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Insect Pathogens as Biocontrol Agents Against Pests

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A special issue of Insects (ISSN 2075-4450). This special issue belongs to the section "Insect Behavior and Pathology".

Deadline for manuscript submissions: closed (28 February 2026) | Viewed by 8792

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Dr. Spiridon Mantzoukas

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Guest Editor

1. Institute of Mediterranean Forest Ecosystems, Terma Alkmanos, 11528 Ilissia, Greece
2. Department of Agriculture, University of Ioannina, Arta Campus, 471 00 Arta, Greece
Interests: biological control of crop and forestry pests; IPM methods; insect–plant interactions; endophytes
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Dr. Tariq Butt

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Guest Editor

Department of Biosciences, Swansea University, Singleton Park, Swansea SA2 PP, UK
Interests: entomopathogenic fungi; endophytes; fungal metabolites; biocontrol; biostimulants; host–pathogen interactions; mass production; formulation; ecological fitness risk assessment
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Panagiotis Eliopoulos

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Guest Editor

Lab of Plant Health Management, Department of Agrotechnology, University of Thessaly, 45100 Larissa, Greece
Interests: biological control of crop pests; IPM methods; insect–plant interactions; stored product pests; precision agriculture methods in crop protection
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Entomopathogens are microorganisms that are pathogenic to arthropods such as insects, mites, and ticks. Several species differ significantly in their biology and behavior and, hence, in their ability to control enemy populations in all environments. The proper use of entomopathogens requires good knowledge of the biological cycle of enemies. Entomopathogens such as bacteria, fungi, nematodes, and viruses infect a variety of arthropod pests and play an important role in their management. The pathogenicity caused by entomopathogens is not the same in all insects and differs even at each insect stage, usually being larger in young specimens, especially during the larval stage. The point of entry or growth of a pathogen also varies depending on the insect and entomopathogen: entomopathogens (usually viruses and bacteria) enter via the oral route, while fungi can invade their host from the insect cuticle. Some entomopathogens are mass-produced in vitro (bacteria, fungi) or in vivo (viruses) and sold commercially. In this Special Issue, we welcome original research and review articles covering this area of study.

Dr. Spiridon Mantzoukas
Dr. Tariq Butt
Prof. Dr. Panagiotis A. Eliopoulos
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

entomopathogens
IPM
tri-trophic interactions
biological control crop and forestry pests
host–pathogen interactions

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Published Papers (9 papers)

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Research

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16 pages, 2917 KB

Open AccessArticle

Effects of the Stress of Beauveria bassiana on the Reproductive Success of an Idiobiont Parasitoid, Sclerodermus guani

by Yuenan Chen, Shasha Wu, Li Li, Hongmei Yao and Lilin Luo

Insects 2026, 17(3), 278; https://doi.org/10.3390/insects17030278 - 4 Mar 2026

Viewed by 571

Abstract

In the complex interplay among parasitic wasps, their insect hosts, and pathogenic microbes, the system involving Sclerodermus guani (Hymenoptera: Bethylidae) (a parasitoid wasp), Monochamus alternatus (Coleoptera: Cerambycidae) (the pine sawyer beetle, its host), and Beauveria bassiana (Hypocreales: Cordycipitaceae) (a fungus) presents a unique scenario where wasp offspring develop within a nearly sealed host gallery. This nursery is vulnerable to fungal invasion, often introduced by the foraging female wasps or M. alternatus itself, creating a three-way interaction where the fungus can infect both M. alternatus and S. guani. To assess how the route and timing of fungal exposure impact the S. guani population, we simulated this system by introducing different concentrations of B. bassiana either directly to the female wasps or to M. alternatus prior to parasitism. We further examined the effect of exposure timing by applying the fungus at different developmental stages of the S. guani offspring. Key population parameters, including the reproductive capacity of female wasps, the survival and developmental fitness of S. guani offspring and the germination period of hyphae, were measured. The results indicated that the most severe damage to populations of S. guani occurs when its host, M. alternatus, is infected by B. bassiana. Among the various developmental stages, S. guani offspring exhibited the greatest vulnerability during mid-to-late larval stages, whereas the egg and pupa within cocoon stages demonstrated a higher tolerance. We conclude that both the pathway and the timing of fungal exposure are critical factors influencing its impact. These findings provide valuable insights for optimizing the integrated use of biological agents in pest management, informing strategies that mitigate adverse effects on beneficial parasitoid wasps. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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22 pages, 9545 KB

Open AccessArticle

Immune and Metabolic Responses in Ectropis grisescens Infected by Metarhizium anisopliae: Insights from Transcriptome and Metabolome Analyses

by Xiaozhu Wu, Xiaomin Xiong, Muxiang Dai, Juanjuan Cai, Suqing Zhu, Lisi He, Gongmin Cheng, Maosheng Gu, Hao Meng, Feng Wen and Liande Wang

Insects 2026, 17(3), 262; https://doi.org/10.3390/insects17030262 - 28 Feb 2026

Viewed by 476

Abstract

The tea geometrid (Ectropis grisescens) is a significant pest in Chinese tea plantations. Although Metarhizium anisopliae serves as an environmentally friendly biocontrol agent against E. grisescens, the molecular mechanisms underlying the insect’s immune response remain unclear. This study investigates changes in immunity-related genes and metabolites in E. grisescens larvae infected with a virulent strain of M. anisopliae through transcriptome sequencing and metabolome analysis. We identified 2409 differentially expressed genes (DEGs) at 48 h post-infection, with 1611 genes up-regulated. GO analysis revealed that 119 DEGs were significantly enriched in immune-related processes. Additionally, 1860 differentially accumulated metabolites (DAMs) were detected, including 652 up-regulated and 1208 down-regulated metabolites, with 236 significantly enriched in 82 KEGG pathways. These findings indicate the activation of immunity-related and detoxifying enzyme-related genes, providing new insights into the physiological and biochemical responses of insects to biopesticides and potential targets for controlling tea geometrid. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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19 pages, 1971 KB

Open AccessArticle

Intraguild Predation and Chemical Cue Responses Between Phytoseiulus persimilis and Neoseiulus californicus in Laboratory Assays

by Fatma Sh. Kalmosh, Bo Zhang, Nikola Đukić, Abdulaziz Alamri, Salman Alrokayan and Xuenong Xu

Insects 2026, 17(2), 157; https://doi.org/10.3390/insects17020157 - 31 Jan 2026

Cited by 1 | Viewed by 618

Abstract

Species sharing the same trophic level can interact not only through competition for resources but also through intraguild predation (IGP). Therefore, an important step toward implementing successful multiple predator releases in biological control strategies requires resolving how predators respond to the presence of heterogeneous competitors. This study examined the compatibility of two predatory mites, N. californicus and P. persimilis, which are both widely employed to suppress two-spotted spider mite populations in greenhouses and open fields. The experiments quantified the frequency and intensity of IGP across different developmental stages of these species on bean leaves, considering scenarios both with and without their shared prey being present. Additionally, a Y-tube olfactometer was employed to assess whether either predator avoided prey patches previously occupied by other heterospecifics, thereby providing insights into potential chemical cues that influence predator behavior. The results revealed that adult females of both predatory mite species predominantly targeted heterospecific eggs and larvae, whereas adults were largely avoided. In the absence of shared prey, N. californicus attacked 83% of the P. persimilis larvae and 37% of the eggs, whereas P. persimilis consumed 67% of the N. californicus eggs. The presence of shared prey reduced IGP risk by approximately 60%. Olfactometer assays revealed no significant avoidance of plants inhabited by heterospecifics at densities of 20 or 40 adults; both predators were similarly attracted to herbivore-induced volatiles. Generalized linear models indicated that host plant experience had a significant influence on the foraging response of N. californicus, whereas the effects of the feeding state weakened over time. Understanding predator foraging plasticity and responsiveness to chemical cues can help optimize biological control strategies in complex agroecosystems. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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19 pages, 3309 KB

Open AccessArticle

Response of Energy Reserves in Entomopathogenic Nematodes to Drought-Stress and Expression Analysis of Energy Metabolism-Related Genes in Arid Areas

by Xia Wu, Wenliang Li, Tingwei Zhang, Hong Chen, Wende Zhang, Xingduo Wang and Xiujuan Qian

Insects 2026, 17(1), 22; https://doi.org/10.3390/insects17010022 - 23 Dec 2025

Viewed by 511

Abstract

The free-living infective juveniles of entomopathogenic nematodes (EPNs) are critical biological control agents against insect pests. The field efficacy of EPNs is largely determined by their tolerance to low-humidity stress, a trait closely linked to the mobilization of their energy reserves. This study aims to investigate how varying levels of humidity stress influence energy reserve dynamics in two EPNs, Steinernema kraussei 0657L and Heterorhabditis brevicaudis 0641TY, and their relationship with the survival rate and pathogenicity. The results demonstrated that lipids were the predominant energy reserve, followed by proteins and sugars. Notably, neutral lipid constituted approximately 3% of the total lipid content. Among sugars, soluble sugar levels were the highest, followed by glycogen and trehalose. Exposure to low-humidity stress resulted in increased levels of protein, total lipid, glycogen, and trehalose in nematodes. These increases were more pronounced in S. kraussei 0657L, a highly drought-resistant strain, compared to H. brevicaudis 0641TY. Furthermore, the accumulation of protein, total lipid, and trehalose was negatively correlated with survival rate and pathogenicity. However, positive correlations were observed between trehalose and both total lipids and soluble sugars. Furthermore, transcriptome analysis revealed that under low-humidity stress, S. kraussei 0657L exhibited an enrichment of differentially expressed genes (DEGs) involved in glycolysis/gluconeogenesis, fatty acid metabolism, and glycerophospholipid metabolism pathways. This indicates that S. kraussei 0657L regulated energy metabolism to adapt to low-humidity stress. These findings provide insights into the mechanisms underlying drought resistance in EPNs and offer an experimental basis for their application in arid environments. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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24 pages, 1629 KB

Open AccessArticle

Analysis of the Bacterial Microbiota in Wild Populations of Prickly Pear Cochineal, Dactylopius opuntiae in Morocco

by Imane Remmal, Youssef El Yamlahi, Naima Bel Mokhtar, Ioannis Galiatsatos, Dimitrios Loukovitis, Eva Dionyssopoulou, Mohammed Reda Britel, Panagiota Stathopoulou, Amal Maurady and George Tsiamis

Insects 2025, 16(12), 1184; https://doi.org/10.3390/insects16121184 - 21 Nov 2025

Viewed by 1250

Abstract

Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae), the wild cochineal scale, is a major pest of prickly pear crops worldwide. This study characterized the bacterial community structure of D. opuntiae from four Moroccan regions using targeted PCR and full-length 16S rRNA MinION sequencing. We report the first detection of Wolbachia (16.6% prevalence) in D. opuntiae, with infection rates varying geographically from 0% (Rabat) to 53.3% (Ouazzane). Spiroplasma was detected at a lower prevalence (3.3%) and exclusively in males. Phylogenetic analysis showed that Wolbachia sequences likely belong to supergroup B, based on their similarity to reference sequences, while Spiroplasma sequences were placed within the poulsonii–citri complex. MinION sequencing revealed Candidatus Dactylopiibacterium as the dominant taxon (97.7%), consistent with its role as an obligate symbiont. After removing this dominant species, we uncovered a diverse bacterial community, including Flavisolibacter, Pseudomonas, Phyllobacterium, Acinetobacter, and Brevibacillus. Beta diversity analysis showed significant geographic variation (PERMANOVA p < 0.008), with distinct communities across regions. Females harbored a more specialized microbiome dominated by Flavisolibacter (except in Agadir), whereas males and nymphs showed Pseudomonas dominance. Core microbiome analysis revealed no universal genera across all groups, with females displaying a more restricted core than males and nymphs. The detection of reproductive symbionts, combined with geographic and sex-specific microbiome patterns, provides valuable insights into the potential roles of these bacteria in host adaptation and their implications for microbiome-based pest management strategies. The complementary use of targeted and untargeted sequencing methods is essential for comprehensive microbiome characterization in this economically important pest. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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12 pages, 2195 KB

Open AccessArticle

Diversity and Influencing Factors of Endosymbiotic Bacteria in Tetranychus truncatus Sourced from Major Crops in Xinjiang

by Kaiqin Mu, Bing Zhang, Zhiping Cai, Jing Chen, Jianping Zhang and Jie Su

Insects 2025, 16(11), 1126; https://doi.org/10.3390/insects16111126 - 4 Nov 2025

Viewed by 729

Abstract

The Xinjiang Uygur Autonomous Region, situated in northwest China, boasts a unique geographical position and a consequent variety of environmental characteristics. T. truncatus is prevalent throughout this region as the primary pest affecting various crops. In this study, we analyzed the microbial community structures of endosymbiotic bacteria in T. truncatus collected from 17 regions and three host plants in Xinjiang using 16S rRNA sequencing. Through composition analysis of the endosymbiotic bacteria in T. truncatus from Xinjiang, it was found that the dominant bacterial phyla were Pseudomonadota and Bacillota. At the genus level, in addition to Wolbachia, Cardinium, and Spiroplasma (common symbiotic bacteria in T. truncatus), the infection rate of Rickettsia in T. truncatus in Xinjiang was found to be 92.8%. The diversity of the endosymbiotic bacteria community in T. truncatus is shaped by both host plant species and geographical region. Specifically, the endosymbiotic bacterial diversity in T. truncatus populations on corn was significantly higher than that observed in populations on cotton and soybean (p < 0.05). Furthermore, we discovered the diversity of endosymbiotic bacteria in T. truncatus was significantly higher in southern Xinjiang than in northern Xinjiang (p < 0.05). Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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16 pages, 2278 KB

Open AccessArticle

Isolation and Characterization of a Native Metarhizium rileyi Strain Mrpgbm2408 from Paralipsa gularis in Maize: First Data on Efficacy and Enzymatic Host Response Dynamics

by Yunhao Yao, Kaiyu Fu, Xiaoyu Wang, Guangzu Du, Yuejin Peng, Guy Smagghe, Wenqian Wang and Bin Chen

Insects 2025, 16(9), 872; https://doi.org/10.3390/insects16090872 - 22 Aug 2025

Viewed by 1181

Abstract

Paralipsa gularis (Zeller) has become an increasingly destructive pest in both storage and field ecosystems, particularly affecting maize crops across China. As chemical control methods face limitations due to resistance development and environmental concerns, biological control presents a promising alternative. In this study, we isolated and identified a novel strain of Metarhizium sp. from naturally infected P. gularis larvae collected in Yunnan Province, China. Morphological characterization, along with ITS-rDNA and EF-1α-rDNA sequencing, confirmed the fungus as Metarhizium rileyi. The optimal growth medium for this strain was SMAY, and the optimal conditions were 25 °C under continuous light (L:D = 24:0). Laboratory bioassays showed that the strain exhibited high virulence against P. gularis larvae, with cumulative mortality reaching 82% following infestation with 5 × 10⁸ conidia/mL. Biochemical analyses revealed that fungal infection significantly inhibited the activity of the key antioxidant enzyme SOD in the host, while activities of POD, CAT, and detoxification enzymes (P450, CarE, AChE, and GSTs) were significantly increased. These results indicate that immune responses were triggered, and systemic colonization of the host was achieved. Overall, this native M. rileyi strain demonstrates strong potential as an effective biological control agent. Its ability to overcome insect defenses and induce high mortality supports its integration into pest management programs targeting P. gularis. This work advances the understanding of fungal–insect interactions and contributes to sustainable, environmentally safe strategies for managing a pest of economic importance in agricultural ecosystems. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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14 pages, 1299 KB

Open AccessArticle

Host-Dependent Variation in Tetranychus urticae Fitness and Microbiota Composition Across Strawberry Cultivars

by Xu Zhang, Hongjun Yang, Zhiming Yan, Yuanhua Wang, Quanzhi Wang, Shimei Huo, Zhan Chen, Jialong Cheng and Kun Yang

Insects 2025, 16(8), 767; https://doi.org/10.3390/insects16080767 - 25 Jul 2025

Viewed by 1289

Abstract

Tetranychus urticae, commonly known as the two-spotted spider mite, is a highly adaptable and polyphagous arthropod in the family Tetranychidae, capable of feeding on over 1200 plant species, including strawberries (Fragaria × ananassa Duch.). The fitness and microbiota of herbivorous arthropods can vary significantly across different plant species and cultivars. In this study, we investigated the fecundity, longevity, growth rate, and microbiota composition of T. urticae reared on seven Chinese strawberry cultivars: Hongyan (HY), Yuexiu (YX), Tianshi (TS), Ningyu (NY), Xuetu (XT), Zhangjj (ZJ), and Xuelixiang (XLX). Our findings revealed significant differences among cultivars: mites reared on the XT cultivar exhibited the highest fecundity (166.56 ± 7.82 eggs), while those on XLX had the shortest pre-adult period (7.71 ± 0.13 days). Longevity was significantly extended in mites reared on XLX, XT, and NY cultivars (25.95–26.83 days). Microbiota analysis via 16S rRNA sequencing showed that Proteobacteria dominated (>89.96% abundance) across all mite groups, with Wolbachia as the predominant symbiont (89.58–99.19%). Male mites exhibited higher bacterial diversity (Shannon and Chao1 indices) than females, though Wolbachia abundance did not differ significantly between sexes or cultivars. Functional predictions highlighted roles of microbiota in biosynthesis, detoxification, and energy metabolism. These findings underscore the influence of host plant variety on T. urticae fitness and microbiota composition, suggesting potential strategies for breeding resistant strawberry cultivars and leveraging microbial interactions for pest management. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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Review

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16 pages, 779 KB

Open AccessReview

Biological Control Strategies and Integrated Arthropod Pest Management for Camellia oleifera

by Yifei Xie, Jinxiu Yu, Wan Deng, Shaofeng Peng, Chi Li, Xuanye Wen, Wuhong Zhong and Mi Li

Insects 2025, 16(12), 1244; https://doi.org/10.3390/insects16121244 - 9 Dec 2025

Viewed by 1073

Abstract

Camellia oleifera, commonly known as oil-tea, serves as one of China’s most economically important oil crops. To ensure continued production yield and quality, biological control measures, operating within the framework of integrated pest management, have been extensively adopted nationwide. Integrated pest management facilitates effective management of arthropod pests afflicting C. oleifera by integrating biological control strategies with traditional chemical control methods. This approach significantly reduces the reliance on chemical pesticides and minimizes adverse environmental impacts. Over 600 natural enemy species targeting pests have been documented within the C. oleifera agroecosystems in China including approximately 38 viral agents along with 41 fungal, 166 parasitoid, 336 predator, and several bacterial species. Notably, both insectile natural enemies and fungal biopesticides derived from microbial resources are currently being used at scale in C. oleifera cultivation regions, serving as crucial alternatives to the use of conventional chemical pesticides. This paper comprehensively reviews recent progress in research and the application of synergistic integration of biological control with traditional pest management strategies for C. oleifera. The current status of research on natural enemy resources is analyzed and knowledge gaps in the domain of C. oleifera pest management are identified. Furthermore, future research trajectories are proposed that are intended to provide a scientific basis for the green and sustainable development of the C. oleifera industry. Full article

(This article belongs to the Special Issue Insect Pathogens as Biocontrol Agents Against Pests)

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