BIOLOGICAL CONTROL: TYPES, STRATEGIES, ADVANTAGES AND EXAMPLES - BIOLOGY - 2025

The biological control is the use of living organisms in order to suppress the population of other harmful individuals called "plague". It is intended to reduce the impact of a certain pest to economically acceptable levels.

The introduction of control organisms in an ecosystem allows to reestablish the ecological balance in environments altered by the overpopulation of pests. Generally, the increase in pests is due to the misuse of practices related to industrial, forestry or agricultural exploitation.

Biologic control. Source: pixabay.com

A pest is any unwanted species, whether animal or plant, that is detrimental to the development of the native species. Pests can act on agricultural or forest crops, stored products, livestock farms, buildings and homes, even man.

The use of pesticides and pesticides of chemical origin is a common practice in agronomic pest management. In fact, it is one of the practices that most increase production costs.

Indeed, the continuous use of chemical products results in ecological imbalance and environmental pollution. In addition, it reduces the presence of beneficial organisms and natural enemies, reinforcing the resistance of pests to pesticides.

On the other hand, the use of chemical products causes the accumulation of toxic residues in food, which is why a natural control alternative is sought that limits the use of agrochemicals in the field.

In this perspective, biological pest control emerges as an alternative to chemical control. Likewise, it is a friendly practice with the environment, which offers healthy food and eliminates the application of chemical pesticides.

Types

The biological control is carried out through the participation and action of the natural enemies of the pests. These organisms feed and multiply at the expense of other organisms that they colonize and destroy.

Biological control agents in agriculture are generally insects, fungi, or microorganisms that act to reduce pest populations. These natural enemies can act as predators, parasitoids, or pathogens.

Predators

They are free-living species that feed on other species during their life cycle. The larvae and adults of the predators seek out and feed on the prey within the crop.

Parasitoids

They are species that during one of their stages of development have the ability to develop on or within a host. The parasitoid lays its eggs on or inside the host, the larva grows and develops, and ends up eliminating it.

Pathogens

They are species (bacteria, fungi or viruses) that cause diseases to specific organisms, weaken and destroy them. Entomopathogens enter the host through the host's digestive tract or cuticle, inoculating disease and causing death.

Characteristics of natural enemies

• Wide range of adaptation to physical and climatic changes in the environment.
• Specificity to a certain pest.
• They must present a higher population growth with respect to the increase of the plague.
• Possess a high level of exploration, especially when there are low plague densities.
• It requires the ability to survive and modify its eating habits in the partial or total absence of the pest.

Strategies

In the integral management of a crop, biological control constitutes a strategy that seeks to reduce the population of organisms considered pests. There are different types or strategies of biological control, depending on the process and the mode of action used.

• Classic
• Inoculation
• Flood
• Conservation

Control b

The strategy used is the introduction of an exotic species in an area or crop that it is desired to protect. The objective is the establishment of a natural enemy that regulates the population levels of the pest organism.

This method is used in areas affected by a pest that does not present natural enemies and its overpopulation can cause considerable damage. Since you want the control agent to establish itself over time, it is ideal for permanent crops, such as forestry or fruit trees.

Examples of this control is the parasitoid Cephalonomia stephanoderis (Ivory Coast Wasp) used for the biological control of Hypothenemus hampei (Coffee Broca). Likewise, the parasitoid Cleruchoides noackae (Parasitoid wasp of eggs) used in the control of Thaumastocoris peregrinus (Eucalyptus bug).

Control b

This method consists of the release of a large-scale biological control agent aimed at controlling a specific pest. The strategy is based on becoming a natural enemy, reproducing and controlling for a certain time.

It is a technique used in short-cycle or annual crops, since the effect is not permanent. In addition, it is used as a preventive control method, it is applied when critical levels of damage have not yet been reported.

Applied efficiently, it becomes a control similar to the application of pesticides, due to its efficiency and speed. Examples of agents used by inoculation are insect or entomopathogenic fungi, used as biocontroller microorganisms.

Spraying of suspensions with entomopathogenic fungi on a crop allows the fungus to invade the body of the insect causing death. For example, in vegetables the pest called whitefly (Trialeurodes vaporariorum) is controlled by suspensions of the fungus Verticillium lacanii or Lecanicillium lecanni.

Control b

The flood technique consists in the release of a large number of control agents from massive hatchlings at the laboratory level. The objective of this technique is to achieve that the biocontrollers act before their dispersion or inactivity in the culture.

With this strategy it is intended that the control agent acts directly on the pest organism, not its offspring. An example is the control of the corn borer (Ostrinia nubilalis) by massive and controlled releases of wasps of the genus Trichogramma.

Control b

It is based on the interaction between the species of an agroecosystem in order to enhance its defense to resist the attack of pests. It includes not only the crop and natural enemies, but the total environment, including environmental conditions and man.

It is related to the integral management of the crop, and even though it is a recent technique, it constitutes a sustainable method. An example is the incorporation of living strips around plantations that favors the creation of a beneficial environment for the natural enemies of pests.

Advantage

A pest control plan that includes effective biological control has many benefits, among which we can mention:

• Biological control allows the pest to be controlled without leaving toxic residues in the environment.
• At an environmental level it is a safe method that favors biodiversity.
• It is specific. There is no detrimental effect on other species that are not considered pests of a certain crop.
• No resistance is observed from pests. So it is very effective.
• The implementation of biological control is long-term, and often permanent.
• Its cost is relatively lower compared to the use of chemical pesticides.
• It is a recommended method for large production systems and on inaccessible terrain.
• This type of control is considered an effective alternative in a comprehensive pest management program.

Disadvantages

Like any control method, poor application and monitoring of biological control can lead to drawbacks, among which the following can be noted:

• Lack of knowledge about the principles, rules and regulations about biological control.
• Scarce economic resources for the purchase of necessary equipment for the manipulation of the control organisms.
• Availability of organisms for biological control.
• Specialized personnel are required, which increases costs at the level of training and contracting.
• Presence of natural enemies of the controlling organisms.
• Disparity between the life cycle of pest organisms and organisms used for control.

Predator example

Predatory mites

Mites of the Phytoseiidae family constitute one of the main biological control agents of other species of arthropod pests. They are species with polyphagous habits capable of feeding on the eggs of other species, the larvae or small insects.

Predatory mites. Source: pixabay.com

These mites are free-living, easily moving on the ground, weeds and crops where they locate their prey. In addition, they are omnivores, managing to survive on other foods such as bark, humus, or pollen; staying in the middle waiting for their prey.

Indeed, these Phytoseiidae are natural enemies of other mites such as Acaridids, Eryophytes, Tarsonemids, Tetraniquids, and Tideids. Likewise, they have been found consuming other insects such as Aleyrodids, Coccids, Psocopterans, and Thysanoptera larvae.

Predatory beetles

The so-called ladybugs or lovebirds characterized by their vivid colorations are the typical beetles used in biological control. They are polyphagous insects that are located in various agroecosystems in constant search of food.

Ladybugs or Lovebirds. Source: pixabay.com

These small beetles belong to the Coccinellidae family and can be found in various ecosystems. They feed on the eggs and larvae of prey insects, as well as smaller adults.

Ladybugs are predators of aphids, mites and mealybugs in natural species and commercial crops, hence their economic importance. However, they in turn have natural enemies such as birds, dragonflies, spiders and amphibians.

Lacewings

Lacewing are small, light green insects with large yellow eyes that are biocontrollers of various crop pests. Its importance lies in its ability to mitigate the pest population and contribute to reducing the use of chemical pesticides.

Lacewing. Source: pixabay.com

These insects belong to the Chrysopid family of the order Neuroptera, being predators of thrips, aphids, spider mites and mealybugs. Their chewing mouth apparatus makes it easy for them to consume eggs and larvae of white flies, butterflies and olive prays.

Example of parasitoids

Parasitoid wasps

Parasitic or parasitoid wasps are various species belonging to the Hymenoptera order that parasitize eggs or larvae of other species. They are natural enemies of lepidopteran caterpillars, coleopteran worms, whiteflies, mites, and aphids.

Parasotoid wasp. Source: allyouneedisbiology.wordpress.com

Its mode of action consists of depositing its eggs on or within the host insect, whether in the egg, larva or adult stage. The parasitoid develops in or on the host, feeding on it to eventually kill it.

These parasitoids are specific, they specialize in parasitizing a specific host, preferably in its first stages of life. There is a great variety of parasitoids, the most common being the Braconidae, Chalcidoidea, Ichneumonidae, Proctotrupoidea and Stephanoidea families.

Parasitic flies

Flies generally belong to the Diptera Order. They are insects considered parasites of different commercial pests, even though these flies have become potential transmitters of diseases in domestic animals and man.

Parasitic flies. Source: pixabay.com

Due to the characteristics of their organs to deposit eggs, they are limited to placing them on the surface of the host. Later, when the larvae emerge, they burrow into the pest, feed and finally devour it.

The species Pseudacteon obtusus is used to control populations of red fire ants (Solenopsis invicta) accidentally introduced into the United States.

The flies deposit their eggs in the ant, as the larvae develop, they release a chemical substance that dissolves the host membrane, eliminating it.

Example of pathogens

Bacillus thuringiensis

Gram (+) bacteria of the Bacillaceae family located in the bacterial flora of the soil and used in the biological control of pests. It is a pathogen of pests such as lepidopteran larvae, flies and mosquitoes, beetles, bed bugs and nematodes.

Bacillus thuringiensis. Source: Todd Parker, Ph.D., Assoc Director for Laboratory Science, Div of Preparedness and Emerging Infections at CDC, via Wikimedia Commons

Bacillus thuringiensis in the sporulation phase produces endotoxin crystals that have insecticidal properties. Applied to the foliage of crops, the insect consumes it, becomes intoxicated and causes death.

Beauveria bassiana

Deuteromycetes class fungus used in the biological control of various insects considered pests, causing the muscardina soft disease. It is a biocontroller of a great variety of arthropods, such as caterpillars, aphids, mites, termites, whiteflies and thrips or spider mites.

Beauveria bassiana attacking lepidopteran larva. Source: Tsanjuan, from Wikimedia Commons

Used as a control agent, the conidia of the fungus are sprinkled on the crop or applied directly to the soil. In contact with the host, the conidia adhere, germinate, penetrate and produce toxins that affect the immune system, causing death.

References

1. Cabrera Walsh Guillermo, Briano Juan and Enrique de Briano Alba (2012) Biological Pest Control. Science Today. Vol. 22, No. 128.
2. Gómez Demian and Paullier Jorge (2015) Biological Pest Control. National Institute of Agricultural Research.
3. Guédez, C., Castillo, C., Cañizales, L., & Olivar, R. (2008). Biological control: a tool for sustainable and sustainable development. Academia, 7 (13), 50-74.
4. Smith Hugh A. and Capinera John L. (2018) Natural enemies and biological control. Publication # ENY-866. Recovered at: edis.ifas.ufl.edu
5. Nicholls Estrada Clara Inés (2008) Biological control of insects: an agroecological approach. Editorial University of Antioquia. ISBN: 978-958-714-186-3.