Multifunctional Potential of Entomopathogenic and Yeast-like Fungi: A Review of Key Tools for Agriculture

Abstract

Modern agriculture, heavily influenced by the Green Revolution, has increased productivity through the intensive use of external inputs and agrochemicals, but at the cost of growing environmental degradation, loss of biodiversity, pest resistance, and risks to human health. This production model has proven to be environmentally unsustainable in the face of current challenges, such as climate change, the increase in the world’s population, and the depletion of natural resources. In this context, agroecology emerges as an integrative scientific approach that promotes the transition from conventional agricultural systems to diversified, resilient, and functionally balanced agroecosystems, based on ecological principles and the progressive reduction of synthetic inputs. This review addresses the role of fungal microorganisms, with an emphasis on entomopathogenic fungi and fungi associated with the plant microbiome, as key tools in the sustainable management of biotic agricultural challenges. This paper addresses the biology and multifunctionality of entomopathogenic fungi, not only as biological control agents but also as crop growth promoters and phytopathogen suppressors. Taken together, the background information presented reinforces the potential of entomopathogenic fungi as strategic components in agroecological transition processes, contributing to productive sustainability, reduced agrochemical use, and the restoration of the ecological functionality of agroecosystems.

1. Introduction

Throughout history, agriculture has been marked by major technological transformations from the “Neolithic Revolution” which is understood as the historical period that corresponds to the beginnings of agriculture, consolidating agricultural work which represented a real step forward for the development of human societies [1], to the “Green Revolution” known for the marked increase increase in the production of highly subsidized grains by external inputs and improved seeds that occurred in several developing countries between the years 1940 and 1970, of the last century [2]. Prior to the Green Revolution, agricultural production depended on internal resources, the recycling of organic matter, the regulation of pests through functional biodiversity and stable water resources [3,4,5].

The use of genetically modified seeds played a fundamental role in the implementation of the Green Revolution. Genetically modified seeds, which offered higher yields than traditional seeds, were widely disseminated and cultivated across large areas. However, to achieve this maximum yield, they require the application of specific inputs, such as fertilizers, insecticides, fungicides, and herbicides, to eliminate diseases and weeds. If any of these inputs are lacking, the harvest falls below the usual yield. This has meant that, over the years, industrialized agricultural production has required significant capital investment, leading to increases in production costs and environmental problems [4,6,7]. A well-known example is that of Bt crops which produce toxins specific to some insects. While they have demonstrated a significant reduction in the need for insecticide applications in early stages, their effectiveness depends heavily on management strategies such as refuge areas and rotation of insecticides with different modes of action. The absence or poor implementation of these practices has favored the evolution of resistance in insect populations, demonstrating that technology alone does not constitute a permanent solution, but rather a tool that requires integrated management. Similarly, herbicide-resistant crops, such as RR soybeans, do not inherently imply an increase in application rates, but they have facilitated the simplification of weed management systems. This simplification translates into a strong dependence on a single mechanism of action, which increases selection pressure on weed communities. Consequently, the emergence of resistant weed biotypes has been widely documented. In production systems such as soybean (Glycine max) in Argentina, this process has been exacerbated by the predominance of large monocultures and simplified management schemes, which has led not only to an increase in the total use of herbicides, but also to the incorporation of more complex mixtures and, in some cases, additional active ingredients to control resistant weeds, reflecting a cycle of chemical intensification rather than a sustainable solution [8].

Over the years, this production model has prevailed over others, and in recent decades it has become evident that agricultural systems are going through an unprecedented and growing crisis, exacerbating the problems of hunger, poverty, migration, and environmental degradation, which is intensified by the phenomena caused by climate change [9,10]. The prevailing (conventional) production system is immersed in an approach where the use of agrochemicals for plant nutrition, arthropod population control, weed control, and disease management is deeply ingrained, leading to a series of social and environmental problems [11] and human health problems [5,12,13,14], among which we can mention serious poisonings that are related to neurological and reproductive disorders, cancer, and birth defects [15].

Some recent estimates (2019) indicate that more than 2 billion tons of pesticides are used worldwide, with over 20,000 commercial products and hundreds of active molecules that act primarily as insecticides, herbicides, and fungicides [16]. Many of these pesticides end up contaminating the soil and groundwater. The presence of pesticides in soil is caused by various means, such as aerial applications by small planes, which results in up to 50% of the product being stored in the soil [17]. Among the most persistent pesticides are organochlorines, such as DDT (Dichlorodiphenyltrichloroethane), a compound considered one of the most toxic and recalcitrant. For this reason, it was banned in 1970; however, it has continued to be used clandestinely in agriculture [15]. Poisoning and environmental contamination are not the only consequences, as the indiscriminate use of synthetic pesticides is the direct cause of resistance in various pest organisms, and consequently, the loss of their effectiveness. Under these circumstances, farmers commonly increase doses and prepare mixtures of various products, often more toxic, so the problem of resistance and environmental contamination, far from being solved, worsens [18,19,20,21,22,23,24]. Furthermore, the formulation of new, next-generation molecules with greater specificity and diverse modes of action has not solved the problems of contamination and biodiversity loss resulting from their use [25]. Today, food production is immersed in a scenario of constant change and an evident environmental crisis. The world’s population is projected to continue growing, reaching 9.7 billion by 2050, which will lead to a significant increase in food demand [26]. In addition, climate change, biodiversity loss, depletion of natural resources, and widespread environmental pollution pose an even greater challenge [27].

Under this scenario, it is of utmost urgency to advance the development of strategies that minimize the adverse effects of agricultural practices and help increase productivity. Agroecology is an inter and transdisciplinary scientific approach that would allow us to address and solve the socio-environmental problems [28]. To achieve this, a global process of productive transformation is essential, with each region contributing its experiences and developing sustainable strategies. This transformation must be gradual, undergoing a productive transition process that will depend on the specific characteristics of each agroecosystem. However, rather than a single, predetermined solution, strategies based on generalized ecological principles can be established. According to [29] productive transition processes from a conventional system based on monoculture and a high dependence on external inputs to diversified and sustainable agroecosystems consist of three phases: in the first phase, the progressive elimination of agrochemicals begins, mainly for crop nutrition and pest management (phytopathogens, herbivorous arthropods and spontaneous plants) through integrated management practices (rotations, resistant cultivars, monitoring, focused applications, others), in the second phase, synthetic inputs are replaced by biological and/or organic inputs, and in the third stage, the agroecosystem is redesigned, diversifying its components and functioning, without dependence on external inputs of synthetic and organic origin. In this transition process, farmers must interpret agricultural diseases or pest infestations as an expression of agroecosystem instability [30], since phytopathogens are highly heterogeneous in their life cycle and respond to agroecosystem design and management variables [31]. In this sense, restorative soil practices and the use of microorganism-based agricultural inputs become especially relevant in production transition processes, given the high dependence on therapeutic inputs in simplified agroecosystems.

This review examines the potential of fungal microorganisms, particularly entomopathogenic fungi, Entomophthorales, and yeast-like antagonists, as multifunctional tools for the agroecological management of biotic challenges in agricultural systems.

2. Materials and Methods

This review was made using a structured approach to synthesize current knowledge on the effects of enthomopathogenic fungi on multifunctional approeach. Scientific literature was collected from the Web of Science, Scopus, and Google Scholar databases using relevant keyword combinations including entomopathogenic fungi, biological control, yeast-like fungi, plant growth promotion, endophytic fungi, and sustainable agriculture. To ensure that the review reflects current developments in the field, priority was given to searching for studies published in the last ten years (2016–2026). However, in exceptional cases, older, fundamental, or highly cited studies were included when they provided essential conceptual or methodological foundations.

The inclusion criteria focused on peer-reviewed scientific publications; research centered on entomopathogenic and/or yeast-like fungi with proven or potential applications in agriculture; studies addressing biological control, plant growth promotion, endophytic behavior, or interactions with crops and agroecosystems; and experimental, field, or review studies that provided relevant empirical or conceptual contributions. The exclusion criteria focused on the exclusion of journals whose publications are not peer-reviewed; research focused exclusively on medical, veterinary, or industrial applications unrelated to agriculture; and publications of scientific experiments lacking methodological detail. This review incorporated a total of 278 bibliographic references, guaranteeing a general and representative view of the current state of knowledge on the subject. The selected studies were analyzed and organized thematically, and the main findings were summarized in tables. This methodology was based on the procedure established by [32].

3. Agricultural Production Based on Agroecology as a Source of Promising Microorganisms for Agriculture

Environmental imbalance in agroecosystems is one of the most significant problems affecting the agricultural sector [33]. Modern agriculture proposes a therapeutic approach to agricultural adversities, where continuous applications of synthetic chemical products and excessive tillage increase the system’s imbalance and perpetuate production problems [28]. This situation has worsened over time, generating a series of significant social and environmental problems, including: disease resistance to fungicides, contamination of waterways through leaching and deep percolation, displacement of native species due to habitat loss, human poisoning from exposure to agrochemicals, decreased soil organic matter and water retention capacity, and the disappearance of food plant species and ecotypes, among many others [5,14,34]. However, this model has both proponents and opponents. This model focuses exclusively on productivity, leading to the use of certain technologies that generate negative effects on the environment and people [35], while other authors attribute the negative effects of modern agriculture to the misuse of mechanization and synthetic chemicals [36]. Other authors claim that conventional precision agriculture is a technological solution that would improve the productivity of agroecosystems and reduce world hunger [37]. Views on this topic are diverse, but the truth is that far from being a sustainable model, the prevailing one is often perpetuated by many factors. Mention that the lack of information and knowledge, as well as the lack of planning and financial support, hinder efforts to implement sustainable agriculture. In this context of growing questioning of the conventional agricultural model and its effects on the environmental and productive stability of agroecosystems, the need arises to rethink agricultural management approaches, incorporating a more holistic and ecological vision of production systems [38]. In particular, understanding the biological processes that sustain the functioning of agroecosystems becomes especially relevant, among which the interactions between plants and their associated microorganisms stand out. These relationships, historically underestimated by intensive production models, represent a key component for the resilience, ecological balance, and sustainability of agricultural systems, generating the possibility of developing management strategies based on enhancing the ecosystem services provided by microbial biodiversity [14,28,39].

The biological relationships between plants and microorganisms are key determinants of the health and stability of agroecosystems. Plants host many microorganisms in a highly regulated and specific relationship known as the plant microbiome, which is diverse and dynamic in its form and functions [40]. The plant microbiome is composed of prokaryotic and eukaryotic organisms, including bacteria, archaea, viruses, fungi, chromists, and protozoa [41], and these can be found in different plant organs and tissues, as well as in associated substrates. This concept of the microbiome is also known as the “holobiont,” which refers to the entire plant or animal together with all its associated microorganisms [42,43,44]. This holobiont plays a fundamental role in plant survival and disease suppression [45]. Soil, and especially the rhizosphere, are the environments with the greatest biodiversity, as they are highly favorable for the proliferation and metabolic activity of numerous microorganisms [46,47,48]. It is estimated that more than a billion microorganisms can coexist in a single gram of soil, stimulating absorption and providing nutrients through the decomposition of organic matter [49]. Along with bacteria, fungi represent the largest percentage of soil microbial biomass [50,51]. Mostly microbial biodiversity is determined by the identity of the plant species with whose rhizosphere it is associated [52]. Different plant species selectively enrich their specific microbiomes by investing in root exudates to feed and modulate the microorganisms inhabiting their rhizosphere. These plants deposit a significant proportion of their photosynthates in the rhizosphere as root deposits and waste products [44,53].

On the other hand, it has been shown that increased fungal diversity leads to increased plant productivity and diversity, as well as the ability of crops to acquire nutrients [54,55]. Agroecological production systems often implement polycultures within their spatiotemporal timeline [56] and management practices aimed at soil conservation and increased biodiversity [57]. Among the management strategies that focus on restoring and improving soil fertility, conserving natural resources, and promoting agricultural practices that are beneficial to both the environment and local farmers and communities, we can mention that minimum tillage or no-till farming improves water use efficiency and increases organic matter; the implementation of hydrological design along contour lines allows for greater infiltration of surface water; the application of compost increases microbial biodiversity and soil nutrients; the use of cover crops reduces water evaporation from the soil, decreases extreme high temperatures, and increases the microbiota associated with roots; the recycling of plant residues reduces nutritional erosion in agroecosystems; agroforestry, which is the integration of crops and livestock and/or poultry; and rotational grazing directed at agricultural systems generates more efficient nutrient recycling, among other productive practices [58,59]. These practices increase the number of microorganisms present in agricultural soils, generating ecological services of great productive relevance, such as the suppression of plant diseases [14,28]. An example of this is evidenced by [60], who identified that plants with a rich and diverse associated microbiome, such as the prickly pear cactus (Opuntia fucus-indic) in arid environments, can benefit the growth and development of neighboring plants through the association of their microbiomes. By including characterized microbiomes, the incidence and severity of plant diseases can be reduced. Among plant diseases, those related to soilborne phytopathogens are especially difficult to manage; therefore, the suppression of soilborne diseases is essential to achieving the proposed yields. The suppression of soilborne diseases by suppressive soils refers to soil health and the specific ecological conditions of the microbial community present, such that phytopathogenic microorganisms causing root diseases are kept at low population levels or do not express their pathogenic potential [61]. Therefore, the search for beneficial microorganisms for agriculture has a greater chance of success if carried out on farms with a greater diversity of plant species within their production matrix [62].

4. Use of Entomopathogenic Fungi for the Management of Agricultural Adversities

Among fungal microorganisms of agricultural relevance, entomopathogenic fungi have attracted increasing attention because of their multifunctionality, including insect pest suppression, plant growth promotion, endophytic colonization, and antagonism against phytopathogens.

Entomopathogenic fungi are ubiquitous microorganisms in agroecosystems, playing a crucial role in regulating arthropod populations. These fungi have the unique ability to parasitize various insect groups and other arthropods, such as spiders and mites, causing disease and death [63]. They infect their host primarily through the integument, unlike some entomopathogenic bacteria that live in a symbiotic relationship with nematodes, which serve as a vehicle for entry into the insect. An example of this is the bacterium Xenorhabdus spp. and the nematode Steinernema spp. [64]. The process of integumentary infection by entomopathogenic fungi begins with the adhesion of a conidium to the insect’s cuticle and is mediated by various cuticular recognition mechanisms. Once attached, and if environmental conditions permit, the conidium germinates and produces anchoring and penetration structures of the appressorium type, penetrating the integument through the combined action of physical pressure, secondary metabolites, and lytic enzymes such as proteases, lipases, and chitinases. Subsequently, the entomopathogenic fungus invades the hemocoel, overcoming the insect’s defense system through the combined action of secondary metabolites, enzymes, and proteins that function as toxins. These toxins also induce a wide range of symptoms in the arthropod host, including abnormal behavior, lack of coordination, severe dehydration, convulsions, difficulty or inability to feed, and metabolic disorders that ultimately cause the arthropod’s death [65]. The infection process culminates in the insect’s death, primarily due to nutrient depletion and the collapse of its organs and central nervous system. Once the entire insect is colonized, the fungus generates reproductive structures at the expense of the carcass, allowing for its dispersal and the continuation of its life cycle. This process has been studied and described by several authors [66,67,68,69,70,71,72]. However, other authors mention that some entomopathogenic fungi, such as Beauveria bassiana var. majus, can initiate infection of the insect through the gut, following the ingestion of conidia [73]. It has recently been discovered that certain entomopathogenic fungi can kill insects without penetrating the integument and subsequently invading the invertebrate completely. They achieve this by causing the collapse of the insect’s defense system through the elevated expression of stress-related genes, influencing the production of enzymes such as caspase (an enzyme involved in apoptosis), leading to a high rate of cell death and ultimately the insect’s death. Following the ingestion of plant material colonized by entomopathogenic fungi, high mortality rates can occur among phytophagous invertebrates. This mortality is related to the secretion and release of biochemical compounds toxic to invertebrates or free radicals generated by the plant following a systemic response induced by the presence of the entomopathogenic fungus [74].

In addition, it has been reported that the carcasses of invertebrates that die after ingesting plant material containing entomopathogenic fungi rarely or very infrequently develop fungal growth [75]. This is of particular interest for the biological management of invertebrates on agricultural land, since the release of microorganisms can affect non-target fauna and lead to the displacement of other invertebrate biological control agents. An example of this is the invertebrate mortality caused by Metarhizium brunneum via the digestive tract, which has been observed in lepidopteran larvae (Spodoptera littoralis). This mortality could be correlated with the presence of the mycotoxin destruxin A, which has a potent insecticidal effect, causing paralysis and death in various invertebrate species [76]. The effects of secondary metabolites and enzymes produced by entomopathogenic fungi on their hosts are varied, and many effects remain unclear. Among the organic acids and secondary metabolites with a biocidal effect produced by entomopathogenic fungi are: oxalic acid; 2,6-pyridinedicarboxylic acid (dipicolinic acid); 4-hydroxymethylazoxybenzene-4-carboxylic acid; peptide toxins such as beauvericin; bassianolides; efrapeptins; destruxins; leucinostatins; kantomycin; bassiacridine; and others [77] (

Table 1. Summary table of secondary metabolites, organic acids, and enzymes of biotechnological interest produced by entomopathogenic fungi.

Organic Acid/Secondary Metabolite/Enzyme	Producing Agent	Susceptible Agent	Mode of Action	References
Oxalic acid (HOOC-COOH)	Beauveria spp., Lecanicillium lecanii, Paecilomyces fumosoroseus, Metarhizium anisopliae, Pleurotus spp.	Melanoplus sanguinipes; Varroa destructor; Lucilia cuprina, Ambylomma americanum, A. maculatum, Ixodes scapularis, phytopathogenic fungi.	Epithelial and digestive damage, corrosive effect due to high acidity	[78,79,80,81,82,83,84,85,86,87]
Dipicolinic acid (2,6-pyridinedicarboxylic acid)	Paecilomyces spp.; Isaria fumosorosea; Beauveria bassiana; B. asiatica; Lecanicillium lecanii.	Fusarium oxysporum, Verticillium dahlia, Spodoptera frugiperda.	Broad-spectrum antifungal and insecticide. Chitinase synthesis inhibitor.	[82,86,87,88,89,90,91]
4-hydroxymethylazoxybenzene-4-carboxylic acid	Entomophthora virulenta	Broad insecticidal effect	Organic compound with insecticidal activity	[92]
Bassianolide (cyclooligomeric non-ribosomal peptides)	Beauveria spp.	Spodoptera exigua, S. frugiperda, Tenebrio molitor.	Insecticidal activity. Suppression of immunocytes. Hemolymph collapse due to toxic action.	[82,93,94,95,96]
Beauvericin	Beauveria spp.; Paecilomyces spp.; Polyporus spp.; Fusarium spp	Aedes aegypti, Broad insecticidal and fungicidal effect	Antifungal, bactericidal, and insecticidal activity. Immune suppression. Hemolymph collapse due to toxic action. Cell membrane collapse.	[82,93,95,96,97,98]
Bassianin	Beauveria bassiana; B. asiatica; Bassiana tenacellus.	Broad insecticidal and fungicidal effect	Insecticidal and antimicrobial activity. Blockage of the host’s immune system.	[78,82,99,100,101]
Tenellin (2-pyridone)	Beauveria spp.	Plasmodium falciparum, Staphylococcus aureus, Colletotrichum acutatum, Curvularia lunata, Alternaria brassicicola, Tenebrio molitor. Broad antimicrobial and cytotoxic effect	Broad antimicrobial effect. Blocks the immune system of arthropods.	[78,82,89,96,102,103]
Oosporein (dibenzoquinone)	Beauveria spp.	Hylobius abietis, Galleria mellonella. Broad antimicrobial and cytotoxic effect	Key metabolite in the arthropod infection process. Antifungal and bactericidal activity	[78,93,95,100,104,105]
Efrapeptins	Tolypocladium niveum, T. geodes, Acremonium sp., Metarhizium anisopliae.	Plasmodium spp. Phytopathogens and insects.	Antifungal, antimalarial, insecticidal, and antitumor activity. Inhibition of ATPase and alteration of the interaction between ATPase and heat shock protein 90 (HSP90).	[106,107]
Bassiacridine	Beauveria bassiana	Locusta migratoria; Schistocerca gregaria.	It possesses β-glucosidase, N-galactosidase, and N-acetylglucosaminidase activity, with a broad insecticidal effect. It also has a cytotoxic effect on cancer cells.	[77,105]
Destruxins	Metarhizium spp.	Manduca sexta; Schistocerca gregaria; Plutella xylostella; Phaedon cochleariae.	Insecticidal activity. Neurotoxin that affects the host’s central nervous system. Inhibits the synthesis of DNA, RNA, and proteins.	[77,95,100,108,109]
Extracellular enzymes: proteases, aminopeptidases, lipases, pectinases, glucanases, leucinoxin, laccase, esterases, and chitinases	Beauveria spp., Lecanicillium spp., Paecilomyces spp., Metarhizium spp., Isaria fumosorosea, Trichoderma virens.	Broad spectrum insecticide and acaricide. Fusarium oxysporum.	Compounds involved in the host infection process. Degradation of proteins, lipids, peptides, and chitin from mites and insects, triggering tissue and organ collapse. Degradation of the cell wall of phytopathogens.	[25,110,111,112,113,114]

). Among these bioactive components, oosporein and beauvericin stand out as crucial metabolites. Both are bioactive peptides produced non-ribosomally by large multimeric enzyme complexes called non-ribosomal peptide synthetases (NRPSs) [78]. It should be noted that older studies may refer to the Paecilomyces fungus by a different genus name (Isaria), because this genus has undergone taxonomic modifications over time.

Some arthropods with a developed immune system counteract fungal infection by regulating antifungal compounds and/or activating an innate immune response, which includes the production of large amounts of Reactive Oxygen Species (ROS), humoral melanization, and phagocytosis [115]. To complete the infection process and ensure their development, entomopathogenic fungi must withstand the adverse physical and chemical environment and overcome the arthropod’s immune barrier [116].

Undoubtedly, the processes by which entomopathogenic fungi infect their hosts are far from being fully described, and these processes depend on the species involved and the environmental conditions present [98]. It is reasonable to expect that the pathways and processes of infection by entomopathogenic fungi are as diverse as the number of species. Entomopathogenic fungi are the most abundant group, comprising approximately 60% of all microbial insect pathogens [20,117]. Most entomopathogenic fungi belong to two orders, Entomophthorales and Hypocreales (formerly Hyphomycetes) [118], and more than 750 species of entomopathogenic fungi have been described, grouped into 100 different genera [119]. The main groups are found in the Phylum Ascomycota, with the most widely studied genera being Beauveria, Metarhizium, and Paecilomyces [120]. The entomopathogenic fungal genus Metarhizium is among the most abundant isolated from soils, with levels reaching 10,000,000 conidia per gram of soil in grasslands [121].

Beauveria bassiana and Metarhizium anisopliae are the two most studied entomopathogenic fungal (EPF) species and have been widely used worldwide to control insect pests [122]. Beauveria bassiana infects more than 200 insect species from different orders, including economically important pests such as the fall armyworm (Spodoptera frugiperda) [85], coffee berry borer (Hypothenemus hampei) [123], and coffee berry borers (Diatrea magnifactella, Ostrinia furnacalis, and Helicoverpa armigera) [122]. While Metarhizium anisopliae, with a broader host spectrum, has been observed in 300 to 400 taxa of Lepidoptera, Coleoptera, Diptera, and Hemiptera. The pathogenic capacity and effectiveness of entomopathogenic fungi have been widely documented. Field applications of Beauveria bassiana strain LPSc 1098 achieved an 86.6% mortality rate of Rachiplusia nu larvae on Glycine max [124]. In field applications, Metarhizium anisopliae strain Ma-35 reduced Spodoptera frugiperda infestation in corn plants (Z. mays) from 68.33% to 20.28% [125]. The CEP591 strain of Beauveria bassiana under field conditions in grapevine crops (Vitis vinifera) generated mortality levels of Lobesia botrana that reached 91 ± 9.8% in spring and 81.58 ± 17.53% in early summer [126]. The study of the biological interactions of entomopathogenic fungi with other agents of the agroecosystem has allowed the scientific community to advance in the understanding of the processes that influence the presence of invertebrate pests [118,127,128], particularly insects that pass through the soil to complete their development [129]. When incorporating this type of strategy into the production system, it is important to keep in mind that the pathogenicity of entomopathogenic fungi is not influenced by a single factor but depends on an interaction of different pathogenicity determinants of the fungus and factors of the host insect [130].

The developmental and survival strategies of entomopathogenic fungi are diverse and vary depending on the species and the community of organisms with which they are associated. In addition to their known effects on insects, these fungi modify their environment through their metabolism and behavior [42], which in turn affects plant productivity [131]. This makes entomopathogenic fungi versatile and promising for use as Biological Control Agents (BCA) within a productive transition program, highlighting the mechanisms associated with the promotion of plant growth, the production of phytohormones, the solubilization of phosphate [132], the sequestration of iron by siderophore, the modulation of plant hormone levels [23] and the control they could generate over phytopathogens and vectors of viral diseases [133]. Although Beauveria and Metarhizium are the most studied genera, they possess distinct properties and applications that determine their use in modern agricultural systems. Fungi of the genus Metarhizium are notable for their adaptability to diverse habitats, primarily soil, and several species have been identified as being used globally as bioinsecticides [134]. On the other hand, Beauveria bassiana exhibits a remarkable capacity to establish itself as a systemic endophyte, influencing not only the direct mortality of arthropods but also the induction of systemic resistance [135]. While Metarhizium has become established due to its large-scale scalability and dual efficacy against insects and phytopathogens, Beauveria is frequently preferred for its versatility in foliar applications and its environmental persistence in the phyllosphere [134,135].

In recent years there has been an increase in scientific studies related to the growth-promoting effect of entomopathogenic fungi on plants [28,112,136,137,138,139,140,141,142,143,144,145,146,147,148]. Most studies focus on evaluating inoculation methods and the physiological responses generated by the entomopathogenic fungus in the plant. The evidence is clear and demonstrates a significant growth-promoting effect, especially on variants related to crop vigor and yield (

Table 2. Summary of reports of entomopathogenic fungi as plant growth promoters.

Species	Substrate/Host	Study Crop/Variables	References
Beauveria bassiana; Metarhizium brunneum; Isaria farinosa.	Hymenoptera: Iraella luteipes; soil.	Sorghum (Sorghum bicolor) - Physiological trials in a controlled culture chamber. - In vitro assays: Fe DTPA production and elevation of pH range	[136]
Metarhizium marquandii; Purpureocillium lilacinum; P. lavendulum.	Soil.	Corn (Zea mays), beans (Phaseolus vulgaris) and Soybeans (Glycine max) - Physiological trials in a ventilated greenhouse under ambient natural conditions. - In vitro assays: Indole Acetic Acid (IAA) production and Phosphate solubilization.	[142]
Beauveria brongniartii; Purpureocillium lilacinum.	Papaya rhizosphere (Carica papaya)	Papaya (Carica papaya) - Physiological trials in a ventilated greenhouse under ambient natural conditions.	[144]
Hirsutella rhossiliensis	Nematode: Heterodera glycines	Arabidopsis (Arabidopsis thaliana) - Physiological trials in a controlled culture chamber.	[147]
Isaria cateinannulata	Soil	Buckwheat (Fagopyrum tataricum) - Physiological trials in field conditions. - In vitro assays: Phosphore solubilization.	[148]
Isaria javanica; Purpureocillium lilacinum.	Hemiptera: Bemisia tabaci.	Tomate (Solanum lycopersicum). - Physiological trials in a controlled culture chamber.	[150]
Paecilomyces variotii	Roots of different native species from Cabo de Gata	Tomato (Solanum lycopersicum) and Paprika (Capsicum annuum) - Morphological trials in field conditions. - In vitro assays: Phosphorus solubilization, Indole Acetic Acid (IAA) and Siderophore production.	[112]
Metarhizium taii	Soil	Tomato (Solanum lycopersicum) - Physiological trials in a controlled culture chamber.	[28]
Beauveria bassiana	Commercial product (KVK 13-39 insulated)	Corn (Zea mays) - Physiological trials in a controlled culture chamber.	[140]
Lecanicillium psalliotae	Hymenoptera: Sciothrips cardamomi	Promoting the growth of cardamom plants (Elettaria cardamomum - Physiological trials in a ventilated greenhouse under ambient natural conditions. - In vitro assays: Indole Acetic Acid (IAA), Siderophore, ammonia, α-amylase and protease production, inorganic phosphate and zinc oxide (ZnO) solubilization	[139]
Cordyceps fumosorosea; Beauveria bassiana: Metarhizium flavoviride	Lepidoptera and Coleoptera	Tomato (Solanum lycopersicum) - Physiological trials in a controlled culture chamber.	[146]
Beauveria bassiana	Cacao plants (Theobroma cacao), coffee (Coffea arabica), wheat (Triticum spp.) and Hemiptera: Leptocorisa acuta.	Chili (Capsicum sp.) - Physiological trials in a controlled culture chamber.	[141]
Beauveria bassiana; Metarhizium brunneum.	Commercial products (NATURALIS; BIPESCO5)	Wheat (Triticum aestivum) - Physiological trials in a controlled greenhouse.	[138]
Metarhizium anisopliae; M. pinghaense; M. robertsii.	Microbial culture repository of AICRP, Anand Agricultural University	Tomato (Solanum lycopersicum) - Physiological trials in a controlled culture chamber. - In vitro assays: Indole Acetic Acid (IAA) production, Phosphate and potassium solubilization activity, ACC (1-Aminocyclopropane-1-carboxylate) deaminase production and Chitinase production	[145]
Beauveria bassiana; Isaria fumosorosea; Lecanicillium lecanii.	Fungal culture bank of Fujian Agriculture and Forestry University (FAFU).	Bean (Phaseolus vulgaris) - Physiological trials in a controlled culture chamber.	[137]
Beauveria bassiana; Metarhizium brunneum.	Fungal culture bank of Agricultural Entomology Unit of the University of Cordoba	Durum wheat (Triticum durum) - Morphological and Physiological trials in field conditions.	[143]

). Promoting crop growth through microorganisms reduces the adverse effects of chemical fertilizers, which are often highly soluble and can contaminate groundwater, increase the salinity of agricultural soils, pose a high risk of phytotoxicity in crops, and increase production costs [5]. Furthermore, their production is energy-intensive, requires a large amount of water, and generates significant greenhouse gas emissions [149]. Microorganisms also have an advantage over chemically synthesized products, since they have the ability to reproduce and if the conditions are right for a consistent population of microorganisms to be established, it might be possible to dispense with the use of chemically synthesized products for crop nutrition and thus increase the sustainability of agroecosystems [14,28].

Another use that can be given to entomopathogenic fungi in agriculture is as a microbial control agent of phytopathogens. Recently, scientific evidence has been published in in vitro and field studies on the growth-inhibiting capacity that certain entomopathogenic fungi and their Volatile Organic Components (VOCs) can exert on different plant pathogenic fungi, among which we can mention Botrytis cinerea, B. fabae, Sclerotinia sclerotiorum, Macrophomina phaseolina, Fusarium oxysporum, F. citri, F. verticillioides, F. culmorum, F. solani, F. graminearum, F. avenaceum, F. poae, Curvularia lunata, Rhizoctonia solani, Eutypella microtheca, Nigrospora oryzae, Alternaria solani, Colletotrichum gloeosporioides, C. capsici, Macrophomina phaseolina, Erysiphe pisi, Cladosporium spp. and Phytophthora capsici [28,126,151,152,153,154,155,156,157,158,159,160,161]. The inhibition of phytopathogenic fungal growth is complemented by the plant growth-promoting characteristics of some entomopathogenic fungi, increasing the chances of overcoming and even preventing the incidence of these pathogens. The use of entomopathogenic fungi for agroecosystem management thus provides more certainty than doubt regarding the efficacy, efficiency, and behavior of the desired effects, which, as previously mentioned, are determined by the prevailing environmental conditions and the formulation in which they are prepared and applied. These microorganisms are traditionally used in isolation, which could diminish their effectiveness. Several studies demonstrate the action of different species and/or strains of microorganisms on the effect of plant pathogens and the promotion of growth when applied in combinations or microbial consortia, such as the work of [162] who demonstrate the inhibitory effect on the mycelial growth of B. cinerea generated by Arbuscular Mycorrhizal Fungi (AMF) when used in conjunction with entomopathogenic fungi of the genera Metarhizium and Beauveria.

Regarding biological control, the introduction of exotic microorganisms into environments where pests are present but their microbial biological control agents are absent has been explored for several years. Examples include the introduction to the United States in the 1900s of the entomopathogenic fungus Entomophaga maimaiga for the control of the lepidopteran Lymantria dispar, which was originally isolated in Japan, and the example of Zoophthora radicans, originally isolated in Israel and introduced to Australia for the control of the aphid Therioaphis trifolii [163]. This corresponds to neoclassical biological control, which is significantly problematic from an environmental perspective, as it can promote environmental imbalances and lead to the displacement of non-target species. This background highlights the importance of microorganism-plant interactions as a key component of plant health and the stability of agroecosystems. Beyond their direct application in biological control, one of the characteristics that acquires particular relevance in this context is the ability of some entomopathogenic fungi to establish endophytic associations with plants. Added to this is the fact that most vascular plants studied to date have associated endophytic organisms, in a relationship where the plants provide the microorganism with food, host, and protection [164]. Endophytes are microorganisms that live for all or part of their life cycle within the tissues of living plants without causing any symptoms or negative effects in their host plant, and whose internal colonization can be demonstrated [128]. Endophytic fungi have been widely reported in association with sorghum (Sorghum spp.), wheat (Triticum spp.), maize (Zea mays), bean (Phaseolus vulgaris), tomato (Solanum lycopersicum), squash (Cucurbita spp.), soybean (Glycine max), coffee (Coffea spp.), jute (Corchorus capsularis), cotton (Gossypium spp.), cacao (Theobroma cacao), opium poppy (Papaver somniferum), cassava (Manihot esculenta), banana (Musa × paradisiaca), alfalfa (Medicago sativa), melon (Cucumis melo), cauliflower (Brassica oleracea), sweet potato (Ipomoea batatas), rapeseed (Brassica napus), grapevine (V. vinifera), among other economically important crops [76,163,165,166].

Several genera of entomopathogenic fungi have been described as endophytic fungi, whose ability to colonize plant tissues varies depending on the species and strain, environmental conditions, host species, and associated organisms [167]. Endophytism is a capacity that can be naturally exercised by microorganisms or artificially induced. Endophytes have been classified according to their host colonization patterns, transmission mechanisms (vertical and horizontal), biodiversity, and biological function [168]. Within this classification are Endophytic Insect Pathogenic Fungi (EIPFs), which can live mutualistically within plant tissues, as well as parasitize arthropods, conferring extra protection to the host plant against herbivore and phytopathogen attacks [169,170]. It has been determined that endophytic fungi not only have ecologically relevant functions when inhabiting living plants, but also that once the host plant dies, these microorganisms influence the decomposition of plant tissues [168]. Many species belonging to the Hypocreales family (Ascomycota) inhabit the soil during a significant part of their life cycle when they are outside an invertebrate host [129]. The diverse characteristics of entomopathogenic fungi make this group of fungi of particular interest to agriculture, since the use of a single species or strain can generate multiple benefits or ecological services, whether in the population control of invertebrate pests, in crop nutrition, nutrient cycling, or in the management of phytopathogens, primarily fungal and viral [14,28]. This multifunctionality can directly impact production costs by promoting a reduction in the use of agricultural machinery dependent on fossil fuels.

5. Entomophthorales Fungi for the Management of Arthropod Pests in Agriculture

Fungi of the order Entomophthorales constitute a group of species that are obligate pathogens of insects and other arthropods [171,172] with great potential for use in the biological control of arthropods harmful to agriculture. They belong to the Phylum Zoopagomycota, Subphylum Entomophthoromycotina, Class Entomophthoromycetes [173], and include almost 290 described species [172]. They possess a set of well-defined structures, including protoplasts, hyphal bodies, conidiophores, conidia, nuclei, cystidia, rhizoids, and resistant spores. Most Entomophthorales species have been reported on insects belonging to the Orders Diptera and Hemiptera; however, they have also been identified on many other insect orders, such as Lepidoptera, Coleoptera, Hymenoptera, Orthoptera, and Dermaptera [174,175]. Other hosts include mites (Acarina) [176] and springtails (Apterygota) [177,178]. Entomophthora fungi offer advantages for use as biological control agents. Among these advantages are their significant role in insect mortality in the field [179], frequently causing epizootics that can rapidly reduce insect populations [180]. They are relatively host-specific and therefore pose minimal or no threat to non-target organisms. Furthermore, the conidia of entomophthora fungi are relatively larger than those of Ascomycete fungi, have a mucous coating on their surface, and sporulate and germinate rapidly. Although a relatively small number of conidia are produced per insect corpse, only a few conidia are needed to initiate infection [181]. One disadvantage of entomophthorales fungi for use as control agents is the difficulty many species present in culturing in vitro [181,182,183,184,185]. Based on their individual requirements for in vitro growth, the different genera of entomophthorales can be classified into four groups [176,181,182]: the first group can be easily cultured in conventional media, such as Conidiobolus spp. [186]. The second group is slightly more difficult; Therefore, fungi belonging to this group require some supplements, but have been cultivated in submerged culture, including Batkoa, Erynia/Pandora, and Zoophthora spp. [187,188,189]. Members of the third group only grow in complex media, for example, some species of Entomophthora and Entomophaga [190,191,192,193,194,195,196,197]. Fungi such as Strongwellsea and Neozygites belong to the fourth group, which until now have only been cultivated in expensive tissue culture media [183,198,199,200]. Some Entomophthorales cannot be cultured in vitro at all [199,201].

The difficulty of culturing Entomophthorales fungi in vitro on a low-cost scale remains a major challenge for their use as biological control agents. For large-scale production, three types of structures can be considered: (1) conidia, (2) resistant spores, and (3) hyphal bodies [186]. Entomophthorales conidia are infectious units, but they have a short lifespan and are sensitive to UV radiation and desiccation [202]. Furthermore, the active discharge of conidia and the characteristic mucous coating [203,204] make conidia collection [205] and subsequent processing difficult [206]. Resting spores are resistant to adverse environmental conditions [207] and have potential for long-term storage [208,209]. However, their dormancy is a disadvantage for technical-scale applications, as it is difficult to reactivate them to form conidia in a synchronized manner [186]. Entomophthorales hyphal bodies occur naturally in infected hosts and can be cultured by submerged fermentation [201]. Submerged fermentation allows for short processing times and can be easily scaled up for mass production [185,210]. Evaluated the biomass production in liquid medium of a novel Pandora species isolated from psyllids and tested its subsequent encapsulation in biopolymer beads or granules, obtaining promising results that pave the way for the large-scale production and formulation of the species for the biological control of psyllids. Recent advances have enabled the mass production of biomass using complex nutrient sources, such as skimmed milk, yeast extract, and low-cost protein hydrolysate supplements [211,212].

On the other hand, Ref. [188] conducted laboratory and field studies to evaluate a dry mycelium formulation of the fungus Zoophthora radicans and to compare the sporulation of the laboratory-produced/formulated fungus with that of the fungus present in naturally infected Empoasca kraemeri carcasses. The results indicated that the dry mycelium formulation is very suitable as an inoculum source to initiate or increase epizootics in leafhopper populations. Due to the difficulties in cultivating them in vitro, the use of Entomophthorales fungi as biological control agents in inundative biological control strategies is limited. However, there are experiences using these fungi in other biological control strategies. For example, [213] implemented a classic biological control strategy in cotton crops in the United States, releasing N. fresenii via dried carcasses of Aphis gossypii. Pre-release samples indicated that N. fresenii was not naturally present in A. gossypii populations. Among the results, they found that N. fresenii persisted and spread within the aphid population. On the other hand, Ref. [214] developed methods for the mass collection of the pathogenic fungus Neozygites fresenii (Entomophthorales: Neozygitaceae) from epizootics in Aphis gossypii (Homoptera: Aphididae) in Arkansas. Aphids infected with N. fresenii in the mature hyphal body stage or in the early conidiophore stages were collected, dried, and frozen. The quality of the collected infected aphids was high, resulting in an average sporulation rate of 70.4%.

On the other hand, due to their ability to cause epizootics, the Entomophthorales group of fungi has high potential for use in Conservation Biological Control (CBC) strategies. CBC is a strategy in which agricultural management practices are modified to improve the living conditions of natural enemies of pests [215,216]. A common CBC practice is the diversification of the agroecosystem through the establishment and conservation of weeds surrounding the crop. Uncultivated plants can act as a reservoir for entomopathogenic fungi [217,218,219,220,221]. Crop-based control with entomopathogenic fungi involves manipulating both the crop and habitats outside of it [221]. Among entomopathogenic fungi, Entomophthoromycota offer high potential for exploitation in CBC strategies against aphids [222,223,224,225,226,227,228]. Entomophthoral fungi have been found to be important antagonists of aphids under field conditions [229] and have the potential to induce dramatic epizootics that drastically reduce aphid population densities [180,230]. The importance of these organisms as natural enemies of aphids lies in their ability to suppress aphid populations under cool, humid conditions, which contrasts with the activity requirements of arthropod natural enemies [231]. Studies on the associations between aphids, their host plants, and antagonistic fungi are crucial for the implementation of CBC.

6. Yeast-like Fungi for Managing Agricultural Challenges

In addition to filamentous fungi, yeast-like fungi have emerged as promising microbial agents for the sustainable management of plant diseases, particularly in postharvest systems, where they offer environmentally safer alternatives to conventional fungicides.

Yeasts are unicellular fungi, primarily belonging to the phyla Ascomycota and Basidiomycota, characterized by their great metabolic versatility, diverse reproductive strategies, and remarkable ability to adapt to a wide variety of environmental conditions. As heterotrophic microorganisms, they utilize carbon and nitrogen sources for growth and can metabolize carbohydrates through aerobic respiration or anaerobic fermentation, producing carbon dioxide, water, or ethanol. Their unicellular morphology and flexible physiology allow them to colonize diverse ecological niches, adhere to surfaces, and form biofilms characteristics that contribute to their persistence in various environments and their high ecological competitiveness [232]. Within the broad spectrum of microbial antagonists, yeasts, like bacteria with similar characteristics, occupy a prominent place [233]. In recent decades, antagonistic yeasts have been the subject of considerable research due to their wide distribution, their marked inhibitory efficacy against various pathogens, and their status as environmentally sustainable and safe agents for humans [234]. Several studies have reported the use of antagonistic yeasts as biological control agents in the postharvest handling of multiple fruits, including apple (Malus domestica), pear (Pyrus communis), banana (Musa x paradisiaca), kiwi (Actinidia deliciosa), citrus fruits, grape (V. vinifera), papaya (Carica papaya), strawberry (Fragaria x ananassa), and pineapple (Ananas comosus). Their application has also been extended to disease control in vegetables such as potato (Solanum tuberosum), tomato (Lycopersicum esculentum), and chili pepper (Capsicum annuum). Furthermore, these yeasts have proven to be promising tools for the control of molds in grains, which are particularly harmful due to the generation of mycotoxins [235].

Antagonist yeasts inhibit other microorganisms through multifactorial mechanisms [236], including efficient competition for essential nutrients, cell contact-dependent inhibition associated with biofilm formation [237], dimorphic structures, mycoparasitism [238], and the production of antimicrobial metabolites such as cell wall lytic enzymes, killer toxins, iron chelating agents (e.g., pulquerriminic acid), and bioactive volatile organic compounds [239,240,241,242]. The biocontrol potential of yeasts is evaluated using various in vitro methodologies, primarily based on Petri dish assays with PDA [239]. Among the most widely used are the yeast-on-indicator (YOI) [243] and indicator-on-yeast (IOY) [244] systems, which detect inhibitory effects by observing inhibition zones or reduced growth of the indicator microorganism. Confrontation assays or dual cultures are also employed, where the yeast and the pathogen are grown simultaneously on the same plate to evaluate mycelial growth inhibition or direct interaction. Other methods include diffusion assays in agar wells, cell-free filtrate analyses to determine the activity of extracellular metabolites, co-culture competition assays, and replica-plating or grid assays to evaluate interactions between multiple strains. Additionally, approaches such as cellophane or filter-layer assays and trap assays [245] are used to study specific inhibition mechanisms, allowing the identification of yeasts with antagonistic capacity against pathogenic microorganisms.

Yeasts such as Aureobasidium pullulans [246], Cryptococcus albidus, Saccharomyces cerevisiae [247], Candida oleophila [248], and Metschnikowia sp. [249,250] are currently used as effective biocontrol agents against a wide variety of plant pathogens. These unicellular fungi are highly adaptable, capable of growing in diverse environmental conditions, require minimal cultivation efforts, and many are generally recognized as safe. This potential is reflected in the development of commercial yeast-based products worldwide, such as Boni-Protect^® (Aureobasidium pullulans), Nexy^® (Candida oleophila), Candifruit^® (Candida sake), Shemer^® (Metschnikowia fructicola), and Romeo^® (Saccharomyces cerevisiae), used for the control of postharvest fungal pathogens and the improvement of plant health [251]. Ref. [252] described that the antagonistic yeasts Wickerhamomyces anomalus, Saccharomyces cerevisiae and Kluyveromyces marxianus act as biocontrol agents against Aspergillus carbonarius by producing VOCs, which effectively inhibit fungal growth and ochratoxin A biosynthesis both in vitro and in food matrices, positioning these yeasts as a technically sound and sustainable strategy for the control of mycotoxigenic fungi in agricultural products. Similarly, other studies [232,253] have identified several antagonistic yeasts, mainly from the genus Aureobasidium and species such as Filobasidium oeirense, Vishniacozyma carnescens, Hanseniaspora uvarum, Hanseniaspora opuntiae and Meyerozyma caribbica, capable of inhibiting the growth of Botrytis cinerea through the production of VOCs. Strains of Hanseniaspora have shown high efficacy in significantly reducing the mycelial growth of the pathogen, with this activity associated with the emission of volatile metabolites such as 3-methyl-1-butanol, 2-methyl-1-butanol, heptan-2-one, and phenethyl alcohol [254]. Similarly, other studies have demonstrated that antagonistic yeasts are also capable of mitigating the accumulation of patulin produced by Penicillium expansum, a highly relevant mycotoxin in fruits such as apples (M. domestica). In particular, Rhodotorula glutinis, along with Cryptococcus laurentii and Aureobasidium pullulans, has shown a high capacity for survival and proliferation in infected fruits, significantly reducing patulin accumulation both in vitro and in vivo. The R. glutinis LS11 strain stands out for its ability to tolerate and actively metabolize this mycotoxin [255]. Antagonistic microorganisms represent a promising strategy for the biological control of postharvest diseases by modulating the microbial communities associated with the fruit surface. In this context, Debaryomyces hansenii has been shown to reduce natural decay in strawberries (Fragaria x ananassa) without affecting quality parameters, in addition to modifying the structure of the fruit’s microbial communities and suppressing plant pathogens [234]. Similarly, Ref. [256] reported that psychrotrophic yeasts isolated from antarctic environments, particularly Candida sake, significantly reduce rot in apples (M. domestica) caused by P. expansum and B. cinerea, partly through the production of antifungal VOCs. The above makes yeasts stand out as sustainable alternatives to chemical fungicides in postharvest disease management.

7. Main Limitations and Prospects

The widespread adoption of new-generation technologies and inputs in agriculture is not only a technical challenge but also a multifaceted problem involving knowledge, economic, and structural barriers. The transition to a global biological production model is hampered primarily by knowledge gaps and information asymmetry [257,258,259]. Unlike chemically synthesized inputs, the use of bio-inputs requires a deep understanding of the interactions between the material and the plant. There is clear heterogeneity in the benefits perceived and the expected profitability for producers, which, coupled with risk aversion and uncertainty about changing ingrained habits, is slowing demand. Furthermore, we can add that the current dissemination systems for this type of agricultural input are deficient and leave many small farmers in a situation of information vulnerability [260,261,262]. Standardization in formulation processes, the use of low-cost substrates, and advancements in techniques for selecting the most suitable microorganisms are undoubtedly areas of knowledge that must be explored to achieve this shift in the production paradigm. Standardizing laboratory protocols to ensure the replicability of formulations is fundamental for large-scale production. Furthermore, these formulations must undergo exhaustive agronomic efficacy studies in different production zones under diverse soil and climate conditions [263,264,265].

The development of these technologies encompasses a series of procedures, from the isolation of promising microorganisms to the final formulation of a standardized product with reproducible effects over time. In the selection and development stages of bio-inputs, candidate microorganisms must be rigorously analyzed from a biosafety perspective. Biosafety is based on a series of procedures designed to prevent biological risks to both humans and the environment. These procedures include detailed guidelines for handling different microorganisms with varying biosafety requirements [266]. While the development of bio-inputs for agriculture is primarily based on non-pathogenic wild microorganisms belonging to the lowest biosafety level (level 1 of 4), which are commonly obtained from soil or plant tissue samples rather than human and/or animal hosts. However, special care must be taken, as there are certain agricultural products based on microorganisms of biosafety level 2, exhibiting certain behaviors as opportunistic pathogens [264,267]. Likewise, it is important to be clear that the introduction of certain microorganisms into agricultural environments can negatively impact non-target organisms (e.g., parasitoids and predators) and/or displace native microbial species. The use of exotic commercial strains versus native ones requires caution. Some studies indicate that the selection of entomopathogenic fungal strains should be based largely on their environmental disruptor characteristics, thereby avoiding the displacement of native species. These studies emphasize that local isolates adapted to the soil and climate conditions of each location offer greater environmental safety and agronomic efficacy [268,269]. Liquid fermentation and the extraction of lytic enzymes produced by entomopathogenic fungi, such as chitinases and proteases, in certain culture media appear to be a good alternative to overcome the problems of “escape” and impact on non-target organisms caused by genera of entomopathogenic fungi such as Beauveria and Metarhizium [270].

Therefore, the use of strategies such as Neoclassical Biological Control (NBC), which is based on the introduction of external biological agents and is widely used in organically certified production systems, presents environmental complexities that must be overcome. On the other hand, agroecology promotes CBC, in which Entomophthorales fungi have certain advantages from an environmental safety standpoint compared to the main genera of Hypocreales fungi used in biological control (Beauveria; Metarhizium). Due to the technical complications of their mass production, CBC is positioned as the most successful management strategy for this group of entomopathogens [271,272]. In recent years the role of entomopathogenic fungi in agriculture has undergone conceptual transformations, evolving from their use as simple biopesticides to their recognition as multifunctional agents in agroecosystems [135,273]. This change in the concept of implementing these microorganisms is based on their ability to act as systemic endophytes, which allows them not only to control pests through direct infection, but also to promote plant growth and strengthen the systemic resistance of crops to biotic and abiotic stresses [274,275,276]. Current research demonstrates that integrating entomopathogenic fungi into modern agricultural strategies, along with their role in modulating the soil microbiome, constitutes an effective strategy for food sovereignty and the sustainability of agroecosystems in the context of production uncertainty [163,268].

The potential of bio-inputs based on entomopathogenic fungi and yeast-like fungi as an effective tool to address the transition processes in the production mode is substantially striking, but it must overcome certain difficulties. The massification and global implementation of these technologies entails several obstacles that can be overcome through the implementation of various joint initiatives: public investment in research and development of bio-inputs, differentiated legislative reforms for bio-input registration costs, promotion of local production of bio-inputs with native microorganisms, promotion of public-private partnerships in bio-input research and production, investment in contextualized research with a social and cultural focus, state implementation of training and adoption programs for these technologies, promotion of innovation and biotechnology with a circular approach, inclusion of farmers perspectives in the development of formulations and adoption policies, awareness-raising of the benefits of their use by farmers, users and society in general, among other relevant initiatives [259,265,277,278].

8. Conclusions

Entomopathogenic fungi, along with antagonistic yeasts, are becoming established as biological mediators with high metabolic plasticity, facilitating their adaptation to heterogeneous ecological niches. The multifunctionality of filamentous ascomycetes, such as Beauveria and Metarhizium, extends beyond arthropod pathogenesis through endophytic colonization mechanisms and the synthesis of bioactive secondary metabolites that modulate the plant holobiont and exert direct antagonism against phytopathogens. Entomophthorales, for their part, offer high host specificity and a unique capacity to induce natural epizootics, making them key players in conservation biological control. Meanwhile, antagonistic yeasts can be of great help in post-harvest phytosanitary management through biofilm formation, competition for resources, and enzymatic detoxification of mycotoxins. This functional synergy can resolve production transition processes, making them less dependent on synthetic inputs and strengthening the resilience of agroecosystems under a sustainable food production paradigm. While scientific advances in this area are significant and there is some certainty regarding the steps to follow, the widespread implementation of these technologies will be a collective responsibility that must involve both public and private institutions. Under this model, research centers and universities will play a fundamental role in the development of these technologies and, together with farmers, will need to design formulations and adoption strategies. Input substitution may be the first step, and perhaps one of the easiest to take, but moving toward a paradigm shift in the production model requires public policies that promote technical and scientific development in this field.