Wolbachia-based strategies for control of agricultural pests

A persistent bacterial Regiella transinfection in the bird cherry-oat aphid Rhopalosiphum padi increasing host fitness and decreasing plant virus transmission

BACKGROUND

The bird cherry-oat aphid, Rhopalosiphum padi, is a major pest of agriculture due to its ability to directly damage crops and transmit plant viruses. As industries move away from chemical pest control, there is interest in exploring new options to suppress the impact of this pest.

RESULTS

We describe the production of a transinfected line of R. padi carrying the bacterial endosymbiont, Regiella insecticola, originating from the green peach aphid, Myzus persicae. We show that Regiella increases the fitness of its novel host despite decreasing fitness in its native host. Regiella also shows a low level of horizontal transmission. Importantly the infection suppresses the ability of R. padi to transmit the barley yellow dwarf virus which damages wheat plants.

CONCLUSION

Our results suggest this Regiella transinfection could be released to suppress virus transmission by aphids with its ability to persist and spread in situations where damage from the virus exceeds that from direct feeding by the aphid. © 2025 Society of Chemical Industry.

Insect Pest Control from Chemical to Biotechnological Approach: Constrains and Challenges

The large growth in the global population requires new solutions for the control of harmful insects that compete for our food. Changing regulatory requirements and public perception, together with the continuous evolution of resistance to conventional insecticides, also require, in addition to innovative molecules with different modes of action, new non-chemical control strategies that can help maintain efficient integrated pest management programs. The last 30 years have inaugurated a new era characterised by the discovery of new mechanisms of action and new chemical families. Although European programs also promote a green deal in the crop protection sector, the existing thorough regulations slow down its spread and the adoption of new products. In light of these changes, this review will describe in more detail the dynamics of discovery and registration of new conventional insecticides and the difficulties that the agrochemical industries encounter. Subsequently, the different innovative control strategies alternative to conventional insecticides based on natural substances of different origin, entomopathogenic microorganisms, semiochemical and semiophysical compounds, and classical and augmentative biological control will be described. The advantages of these green strategies will be illustrated and also the constrains to their diffusion and commercialisation. Finally, the main biotechnological discoveries will be described, from transgenic plants to symbiotic control, classical genetic control, and, more recently, control based on insect genomic transformation or on RNAi. These new biotechnologies can revolutionise the sector despite some constrains related to the regulatory restrictions present in different countries.

"Hostbusters": The Bacterial Endosymbiont Wolbachia of the Parasitoid Wasp Habrobracon hebetor Improves Its Ability to Parasitize Lepidopteran Hosts

Habrobracon hebetor is a globally acknowledged larval ectoparasitoid that is widely used to control lepidopteran pests. Wolbachia is a natural endosymbiont that regulates various aspects of the insect host biology. The ability of H. hebetor to paralyze and develop on lepidopteran larvae from five families was tested under laboratory conditions. Two lines of the wasp were used, "W+" containing a naturally occurring Wolbachia from the supergroup B, and "W-", with the endosymbiont eradicated by antibiotic treatment, followed by propagation of 20 subsequent generations. The proportions of larvae in which host paralysis, as well as parasitoid oviposition, larval, pupal, and adult development were observed, were usually higher in W+ compared to W-. In Loxostege sticticalis, differences in these indices were not statistically significant. In Galleria mellonella, Mamestra brassicae, and Ostrinia nubilalis, some of the parasitism indices were significantly higher in W+ than in W-. In Bombyx mori and Plutella xylostella, H. hebetor could not complete its life cycle, but parasitism levels at the initial steps (from paralysis symptoms to the presence of larvae/pupae of the parasitoid) were 2-5 times lower in W- compared to W+ (p < 0.01). It can be suggested that the presence of Wolbachia is advantageous for H. hebetor, as it increases the success of parasitism in a broad range of lepidopteran hosts.

Metabolomics Provides New Insights into the Mechanisms of Wolbachia-Induced Plant Defense in Cotton Mites

Endosymbiotic bacteria play a significant role in the co-evolution of insects and plants. However, whether they induce or inhibit host plant defense responses remains unclear. In this study, non-targeted metabolomic sequencing was performed on cotton leaves fed with Wolbachia-infected and uninfected spider mites using parthenogenetic backcrossing and antibiotic treatment methods. A total of 55 differential metabolites were identified, which involved lipids, phenylpropanoids, and polyketides. KEGG pathway enrichment analysis revealed seven significantly enriched metabolic pathways. Among them, flavonoid and flavonol biosynthesis, glycerophospholipid metabolism, and ether lipid metabolism showed extremely significant differences. In Wolbachia-infected cotton leaves, the flavonoid biosynthesis pathway was significantly up-regulated, including quercetin and myricetin, suggesting that the plant produces more secondary metabolites to enhance its defense capability. Glycerophosphocholine (GPC) and sn-glycerol-3-phosphoethanolamine (PE) were significantly down-regulated, suggesting that Wolbachia may impair the integrity and function of plant cell membranes. The downregulation of lysine and the upregulation of L-malic acid indicated that Wolbachia infection may shorten the lifespan of spider mites. At various developmental stages of the spider mites, Wolbachia infection increased the expression of detoxification metabolism-related genes, including gene families such as cytochrome P450, glutathione S-transferase, carboxylesterase, and ABC transporters, thereby enhancing the detoxification capability of the host spider mites. This study provides a theoretical basis for further elucidating the mechanisms by which endosymbiotic bacteria induce plant defense responses and expands the theoretical framework of insect-plant co-evolution.

Wolbachia enhances the survival of Drosophila infected with fungal pathogens

BACKGROUND

Wolbachia bacteria of arthropods are at the forefront of basic and translational research on multipartite host-symbiont-pathogen interactions. These vertically transmitted microbes are the most widespread endosymbionts on the planet due to factors including host reproductive manipulation and fitness benefits. Importantly, some strains of Wolbachia can inhibit viral pathogenesis within and between arthropod hosts. Mosquitoes carrying the wMel Wolbachia strain of Drosophila melanogaster have a greatly reduced capacity to spread viruses like dengue and Zika to humans. While significant research efforts have focused on viruses, relatively little attention has been given to Wolbachia-fungal interactions despite the ubiquity of fungal entomopathogens in nature.

RESULTS

Here, we demonstrate that Wolbachia increase the longevity of their Drosophila melanogaster hosts when challenged with a spectrum of yeast and filamentous fungal pathogens. We find that this pattern can vary based on host genotype, sex, and fungal species. Further, Wolbachia correlates with higher fertility and reduced pathogen titers during initial fungal infection, indicating a significant fitness benefit. Finally, RNA sequencing results show altered expression of many immune and stress response genes in the context of Wolbachia and fungal infection, suggesting host immunity may be involved in the mechanism.

CONCLUSIONS

This study demonstrates Wolbachia's protective role in diverse fungal pathogen interactions and determines that the phenotype is broad, but with several variables that influence both the presence and strength of the phenotype. It also is a critical step forward to understanding how symbionts can protect their hosts from a variety of pathogens.

Wolbachia Infection Alters the Microbiota of the Invasive Leaf-Miner Liriomyza huidobrensis (Diptera: Agromyzidae)

Microbe-microbe interactions within a host drive shifts in the host's microbiota composition, profoundly influencing host physiology, ecology, and evolution. Among these microbes, the maternally inherited endosymbiont Wolbachia is widespread in the invasive pest Liriomyza huidorbrensis (Diptera: Agromyzidae). However, its influence on the host microbiota remains largely unexplored. In the study presented herein, we investigated the bacterial communities of Wolbachia wLhui-infected (wLhui+) and -uninfected lines (wLhui-) of L. huidorbrensis using 16S rRNA gene high-throughput sequencing. For both leaf-miner lines, Bacteroidota was the dominant phylum (relative abundance: 59.18%), followed by Pseudomonadota (36.63%), Actinomycetota (2.42%), and Bacillota (0.93%). We found no significant differences in alpha-diversity indices between the wLhui+ and wLhui- lines (p > 0.05). However, principal coordinates analysis revealed significant differences in microbiota composition between the wLhui+ and wLhui- lines (PERMANOVA: p < 0.001), explaining 76.70% of the variance in microbiota composition. Correlation network analysis identified robust negative and positive associations between Wolbachia and several genera, suggesting that Wolbachia shapes microbial composition through competitive or cooperative interactions with specific taxa. Overall, our study suggests that Wolbachia plays a key role in shaping the leaf-miner microbiome, potentially affecting host fitness.

Bacterial communities in Asecodes hispinarum (Hymenoptera: Eulophidae) and its host Brontispa longissima (Coleoptera: Chrysomelidae), with comparison of Wolbachia dominance

The endoparasitoid Asecodes hispinarum (Bouček) (Hymenoptera: Eulophidae) serves as an effective biological control agent against Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), a notorious palm pest. Endosymbionts found in parasitoids and their hosts have attracted significant attention due to their substantial influence on biocontrol efficacy. In this study, we employed 16S rRNA sequencing, polymerase chain reaction, and fluorescence in situ hybridization to assess the symbiotic bacteria composition, diversity, phylogeny, and localization in A. hispinarum and its host B. longissima. Our findings showed significant differences in the richness, diversity, and composition of symbiotic bacteria among different life stages of B. longissima. Notably, the bacterial richness, diversity, and composition of A. hispinarum was similar to that of B. longissima. Firmicutes and Proteobacteria were the dominant phyla, while Wolbachia was the dominant genera across the parasitoid and host. It was discovered for the first time that Wolbachia was present in A. hispinarum with a high infection rate at ≥ 96.67%. Notably, the Wolbachia strain in A. hispinarum was placed in supergroup A, whereas it was categorized under supergroup B in B. longissima. Furthermore, Wolbachia is concentrated in the abdomen of A. hispinarum, with particularly high levels observed in the ovipositors of female adults. These findings highlight the composition and diversity of symbiotic bacteria in both A. hispinarum and its host B. longissima, providing a foundation for the development of population regulation strategies targeting B. longissima.

No Evidence for Wolbachia Effects on the Thermal Preference of the Invasive Pest Liriomyza huidobrensis

Heritable endosymbiont Wolbachia is prevalent among arthropods, serving multiple functions for their hosts. However, the role of Wolbachia in mediating thermal preference selection remains largely unexplored. In this study, we utilized a custom-built thermal gradient to evaluate the thermal preference (Tp) of 1367 individuals of the invasive leaf-miner Liriomyza huidobrensis with or without Wolbachia wLhui from Yunnan and Xinjiang populations. Under meticulously controlled conditions and with a vast sample size, we found no significant difference in the mean Tp between wLhui-infected and uninfected leaf miners from either population when host age and sex were not considered. Furthermore, generalized linear model (GLM) analysis revealed no significant correlation between average Tp and age, sex, or Wolbachia infection, nor interactions among these factors, except in the Xinjiang population, where Tp was strongly associated with host age. Finally, we discuss the ecological implications of these findings and propose future research directions on Wolbachia-mediated host Tp in the leaf miner. Overall, our findings do not provide evidence that Wolbachia significantly affects the thermal preference of L. huidobrensis. Further studies across different systems are needed to investigate the complex interactions between Wolbachia and insect thermal behavior.

Wolbachia modify host cell metabolite profiles in response to short-term temperature stress

Wolbachia are common heritable endosymbionts that influence many aspects of ecology and evolution in various insects, yet Wolbachia-mediated intracellular metabolic responses to temperature stress have been largely overlooked. Here, we introduced the Wolbachia strain wLhui from the invasive Liriomyza huidobrensis (Blanchard) into a Drosophila Schneider 2 cell line (S2) and investigated the metabolite profile of wLhui-infected (S2_wLhui) and uninfected cell lines (S2_wu) under short-term exposure to either high (37°C), moderate (27°C), or low (7 and 17°C) temperatures. We find that Wolbachia infection, temperature stress, and their interactions significantly affect cellular metabolic profiles. Most significantly, when comparing the changes in metabolites between S2_wLhui and S2_wu, glycerophospholipids, amino acids, and fatty acids associated with metabolic pathways, microbial metabolism in diverse environments, and other pathways were significantly accumulated at either low or high temperatures. Our findings suggest Wolbachia-induced cellular physiological responses to short-term temperature stress, which may in turn affect the fitness and adaptive ability of its host as an invasive species.

A survey of Wolbachia infection in brachyceran flies from Iran

Wolbachia is a maternally inherited intracellular bacterium that is considered to be the most plentiful endosymbiont found in arthropods. It reproductively manipulates its host to increase the chances of being transmitted to the insect progeny; and it is currently used as a means of suppressing disease vector populations or controlling vector-borne diseases. Studies of the dissemination and prevalence of Wolbachia among its arthropod hosts are important for its possible use as a biological control agent. The molecular identification of Wolbachia relies on different primers sets due to Wolbachia strain variation. Here, we screened for the presence of Wolbachia in a broad range of Brachycera fly species (Diptera), collected from different regions of Iran, using nine genetic markers (wsp, ftsZ, fbpA, gatB, CoxA, gltA, GroEL dnaA, and 16s rRNA), for detecting, assessing the sensitivity of primers for detection, and phylogeny of this bacterium. The overall incidence of Wolbachia among 22 species from six families was 27.3%. The most commonly positive fly species were Pollenia sp. and Hydrotaea armipes. However, the bacterium was not found in the most medically important flies or in potential human disease vectors, including Musca domestica, Sarcophaga spp., Calliphora vicinia, Lucilia sericata, and Chrysomya albiceps. The primer sets of 16s rRNA with 53.0% and gatB with 52.0% were the most sensitive primers for detecting Wolbachia. Blast search, phylogenetic, and MLST analysis of the different locus sequences of Wolbachia show that all the six distantly related fly species likely belonging to supergroup A. Our study showed some primer sets generated false negatives in many of the samples, emphasizing the importance of using different loci in detecting Wolbachia. The study provides the groundwork for future studies of a Wolbachia-based program for control of flies.

The Effect of Genotype Combinations of Wolbachia and Its Drosophila melanogaster Host on Fertility, Developmental Rate and Heat Stress Resistance of Flies

The best-known effect of the intracellular bacterium Wolbachia is its mostly negative influence on the reproduction of the host. However, there is evidence of a positive influence of Wolbachia on the host's resistance to stress, pathogens, and viruses. Here, we analyzed the effects of two Wolbachia strains belonging to wMel and wMelCS genotypes on D. melanogaster traits, such as fertility, survival under acute heat stress, and developmental rate. We found that D. melanogaster lines under study differ significantly in the above-mentioned characteristics, both when the natural infection was preserved, and when it was eliminated. One of Wolbachia strains, wMel, did not affect any of the studied traits. Another strain, wMelPlus, had a significant effect on the development time. Moreover, this effect is observed not only in the line in which it was discovered but also in the one it was transferred to. When transferred to a new line, wMelPlus also caused changes in survival under heat stress. Thus, it could be concluded that Wolbachia-Drosophila interaction depends on the genotypes of both the host and the symbiont, but some Wolbachia effects could depend not on the genotypes, but on the fact of recent transfer of the symbiont.

The impact of predators of mosquito larvae on Wolbachia spreading dynamics

Dengue fever creates more than 390 million cases worldwide yearly. The most effective way to deal with this mosquito-borne disease is to control the vectors. In this work we consider two weapons, the endosymbiotic bacteria Wolbachia and predators of mosquito larvae, for combating the disease. As Wolbachia-infected mosquitoes are less able to transmit dengue virus, releasing infected mosquitoes to invade wild mosquito populations helps to reduce dengue transmission. Besides this measure, the introduction of predators of mosquito larvae can control mosquito population. To evaluate the impact of the predators on Wolbachia spreading dynamics, we develop a stage-structured five-dimensional model, which links the predator-prey dynamics with the Wolbachia spreading. By comparatively analysing the dynamics of the models without and with predators, we observe that the introduction of the predators augments the number of coexistence equilibria and impedes Wolbachia spreading. Some numerical simulations are presented to support and expand our theoretical results.

Wolbachia enhances the survival of Drosophila infected with fungal pathogens

Wolbachia bacteria of arthropods are at the forefront of basic and translational research on multipartite host-symbiont-pathogen interactions. These microbes are vertically inherited from mother to offspring via the cytoplasm. They are the most widespread endosymbionts on the planet due to their infamous ability to manipulate the reproduction of their hosts to spread themselves in a population, and to provide a variety of fitness benefits to their hosts. Importantly, some strains of Wolbachia can inhibit viral pathogenesis within and between arthropod hosts. Mosquitoes carrying the wMel Wolbachia strain of Drosophila melanogaster have a greatly reduced capacity to spread viruses like dengue and Zika to humans. Therefore, Wolbachia are the basis of several global vector control initiatives. While significant research efforts have focused on viruses, relatively little attention has been given to Wolbachia-fungal interactions despite the ubiquity of fungal entomopathogens in nature. Here, we demonstrate that Wolbachia increase the longevity of their Drosophila melanogaster hosts when challenged with a spectrum of yeast and filamentous fungal pathogens. We find that this pattern can vary based on host genotype, sex, and fungal species. Further, Wolbachia correlates with higher fertility and reduced pathogen titers during initial fungal infection, indicating a significant fitness benefit. This study demonstrates Wolbachia's role in diverse fungal pathogen interactions and determines that the phenotype is broad, but with several variables that influence both the presence and strength of the phenotype. These results enhance our knowledge of the strategies Wolbachia uses that likely contribute to such a high global symbiont prevalence.

Using Wolbachia to control rice planthopper populations: progress and challenges

Wolbachia have been developed as a tool for protecting humans from mosquito populations and mosquito-borne diseases. The success of using Wolbachia relies on the facts that Wolbachia are maternally transmitted and that Wolbachia-induced cytoplasmic incompatibility provides a selective advantage to infected over uninfected females, ensuring that Wolbachia rapidly spread through the target pest population. Most transinfected Wolbachia exhibit a strong antiviral response in novel hosts, thus making it an extremely efficient technique. Although Wolbachia has only been used to control mosquitoes so far, great progress has been made in developing Wolbachia-based approaches to protect plants from rice pests and their associated diseases. Here, we synthesize the current knowledge about the important phenotypic effects of Wolbachia used to control mosquito populations and the literature on the interactions between Wolbachia and rice pest planthoppers. Our aim is to link findings from Wolbachia-mediated mosquito control programs to possible applications in planthoppers.