“Suddenly, a dormant pathogen starts generating infections through contact, spreading rapidly and altering the behavior of its hosts, leading them to death and further disseminating the disease in the environment, resulting in a drastic impact on the once thriving population.”
While it may sound like something out of a science fiction story, this narrative is a reality in the world of insects. Science fiction tales involving fungi and zombies are inspired by the incredible ability of certain species of fungi, such as those from the Ophiocordyceps genus, to parasitize and remarkably manipulate the behavior of their insect hosts even after death. Before you get alarmed, rest assured! These fungi act upon some arthropods and insects like ants, and they belong to a group of microorganisms called entomopathogenic fungi, which means they cause diseases in insects.
Continue reading this article to learn more about these incredible fungi, its application in agriculture, and how they help us achieve safer and more responsible agriculture.
1 - How do entomopathogenic fungi act and what is their role in nature?
Despite sounding frightening, these fungi play a beneficial role in the environment, contributing to ecological balance. To infect their hosts, these fungi penetrate the insects, multiply inside them, and in the final stages of infection, grow on their bodies and are released into the environment to infect new individuals (Figure 1).
An interesting example of this group is the fungus Cordyceps javanica, formerly known as Isaria javanica (for more information, click here), which has been identified affecting populations of one of the worst pests in Brazilian and global agriculture, the whitefly, causing damage to various crops and jeopardizing our food security (see the study here). Surprisingly, this fungus has become a valuable ally for humans, now being used as a tool in agriculture (Figure 2), offering a responsible and safe approach.
2 - Can Cordyceps sp. fungi infect humans?
No, entomopathogenic fungi like those from the Cordyceps genus have specifically evolved to exploit arthropods, such as insects, and make them their hosts. These fungi have biochemical and structural adaptations that allow them to infect and multiply within the bodies of some arthropods. Although they cause diseases, leading to the death of insects and mites and subsequently releasing into the environment, these fungi do not pose a risk to humans or other vertebrates in general. This is because we have different physiology and immune responses compared to invertebrates such as insects. In other words, our cells, immune system, body temperature, and tissues have distinct characteristics that make us resistant and unsuitable for these fungi that are specific to insects.
it is totally safe
3 - Can other beneficial insects and arthropods be harmed by entomopathogenic fungi?
While entomopathogenic fungi can infect a wide variety of insects, not all arthropods are equally susceptible to these infections. There are several reasons why some are not affected by these fungi, as each species and even strains/isolates (learn more here) may have unique abilities and can infect specific hosts or groups of insects, usually selected for use in applied biological control based on this characteristic.
Moreover, there are insects that possess natural defense mechanisms adapted to protect them against fungal infections. These mechanisms can include the production of chemical compounds or secondary metabolites that are toxic to fungi, as well as thicker and more impermeable exoskeleton that hinders penetration and infection. Various anatomical, physiological, behavioral and spatial adaptations are observed in arthropods that can prevent fungal infections. Predator bugs can identify areas with fungi and avoid contact with them, minimizing the risk of infection. Ants have cleaning behaviors, actively removing fungi from their cuticles, and some species have glands that release secretions with antimicrobial properties, contributing to their protection. Worker honeybees also exhibit hygienic behavior, detecting and eliminating fungi present in the nest and larvae. Additionally, there are insects that inhabit dry and low-humidity environments that create unfavorable conditions for fungal growth (locusts exhibit behavioral fevers when they warm up in the sun, which can limit the fungal infections).
These adapted defense mechanisms, combined with specific immune responses, make beneficial insects less susceptible to different types of entomopathogenic fungi, allowing them to survive in their habitats. These complex interactions between fungi and arthropods contribute to the diversity and dynamics of insect and fungal populations in nature.
4 - How did Cordycepssp. fungus become a product for pest control, and what guarantees do we have regarding environmental safety and human health of a product?
Researchers from the Brazilian Agricultural Research Corporation (EMBRAPA) observed the natural occurrence of the fungus Cordyceps javanica in Brazil with potential as a biological control agent for pests, specifically the whitefly, and detailed studies were conducted to identify, characterize, and compare this fungus with other similar ones. Based on promising results, rigorous tests were conducted, including laboratory studies, greenhouse, and field trials, to assess the effectiveness and safety of this fungus as a pest control agent.
To ensure environmental safety and human health, environmental risk assessment and toxicity studies were conducted on beneficial insects and non-target organisms of the product, such as bees, fish, mammals, plants, and environmental microorganisms. Safety assessments were also carried out to verify that the product poses no risks to humans, animals, or ecosystems. Inspections, and assessments were conducted to demonstrate compliance with good manufacturing practices, ensuring the quality, consistency, and safety of the product at all stages of the production process. These assessments were performed according to specific regulations and criteria established by responsible regulatory bodies.
After years of research and development, the Cordyceps javanica based product went through a registration and approval process by competent authorities, taking into consideration the agronomic efficiency, environmental safety, and human health studies. Only after the analysis and approval of this information was the product granted for commercialization and use. Therefore, all necessary safety assessments were conducted to ensure environmental safety and human health, in accordance with regulatory requirements, prior to the approval of the product as a pest control agent.
Biological control using entomopathogenic fungi has been in existence for 144 years already, when the pioneering immunologist Elie Metchnickoff initiated trials using entomopathogenic fungi against the wheat cockchafer Anisoplia austriaca in 1879. In a century of use, there has never been reported of any danger to human health or harm to the environment due to the use of these fungi, despite their widespread and inundative applications in agriculture and a plethora of scientific literature and rigorous study on the topic.
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