Entomopathogenic fungi, a solution to our pesticide problem?

Chemical Pesticides are our current saviours, and natures enemy.

Tackling food shortages and massive industry losses has led to a an imperative reliance on chemical pesticides. Invasive insects alone cause $70 billion losses worldwide and lead to hunger and loss of livelihoods. However, it is well understood that these chemicals pose significant threats to pollinators, surrounding wildlife and human health.

These pesticides contribute to colony collapse disorder and bee fertility leading to our falling bee populations. They also affect biodiversity of the surrounding environments by contaminating rain, rivers and lakes causing widespread destruction at all levels of the food chain. Chronic (long-term) pesticide exposure to humans such as farmers and neighbouring communities has been linked to several life-altering and fatal diseases such as Parkinson's disease and cancer. Furthermore, a shocking 20% of global suicides occur by acute pesticide poisoning due to their extremely low fatal dose and ease of access.

Use of biopesticides, naturally occurring pesticides namely entomopathogens such as fungi is on the rise. Brazil has seen a near 400% increase in registered biopesticides in the last decade and with further research, this will increase significantly.

Worldwide, efforts are being made to rely less on chemical pesticides by use of biopesticide alternatives because they target pest species better and pose a much lower risk to pollinators, humans and the wider ecosystem.

The Aftermath...

Several stories published by National Geographic highlight some of the unintended consequences our use of chemical pesticides has caused for wildlife. Now banned in the EU except for emergency usage, imidacloprid, a once widely used neonicotinoid applied to seeds, was used as a 'safer' alternative to more destructive pesticides due to its apparent 'selectivity' for arthropods. This chemical caused significant harm to the fertility of the blue-orchard bee. A single exposure lead to a 20% decrease in offspring with additive damage upon repeat exposures. Whats more is this damage didn't just affect the individuals exposed but also harmed the future generations leading to unprecedented damage to the entire species.

Imidacloprid is also responsible for sudden weight loss in migratory song-birds, a seemingly trivial effect. However this leads to the birds making more stops to feed, and potentially being re-exposed. This can lead to significant delays in reaching their destination hence harming their chances of survival. Imidacloprid also caused significant losses in a Japanese fishery by means of culling the Zoo-plankton due to accidental run-offs into the water. This disrupted the food chain leading to many fish dying from starvation.

Time for change

Many pests such as the potato beetle and diamondback moth are developing resistance to chemical pesticides leading to lower returns on investment in once valuable products. Additionally, consequences increase substantially with improper use, alongside many unpredictable consequences. This means that these chemicals have to be heavily monitored and regulated to reduce unintended harm.

Biopesticides are screened for their effectiveness, safety to humans, pollinators and the environment as well as their selectivity to specific pests. This means they can be used without monitoring and the risks they pose are minimal. They can also be mass produced easily and with sustainable and inexpensive raw materials. They also provide a solution for resistance as they develop new strategies for their target host as soon as resistance arises via the process of natural selection.

The Current obstacles

Biopesticides don't currently meet the global demand for pesticides, more investment is required to increase the size and efficiency of mass production. It also costs a lot of time and money to select a potential candidate, formulate a strain viable for use, screen it for efficiency and safety before attempting to obtain regulatory approval.

Although their specificity is largely a benefit, it means that farm owners will need to invest in many bio-insecticides, fungicides, nematicides and bactericides that target each individual pest they face. This creates barriers for access and discourages farmers from investing, particularly in developing nations and agricultural industries with already low profit margins.

In addition, entomopathogenic fungi are slow to act, they need to first develop conidia and act by penetrating the cuticles of arthropods before killing them. Therefore they cant be used as a fast acting solution to an emergency. However, promising research in recent years is suggesting the mass production of fungal insecticidal enzymes may be a solution to this issue as they can act immediately after application.

What's Next

Research is ongoing to increase the diversity of entomopathogens in our biopesticide artillery to fight a broader range of pests. A study this year found the fungus Trichoderma hermatum demonstrated insecticidal capabilities similar to B.bassiana; the current most powerful fungal biopesticide, against the cotton leafworm. This fungus was not previously recognised as entomopathogenic but through investigation is was seen as a viable candidate for screening. It is unknown as to whether this species will become commercially available but this research is imperative to find new alternatives.

In order to do better in our future approaches, we must learn from the past. Legislation has been influenced by investigation into the acute immediate effects of pesticides, however more longitudinal research into the chronic effects of long term exposure needs to be done before legislative approval is given to any pesticide. This means that the inter-generational health and ecological effects need to be considered. Furthermore, the question as to whether culling a species by any means is going to cause devastation to a food chain needs to be considered. Aside from social and environmental ramifications, soil erosion and fertility, biodiversity and damage to pollinators mean long term consequences for the industry. The more agriculturalists understand about the complex ecology in soil and the effects these chemicals have on decomposers and nitrogen-fixing bacteria, the more they can do to help prevent long term damage to their land.

A potential alternative to any pesticide is however on the rise, these are non-pesticidal methods such as multiple-cropping systems which are strategic planting methods in order to prevent disease spread and restrict pests to minimise losses. These include mosaic cropping, crop rotation with biocidal plants and push-pull cropping. These methods effectively restrict movement of pests and diseases via habitat fragmentation and resource restriction, prevent pests from completing their life cycles and draw pests away from the desired crop. These strategies minimise the need for any pesticidal intervention and with careful planning with knowledge of the ecology can be highly effective.

Overall with further investment and research into smarter pest-management methods, we can tackle these issues and cause less destruction.

References

1. Faria, M., Mascarin, G. M., Butt, T., & Lopes, R. B. (2023). On-farm Production of Microbial Entomopathogens for use in Agriculture: Brazil as a Case Study. Neotropical Entomology, 52(2), 122–133. https://doi.org/10.1007/s13744-023-01033-5

2. Ferreira, J. M., & Soares, F. E. de F. (2023). Entomopathogenic fungi hydrolytic enzymes: A new approach to biocontrol? Journal of Natural Pesticide Research, 3, 100020. https://doi.org/10.1016/j.napere.2023.100020

3. Gaba, S., Lescourret, F., Boudsocq, S., Enjalbert, J., Hinsinger, P., Journet, E.-P., Navas, M.-L., Wery, J., Louarn, G., Malézieux, E., Pelzer, E., Prudent, M., & Ozier-Lafontaine, H. (2015). Multiple cropping systems as drivers for providing multiple ecosystem services: from concepts to design. Agronomy for Sustainable Development, 35(2), 607–623. https://doi.org/10.1007/s13593-014-0272-z

4. Lana, M., Simón, O., Velasco, P., Rodríguez, V. M., Caballero, P., & Poveda, J. (2023). First study on the root endophytic fungus Trichoderma hamatum as an entomopathogen: Development of a fungal bioinsecticide against cotton leafworm (Spodoptera littoralis). Microbiological Research, 270, 127334. https://doi.org/10.1016/j.micres.2023.127334

5. National geographic. (n.d.). Insecticide exposure harms bees across generations. Retrieved June 9, 2023, from https://www.nationalgeographic.com/animals/article/insecticide-exposure-harms-bees-across-generations

6. National geographic. (n.d.). Neonicotinoid insecticides cause fish declines in japan. Retrieved June 9, 2023, from https://www.nationalgeographic.com/animals/article/neonicotinoid-insecticides-cause-fish-declines-japan

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8. Pesticide action UK. (n.d.). Pesticide Action UK . Retrieved June 9, 2023, from https://www.pan-uk.org/health-effects-of-pesticides/

9. Sabbahi, R., Hock, V., Azzaoui, K., Saoiabi, S., & Hammouti, B. (2022). A global perspective of entomopathogens as microbial biocontrol agents of insect pests. Journal of Agriculture and Food Research, 10, 100376. https://doi.org/10.1016/j.jafr.2022.100376

10. US EPA. (n.d.). Colony collapse Disorder. Retrieved June 9, 2023, from https://www.epa.gov/pollinator-protection/colony-collapse-disorder#:~:text=Colony%20Collapse%20Disorder%20is%20the,immature%20bees%20and%20the%20queen.

11. WHO. (n.d.). WHO. Retrieved June 9, 2023, from https://www.who.int/news-room/fact-sheets/detail/parkinson-disease