Hormesis: How Low-Dose Insecticides Can Enhance Pest Control

Insecticide Efficacy & Hormesis

Understanding Hormesis: How Low-Dose Insecticides Can Be More Effective in Pest Control

What is hormesis?

Insecticides are designed to control pests effectively, yet there are instances where lower doses result in higher insect mortality compared to higher doses. This counterintuitive phenomenon, known as “hormesis,” reveals the complexity of biological responses to toxic substances. Hormesis describes a scenario where a low dose of a toxin can have a stimulatory or beneficial effect, while a higher dose becomes less effective or even harmful.

Mechanisms of Hormesis:

Several mechanisms can explain this paradox:

1. Behavioral Changes: At lower doses, insects might not detect the insecticide and continue to consume or come into contact with it, leading to higher mortality. At higher doses, insects may sense and avoid the toxic substance, reducing their exposure.
2. Metabolic Activation: Some insecticides require metabolic activation within the insect’s body to become toxic. At higher doses, the insect’s detoxification systems might become overwhelmed or inhibited, reducing the efficiency of this activation process. Conversely, lower doses might allow the insect’s metabolism to activate the insecticide more effectively, resulting in higher mortality.
3. Detoxification Mechanisms: Insects have detoxification enzymes that help break down toxic substances. At higher doses, these enzymes might be upregulated, enhancing the insect’s ability to detoxify the insecticide and survive. Lower doses might not trigger such a strong detoxification response, leading to higher mortality.
4. Stress Response: High doses of insecticides can induce a stress response in insects, triggering mechanisms that protect against the toxin. Lower doses might not trigger these protective mechanisms, resulting in higher mortality.
5. Target Site Saturation: In some cases, the target sites (such as receptors or enzymes) for the insecticide within the insect’s body can become saturated at higher doses. Once saturated, additional insecticide molecules have no further toxic effect, leading to a plateau or even a decrease in mortality.
6. Physiological Responses: Lower doses might induce subtle physiological changes in insects that make them more susceptible to the toxic effects of the insecticide, whereas higher doses might cause immediate but less lethal disruptions.

Understanding these mechanisms requires detailed studies on specific insecticides and insect species. The concept of hormesis underscores the need to consider dosage carefully in pest control strategies.

Evidence from Scientific Literature:

• Calabrese and Baldwin (2003) provide a foundational understanding of hormesis, emphasizing the dose-response revolution in toxicology. They highlight how low doses of toxic substances can have beneficial or stimulatory effects, while higher doses are detrimental. This foundational work establishes the broad relevance of hormesis across various biological systems.
• Guedes et al. (2016) explore the impact of sub-lethal doses of pesticides on arthropods, revealing how these doses can induce stress responses that affect the insects’ physiology and behavior. They emphasize the potential of leveraging hormesis to optimize integrated pest management (IPM) programs by understanding and exploiting these stress-induced responses.
• Cutler (2013) reviews evidence of hormesis in insects exposed to insecticides, discussing the complexities and methodological considerations necessary for studying these effects. The review provides examples of how low doses of insecticides can sometimes be more lethal than higher doses, thus highlighting the paradoxical nature of hormesis in pest management.
• Desneux et al. (2007) investigate the sublethal effects of pesticides on beneficial arthropods, including bees and predatory insects. They note that lower doses can lead to significant behavioral and physiological changes, sometimes resulting in higher mortality or reduced fitness. This work underscores the importance of considering sub-lethal doses in the broader ecosystem health and pest control context.
• Guedes and Cutler (2014) delve into the potential applications of insecticide-induced hormesis in pest management strategies. They highlight how a deep understanding of hormesis can lead to developing more effective and sustainable pest control methods by optimizing the use of insecticides to exploit hormetic responses.
• Ricupero et al. (2020) investigate the hormetic effects of chlorantraniliprole on Trichogramma chilonis, a key egg parasitoid used in managing rice lepidopterans. They demonstrate that low chlorantraniliprole doses can enhance certain parasitoid biological functions, exemplifying the hormesis phenomenon. This study provides valuable insights into how hormesis can be beneficially leveraged in biological control programs.
• Cutler et al. (2022) provide a comprehensive review of the hormetic effects of insecticides on various insects. They discuss the underlying mechanisms of hormesis and the potential implications for managing insect populations in agroecosystems. This paper emphasizes the need for a nuanced approach to pesticide application, taking into account the hormetic effects to improve efficacy and sustainability.
• Guedes et al. (2022) discuss how pesticide-induced hormesis affects arthropods. They emphasize the necessity for a better understanding of these effects to enhance pest management strategies and increase the effectiveness of pesticides. This study contributes to the growing body of literature that calls for more sophisticated pest management approaches.
• Fouad et al. (2022) highlight the transgenerational hormetic effects of the insecticide Flupyradifurone on the cowpea aphid. They demonstrate that lower doses can have significant biological impacts, affecting the treated generation and subsequent ones. This research underscores the long-term implications of hormesis in pest management.
• Silva et al. (2024) examine how temperature and insecticide mixtures interact to influence the hormetic response in the green peach aphid Myzus persicae. They show that environmental factors, such as temperature, can modulate the effects of sub-lethal doses, leading to varied responses in insect mortality. This study highlights the importance of considering environmental variables when applying insecticides.

Conclusion:

Hormesis in insecticides highlights the need for optimized pest management strategies that leverage these effects to enhance efficacy. Understanding the intricate mechanisms behind this phenomenon can lead to more effective and sustainable pest control solutions. By carefully considering dosage and environmental factors, pest management can be improved, leading to better outcomes in agroecosystems.

References:

Calabrese, E. J., & Baldwin, L. A. (2003). Hormesis: The dose-response revolution. Annual Review of Pharmacology and Toxicology, 43(1), 175-197.

Cutler, G. C. (2013). Insects, insecticides, and hormesis: Evidence and considerations for study. Dose-Response, 11(2), 154-177.

Cutler, G. C., Amichot, M., Benelli, G., Guedes, R. N. C., Qu, Y., Rix, R. R., Ullah, F., & Desneux, N. (2022). Hormesis and insects: Effects and interactions in agroecosystems. Science of The Total Environment, 825, 153899.

Desneux, N., Decourtye, A., & Delpuech, J. M. (2007). The sublethal effects of pesticides on beneficial arthropods. Annual Review of Entomology, 52, 81-106.

Fouad, E. A., El-Sherif, S. A., & Mokbel, E. S. M. (2022). Flupyradifurone induces transgenerational hormesis effects in the cowpea aphid Aphis craccivora. Ecotoxicology, 31(8), 909-918.

Guedes, R. N. C., Rix, R. R., & Cutler, G. C. (2022). Pesticide-induced hormesis in arthropods: Towards biological systems. Current Opinion in Toxicology, 29, 43-50.

Guedes, R. N. C., Smagghe, G., Stark, J. D., & Desneux, N. (2016). Pesticide-induced stress in arthropod pests for optimized integrated pest management programs. Annual Review of Entomology, 61, 43-62.

Guedes, R. N. C., & Cutler, G. C. (2014). Insecticide-induced hormesis and its potential role in pest management. In J. A. Radosevich (Ed.), Hormesis in Health and Disease (pp. 71-98). CRC Press.

Ricupero, M., Desneux, N., Zappalà, L., & Biondi, A. (2020). Hormesis effects of chlorantraniliprole on a key egg parasitoid used for management of rice lepidopterans. Pest Management Science, 76(6), 1982-1990. Doi: 10.1002/ps.5754

Silva, A. P. N., Carvalho, G. A., & Haddi, K. (2024). The interplay between temperature and an insecticide mixture modulates the stimulatory response of sublethally exposed Myzus persicae. Ecotoxicology. https://doi.org/10.1007/s10646-024-02780-w