, are employed to safeguard natural enemies. In some cases, natural enemies are collected from the field, mass-bred in laboratories, and then released into the field, similar to biological insecticides.
• Manipulation of Natural Enemies: When a parasite or predator fails to have the desired impact, ecological, biological, and physiological studies are conducted to identify the reasons for failure. Enhancing the effectiveness of natural enemies can involve developing resistant strains through artificial selection, providing supplementary food for adults, using behavior-modifying chemicals, and genetic improvement through hybridization and artificial selection.

Advantages and Disadvantages of Biological Control

Advantages

• It provides long-term, self-sustaining pest control.
• Unlike insecticides, it does not contribute to the development of pest resistance.
• There is no risk of environmental pollution.
• It maintains the balance of nature within the ecosystem.
• This method is cost-effective for long-term pest control.
• There is no fear of pest resurgence, which is often observed with the application of insecticides.

Disadvantages

• Biological control is a lengthy process, taking years for natural enemies to become established. During this period, pests can cause significant damage.
• Natural enemies sometimes fail to establish, leading to program failure.
• In cases of pest outbreaks, biological control may not provide immediate relief.
• Occasionally, natural enemies may harm useful animals or plants.
• Biocontrol does not offer certainty, with projects having equal chances of success or failure.

Indian Examples of Biological Control

India has its share of success stories in biological control, including:

• Biological control of cottony cushion scale in southern India by introducing and releasing Rodolia cardinalis from the USA in 1928.
• Control of woolly apple aphid, Eriosoma lanigerum, by introducing Aphelinus mali from the USA in 1941.
• Partial control of San Jose scale through the introduction and release of Prospaltella perniciosi and Aphytis diaspiditis from the USA in 1961.
• Control of sugarcane stemborers in some Indian states through inundative releases of Trichogramma minutum, T. japonicum, and T. australicum.
• Control of Lantana weed through the anthocorid bug, Teleonemia scrupulosa, along the foothills of the Himalayas.
• Biological control of mosquito larvae using the fish Gambusia and Nothobranchius guntheri.
• Partial control of Opuntia spp. by introducing the cochineal insect, Dactylopius tomentosus, from South America in 1900.

Conclusion

Biological control is a dynamic and evolving field that plays a pivotal role in pest management. It not only serves as a sustainable, eco-friendly solution but also contributes significantly to the preservation of the natural balance within ecosystems. In conclusion, biological control of pests is a subject of paramount importance, offering a holistic approach to managing pest populations and maintaining ecological equilibrium.