Los entomopathogenic fungi have revolutionized agricultural and forestry pest management in recent decades. Their ability to naturally attack insects that transmit diseases or cause crop damage is increasingly valued in a context where the environmental impact of traditional chemical products is a source of concern.
Today, research teams, specialized companies, and farmers are working hard to develop biological solutions in which these fungi play a crucial role. Thanks to their targeted action against numerous insect vectors and pests, they represent a sustainable, effective, and safe alternative to chemically synthesized pesticides.
What are entomopathogenic fungi and how do they act?
Entomopathogenic fungi are organisms that can cause disease and eventually death in insects and other arthropods. More than 750 species are currently known, grouped mainly in the orders Hypocreales (Ascomycota) and Entomophthorales (Zygomycota). These fungi have two main phases in their life cycle: a parasitic phase, which spans from infection to the death of the host, and a saprophytic phase, which occurs after the insect dies and the fungus survives by utilizing the organic matter available in the environment.
Infection begins when fungal spores (conidia) are deposited on the insect's cuticle. Unlike other pathogens such as bacteria or viruses, the insect does not need to ingest the fungus; infection occurs directly through the body surface. The process involves several stages, which proceed as follows:
- Accession: The spores attach to the insect's cuticle. Once attached, they germinate and form a specialized structure called an appressorium, which facilitates attachment and subsequent penetration.
- Germination and penetration: The spore generates a germ tube that passes through the cuticle, thanks to the combination of physical pressure and the action of enzymes such as proteases, lipases and chitinases.
- Colonization and toxin production: The fungus invades the insect's internal tissues, branching its hyphae and producing toxins such as beauvericin and other compounds, which weaken the host's immune system and accelerate its death.
- Death and sporulation: After the insect dies, the fungus multiplies within the corpse, producing new spores that can infect other individuals if environmental conditions are favorable.
This process causes the death of the insect either by the physical growth of the mycelium within its body or by the toxic action of the metabolites released by the fungus. This specificity and efficacy have made entomopathogenic fungi essential allies for biological control.
Main species of entomopathogenic fungi in pest control
Two of the most studied and used entomopathogenic fungi in the agricultural world are beauveria bassiana y Metarhizium brunneum (and its variety anisopliae). Each one has particular characteristics that make them suitable for combating different species of pests and vectors.
Beauveria bassiana:
This cottony, white or creamy-yellow fungus is capable of infecting more than 200 species of insects belonging to different orders. It is widely used as a biopesticide and has demonstrated great effectiveness in horticultural, fruit, and ornamental crops, as well as in forest protection. Its mode of action is based on the steps described above, where penetration and internal colonization are facilitated by the secretion of toxins such as beauvericin, beauverolides, and other substances with insecticidal properties.
In practical applications, beauveria bassiana It can be applied by foliar sprays, in traps with inoculated organisms or even by localized irrigation. The key to its effectiveness lies in the fact that it must come into direct contact with the target insect; without this contact, the desired effect will not be achieved. Factors such as relative humidity (ideally above 90%) and a temperature between 23 and 25°C favor the germination and action of the fungus.
Metarhizium brunneum:
Formerly known as Metarhikum anisopliae, this fungus is especially effective in controlling soil pests and insect vectors such as philaenus spumarius, a key transmitter of the bacteria Xylella fastidiosa which has caused serious problems in olive trees and other Mediterranean crops. In trials, the EAMa 01/58-Su strain of M. brunneum has managed to significantly reduce the survival of these insects both by direct contact and by feeding on previously treated plants.
The action of Metarhizium brunneum It's not limited to insects; it can also colonize the root environment of plants, offering added benefits such as improved root system function, increased nutrition, and resistance to abiotic stress conditions. This makes these fungi valuable tools in sustainable integrated management.
Recent research and advances in the use of entomopathogenic fungi
In recent years, studies have intensified to develop practical and effective applications of entomopathogenic fungi in various agricultural settings. Teams such as the one at the University of Córdoba (UCO) are focused on identifying native strains capable of combating insect vectors of diseases as serious as Xylella fastidiosa or HLB (citrus greening).
A prominent example is the use of M. brunneum to reduce the vector population philaenus spumarius in olive trees, demonstrating in the laboratory a reduction in survival and alterations in the pathogen's transmission capacity. In addition, field trials are being prepared to further validate these results in real-world settings, especially in severely affected areas such as southern Italy.
In the citrus sector, companies such as Koppert and international consortia are testing the effectiveness of entomopathogenic fungi to control pests such as African psylla (Trioza erytreae), HLB vector. This type of strategy is crucial, since the disease currently has no cure, and controlling the insect vectors is the best defense against its spread.
How entomopathogenic fungi are applied: methods and recommendations
The effectiveness of entomopathogenic fungi depends largely on how and when they are applied. Some common methods include:
- Foliar applications: They consist of spraying liquid or solid formulations onto crops, allowing the spores to come into contact with insects found on leaves and stems.
- Localized irrigation or "drench": It is mainly used for soil pests, applying the fungus to the root zone or around the plant.
- Inoculated traps or baits: Insects are attracted to specific spots where the fungus is in optimal conditions to infect them.
To achieve the best results, fungi should be applied under suitable environmental conditions, maintaining high humidity and medium temperatures. In addition, it is important to apply the product at times when the target insect is most prevalent and to ensure that the formulation is compatible with other biological treatments or agronomic practices (e.g., cover crops or the presence of auxiliary insects).
Compatibility and synergies: vegetation cover and auxiliary fauna
One of the most innovative lines of research explores the combination of entomopathogenic fungi with the implementation of plant cover to promote greater biodiversity and the presence of natural enemies. Studies by the Universitat Jaume I and the UCO demonstrate that the combined use of plant covers and fungi as Metarhizium brunneum It improves the control of pests such as fruit flies, increasing the infectious efficiency of the fungus and reducing the progression of harmful insects to adult stages.
An essential aspect is to analyze the possible impact on beneficial predators. Field trials have revealed that although the activity of some groups such as the beetles, the use of entomopathogenic fungi does not negatively affect other key predators (earwigs, spiders) and even enhances the activity of ants that also contribute to biological control.
This compatibility between different management techniques opens up new possibilities for integrated control capable of keeping pest pressure to a minimum and minimizing the use of chemicals.
Advantages and limitations of using entomopathogenic fungi compared to other strategies
Compared to traditional insecticides, entomopathogenic fungi have numerous advantages:
- Selectivity and specificity: They usually attack only certain groups of pest insects, sparing auxiliary fauna and other beneficial organisms.
- Safety: They do not leave hazardous residues or affect the health of humans, domestic or wild animals.
- Easy production and handling: They can be multiplied in large volumes and applied with existing machinery, easily integrating into agricultural practices.
- Adaptability: Native strains can be selected for each environment, increasing their effectiveness and persistence.
However, there are some factors that can limit its effectiveness:
- Environmental conditions: Mushrooms require high humidity and mild temperatures to germinate and develop properly.
- Direct contact: It's essential that the spores reach the insect's body surface; therefore, application coverage and distribution are key.
- Persistence: Adverse environmental conditions or direct sunlight can reduce spore viability in the field, although formulations are being improved to increase their shelf life.
Success stories and examples of controlled pests
The potential of entomopathogenic fungi is evident in the wide variety of pests on which they have proven effective, both in scientific trials and on large-scale agricultural farms. Notable examples include:
- Fruit fly control in citrus: Applications of Metarhizium brunneum They have achieved infection rates of over 60% under field conditions combined with plant cover.
- Reduction of populations of philaenus spumarius and containment of the Xylella fastidiosa in olive trees: The use of selected strains has been successful in reducing vector survival and reducing the risk of the bacteria spreading.
- Control of common pests in vegetables and fruit trees: White grubs, curculionids, tomato moths, whiteflies, whiteflies, aphids, mealybugs, and thrips are on the list of target species against which these fungi are already being used successfully.
In Chile, thanks to the work of the Quilamapu Experimental Station and its collection of more than 800 native strains, good results have been achieved in the control of key agricultural pests. At the European level, agricultural policies are promoting the integration of environmentally friendly techniques—such as the use of these mushrooms—in line with the objectives of the European Green Deal and the Common Agricultural Policy.
Challenges, lines of future research and perspectives
The development and application of entomopathogenic fungi as a primary and complementary tool in biological control continues to advance at a rapid pace. There are internationally recognized projects, such as BeXyl or TropicSafe, which integrate research, development of new formulations and international coordination to respond to challenges such as the containment of X. annoying or HLB in citrus fruits.
A crucial aspect for future success lies in the selection of appropriate plant cover to discourage insect vectors, as well as in assessing the ecological and economic impact of quarantine, containment, and eradication measures. Researchers are continually searching for specific strains adapted to each environment, as well as for application methods that maximize efficacy and minimize unintended effects on local biodiversity.
The combination of entomopathogenic microorganisms, plant cover crops, and other biological methods, along with sustainable agricultural policies and a reduction in the use of synthetic pesticides, is key to addressing the challenges of pest control in the context of climate change, environmental demands, and the protection of agricultural production.
