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Augmentative biological control: The power of enhancing ecosystems

Theme: Basics of biocontrol

Theme: Integrated pest management

Overview

Agriculture, involving crops and livestock production, is essential for satisfying the basic human need for food. However, as the global population grows, so does the demand for food1, adding pressure to the farming industry to achieve higher crop and meat yields.

As a result, the additional demand on the environment has reduced crop diversity and contributed to biodiversity loss2. Modern agriculture relies heavily on synthetic inputs like chemical pesticides, which can harm human and environmental health and damage the land, making agriculture unsustainable3.

A landscape picturing rice fields
Rice production in the field © CABI

Consequently, there is an urgent need for more sustainable farming practices. Biological control, a natural pest management method, offers a sustainable alternative to chemical pesticides with a reduced environmental impact4. Here, we look at augmentative biological control and explore its potential, challenges, and strategies for increasing uptake among farmers globally.

Understanding biological control

Biological control, also known as bioprotection or biocontrol, involves harnessing naturally sourced compounds, nature-identical compounds, or living organisms to control weeds, pests, and diseases by reducing their population to manageable levels. Biocontrol is not new; it has been used successfully for over 100 years and pre-dates chemical control with pesticides4.

Uncontrolled pests and weeds can devastate crops, livestock, and ecosystems, impacting economies and human health. Biocontrol offers a sustainable and cost-effective alternative to chemical or manual methods, which have significant drawbacks. Chemicals, while effective, damage environmental and human health. Manual or mechanical methods tend to be laborious and expensive.

A farmer spraying a biopesticide in the field
A farmer spraying a biopesticide in the field © CABI

What are the three types of biological control?

There are three distinct categories of biological control:  

  • Augmentative biocontrol is a pest control strategy that involves increasing the population of natural enemies and pathogens by releasing more into the environment.
  • Classical biological control, also known as importation biocontrol, involves using a non-native organism, such as a predator, and introducing it into the affected area, where it can bring pest density down to manageable levels.  
  • Conservation bioprotection harnesses strategies to preserve the population of natural enemies already in the affected environment.

Here, we focus on augmentative biocontrol only. Two more blogs specific to classical and conservation biological control will follow. In the meantime, read our blog ‘Types of biological control‘ for more details.

Augmentative biological control: what is it, and why use it?

Augmentation in biocontrol involves increasing the population of natural enemies or pathogens present. This is achieved by releasing natural enemies (macrobials or invertebrate biocontrol agents) or pathogens (microbial agents) in a controlled manner. Although biocontrol methods, namely classical biological control, have existed for a long time, augmentative control is relatively new. Since its discovery, scientists have identified numerous natural enemies and pathogens, and developed optimal production, shipment, and release strategies.

A parasitoid (Trichogramma dendroliti) female on a armyworm (Noctuidae) egg
A parasitoid wasp (Trichogramma dendrolimi) parasitizing an armyworm egg. Credit: Victor Fursov via Wikimedia commons.

Several studies have shed light on the promise of augmentative control. One paper explored the success of releasing lab-reared egg parasitoids (Hadronotus pennsylvanicus) in managing squash bugs (Anasa tristis) by decreasing the rate of hatching5. Other reports have highlighted the importance of carefully designed augmentative control strategies considering optimal release rates and landscape context6,7.

Augmentative biocontrol can be used in different strategies based on the frequency and volume of agent release:

  • Inoculative control involves small, consistent releases of natural enemies or pathogens throughout the season(s). This preventative strategy is generally used when a pest is present but not a significant problem.  
  • Inundative control is a reactive or curative approach to a pest outbreak that requires immediate control. It involves releasing large numbers of biocontrol agents to achieve a rapid effect.  

What are the advantages of augmentative biological control?

Augmentative biological control has several advantages over other methods, such as chemical control with pesticides. It is based on natural methods or compounds, making it nontoxic to humans and the environment. It is far safer and more environmentally sustainable as it avoids the acute and chronic damage to health and the environment from chemical pesticides.

Biocontrol strategies are developed by selecting a biocontrol agent that naturally targets the pest; research has shown that targeted strategies achieve improved efficiency. Additionally, the resistance rate is far lower than for chemical methods, and ongoing research efforts are looking to identify new control agents and develop optimized strategies.

In terms of cost, augmentative control is usually more economically sustainable than chemical control since it avoids the damaging impact on soil health, which can improve crop yield in the long term. Preventative augmentation strategies evade the risk of pest outbreaks, overcoming the loss of income from yields destroyed by pests. Finally, these strategies are viable for organic growers, allowing growers to enter organic markets8.

Close of soil where young maize plants are growing
Young maize plants can grow more robustly in healthier soil. Credit: Steven Weeks via Unsplash

What are the challenges associated with augmentative biological control?

Despite its potential and associated success stories, augmentative biological control is not without its limitations, and strategies to overcome these challenges are crucial for promoting the uptake of this sustainable farming strategy8.

Although biological augmentation has considerable long-term cost benefits, biocontrol agents are not always cheaper than their chemical counterparts. Furthermore, owing to the live nature of many natural enemies, they may require storage in specific conditions or specialized facilities that may not be available to all growers. However, not all biocontrol agents require this, and future research will likely develop strategies to address this.

Augmentative control requires knowledge, planning, and patience:

  1. Growers and advisors must identify the pest successfully.
  2. They need to develop an augmentation strategy, which involves selecting the correct biocontrol agent and deciding on the release dosage, timing, and frequency.

Advisors can reduce the burden of research and planning and support growers in optimizing the strategy. Despite the advantages of augmentative approaches, they require labour, with frequent reapplications and observations of pest populations needed. Additionally, the targeted nature of biocontrol can represent a challenge since the strategy will be specific to a particular pest. Ongoing research and development efforts are working to overcome this.

farmer and advisors in the field monitoring pests and taking notes
A farmer and advisors monitoring pests in a tobacco field in Argentina © CABI

A significant barrier to uptake is a need for more education surrounding the advantages of biological augmentation and how to implement it successfully. Understandably, users are often more inclined to stick to what they know, the chemical pesticides, rather than trying something new. Aside from utilizing advisors as an information source, open-access resources such as the CABI BioProtection Portal aim to educate users on sustainable agriculture.

Future directions

Augmentative biological control presents a promising, sustainable solution for modern agriculture, addressing the urgent need for environmentally friendly pest management. Its advantages over chemical methods include safety, effectiveness, and economic and environmental sustainability. Future research and development efforts should address challenges like cost, storage requirements, and knowledge gaps. Crucially, education on biocontrol is also critical to promoting awareness of alternatives to pesticides and increasing uptake globally.

To learn more about augmentative biocontrol strategies, check out the range of valuable resources available in the CABI BioProtection Portal resources, or if you’re ready to choose a product, visit our products page.

Sources

1. Nations U. Population. United Nations. Accessed December 6, 2023. https://www.un.org/en/global-issues/population
2. Gámez-Virués S, Perović DJ, Gossner MM, et al. Landscape simplification filters species traits and drives biotic homogenization. Nat Commun. 2015;6(1):8568. doi:10.1038/ncomms9568
3. Meehan TD, Werling BP, Landis DA, Gratton C. Agricultural landscape simplification and insecticide use in the Midwestern United States. Proc Natl Acad Sci. 2011;108(28):11500-11505. doi:10.1073/pnas.1100751108
4. Bale JS, Van Lenteren JC, Bigler F. Biological control and sustainable food production. Philos Trans R Soc B Biol Sci. 2008;363(1492):761-776. doi:10.1098/rstb.2007.2182
5. Boyle SM, Salom S, Schultz P, Lopez L, Weber DC, Kuhar TP. Augmentative biological control for squash bug (Hemiptera: Coreidae) using the egg parasitoid, Hadronotus pennsylvanicus (Hymenoptera: Scelionidae). Prischmann-Voldseth D, ed. Environ Entomol. 2023;52(5):779-786. doi:10.1093/ee/nvad079
6. Crowder DW. Impact of Release Rates on the Effectiveness of Augmentative Biological Control Agents. J Insect Sci. 2007;7(15):1-11. doi:10.1673/031.007.1501
7. Perez-Alvarez R, Nault BA, Poveda K. Effectiveness of augmentative biological control depends on landscape context. Sci Rep. 2019;9(1):8664. doi:10.1038/s41598-019-45041-1
8. Bianchi FJJA, Ives AR, Schellhorn NA. Interactions between conventional and organic farming for biocontrol services across the landscape. Ecol Appl. 2013;23(7):1531-1543. doi:10.1890/12-1819.1
9. Van Lenteren JC. The state of commercial augmentative biological control: plenty of natural enemies, but a frustrating lack of uptake. BioControl. 2012;57(1):1-20. doi:10.1007/s10526-011-9395-1

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