Exploration of culturable bacterial associates of aphids and their interactions with entomopathogens.

Aphids shelter several bacteria that benefit them in various ways. The associates having an obligatory relationship are non-culturable, while a few of facultative associates are culturable in insect cell lines, axenic media or standard microbiology media. In the present investigation, isolation, and characterization of the culturable bacterial associates of various aphid species, viz., Rhopalosiphum maidis, Rhopalosiphum padi, Sitobion avenae, Schizaphis graminum, and Lipaphis erysimi pseudobrassicae were carried out. A total of 42 isolates were isolated using different growth media, followed by their morphological, biochemical, and molecular characterization. The isolated culturable bacterial associates were found to belong to the genera Acinetobacter, Bacillus, Brevundimonas, Cytobacillus, Fictibacillus, Planococcus, Priestia, Pseudomonas, Staphylococcus, Sutcliffiella, and Tumebacillus which were grouped under seven families of four different orders of phyla Bacillota (Firmicutes) and Pseudomonata (Proteobacteria). Symbiont-entomopathogen interaction study was also conducted, in which the quantification of colony forming units of culturable bacterial associates of entomopathogenic fungal-treated aphids led us to the assumption that the bacterial load in aphid body can be altered by the application of entomopathogens. Whereas, the mycelial growth of entomopathogens Akanthomyces lecanii and Metarhizium anisopliae was found uninhibited by the bacterial associates obtained from Sitobion avenae and Rhopalosiphum padi. Analyzing persistent aphid microflora and their interactions with entomopathogens enhances our understanding of aphid resistance. It also fosters the development of innovative solutions for agricultural pest management, highlighting the intricate dynamics of symbiotic relationships in pest management strategies.

Diversity study of Beauveria bassiana species for finding the most virulent strain to manage Bemisia tabaci in cotton.

Beauveria bassiana (Bal.-Criv.) is an important entomopathogenic fungus being used for the management of various agricultural pests worldwide. However, all strains of B. bassiana may not be effective against whitefly, Bemisia tabaci, or other pests, and strains show diversity in their growth, sporulation, virulence features, and overall bioefficacy. Thus, to select the most effective strain, a comprehensive way needs to be devised. We studied the diversity among the 102 strains of B. bassiana isolated from 19 insect species based on their physiological features, virulence, and molecular phylogeny, to identify promising ones for the management of B. tabaci. Strains showed diversity in mycelial growth, conidial production, and their virulence against B. tabaci nymphs. The highest nymphal mortality (2nd and 3rd instar) was recorded with MTCC-4511 (95.1%), MTCC-6289 (93.8%), and MTCC-4565 (89.9%) at a concentration of 1 × 106 conidia ml-1 under polyhouse conditions. The highest bioefficacy index (BI) was in MTCC-4511 (78.3%), MTCC-4565 (68.2%), and MTCC-4543 (62.1%). MTCC-4511, MTCC-4565, and MTCC-4543 clustered with positive loading of eigenvalues for the first two principal components and the cluster analysis also corresponded well with PCA (principal component analysis) (nymphal mortality and BI). The molecular phylogeny could not draw any distinct relationship between physiological features, the virulence of B. bassiana strains with the host and location. The BI, PCA, and square Euclidean distance cluster were found the most useful tools for selecting potential entomopathogenic strains. The selected strains could be utilized for the management of the B. tabaci nymphal population in the field through the development of effective formulations. KEY POINTS: • 102 B. bassiana strains showed diversity in growth and virulence against B. tabaci. • Bioefficacy index, PCA, and SED group are efficient tools for selecting potential strains. • MTCC-4511, 4565, and 4543 chosen as the most virulent strains to kill whitefly nymphs.

Pathogens of the oak processionary moth Thaumetopoea processionea: Developing a user-friendly bioassay system and metagenome analyses for microorganisms.

The oak processionary moth (OPM) Thaumetopoea processionea is a pest of oak trees and poses health risks to humans due to the urticating setae of later instar larvae. For this reason, it is difficult to rear OPM under laboratory conditions, carry out bioassays or examine larvae for pathogens. Biological control targets the early larval instars and is based primarily on commercial preparations of Bacillus thuringiensis ssp. kurstaki (Btk). To test the entomopathogenic potential of other spore-forming bacteria, a user-friendly bioassay system was developed that (i) applies bacterial spore suspensions by oak bud dipping, (ii) targets first instar larvae through feeding exposure and (iii) takes into account their group-feeding behavior. A negligible mortality in the untreated control proved the functionality of the newly established bioassay system. Whereas the commercial Btk HD-1 strain was used as a bioassay standard and confirmed as being highly efficient, a Bacillus wiedmannii strain was ineffective in killing OPM larvae. Larvae, which died during the infection experiment, were further subjected to Nanopore sequencing for a metagenomic approach for entomopathogen detection. It further corroborated that B.wiedmannii was not able to infect and establish in OPM, but identified potential insect pathogenic species from the genera Serratia and Pseudomonas.

Unearthing diverse culturable fungal communities associated with Ophiocordyceps indica sp. nov. from Indian Western Himalaya.

Fungal communities colonizing Ophiocordyceps spp. plays a crucial ecological role in their natural habitat, contributing to infect the host larvae, and influencing their occurrence. Although associated fungi with the newly described Ophiocordyceps indica, from the Indian Western Himalaya remains unclear. Therefore, we untangled the culturable fungal communities associated with O. indica and soil adhered to it, collected from low-height areas of Himachal Pradesh, India. The study resulted in the identification of 111 fungal isolates representing 17 families, with maximum fungal isolates (36.03%) within Cordycipitaceae. Interestingly, a total of 24 genera were found associated with O. indica and adhered soil, of which 12 were common, 8 were exclusive to O. indica and 4 were only limited to soil. Additionally, the influence of soil physicochemical parameters on fungal diversity indices revealed a positive correlation with humidity and available nitrogen and a negative correlation with pH and available phosphorus. These findings provide insights into the culturable fungal diversity of O. indica and the soil adhering to it, thus can contribute to the understanding of host-microbial interactions. Furthermore, these associations can be explored as a source of bioactive metabolites to combat the unending industrial demands.

Use of an exotic host plant reduces viral burden in a native insect herbivore.

Incorporation of exotic plants into the diets of native herbivores is a common phenomenon, influencing interactions with natural enemies and providing insight into the tritrophic costs and benefits of dietary expansion. We evaluated how use of an exotic plant, Plantago lanceolata, impacted immune performance, development and susceptibility to pathogen infection in the neotropical herbivore Anartia jatrophae (Lepidoptera: Nymphalidae). Caterpillars were reared on P. lanceolata or a native plant, Bacopa monnieri, and experimentally infected with a pathogenic virus, Junonia coenia densovirus. We found that virus-challenged herbivores exhibited higher survival rates and lower viral burdens when reared on P. lanceolata compared to B. monnieri, though immune performance and development time were largely similar on the two plants. These findings reveal that use of an exotic plant can impact the vulnerability of a native herbivore to pathogen infection, suggesting diet-mediated protection against disease as a potential mechanism facilitating the incorporation of novel resources.

The possibility of using Serratia isolates for the production of biopreparations in the protection of plants against diseases and pests.

The agriculture is extremely important for the life of human beings. Therefore, it is needed to control the enemies that destroy vast areas of crops causing great economic losses. Chemical pesticides were the option for many decades, but the damage that they cause to environment and human health led to the idea of changing the use of these for more sustainable options such as biopesticides as a biological control. Among microbial pesticides, Serratia species have been found as suitable options to apply against several pests or pathogens. Serratia species produce a wide range of secondary metabolites with several biological activities such as antifungal, antibacterial, and pesticides which can be used in sustainable agriculture. It has been reported that several Serratia species are able to suppress some crop diseases caused by Fusarium oxysporum, Rhizoctonia solani, Phytophthora parasitica, Sclerotinia sclerotiorum, Verticillium dahlia, and Phytophthora capsici among others. Therefore, they have been used as biocontrol agents in agriculture. In this review, we summarized the genus Serratia describing its history and development and the metabolites it secretes, which are responsible for their antibacterial and antifungal activity. We have analyzed the insecticide capacity of several Serratia species as well antifungal properties of Serratia species against most important crops' pathogens. In conclusion, the use of Serratia as a biological control agent against plant pathogens can be a good option for a sustainable agriculture. More work is needed to assess the safety of the isolated new strains and their effectiveness against pathogens in in vivo conditions.

Beauveria bassiana exhibits strong virulence against Dendroctonus ponderosae in greenhouse and field experiments.

The mountain pine beetle (MPB) has infested over 16 million hectares of pine forests in western Canada, killing over 50% of mature lodgepole pine, Pinus contorta, in British Columbia alone. There are few tools available to manage irruptive bark beetle populations and to mitigate tree mortality. Beauveria bassiana is an entomopathogenic fungus that causes mortality to several bark beetle species. However, the potential for B. bassiana as a biocontrol agent against pine beetle populations is unknown. We selected three strains of B. bassiana from several culture collections and evaluated their conidial stability under cold storage, in planta (greenhouse, and pine bolts) and in natura (forest stand, pine bolts, and live pines) conditions. The stability assays showed that all fungal strains maintained a minimum effective conidial yield through the assay durations (3-12 weeks). In addition, we adapted a biphasic liquid-solid fermentation approach for the large-scale production of conidial biomass, yielding up to a 100-fold increase in production. In greenhouse virulence assays, the mean lethal time of MPBs was reduced to 3-4 days upon treatment with B. bassiana, where high B. bassiana-associated mycosis was also observed. Furthermore, the application of B. bassiana formulation substantially affected the gallery network of MPBs in bolts in the field, resulting in shorter larval galleries and significantly reduced offspring production. Indeed, high titer treatments reduced the mean larvae per gallery to virtually zero. Together these results demonstrate that B. bassiana may be a viable biocontrol tool to reduce mountain pine beetle populations in pine forests in western Canada. KEY POINTS: • Three B. bassiana strains identified to be stable at various test conditions. • Large-scale conidial biomass production using liquid-solid biphasic fermentation. • Reproductive success of D. ponderosae significantly reduced by B. bassiana formulation.

Entomopathogens infecting brown marmorated stink bugs before, during, and after overwintering.

The microsporidian, Nosema maddoxi Becnel, Solter, Hajek, Huang, Sanscrainte & Estep, infects brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), populations in North America and Asia and causes decreased fitness in infected insects. This host overwinters as adults, often in aggregations in sheltered locations, and variable levels of mortality occur over the winter. We investigated pathogen prevalence in H. halys adults before, during, and after overwintering. Population level studies resulted in detection of N. maddoxi in H. halys in 6 new US states, but no difference in levels of infection by N. maddoxi in autumn versus the following spring. Halyomorpha halys that self-aggregated for overwintering in shelters deployed in the field were maintained under simulated winter conditions (4°C) for 5 months during the 2021-2022 winter and early spring, resulting in 34.6 ± 4.8% mortality. Over the 2020-2021 and 2021-2022 winters, 13.4 ± 3.5% of surviving H. halys in shelters were infected with N. maddoxi, while N. maddoxi infections were found in 33.4 ± 10.8% of moribund and dead H. halys that accumulated in shelters. A second pathogen, Colletotrichum fioriniae Marcelino & Gouli, not previously reported from H. halys, was found among 46.7 ± 7.8% of the H. halys that died while overwintering, but levels of infection decreased after overwintering. These 2 pathogens occurred as co-infections in 11.1 ± 5.9% of the fungal-infected insects that died while overwintering. Increasing levels of N. maddoxi infection caused epizootics among H. halys reared in greenhouse cages after overwintering.

Endophytic insect pathogenic fungi-host plant-herbivore mutualism: elucidating the mechanisms involved in the tripartite interactions.

Various techniques used by crop plants to evade insect pests and pathogen attacks have been documented. Among these, plant defense strategies induced by endophytic insect pathogenic fungi are arguably one of the most discussed. Endophytic fungi frequently colonize plants and inhabit their internal tissues for a portion of their lifespan without producing visible symptoms of the disease. This phenomenon is widespread and diverse in both natural and agricultural ecosystems, and is present in almost all plant organs. Many fungi can obtain nutrients by infecting and killing insects, and this ability has been developed numerous times in different fungal lineages. These species mainly consist of those in the order Hypocreales (Ascomycota), where the generalist insect pathogens, Beauveria sp. (Cordycipitaceae) and Metarhizium sp. (Clavicipitaceae) are two of the most studied endophytic entomopathogenic fungal genera. However, most fungi that kill insects do not survive in the tissues of living plants. The data published thus far show a high degree of variability and do not provide consistent explanations for the underlying mechanisms that may be responsible for these effects. This implies that available knowledge regarding the colonization of plant tissues by endophytic insect pathogenic fungi, the effects of colonization on plant metabolism, and how this contributes to a decrease in herbivore and pathogens damage is limited. To adequately utilize fungal-based products as biological control agents, these products must be effective and the reduction of pests and infection must be consistent and similar to that of chemical insecticides after application. This article discusses this possibility and highlights the benefits and the specific techniques utilized by endophytically challenged plants in invading insect pests and disease pathogens.

Hijacking time: How Ophiocordyceps fungi could be using ant host clocks to manipulate behavior.

Ophiocordyceps fungi manipulate ant behaviour as a transmission strategy. Conspicuous changes in the daily timing of disease phenotypes suggest that Ophiocordyceps and other manipulators could be hijacking the host clock. We discuss the available data that support the notion that Ophiocordyceps fungi could be hijacking ant host clocks and consider how altering daily behavioural rhythms could benefit the fungal infection cycle. By reviewing time-course transcriptomics data for the parasite and the host, we argue that Ophiocordyceps has a light-entrainable clock that might drive daily expression of candidate manipulation genes. Moreover, ant rhythms are seemingly highly plastic and involved in behavioural division of labour, which could make them susceptible to parasite hijacking. To provisionally test whether the expression of ant behavioural plasticity and rhythmicity genes could be affected by fungal manipulation, we performed a gene co-expression network analysis on ant time-course data and linked it to available behavioural manipulation data. We found that behavioural plasticity genes reside in the same modules as those affected during fungal manipulation. These modules showed significant connectivity with rhythmic gene modules, suggesting that Ophiocordyceps could be indirectly affecting the expression of those genes as well.

Life-history attributes of juvenile Anopheles gambiae s.s. in central Uganda; implications for malaria control interventions.

Malaria is among the leading causes of death in Uganda, and Anopheles gambiae sensu stricto (s.s.) is the predominant vector. Although current vector control interventions have greatly reduced the malaria burden, the disease persists. New interventions are needed in order to eradicate them. Evaluation of new tools will require the availability of well-characterized test vector populations. Juvenile An. gambiae s.s. from Kibbuye and Kayonjo-derived populations were characterized under semi-field and laboratory conditions, given that various vector traits, including abundance and fitness are dependent on development profiles at this life stage. Ten replicates comprising 30 first instar larvae each were profiled for various life-history attributes (egg hatching, larval development time, larval survivorship, pupal weight and pupation rate). All parameters were similar for the two sites under laboratory conditions. However, the similarities or differences between field and laboratory development were parameter-specific. Whereas, larval survivorship and pupal weight were similar across seasons and laboratory in colonies from both sites, in the semi-field settings, pupation rate and larval survivorship differed between seasons in both sites. In addition, the average larval development time during the wet season was longer than that of the laboratory for both sites. Availability of mirror field sites is important for future tool evaluations.

RNA viruses in the house dust mite Dermatophagoides pteronyssinus, detection in environmental samples and in commercial allergen extracts used for in vivo diagnosis.

BACKGROUND: Allergy to house dust mites (HDM), the most important source of indoor allergens worldwide, is diagnosed and treated using natural extracts from cultures that can contain immunoactive components from the HDM microbiome, including mite-infecting viruses. This study aimed to contribute to the discovery and characterization of RNA viruses from Dermatophagoides pteronyssinus, followed by their detection in different mite-derived sources. METHODS: Viruses were assembled after in silico metatranscriptomic analysis of D. pteronyssinus RNA samples, visualized by electron microscopy, and RNA detected by direct RT-PCR or data mining. Mite culture performance was evaluated in vivo. RESULTS: Seven RNA viruses were identified in our laboratory stock colony. Picornavirus-like viral particles were detected in epithelial cells of the digestive system and in fecal pellets. Most of these viruses could be persistently transmitted to an inbred virus-free colony by inoculating fecal material from the stock colony. Upon viral infection, no significant effect could be seen on mite population growth. Transcriptomic screening confirmed the presence of homolog sequences to these viruses in independent laboratory stocks of D. pteronyssinus and in other Astigmata mites. Noteworthy, RNA from most of the viruses could be detected by RT-PCR on house dust samples, reference standards, and/or commercial diagnostic D. pteronyssinus extracts. CONCLUSIONS: Our results show that viral infections are common and widespread in D. pteronyssinus, both in natural and culture-based growth conditions. Potential effects on the mites themselves and consequences toward allergenicity in humans whether exposed naturally or after immunotherapy are discussed.

A Neurotoxic Insecticide Promotes Fungal Infection in Aedes aegypti Larvae by Altering the Bacterial Community.

Symbiotic bacteria have a significant impact on the formation of defensive mechanisms against fungal pathogens and insecticides. The microbiome of the mosquito Aedes aegypti has been well studied; however, there are no data on the influence of insecticides and pathogenic fungi on its structure. The fungus Metarhizium robertsii and a neurotoxic insecticide (avermectin complex) interact synergistically, and the colonization of larvae with hyphal bodies is observed after fungal and combined (conidia + avermectins) treatments. The changes in the bacterial communities (16S rRNA) of Ae. aegypti larvae under the influence of fungal infection, avermectin toxicosis, and their combination were studied. In addition, we studied the interactions between the fungus and the predominant cultivable bacteria in vitro and in vivo after the coinfection of the larvae. Avermectins increased the total bacterial load and diversity. The fungus decreased the diversity and insignificantly increased the bacterial load. Importantly, avermectins reduced the relative abundance of Microbacterium (Actinobacteria), which exhibited a strong antagonistic effect towards the fungus in in vitro and in vivo assays. The avermectin treatment led to an increased abundance of Chryseobacterium (Flavobacteria), which exerted a neutral effect on mycosis development. In addition, avermectin treatment led to an elevation of some subdominant bacteria (Pseudomonas) that interacted synergistically with the fungus. We suggest that avermectins change the bacterial community to favor the development of fungal infection.

Selection of entomopathogenic fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes) for the biocontrol of Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae) in Western Canada.

The mountain pine beetle, Dendroctonus ponderosae, has infested over ~16 Mha of pine forests in British Columbia killing >50% of mature lodgepole pine, Pinus contorta, trees in affected stands. At present, it is functionally an invasive species in Alberta, killing and reproducing in evolutionarily naïve populations of lodgepole pine (P. contorta), novel jack pine (P. banksiana), and their hybrids. The entomopathogenic fungus Beauveria bassiana has shown some potential as a biocontrol agent of several bark beetle species. In this study, nine isolates of B. bassiana were examined for insect virulence characteristics, including conidiation rate, pigmentation, and infection rate in laboratory-reared D. ponderosae, to assess for their potential as biocontrol agents. The strains were categorized into three phenotypic groups based on pigmentation, conidial density, and myceliation rate. Virulence screening utilizing insect-based agar medium (D. ponderosae and European honeybee Apis mellifera carcasses) revealed no difference in selection of fungal growth. However, infection studies on D. ponderosae and A. mellifera showed contrasting results. In vivo A. mellifera infection model revealed ~5% mortality, representing the natural death rate of the hive population, whereas laboratory-reared D. ponderosae showed 100% mortality and mycosis. The LT50 (median lethal time 50) ranges from 2 to 5 ± 0.33 days, and LT100 ranges from 4 to 6 ± 0.5 days. We discuss the selective advantages of the three phenotypic groups in terms of virulence, pigmentation, conidial abundance, and tolerance to abiotic factors like UV and host tree monoterpenes. These results can further provide insights into the development of several phenotypically diverse B. bassiana strains in controlling the spread of the invasive D. ponderosae in Western Canada. KEY POINTS: • Three B. bassiana morphotype groups have been demonstrated to kill D. ponderosae. • A range of effective lethal times (LT50 and LT100) was established against D. ponderosae. • Variable tolerance to UV light and pine monoterpenes were observed in B. bassiana.

Earthworms and their cutaneous excreta can modify the virulence and reproductive capability of entomopathogenic nematodes and fungi.

Earthworms are ecological engineers that can contribute to the displacement of biological control agents such as the entomopathogenic nematodes (EPNs) and fungi (EPF). However, a previous study showed that the presence of cutaneous excreta (CEx) and feeding behavior of the earthworm species Eisenia fetida (Haplotaxida: Lumbricidae) compromise the biocontrol efficacy of certain EPN species by reducing, for example, their reproductive capability. Whether this phenomenon is a general pattern for the interaction of earthworms-entomopathogens is still unknown. We hypothesized that diverse earthworm species might differentially affect EPN and EPF infectivity and reproductive capability. Here we investigated the interaction of different earthworm species (Eisenia fetida, Lumbricus terrestris, and Perionyx excavatus) (Haplotaxida) and EPN species (Steinernema feltiae, S. riojaense, and Heterorhabditis bacteriophora) (Rhabditida) or EPF species (Beauveria bassiana and Metarhizium anisopliae) (Hypocreales), in two independent experiments. First, we evaluated the application of each entomopathogen combined with earthworms or their CEx in autoclaved soil. Hereafter, we studied the impact of the earthworms' CEx on entomopathogens applied at two different concentrations in autoclaved sand. Overall, we found that the effect of earthworms on entomopathogens was species-specific. For example, E. fetida reduced the virulence of S. feltiae, resulted in neutral effects for S. riojaense, and increased H. bacteriophora virulence. However, the earthworm P. excavates increased the virulence of S. feltiae, reduced the activity of H. bacteriophora, at least at specific timings, while S. riojaense remained unaffected. Finally, none of the EPN species were affected by the presence of L. terrestris. Also, the exposure to earthworm CEx resulted in a positive, negative or neutral effect on the virulence and reproduction capability depending on the earthworm-EPN species interaction. Concerning EPF, the impact of earthworms was also differential among species. Thus, E. fetida was detrimental to M. anisopliae and B. bassiana after eight days post-exposure, whereas Lumbricus terrestris resulted only detrimental to B. bassiana. In addition, most of the CEx treatments of both earthworm species decreased B. bassiana virulence and growth. However, the EPF M. anisopliae was unaffected when exposed to L. terrestris CEx, while the exposure to E. fetida CEx produced contrasting results. We conclude that earthworms and their CEx can have positive, deleterious, or neutral impacts on entomopathogens that often coinhabit soils, and that we must consider the species specificity of these interactions for mutual uses in biological control programs. Additional studies are needed to verify these interactions under natural conditions.

Studies on biochemical and synergistic effects of immunosuppressive concentration of imidacloprid with Beauveria bassiana and Metarhizium anisopliae for enhancement of virulence against vector mosquito Culex quinquefasciatus.

In order to increase the virulence of two commonly used entomopathogens namely Beauveria bassiana and Metarhizium anisopliae for effective mosquito control programs, we developed new combined formulation by the use of immunosuppressive concentration of imidacloprid. Exposure of sublethal concentration (LC10 1.34 ppb) of imidacloprid to second instar larvae for 92 h that differently modulated the larval biochemical markers by decreasing the total protein (20.65% reduction), acetylcholinesterase (35.74% reduction) and increases the ß-carboxylesterase (26.59% increase) and acid phosphatase (30.69% increase) levels while no significant difference was noticed in alkaline phosphatase of C. quinquefasciatus. Further we demonstrated that the imidacloprid exposure brings about reduction in phenoloxidase level (39.48% decrease) and nitric oxide production (37.64% decrease) in larval homogenate over control. The reduction in viability of hemocytes (15.37% decrease) and phagocytic activity of hemocytes (32.18% decrease) was noticed in imidacloprid treatment. Moreover in laboratory condition, exposure of 1 × 107 spores/ml of B. bassiana (984) and M. anisopliae (6060) alone for 92 h cumulative toxicity assay exhibited larval mortality of 36.47% and 47.64% respectively against C. quinquefasciatus. However in the synergistic experimental studies with LC10 of imidacloprid and 1 × 107 spores/ml of B. bassiana or M. anisopliae to the larvae for 92 h cumulative assay brought 60% and 50.59% more insecticidal activity than the respective entomopathogens alone. The substantial increase of larvicidal activity noticed in the synergistic test conditions against larvae of C. quinquefasciatus revealed that the inclusion of sublethal concentration was proved to be useful for effective larval control.

Role of serine protease inhibitors in insect-host-pathogen interactions.

Serine protease inhibitors (serpins), evolutionary old, structurally conserved molecules, are a superfamily of proteins found in almost all living organisms. Serpins are relatively large, typically 350-500 amino acids in length, with three ß-sheets and seven to nine α-helices folding into a conserved tertiary structure with a reactive center loop. Serpins perform various physiological functions in insects, including development, digestion, host-pathogen interactions, and innate immune response. In insects, the innate immune system is characterized as the first and major defense system against the invasion of microorganisms. Serine protease cascades play a critical role in the initiation of innate immune responses, such as melanization and the production of antimicrobial peptides, and are strictly and precisely regulated by serpins. Herein, we provide a microreview on the role of serpins in the insect-host-pathogen interactions, emphasizing their role in immune responses, particularly in diamondback moth (Plutella xylostella), highlighting the important discoveries and also the gaps that remain to be explored in future studies.

Microbial insecticides in Iran: History, current status, challenges and perspective.

Biological control programs with arthropods have been in practice in Iran since the 1930s. However, development and registration of microbial biopesticides is much more recent. Currently, about 15 biopesticide products are registered or pending registration for commercial use on various crops. Products based on Bacillus thuringiensis subsp. kurstaki are most widely sold for lepidopteran pest control, followed by B. thuringiensis subsp. isralensis against dipteran pests in vector control programs. Additionally, mycoinsecticides based on Lecanicillium lecanii and Beauveria bassiana, against various arthropod pests, and a mycofungicide based on Trichoderma harzianum for controlling soilborne diseases are also registered. In Iran, the national Plant Protection Organization (PPO) manages regulation of microbial pesticides and the Pesticide Supervision Board within the PPO oversees registration of all pesticides. Currently, two Iranian companies produce microbial pesticides and two more companies are approved to start production in the near future. We review the history of microbial control of arthropod pests in Iran with examples of sustainable agricultural practices, the current status of the market and registration procedures for microbial pesticides, along with the challenges and opportunities for the advancement of microbial control in Iran.

Microbial biopesticides for insect pest management in India: Current status and future prospects.

The biopesticide industry in India is undergoing rapid change, reflecting increased global trade in agricultural commodities, a changing regulatory environment and evolving consumer preferences. Currently biopesticides comprise ≈ 5% of the Indian pesticide market, with at least 15 microbial species and 970 microbial formulations registered through the Central Insecticides Board and Registration Committee (CIBRC). As of 2017, over 200 products based on entomopathogenic fungi (Beauveria bassiana, B. brongniartii, Metarhizium anisopliae s.l., Lecanicillium lecanii and Hirsutella thompsonii) and nematicidal fungi (Purpureocillium lilacinum and Pochonia chlamydosporia) are registered for use against various arthropods and plant parasitic nematodes. Regarding bacteria, over 30 products based on Bacillus thuringiensis (Bt) subsp. kurstaki are registered against bollworms, loopers and other lepidopterans, while 12 based on Bt subsp. israelensis and three with Bt subsp. sphaericus have been used against mosquitoes. Two viruses are registered, namely Helicoverpa armigera nucleopolyhedrovirus (22 products) and Spodoptera litura nucleopolyhedrovirus (5 products) for use against bollworms and armyworms. Four entomopathogenic nematode species are sold in Indian market. These include long-lasting wettable powder formulations of Heterorhabditis indica developed by the ICAR-National Bureau of Agricultural Insect Resources, Bengaluru which have been distributed on a large scale to control white grubs and other sugarcane pests. Biopesticide research on the subcontinent is at a relatively early stage, but evolving rapidly, and focusing on indigenous entomopathogens. Despite onerous regulation, quality-control issues and limited large-scale production facilities, investment in domestic fermentation technologies, improved delivery systems, and promotion of biological control through private and public initiative will increase the share of microbial biopesticides in the country.

Microbial control of phytophagous invertebrate pests in South Africa: Current status and future prospects.

Invertebrate pests pose a significant threat to food security on the African continent. In response, South Africa has become one of the largest importers of chemical pesticides in sub-Saharan Africa, with several hundred active ingredients registered. To address the over-reliance on such chemicals, the South African Department of Agriculture, Forestry and Fisheries (DAFF) has eliminated or restricted several pesticides since the late 1970s. The recent launch of the South African National Bio-Economy Strategy and establishment of the South African Bioproducts Organisation (SABO), together with new guidelines for registration of biopesticides in 2015, also support this endeavour. Concurrently, entomopathogen-related research and bioproduct development has increased over the past decade. Currently, 31 products (seven manufactured locally) are registered under the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 of 1947. Commercially important microbes include Beauveria bassiana (Cordycipitaceae), Metarhizium anisopliae (Clavicipitaceae), Cydia pomonella granulovirus, Cryptophlebia leucotreta granulovirus, Helicoverpa armigera nucleopolyhedrovirus (Baculoviridae) and Bacillus thuringiensis subsp. kurstaki and B. thuringiensis subsp. aizawai (Bacillaceae). Both parasitic and entomopathogenic nematodes (EPNs) show potential for development as bioinsecticides with one commercial EPN product, based on Heterorhabditis bacteriophora (Heterorhabditidae), registered under the Act. Rapid scientific progression, supported by a favourable legislative environment, should facilitate further advances in microbial control of phytophagous invertebrate pests in South Africa.