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Background: Entomopathogenic nematodes (EPN) are used as a biological control agent for different insect pests in agriculture. The genera Heterorhabditis and Steinernema are the most used commercially. For an EPN species to be used as a biological controller, it is necessary to know its ecological aspects, including reproductive potential, movement capacity, and mean lethal concentration (LC50). These aspects were evaluated in three EPN strains isolated in Galleria mellonella larvae collected in the Lambayeque-Peru region, to determine if they are promising as biological controllers. The strains of EPN studied are Heterorhabditis sp. (PC9 strain), H. bacteriophora Poinar (PM10 strain), and Steinernema diaprepesi Nguyen y Duncan (SV19 strain). Results: Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) had high production of infective juveniles (IJs): 217.750 and 186.800, respectively, while S. diaprepesi (SV19 strain) only reached 84.150 IJs. The movement capacity of Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) reached a depth of 15 cm to parasitize G. mellonella larvae, while S. diaprepesi (SV19 strain) only reached 10 cm. In decreasing order, the LC50 value of S. diaprepesi (SV19 strain), Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) were: 24.03, 13.74, and 8.19 IJs/ml, respectively. Conclusions: Heterorhabditis sp. PC9 and H. bacteriophora PM10 are promising a biological control agent because they present great production of IJs, great displacement capacity, and high pathogenicity against G. mellonella. Additionally, both strains present a mixed search strategy or seeker-hunter (seeker-browser). [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs), especially Heterorhabditis bacteriophora, are promising candidates for biological control of Popillia japonica larvae. Thus, there is a need to study native strains to ensure biological agents adapted to specific environmental conditions to improve their effectiveness in field applications. This work aimed to test the pathogenicity of five Azorean isolates of H. bacteriophora strains to third‐instar larvae of P. japonica under laboratory and semi‐field conditions. All EPNs were able to quickly infect larvae with LT50's ranging between 3.66 and 4.54 days in controlled laboratory conditions. The semi‐field experiment consisted of an EPN application in buried tubes containing five larvae each in May and October. After 15 days, larvae were recovered and confirmed for nematode parasitism. In May, Az29, Az148, Az170, and Az171 displayed a mean of 37% infected larvae per tube. In contrast, EPNs showed a lower infection ability during the experiment in October, and only Az148 maintained the number of parasitized larvae, with a proportion of 40% of infectivity. The results suggest that native EPNs, like Az148, could be better adapted to climatic and edaphic conditions to control P. japonica larvae. [ABSTRACT FROM AUTHOR]

AbstractLeopard moth Zeuzera multistrigata (Lepidoptera: Cossidae) is a xylophagous insect whose larval stages are cryptic woodborers in apple and many other horticultural and forestry crops. The present study was carried out to test effectiveness of some biocontrol agents along with most effective pesticide against this pest on apple (cv. Royal Delicious) in Himachal Pradesh, India, for three consecutive years by injecting biocontrol agents/chemicals directly into galleries made by pest larvae. Investigations were conducted to observe the effect of Beauveria bassiana, Metarhizium anisopliae, Steinernemma feltiae, Heterorhabditis bacteriophora and azadirachtin along with a synthetic pesticide chlorpyriphos. The application of chlorpyriphos (0.04%) caused a 100%%larval mortality, whereas among the biocontrol agents H. bacteriophora (5000 IJs/gallery) exhibited the highest mortality of 66.7 to 80.0%% during these three years, which was significantly at par with application of azadirachtin (Neem baan) 1500 ppm @ 2 ml/Litre and S. feltiae @ 5000 IJs/gallery. The lowest mortality (33.3%) was observed with B. bassiana (5 g/Litre) for the first two years and with M. anisopliae (5 g/L) in the third year i.e. 40.0%. Application of entomopathogenic nematode H. bacteriophora (5000 IJs/gallery) is proven to be best among all biocontrol agents. [ABSTRACT FROM AUTHOR]

The Mediterranean Corn Borer (MCB), Sesamia nonagrioides, poses a significant threat to maize crops, necessitating effective pest management strategies. This study investigates the compatibility of two entomopathogenic nematode (EPN) isolates, Steinernema feltiae KV6 and Heterorhabditis bacteriophora EO7, with four registered insecticides for MCB control: deltamethrin, flubendiamide, spinetoram, and betacyfluthrin. The impact of these insecticides on EPN mortality, infectivity, and reproduction was assessed. Results indicate that deltamethrin exhibits the lowest toxicity to EPNs, with mortality rates of 1.3% for S. feltiae and 0.63% for H. bacteriophora at field dose (FD) after 24 h and 4.63% and 1.96%, respectively, after 48 h. In contrast, betacyfluthrin showed higher toxicity, with mortality rates of 38.04% and 14.17% for S. feltiae at 2FD and FD after 48 h. The infectivity assays demonstrated that deltamethrin-treated EPNs caused up to 100% mortality in MCB larvae, while the reproduction capacity varied significantly between the EPN species and insecticides. H. bacteriophora exhibited higher progeny production, especially in the presence of deltamethrin (87,900 IJs/larva). The findings suggest that integrating EPNs with selective insecticides like deltamethrin can enhance pest control efficacy and support sustainable agricultural practices. This study provides valuable insights for developing integrated pest management (IPM) strategies aimed at mitigating MCB infestations in maize while minimizing environmental impacts. [ABSTRACT FROM AUTHOR]

AbstractCarpophilus hemipterus (L.) (Coleoptera: Nitidulidae), a dried fruit beetle is a major pest on various grains and fruits all over the world and causes significant economic losses. Recently, due to the negative effects of pesticides on the environment and humans, biological control agents such as entomopathogenic nematodes (EPNs) used to control insects are gaining importance. The aim of this study was carried out to determine biocontrol potential of three local entomopathogenic nematode isolates against different stages of dried fruit beetle (larvae, pupae, and adults) under controlled conditions. S. carpocapsae isolate Bakışlı05, H. bacteriophora isolate Z-1 and H. bacteriophora isolate TOK-20 used in experiments. Isolates were applied at four different concentrations i.e. 0, 250, 500, and 1000 IJs/ml at 25 °C. Mortality rates of larvae, pupae, and adults of C. hemipterus were determined four times (24, 48, 72, and 96 h) following inoculation. The highest mortality rate of larvae of C. hemipterus was caused by Heterorhabditis bacteriophora isolate Z-1 with 98.67% mortality followed by H. bacteriophora isolate TOK-20 with 93.85% and then Steinernema carpocapsae isolate Bakışlı05 with 86.67% at the highest concentration (1000 IJs/ml). The highest mortality rate on C. hemipterus pupae was recorded at the highest concentration of S. carpocapsae isolate Bakışlı05, which was 48.00%, followed by H. bacteriophora isolate Z-1 and H. bacteriophora isolate TOK-20, which had mortality rates of 43.33% and 38.00%, respectively. Moreover, the highest adult mortality rate was determined at the maximum concentration of S. carpocapsae (Bakışlı05), with 42.67% among all EPN isolates tested. This study shows that the use of entomopathogenic nematodes (EPN) for the management of dried fruit beetle can be an alternative method to pest control. [ABSTRACT FROM AUTHOR]

With the loss of effective chemical controls of crop pests, a move towards biological controls is a way to future‐proof our agricultural system. Floral field margins have shown successes in reducing crop pests, though the effect may not be precise enough to control infestations in commercial crops. Entomopathogenic nematodes (EPNs) may provide a more species‐ and time‐specific control and combining these methods may have synergy. Three in‐field vegetation margins, divided into four plots each (two floral and two grass), were established in March 2022. Three strips of sprouting broccoli were planted parallel in April, May and June. Each strip had a split‐plot design, with eight replicates of four nematode treatments placed alongside each floral/grass plot: Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora and a nematode‐free control. Pest pressure was assessed using adult counts. Assessments of crop yield and crop damage associated specifically with the swede smidge (Contarinia nasturtii) were also made. It was found that utilising a combination of control measures was successful in controlling a wider range of pests, though the success of each control method was highly dependent on the time of crop plantings. Field margins had a significant influence on crop damage associated with the swede midge. The EPN H. bacteriophora was an effective control method for the cabbage stem flea beetle and the swede midge, as well as reducing crop damage and yield loss. Field margins and EPNs combined have an interactive effect on crop yield, highlighting the need for control methods to be tested in combination in future integrated pest management research to accurately understand their effects within an integrated system. [ABSTRACT FROM AUTHOR]

In the present work, laboratory assays were performed to appraise the biocontrol potential of Metarhabditis amsactae, a Rhabditid nematode, against fifth instar larvae of Corcyra cephalonica. Virulence was tested at four different doses, i.e. 20, 40, 80 and 160 IJs/L (infective juveniles per larva) and mortality was documented from 24 up to 96 h of nematode treatment. Concentration and time-based enhancement in larval mortality was observed with 100% mortality recorded at 160 IJs/L after 96 h. Even at 20 IJs/L concentration, 60% and 76.7% larval mortality was recorded after 72 and 96 h, respectively. At 80 IJs/L, the mortality increased from 33.3% at 48 h to more than 90% at 96 h of nematode inoculation. Whereas, at 40 IJs/L, it enhanced from 16.7% at 48 h to 83.3% at 96 h. The effect of M. amsactae infection on the immune system of C. cephalonica was also evaluated at a dose of 100 IJs/L after 12, 24, 36 and 48 h time intervals. Insect larvae displayed augmented levels of antioxidant and detoxifying enzymes. The peak activities of superoxide dismutase, catalase, ascorbate peroxidase, phenol oxidase and glutathione-S-transferase in infected larvae were observed after 36 h, whereas acetylcholine esterase levels peaked after 48 h, as compared to control. Malondialdehyde content was also increased post nematode infection. Thus the current study is the first report that depicts the significant bioefficacy and immunomodulatory effects of M. amsactae against C. cephalonica under laboratory conditions. However, further research to assess its efficiency under field conditions is required. [ABSTRACT FROM AUTHOR]

Simple Summary: Entomopathogenic nematodes and their symbiotic bacteria are widely utilized for biological control. However, whether nematode-derived signals influence the immune response of insects remains unexplored. In this study, we provide comprehensive insight into the interactions among symbiotic bacteria, nematode pheromone ascarosides, and the G. mellonella insect host. Our findings reveal that under the induction of Photorhabdus bacteria, ascarosides enhance the host's immunity response. Specifically, they suppress the intensity of body color change and increase the expression of related-immunity gene expression. Additionally, ascarosides reduce the Photorhabdus cell load and delay G. mellonella larval mortality. These results imply that G. mellonella larvae may employ nematode pheromones to enhance insect immunity in the presence of symbiotic bacteria, thereby enhancing the resistance to invasive bacteria. Insects protect themselves through their immune systems. Entomopathogenic nematodes and their bacterial symbionts are widely used for the biocontrol of economically important pests. Ascarosides are pheromones that regulate nematode behaviors, such as aggregation, avoidance, mating, dispersal, and dauer recovery and formation. However, whether ascarosides influence the immune response of insects remains unexplored. In this study, we co-injected ascarosides and symbiotic Photorhabdus luminescens subsp. kayaii H06 bacteria derived from Heterorhabditis bacteriophora H06 into the last instar larvae of Galleria mellonella. We recorded larval mortality and analyzed the expressions of AMPs, ROS/RNS, and LPSs. Our results revealed a process in which ascarosides, acting as enhancers of the symbiotic bacteria, co-induced G. mellonella immunity by significantly increasing oxidative stress responses and secreting AMPs (gallerimycin, gloverin, and cecropin). This led to a reduction in color intensity and the symbiotic bacteria load, ultimately resulting in delayed host mortality compared to either ascarosides or symbiotic bacteria. These findings demonstrate the cross-kingdom regulation of insects and symbiotic bacteria by nematode pheromones. Furthermore, our results suggest that G. mellonella larvae may employ nematode pheromones secreted by IJs to modulate insect immunity during early infection, particularly in the presence of symbiotic bacteria, for enhancing resistance to invasive bacteria in the hemolymph. [ABSTRACT FROM AUTHOR]

The cross-hybridization of American chestnut (Castanea dentata (Marsh.) Borkh.) with Chinese chestnut (Castanea mollissima Bl.) is a promising strategy for restoring a blight-resistant strain of this keystone species to the Appalachian mountains. To assess the ecological impacts of hybridization on invertebrate communities, we conducted a study across chestnut plots with varying degrees of hybridization (75%, 94%, or 100% American chestnut). Our findings indicate American chestnut hybridization impacted invertebrate communities above- and belowground. Aboveground insect community composition, insect herbivory, gall infestation, and belowground invertebrate diversity were all altered. While some of these differences could be explained by different growth habits or environmental differences, stark differences in Asian chestnut gall wasp infestation (Dryocosmus kuriphilus Yasumatsu.) suggest a genetic component. These results suggest that chestnut hybridization, and particularly expanded restoration efforts using chestnut hybrids, could impact invertebrate communities above- and belowground in addition to pest dynamics. Understanding these effects is crucial for successful chestnut restoration and ecosystem management. [ABSTRACT FROM AUTHOR]

Abstract Background Entomopathogenic nematodes (EPN) are used as a biological control agent for different insect pests in agriculture. The genera Heterorhabditis and Steinernema are the most used commercially. For an EPN species to be used as a biological controller, it is necessary to know its ecological aspects, including reproductive potential, movement capacity, and mean lethal concentration (LC50). These aspects were evaluated in three EPN strains isolated in Galleria mellonella larvae collected in the Lambayeque-Peru region, to determine if they are promising as biological controllers. The strains of EPN studied are Heterorhabditis sp. (PC9 strain), H. bacteriophora Poinar (PM10 strain), and Steinernema diaprepesi Nguyen y Duncan (SV19 strain). Results Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) had high production of infective juveniles (IJs): 217.750 and 186.800, respectively, while S. diaprepesi (SV19 strain) only reached 84.150 IJs. The movement capacity of Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) reached a depth of 15 cm to parasitize G. mellonella larvae, while S. diaprepesi (SV19 strain) only reached 10 cm. In decreasing order, the LC50 value of S. diaprepesi (SV19 strain), Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) were: 24.03, 13.74, and 8.19 IJs/ml, respectively. Conclusions Heterorhabditis sp. PC9 and H. bacteriophora PM10 are promising a biological control agent because they present great production of IJs, great displacement capacity, and high pathogenicity against G. mellonella. Additionally, both strains present a mixed search strategy or seeker-hunter (seeker-browser).

Abstract Background The fall armyworm (FAW), Spodoptera frugiperda (J.E. Nixon) (Lepidoptera: Noctuidae), is the major insect pest that infests cereal crops recently in African and Asian countries. The insect is polyphagous that attacks large numbers of host plants, especially maize and rice, causing considerable losses in their annual yield. The integrated pest management (IPM) of the insect depended mainly on insecticides and to some extent on biological control agents including insect pathogens (nematodes, fungi, bacteria and viruses). Results Different species of entomopathogens (nematodes, fungi, viruses and bacteria) infecting the insect could be isolated in such newly invaded countries. Laboratory and field experiments indicated that the insect was found to be susceptible to the isolated entomopathogens, and thus, they could be promising biocontrol agents against this insect. Conclusion This review article proved the susceptibility of S. frugiperda to the most of tested entomopathogens. However, more field studies have to be carried out in order to include such entomopathogens within integrated pest management programs against this insect pest.

Background: The fall armyworm (FAW), Spodoptera frugiperda (J.E. Nixon) (Lepidoptera: Noctuidae), is the major insect pest that infests cereal crops recently in African and Asian countries. The insect is polyphagous that attacks large numbers of host plants, especially maize and rice, causing considerable losses in their annual yield. The integrated pest management (IPM) of the insect depended mainly on insecticides and to some extent on biological control agents including insect pathogens (nematodes, fungi, bacteria and viruses). Results: Different species of entomopathogens (nematodes, fungi, viruses and bacteria) infecting the insect could be isolated in such newly invaded countries. Laboratory and field experiments indicated that the insect was found to be susceptible to the isolated entomopathogens, and thus, they could be promising biocontrol agents against this insect. Conclusion: This review article proved the susceptibility of S. frugiperda to the most of tested entomopathogens. However, more field studies have to be carried out in order to include such entomopathogens within integrated pest management programs against this insect pest. [ABSTRACT FROM AUTHOR]

Secondary metabolites, bioactive compounds produced by living organisms, can unveil symbiotic relationships in nature. In this study, soilborne entomopathogenic nematodes associated with symbiotic bacteria (Xenorhabdus stockiae and Photorhabdus luminescens) were extracted from solvent supernatant containing secondary metabolites, demonstrating significant inhibitory effects against E. coli, S. aureus, B. subtilus, P. mirabilis, E. faecalis, and P. stutzeri. The characterization of these secondary metabolites by Fourier transforms infrared spectroscopy revealed amine groups of proteins, hydroxyl and carboxyl groups of polyphenols, hydroxyl groups of polysaccharides, and carboxyl groups of organic acids. Furthermore, the obtained crude extracts were analyzed by high-performance liquid chromatography for the basic identification of potential bioactive peptides. Gas chromatography–mass spectrometry analysis of ethyl acetate extracts from Xenorhabdus stockiae identified major compounds including nonanoic acid derivatives, proline, paromycin, octodecanal derivatives, trioxa-5-aza-1-silabicyclo, 4-octadecenal, methyl ester, oleic acid, and 1,2-benzenedicarboxylicacid. Additional extraction from Photorhabdus luminescens yielded functional compounds such as indole-3-acetic acid, phthalic acid, 1-tetradecanol, nemorosonol, 1-eicosanol, and unsaturated fatty acids. These findings support the potential development of novel natural antimicrobial agents for future pathogen suppression. [ABSTRACT FROM AUTHOR]

The Guatemalan potato moth (Tecia solanivora) is one of the most destructive pests affecting potatoes in Colombia. Our objective was to evaluate the susceptibility of T. solanivora to a combination of entomopathogenic nematodes and entomopathogenic fungi, to study the interactions of these two agents under laboratory conditions. We evaluated the mortality of fourth instar larvae against 200 Infective Juveniles (IJs) per larva of ten strains of entomopathogenic nematodes, and 104–108 conidia per larva of Beauveria bassiana sensu lato Bb9205 and Metarhizium anisopliae sensu lato Ma9236. We found that Steinernema feltiae SC125 caused a mortality rate of 98.2% with an LC50 of 33 IJs/larva. M. anisopliae sensu lato Ma9236 achieved a mortality rate of 88.8% with an LC50 of 6.9 × 105 conidia/larva. We selected these strains for the interaction tests. We determined that the interaction test results were statistically additive regardless of any difference in application times of the entomopathogens and despite the observation of signs of infection in the hosts from both the nematode and the fungus. Despite not having found synergistic interactions between the evaluated control agents, these laboratory tests suggest a possible strategy of combining entomopathogenic nematode and fungi for biological management of the guatemalan moth T. solanivora in potato crops. [ABSTRACT FROM AUTHOR]

The Colorado potato beetle (CPB), Leptinotarsa decemlineata, poses a significant threat to potato crops globally and has developed resistance to numerous insecticides. Entomopathogenic nematodes (EPNs), from the genera Steinernema and Heterorhabditis, are promising biocontrol agents. This study aimed to identify the bacterial symbionts of ten native EPN isolates, evaluate the efficiency of cell free supernatants (CFSs) from their symbiotic bacteria against different developmental stages of CPB, and determine the effect of these CFSs on CPB developmental stages and lifespan. The recA gene region was utilized to determine the symbiotic bacteria of ten local EPNs. CFSs from these bacteria were applied orally and through contact to CPB's various developmental stages (L1/L2, L3/L4 larval stages, and adults). Mortalities, developmental transition times, and lifespans of adults were observed. The CFSs showed significant toxicity to CPB, with higher efficiency against young larvae. The CFSs exhibited cumulatively lethal effects over time, particularly on L1/L2 larval stages. CFSs from X. bovienii exhibited the highest efficacy. In all cases, where larvae received CFSs orally or by contact, they failed to develop into pupae and adults. In contrast, the transition periods of old larvae to pupal and adult stages were comparable to those of the control group. Lifespans of adults differed based on bacterial isolates and application methods. This study shows the potential efficacy of CFSs from Xenorhabdus and Photorhabdus as biocontrol agents against CPB, particularly in its young larval stages. Further research is needed to unravel the mechanisms behind these effects and examine the impact on CPB mating and oviposition behaviors. [ABSTRACT FROM AUTHOR]

Simple Summary: Thrips are among the most damaging insect pests affecting greenhouse horticulture crops. Research on biological control of these pests has focused on the dominant species, western flower thrips (WFT). However, a second species, onion thrips (OT), has become more prevalent in greenhouse ornamentals in Ontario, and biocontrol strategies for WFT do not control OT sufficiently to prevent crop losses. Although thrips' natural enemies have been tested against OT alone, there are few studies examining how effective they are for OT compared to WFT. We conducted several laboratory trials examining the relative efficacy of several natural enemies typically used in thrips biocontrol, including predators, parasitic nematodes, and a fungal-based biopesticide. All of the natural enemies tested were at least as effective at killing OT as they were for WFT in the laboratory, indicating that they all have the potential to manage both species equally well. Possible explanations why this potential is not realized in commercial greenhouse operations are explored. Thrips biocontrol research in greenhouse crops has focused primarily on western flower thrips (WFT; Frankliniella occidentalis). However, recent outbreaks of onion thrips (OT; Thrips tabaci) in Ontario, Canada, demonstrate that biocontrol-based IPM programs for WFT do not control OT sufficiently to prevent crop losses. A lack of comparative studies makes it difficult to determine which program components for WFT are failing for OT. We conducted several laboratory trials examining the extent to which commercial biocontrol products kill OT compared to WFT. These included phytoseiid mites (Amblyseius swirskii, Neoseiulus cucumeris, Amblydromalus limonicus, Iphiseius degenerans), a large generalist predator (Orius insidiosus), an entomopathogenic fungus (Beauveria bassiana strain GHA), and entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora). In no-choice trials, A. swirskii and O. insidiosus consumed more OT than WFT (first instars and adults, respectively). In choice trials, A. swirskii, N. cucumeris, and O. insidiosus consumed more OT than WFT. Steinernema feltiae caused higher mortality in OT than WFT. There was no difference in mortality between thrips species exposed to other biocontrol agents. This suggests available tools have the potential to manage OT as well as WFT. Possible explanations why this potential is not realized in commercial settings are explored. [ABSTRACT FROM AUTHOR]

Aphids (Hemiptera: Aphididae) are small, phloem-feeding insects that exhibit remarkable adaptability and resilience to various environmental conditions, including heat stress. Recent research has shed light on the role of bacterial symbionts in influencing the heat tolerance of aphids. Additionally, an intriguing avenue of investigation has explored how aphids can acquire bacterial symbionts through a unique mechanism involving soil nematodes. In this paper, we provide an in-depth overview of the interplay between heat stress, bacterial symbionts, and soil nematodes in the context of aphid biology. In reviewing the existing literature and collating available knowledge, we highlight the mechanisms by which bacterial symbionts contribute to aphid heat stress tolerance and examine the symbiont acquisition process facilitated by soil nematodes. Furthermore, we discuss the implications of these symbiotic associations in relation to the ecology, evolution, and agricultural management of a major globally expanding pest aphid, the corn leaf aphid, Rhopalosiphum maidis (Fitch). Overall, it may be concluded that both primary and secondary bacterial endosymbionts play a significant role in aphid biology with evolutionary consequences. These include adaptations through bacterial symbionts in terms of longevity and fecundity, heat shock tolerance, and resistance to fungal pathogens and primary hymenopterous wasp parasitoids. [ABSTRACT FROM AUTHOR]

The most important aim of the integrated management of forest insect pests remains the prevention of insect outbreaks, which are a consequence of the interaction of many factors in forest ecosystems, including species composition, age and health of the forest, soil type, the presence of natural enemies, and climatic factors. Integrated pest management until now has been achieved using measures aimed at shaping the functioning of stands in a changing environment. The aim of this review is to summarize research on the use of entomopathogens (microorganisms and nematodes) in the management of forest insect pests and to identify the principal knowledge gaps. We briefly describe the main research directions on the use of pathogens and nematodes to control insect pests and discuss limitations affecting their implementation. Research on entomopathogens for the biocontrol of forest insects has provided a wealth of knowledge that can be used effectively to reduce insect populations. Despite this, few entomopathogens are currently used in integrated pest management in forestry. They are applied in inoculation or inundation biocontrol strategies. While the use of entomopathogens in forest pest management shows great promise, practical implementation remains a distant goal. Consequently, sustainable reduction of forest pests, mainly native species, will be largely based on conservation biological control, which aims to modify the environment to favor the activity of natural enemies that regulate pest populations. This type of biocontrol can be supported by a range of silvicultural measures to increase the resilience of stands to insect infestations. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Global pesticide usage is 3.5 million tonnes at an average of 1.81kg/ha, while Indian usage is at 55,000 metric tonnes (2023) with an average of 0.517kg/ha. Compared to the pesticide market, the Indian biopesticide market remains small-cumulative annual biopesticide production at 9000 metric tonnes and a growth rate of 3-5% in consumption which is projected to reach a CGR of 8-10% by 2030. The utilization of biopesticides amounts to approximately 9% of overall pesticide use and is projected to increase to 50% of the total pesticide market by 2050. Among several microbial biocontrol agents, Entomopathogenic Nematodes (EPN) has been realised to be dependable IPM component against several insect pests. EPNs are soil-inhabiting beneficial nematodes that parasitize and kill insect pests, with immense potential for ecological services making them valuable tools in IPM. Worldwide, the demand for the development of EPN-containing products is mounting with several companies involved in their production, distribution and sales. India's estimated demand for EPN is 24,000 metric tonnes, while the current production is 1800 metric tonnes from 25-30 firms. In India and other developing countries, the current EPN production and supply chain are in their infancy and operate as a cottage industry. The market is flourishing with products that are spurious, expensive, and unregulated due to the wide gap between demand and availability of EPN products. The authors present an overview of the status and prospects of EPN as an IPM component, contemporary and futuristic issues for the transformation of the upcoming EPN industry to a self-reliant, self-sufficient and profitable enterprise and accomplish better uptake of EPN individually or in IPM. [ABSTRACT FROM AUTHOR]

Background: Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is a polyphagous, holometabolous and multivoltine insect that has spread from its supposed origin in sub-Saharan Africa to regions between 45° north and 45° south geographic latitude. It is considered an important economic pest worldwide, due to the direct damage caused to fruit, the high cost of its management and the restriction of the export of fruit from infested countries to markets in countries exempt from infestation. If no control measures are applied against this pest, C. capitata can destroy 50% of total production or 100% in "preferred" hosts. Currently, chemical insecticides are commonly applied to control medflies due to their rapid and satisfactory action; however, this method has many problems, including the destruction of non-target organisms, residues on agricultural products, environmental pollution and the development of insect resistance to insecticides. These negative effects have led scientists to search for more sustainable and ecological new control methods. Recently, great attention has been given to biological control, which has become a practical option for the ecological control of pests. Among biological control, entomopathogenic nematodes (EPNs) have great potential as control agents for soil-borne pests, like C. capitata. Main body: This review focuses particularly on the control of C. capitata, specifically emphasizing the use of EPNs as biological control agents and their integration into integrated pest management. It is apparent from this study that species of Steinernema sp. and Heterorhabditis sp. are highly virulent against the late instars larvae and adults of C. capitata under controlled laboratory conditions, as well as these EPNs significantly reduce the population of this pest in semi-field and field trials. The pathogenicity of entomopathogenic nematodes against C. capitata was influenced by natural physicochemical and anthropogenic factors. The most effective EPNs were found to be compatible with certain mineral, chemical and biological products with insecticidal activity, indicating that these products can be combined with EPNs in the context of integrated control. Conclusion: Based on this, EPNs have a promising future as an alternative to conventional chemicals against Mediterranean fruit fly. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPN) are potential nematodes as biological agents because they actively search for insect pests and are parasitic on their hosts. Two genera of EPN can be used as biological agents: Steinernema and Heterohabditis. It is necessary to explore local EPN on land suspected of having potential as a habitat for the nematodes. This study aimed to determine the genus and population of the EPN from corn and rice farms in Jember by identifying and characterizing them. The method used was the descriptive method. The EPN population was analyzed using the T-test. The results showed that the EPN from the corn and rice fields belonged to the Steinernema genus. EPN from the corn field isolate was characterized by a body length of 826,77 μm, body width of 47.14 μm, and tail length of 73.16 μm, while from the rice field, the isolate was characterized by a body length of 840.54 μm, body width of 37.70 μm, tail length 57.52 μm. EPN populations in maize and rice fields were not significantly different. [ABSTRACT FROM AUTHOR]

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Abstract Background The invasive peach fruit fly (PFF), Bactrocera zonata (Saunders) (Diptera: Tephritidae), is a native of Southeast Asia. Entomopathogens like nematodes, bacteria, viruses and fungi have been shown to be effective as a biological control agent against B. zonata. Evaluation the efficacy of different entomopathogenic nematode isolates (EPNs) belonged to the two families (Steinernematidae and Heterorhabditidae); (Steinernema carpocapsae (AII), S. carpocapsae (EGAZ10), Heterorhabditis bacteriophora (HP88) and H. indica (EGAZ2) was carried out against the full-grown larvae of B. zonata under laboratory, semi-field and field conditions. Results Data revealed that in all the tested nematode isolates succeeded to reduce the emerging of the PFF, B. zonata compared to controls with significant differences. The LC50 values were 794.3, 1063.2, 1249.8 and 1446.8 IJs/ml, for S. carpocapsae (AII), S. carpocapsae (EGAZ10), H. bacteriophora (HP88) and H. indica (EGAZ2), respectively, at 3 days post treatments. The strain, S. carpocapsae (AII) was effective than S. carpocapsae (EGAZ10). Also, the strain H. bacteriophora (HP88) was more effective than H. indica (EGAZ2). Therefore, the combination between the effective two steinernematid strains (S. carpocapsae (AII) & S. carpocapsae (EGAZ10)) and the two heterorhabditis strains (H. bacteriophora (HP88) & H. indica (EGAZ2)) was efficient in the semi-field experiment. In field condition, the combination of the two efficient strains S. carpocapsae (AII) and H. bacteriophora (HP88) at the concentration of 3000 IJs/ml was more effective in controlling B. zonata causing mortality 97.5%. The Co-Toxicity factor values were − 67.6 for the combination of S. carpocapsae (AII) with S. carpocapsae (EGAZ10) which recorded an antagonistic effect. Also, antagonistic effects were observed for the combined application of H. bacteriophora (HP88) with H. indica (EGAZ2) (− 66.6) in semi-field application; and the same effect was recorded for the combination of S. carpocapsae (AII) with H. bacteriophora (HP88) (− 42.6) in field application. Conclusion All EPNs’ experiments showed that the efficacy of foreign nematodes than the local ones. So, combination of the two highly effective imported strains gave satisfied results, especially in the field experiment.

Abstract Background Isolation of novel species of entomopathogenic nematodes (EPNs) with biocontrol potential against important insect pests is very important for the sustainable management of economic pests damaging food crops and providing protection to the agricultural environment. This study was aimed to new indigenous EPN isolates from Egyptian agricultural soils and studies its biocontrol potential for further use in the biological control programs. Five out of 15 soil samples obtained from a farm located at the Cairo–Alexandria desert highway was positive for the presence of EPN, using the greater wax moth baiting method. Results Sequencing of the internal transcribed spacer (ITS) region of 4 of the nematode isolates suggested that they belong to the species Heterorhabditis indica. However, one isolate does not show a high similarity to any of the H. indica previously recorded in the database of the Gen Bank and hence was identified as a new Heterorhabditis species and was deposited at the National Center for Biotechnology Information (NCBI) and registered under accession no. (OP555450) under the name of Heterorhabditis alii. This new species was also registered in the ZooBank under the registration link of: LSID urn: lsid: zoobank.org: act: 306F9D57-CC30-4B8E-8B19-4F0E42B08F34. No males were found in this species. Morphological characterization using the light microscope (LM) and scanning electron microscope (SEM) confirmed the identification of this nematode as a new species of the genus Heterorhabditis. Moreover, virulence of this new species against the fall armyworm (FAW), Spodoptera frugiperda (Smith 1797) (Lepidoptera: Noctuidae) was tested in comparison with the foreign EPN species, Heterorhabditis bacteriophora (HP88) and the local Heterorhabditis indica (Mango 2 isolate) and proved to be more effective against this devastative insect pest than the two compared species. Conclusions The present study found out a new species of the EPN genus, Heterorhabditis in Egypt. Our results were confirmed by both morphological and molecular analyses. The efficacy of this new species against the FAW proved to be a potent and safe biocontrol agent that can be used in biological control programs against this invasive insect pest of corn in Egypt and other global countries.

Summary: Considerable progress has been made in the surveying, taxonomy, screening, mass production and formulation of entomopathogenic nematodes (EPN) and their associated symbiotic bacteria in South Africa. Steinernema yirgalemense isolate 157-C is one of the most promising native EPN candidates with regards to virulence, its broad insect-host spectrum, and can be readily mass-produced and formulated into a commercial product. The banded fruit weevils, Phlyctinus callosus sensu stricto and Phlyctinus xerophilus , previously grouped together under the Phlyctinus callosus sensu lato species concept, are native entimine weevils of economic importance to deciduous fruit, grapevine and berries in the Western Cape province of South Africa. This study investigated potential differences in baseline susceptibility of larvae and pupae of the two weevil species to S. yirgalemense in laboratory screenings. The test arena used was 24-well bioassay plates, with an inoculation concentration of 200 infective juveniles (IJ) insect−1 for larvae and 100 IJ insect−1 for pupae. Infection was determined 48 h and 96 h after inoculation. Field-efficacy of S. yirgalemense , applied at a concentration of 60 IJ cm−2, against larvae of the two weevil species was determined in an ecologically relevant semi-field trial. In all cases in vitro mass-produced IJ of S. yirgalemense were used. No baseline differential susceptibility between P. callosus and P. xerophilus larvae was obtained in laboratory screenings. Phlyctinus pupae were approximately twice as susceptible compared to larvae, with significant differences between bioassay batches. Approximately 45% control of P. xerophilus larvae was obtained after 96 h of exposure to S. yirgalemense in the field, differing significantly from the control and P. callosus treatment. Low levels of Phlyctinus larval infection by native EPN (confirmed as Heterorhabditis bacteriophora from one P. xerophilus cadaver) occurred in both control and EPN treatment groups under field conditions. [ABSTRACT FROM AUTHOR]

Background: Isolation of novel species of entomopathogenic nematodes (EPNs) with biocontrol potential against important insect pests is very important for the sustainable management of economic pests damaging food crops and providing protection to the agricultural environment. This study was aimed to new indigenous EPN isolates from Egyptian agricultural soils and studies its biocontrol potential for further use in the biological control programs. Five out of 15 soil samples obtained from a farm located at the Cairo–Alexandria desert highway was positive for the presence of EPN, using the greater wax moth baiting method. Results: Sequencing of the internal transcribed spacer (ITS) region of 4 of the nematode isolates suggested that they belong to the species Heterorhabditis indica. However, one isolate does not show a high similarity to any of the H. indica previously recorded in the database of the Gen Bank and hence was identified as a new Heterorhabditis species and was deposited at the National Center for Biotechnology Information (NCBI) and registered under accession no. (OP555450) under the name of Heterorhabditis alii. This new species was also registered in the ZooBank under the registration link of: LSID urn: lsid: zoobank.org: act: 306F9D57-CC30-4B8E-8B19-4F0E42B08F34. No males were found in this species. Morphological characterization using the light microscope (LM) and scanning electron microscope (SEM) confirmed the identification of this nematode as a new species of the genus Heterorhabditis. Moreover, virulence of this new species against the fall armyworm (FAW), Spodoptera frugiperda (Smith 1797) (Lepidoptera: Noctuidae) was tested in comparison with the foreign EPN species, Heterorhabditis bacteriophora (HP88) and the local Heterorhabditis indica (Mango 2 isolate) and proved to be more effective against this devastative insect pest than the two compared species. Conclusions: The present study found out a new species of the EPN genus, Heterorhabditis in Egypt. Our results were confirmed by both morphological and molecular analyses. The efficacy of this new species against the FAW proved to be a potent and safe biocontrol agent that can be used in biological control programs against this invasive insect pest of corn in Egypt and other global countries. [ABSTRACT FROM AUTHOR]

Background: The invasive peach fruit fly (PFF), Bactrocera zonata (Saunders) (Diptera: Tephritidae), is a native of Southeast Asia. Entomopathogens like nematodes, bacteria, viruses and fungi have been shown to be effective as a biological control agent against B. zonata. Evaluation the efficacy of different entomopathogenic nematode isolates (EPNs) belonged to the two families (Steinernematidae and Heterorhabditidae); (Steinernema carpocapsae (AII), S. carpocapsae (EGAZ10), Heterorhabditis bacteriophora (HP88) and H. indica (EGAZ2) was carried out against the full-grown larvae of B. zonata under laboratory, semi-field and field conditions. Results: Data revealed that in all the tested nematode isolates succeeded to reduce the emerging of the PFF, B. zonata compared to controls with significant differences. The LC50 values were 794.3, 1063.2, 1249.8 and 1446.8 IJs/ml, for S. carpocapsae (AII), S. carpocapsae (EGAZ10), H. bacteriophora (HP88) and H. indica (EGAZ2), respectively, at 3 days post treatments. The strain, S. carpocapsae (AII) was effective than S. carpocapsae (EGAZ10). Also, the strain H. bacteriophora (HP88) was more effective than H. indica (EGAZ2). Therefore, the combination between the effective two steinernematid strains (S. carpocapsae (AII) & S. carpocapsae (EGAZ10)) and the two heterorhabditis strains (H. bacteriophora (HP88) & H. indica (EGAZ2)) was efficient in the semi-field experiment. In field condition, the combination of the two efficient strains S. carpocapsae (AII) and H. bacteriophora (HP88) at the concentration of 3000 IJs/ml was more effective in controlling B. zonata causing mortality 97.5%. The Co-Toxicity factor values were − 67.6 for the combination of S. carpocapsae (AII) with S. carpocapsae (EGAZ10) which recorded an antagonistic effect. Also, antagonistic effects were observed for the combined application of H. bacteriophora (HP88) with H. indica (EGAZ2) (− 66.6) in semi-field application; and the same effect was recorded for the combination of S. carpocapsae (AII) with H. bacteriophora (HP88) (− 42.6) in field application. Conclusion: All EPNs' experiments showed that the efficacy of foreign nematodes than the local ones. So, combination of the two highly effective imported strains gave satisfied results, especially in the field experiment. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes from the genus Steinernema (Nematoda: Steinernematidae) are capable of causing the rapid killing of insect hosts, facilitated by their association with symbiotic Gram-negative bacteria in the genus Xenorhabdus (Enterobacterales: Morganellaceae), positioning them as interesting candidate tools for the control of insect pests. In spite of this, only a limited number of species from this bacterial genus have been identified from their nematode hosts and their insecticidal properties documented. This study aimed to perform the genome sequence analysis of fourteen Xenorhabdus strains that were isolated from Steinernema nematodes in Argentina. All of the strains were found to be able of killing 7th instar larvae of Galleria mellonella (L.) (Lepidoptera: Pyralidae). Their sequenced genomes harbour 110 putative insecticidal proteins including Tc, Txp, Mcf, Pra/Prb and App homologs, plus other virulence factors such as putative nematocidal proteins, chitinases and secondary metabolite gene clusters for the synthesis of different bioactive compounds. Maximum-likelihood phylogenetic analysis plus average nucleotide identity calculations strongly suggested that three strains should be considered novel species. The species name for strains PSL and Reich (same species according to % ANI) is proposed as Xenorhabdus littoralis sp. nov., whereas strain 12 is proposed as Xenorhabdus santafensis sp. nov. In this work, we present a dual insight into the biocidal potential and diversity of the Xenorhabdus genus, demonstrated by different numbers of putative insecticidal genes and biosynthetic gene clusters, along with a fresh exploration of the species within this genus. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs) are a well-established biocontrol agent for insect pests. Using such a bio-agent to eliminate ticks has only been reported in a few cases. The current study intended to determine how the camel tick, Hyalomma dromedarii Koch, 1844 (Acari: Ixodidae), engorged female, was affected by various concentrations and timing of exposure to infected juveniles of five EPN isolates from two species. The six groups of engorged females, each with 25 ticks, were subjected to five concentrations of 50, 100, 150, 300, and 600 infective juveniles (IJs)/female in order to perform the work. Female mortality was observed every day for up to 72 h. The groups' average weights were statistically equivalent. The following biological parameters: initial weight of the female (mg); pre- and oviposition periods (days); survival period (days); initial weight of the egg mass (mg); hatching percentage (%H); nutritional efficacy index (NEI); and the control efficacy (%) of the engorged females as influenced by Heterorhabditis indica NEM-23 and H. bacteriophora NEM-26 infections were also measured. The results showed a linear increment in female mortality with the increase in EPN concentrations. Three days after being exposed to H. bacteriophora at 300 or 600 IJs/Female, all H. dromedarii individuals died, while the group containing 50 IJs/Female of the same EPN reached 75 %. All biological parameters were altered by EPNs, and there were extremely noticeable variations between the concentrations and the untreated group. These findings indicate that both Heterorhabditis isolates acted negatively on the parameters that were being observed, encouraging one to believe that this EPN was effective in controlling engorged females of H. dromedarii in the laboratory.

Analysis of biochemical energy reserves of five isolates of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) were conducted. SDS-PAGE of total protein of infective juveniles of all the five EPN isolates viz. 5S, 13S, 17H, 19H and 20H, differentiated them in to two genus. This study showed marked qualitative differences in IJs (Steinernema and Heterorhabditis) electrophoresis by SDS-PAGE resulting different band patterns. Therefore, it may be speculated that the nematode isolate 5S and 13S were may be the same species of Steinernema and isolate 17H, 19H and 20H were may be the same species of Heterorhabditis. [ABSTRACT FROM AUTHOR]

Abstract Background The emergence of pink bollworm (PBW), Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), in cotton due to Bt resistance and concealed feeding habit has created a need for alternative, eco-friendly, and cost-effective control methods. This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes (EPNs), Heterorhabditis indica, namely CICR-HI-CL and CICR-HI-MN, against PBW larvae and pupae under in-vitro conditions. Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd, 3rd, and 4th instar larvae, with median lethal dose (LD 50) values of 5.45, 4.45, and 4.60 infective juveniles (IJs) per larva, respectively. In case of pupal bioassay, both EPN strains demonstrated greater virulence when applied directly (LD 50 values: 29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN, respectively) compared to soil application (147.84 and 272.38 IJs per pupa). Both EPN strains successfully penetrated and reproduced on 4th instar larvae, resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva. Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H. indica (CICR-HI-CL and CICR-HI-MN) against PBW, a dreaded pest of cotton. Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply, sustain and perpetuate on larval and pupal stages of PBW. The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate. The soil-dwelling life stages viz., last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H. indica for sustainable management of PBW in the cotton ecosystem. However, before taking these EPN strains to field for managing PBW, detailed studies investigating their biocontrol potential against PBW under field conditions are needed.

As trophic organisms, nematodes play an essential role in the soil environment: they mineralize nutrients into plant-available forms, are a food source for other soil organisms, and feed on pathogenic organisms and plant pests, therefore regulating populations of soil microorganisms. The plant-parasitic nematodes are important pests of crops. Nanoparticles (NP) are increasingly used in agriculture and other production sectors. They are present in the soil, not necessarily in trace amounts, and can affect various soil organisms, including nematodes. In this article, the effects of silver (Ag), gold (Au), and platinum (Pt) nanoparticles on the mortality and reproduction activity of selected nematode species from two trophic groups: entomopathogenic nematodes (EPN) (Heterorhabditis bacteriophora and Steinernema feltiae) and plant parasitic nematodes (PPN) (Xiphinema diversicaudatum, Ditylenchus dipsaci, Heterodera schachtii) were studied under laboratory conditions. All nanoparticles decreased the nematode population to an extent depending on the nematode species, nanoparticle type, and exposure time. AgNP had the greatest nematicidal effect, except for AuNP, which reduced the population of H. schachtii the most. The greatest sensitivity to AgNP was observed in X. diversicaudatum (100% mortality), D. dipsaci (90% mortality), and 37 to 13% mortality in other species. Effect of AuNP and PtNP on entomopathogenic nematodes was comparable to the control, not treated with nanoparticles. AuNP and PtNP similarly influenced nematode mortality. However, the effect of nanoparticles on new generations of entomopathogenic nematodes developing in host larvae Galleria mellonella was inconclusive. All nanoparticles decreased the number of larvae of S. feltiae and increased the number of H. bacteriophora migrating outside the cadavers compared to the control.

The infective juveniles (IJs) of entomopathogenic nematode (EPN) Heterorhabditis bacteriophora find and infect their host insects in heterogeneous soil ecosystems by sensing a universal host cue (CO2) or insect/plant-derived odorants, which bind to various sensory receptors, including G protein-coupled receptors (GPCRs). Nematode chemosensory GPCRs (NemChRs) bind to a diverse set of ligands, including odor molecules. However, there is a lack of information on the NemChRs in EPNs. Here we identified 21 GPCRs in the H. bacteriophora genome sequence in a triphasic manner, combining various transmembrane detectors and GPCR predictors based on different algorithms, and considering inherent properties of GPCRs. The pipeline was validated by reciprocal BLAST, InterProscan, GPCR-CA, and NCBI CDD search. Functional classification of predicted GPCRs using Pfam revealed the presence of four NemChRs. Additionally, GPCRs were classified into various families based on the reciprocal BLAST approach into a frizzled type, a secretin type, and 19 rhodopsin types of GPCRs. Gi/o is the most abundant kind of G-protein, having a coupling specificity to all the fetched GPCRs. As the 21 GPCRs identified are expected to play a crucial role in the host-seeking behavior, these might be targeted to develop novel insect-pest management strategies by tweaking EPN IJ behavior, or to design novel anthelminthic drugs. Our new and stringent GPCR detection pipeline may also be used to identify GPCRs from the genome sequence of other organisms.

Abstract Background Gonioctena fornicata (Brüggemann, 1873) (Coleoptera: Chrysomelidae) inflicts substantial crop damage by consuming alfalfa leaves. The main aim of the study was to develop an efficient, sustainable control method against the pest, considering entomopathogenic nematodes (EPNs) as a potential control agent against soil-dwelling insect pests. This study investigated the impact of two native entomopathogenic nematodes (EPNs), Heterorhabditis bacteriophora (isolate Z-1) and Steinernema feltiae (isolate A-16), on mature larvae and adults of G. fornicata. Concentrations of 250, 500, and 1000 IJs/ml were used for adult and larval stages, and mortality rate was determined at the end of 144 h for larvae and 240 h for adults. Results The highest effect was 94.7% at 120 h for isolate Z-1 and 91.0% at 168 h for isolate A-16 at a concentration of 1000 IJs/ml for adult stages. The highest effect on larval stage was 97.6% at 96 h for isolate Z-1 and 85.8% at 120 h for isolate A-16 at the concentration of 1000 IJs/ml. On the adult stage, isolate Z-1 showed 50.0–67.1% effect at concentrations of 250 and 500 IJs/ml, respectively, while isolate A-16 showed an effect ranging from 46.7 to 63.6%. In the larval stage, isolate Z-1 caused 39.7–77.6% mortality at 250 and 500 IJs/ml concentrations, respectively, while the rate was 32.9–63.9% for isolate A-16. In the trial, isolate Z-1 showed a high efficacy in both stages of G. fornicata. Conclusions This study represents the first laboratory investigation encompassing both adult and mature larval stages of G. fornicata. The obtained data offer valuable insights for alternative control strategies targeting G. fornicata.

Abstract Background Nematodes of the genus Heterorhabditis are important biocontrol agents as they form a lethal combination with their symbiotic Photorhabdus bacteria against agricultural insect pests. This study describes a new species of Heterorhabditis. Methods Six Heterorhabditis nematode populations were recovered from agricultural soils in Jammu and Kashmir, India. An initial examination using mitochondrial and nuclear genes showed that they belong to a new species. To describe this new species, a variety of analyses were conducted, including reconstructing phylogenetic relationships based on multiple genes, characterizing the nematodes at the morphological and morphometric levels, performing self-crossing and cross-hybridization experiments, and isolating and characterizing their symbiotic bacteria. Results The newly discovered species, Heterorhabditis casmirica n. sp., shares 94% mitochondrial cytochrome C oxidase subunit I gene (COI) sequence identity with Heterorhabditis bacteriophora and Heterorhabditis ruandica, and 93% with Heterorhabditis zacatecana. Morphologically, it differs from H. bacteriophora in its infective juvenile phasmids (present vs. inconspicuous) and bacterial pouch visibility in the ventricular portion of the intestine (invisible vs. visible); genital papilla 1 (GP1) position (at manubrium level vs. more anterior), and in its b ratio (body length/neck length), c ratio (tail length/bulb width), and D% [(excretory pore/neck length) × 100]. Other morphological differences include anterior end to the nerve ring distance (77–100 vs. 121–130 μm), V% [(anterior end of vulva/body length) × 100] (46–57 vs. 41–47) in hermaphroditic females; rectum size (slightly longer than the anal body diameter vs. about three times longer), phasmids (smaller vs. inconspicuous), body length (0.13–2.0 vs. 0.32–0.39 mm), body diameter (73–150 vs. 160–220 μm), anterior end to the excretory pore distance (135–157 vs. 174–214 μm), and demanian ratios in amphimictic females. Morphological differences with H. ruandica and H. zacatecana were also observed. Furthermore, H. casmirica n. sp. did not mate or produce fertile progeny with other Heterorhabditis nematodes reported from India. It was also discovered that H. casmirica n. sp. is associated with 'Photorhabdus laumondii subsp. clarkei symbiotic bacteria. Conclusions The discovery of H. casmirica n. sp. provides novel insights into the diversity and evolution of Heterorhabditis nematodes and their symbiotic bacteria. This new species adds to the catalog of entomopathogenic nematodes in India. Graphical Abstract

The Mediterranean Corn Borer (MCB), Sesamia nonagrioides, poses a significant threat to maize crops, necessitating effective pest management strategies. This study investigates the compatibility of two entomopathogenic nematode (EPN) isolates, Steinernema feltiae KV6 and Heterorhabditis bacteriophora EO7, with four registered insecticides for MCB control: deltamethrin, flubendiamide, spinetoram, and betacyfluthrin. The impact of these insecticides on EPN mortality, infectivity, and reproduction was assessed. Results indicate that deltamethrin exhibits the lowest toxicity to EPNs, with mortality rates of 1.3% for S. feltiae and 0.63% for H. bacteriophora at field dose (FD) after 24 h and 4.63% and 1.96%, respectively, after 48 h. In contrast, betacyfluthrin showed higher toxicity, with mortality rates of 38.04% and 14.17% for S. feltiae at 2FD and FD after 48 h. The infectivity assays demonstrated that deltamethrin-treated EPNs caused up to 100% mortality in MCB larvae, while the reproduction capacity varied significantly between the EPN species and insecticides. H. bacteriophora exhibited higher progeny production, especially in the presence of deltamethrin (87,900 IJs/larva). The findings suggest that integrating EPNs with selective insecticides like deltamethrin can enhance pest control efficacy and support sustainable agricultural practices. This study provides valuable insights for developing integrated pest management (IPM) strategies aimed at mitigating MCB infestations in maize while minimizing environmental impacts.

The cross-hybridization of American chestnut (Castanea dentata (Marsh.) Borkh.) with Chinese chestnut (Castanea mollissima Bl.) is a promising strategy for restoring a blight-resistant strain of this keystone species to the Appalachian mountains. To assess the ecological impacts of hybridization on invertebrate communities, we conducted a study across chestnut plots with varying degrees of hybridization (75%, 94%, or 100% American chestnut). Our findings indicate American chestnut hybridization impacted invertebrate communities above- and belowground. Aboveground insect community composition, insect herbivory, gall infestation, and belowground invertebrate diversity were all altered. While some of these differences could be explained by different growth habits or environmental differences, stark differences in Asian chestnut gall wasp infestation (Dryocosmus kuriphilus Yasumatsu.) suggest a genetic component. These results suggest that chestnut hybridization, and particularly expanded restoration efforts using chestnut hybrids, could impact invertebrate communities above- and belowground in addition to pest dynamics. Understanding these effects is crucial for successful chestnut restoration and ecosystem management.

Insects protect themselves through their immune systems. Entomopathogenic nematodes and their bacterial symbionts are widely used for the biocontrol of economically important pests. Ascarosides are pheromones that regulate nematode behaviors, such as aggregation, avoidance, mating, dispersal, and dauer recovery and formation. However, whether ascarosides influence the immune response of insects remains unexplored. In this study, we co-injected ascarosides and symbiotic Photorhabdus luminescens subsp. kayaii H06 bacteria derived from Heterorhabditis bacteriophora H06 into the last instar larvae of Galleria mellonella. We recorded larval mortality and analyzed the expressions of AMPs, ROS/RNS, and LPSs. Our results revealed a process in which ascarosides, acting as enhancers of the symbiotic bacteria, co-induced G. mellonella immunity by significantly increasing oxidative stress responses and secreting AMPs (gallerimycin, gloverin, and cecropin). This led to a reduction in color intensity and the symbiotic bacteria load, ultimately resulting in delayed host mortality compared to either ascarosides or symbiotic bacteria. These findings demonstrate the cross-kingdom regulation of insects and symbiotic bacteria by nematode pheromones. Furthermore, our results suggest that G. mellonella larvae may employ nematode pheromones secreted by IJs to modulate insect immunity during early infection, particularly in the presence of symbiotic bacteria, for enhancing resistance to invasive bacteria in the hemolymph.

Background: The emergence of pink bollworm (PBW), Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), in cotton due to Bt resistance and concealed feeding habit has created a need for alternative, eco-friendly, and cost-effective control methods. This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes (EPNs), Heterorhabditis indica, namely CICR-HI-CL and CICR-HI-MN, against PBW larvae and pupae under in-vitro conditions. Results: The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd, 3rd, and 4th instar larvae, with median lethal dose (LD50) values of 5.45, 4.45, and 4.60 infective juveniles (IJs) per larva, respectively. In case of pupal bioassay, both EPN strains demonstrated greater virulence when applied directly (LD50 values: 29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN, respectively) compared to soil application (147.84 and 272.38 IJs per pupa). Both EPN strains successfully penetrated and reproduced on 4th instar larvae, resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva. Conclusion: The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H. indica (CICR-HI-CL and CICR-HI-MN) against PBW, a dreaded pest of cotton. Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply, sustain and perpetuate on larval and pupal stages of PBW. The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate. The soil-dwelling life stages viz., last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H. indica for sustainable management of PBW in the cotton ecosystem. However, before taking these EPN strains to field for managing PBW, detailed studies investigating their biocontrol potential against PBW under field conditions are needed. [ABSTRACT FROM AUTHOR]

Background: Gonioctena fornicata (Brüggemann, 1873) (Coleoptera: Chrysomelidae) inflicts substantial crop damage by consuming alfalfa leaves. The main aim of the study was to develop an efficient, sustainable control method against the pest, considering entomopathogenic nematodes (EPNs) as a potential control agent against soil-dwelling insect pests. This study investigated the impact of two native entomopathogenic nematodes (EPNs), Heterorhabditis bacteriophora (isolate Z-1) and Steinernema feltiae (isolate A-16), on mature larvae and adults of G. fornicata. Concentrations of 250, 500, and 1000 IJs/ml were used for adult and larval stages, and mortality rate was determined at the end of 144 h for larvae and 240 h for adults. Results: The highest effect was 94.7% at 120 h for isolate Z-1 and 91.0% at 168 h for isolate A-16 at a concentration of 1000 IJs/ml for adult stages. The highest effect on larval stage was 97.6% at 96 h for isolate Z-1 and 85.8% at 120 h for isolate A-16 at the concentration of 1000 IJs/ml. On the adult stage, isolate Z-1 showed 50.0–67.1% effect at concentrations of 250 and 500 IJs/ml, respectively, while isolate A-16 showed an effect ranging from 46.7 to 63.6%. In the larval stage, isolate Z-1 caused 39.7–77.6% mortality at 250 and 500 IJs/ml concentrations, respectively, while the rate was 32.9–63.9% for isolate A-16. In the trial, isolate Z-1 showed a high efficacy in both stages of G. fornicata. Conclusions: This study represents the first laboratory investigation encompassing both adult and mature larval stages of G. fornicata. The obtained data offer valuable insights for alternative control strategies targeting G. fornicata. [ABSTRACT FROM AUTHOR]

Background: Nematodes of the genus Heterorhabditis are important biocontrol agents as they form a lethal combination with their symbiotic Photorhabdus bacteria against agricultural insect pests. This study describes a new species of Heterorhabditis. Methods: Six Heterorhabditis nematode populations were recovered from agricultural soils in Jammu and Kashmir, India. An initial examination using mitochondrial and nuclear genes showed that they belong to a new species. To describe this new species, a variety of analyses were conducted, including reconstructing phylogenetic relationships based on multiple genes, characterizing the nematodes at the morphological and morphometric levels, performing self-crossing and cross-hybridization experiments, and isolating and characterizing their symbiotic bacteria. Results: The newly discovered species, Heterorhabditis casmirica n. sp., shares 94% mitochondrial cytochrome C oxidase subunit I gene (COI) sequence identity with Heterorhabditis bacteriophora and Heterorhabditis ruandica, and 93% with Heterorhabditis zacatecana. Morphologically, it differs from H. bacteriophora in its infective juvenile phasmids (present vs. inconspicuous) and bacterial pouch visibility in the ventricular portion of the intestine (invisible vs. visible); genital papilla 1 (GP1) position (at manubrium level vs. more anterior), and in its b ratio (body length/neck length), c ratio (tail length/bulb width), and D% [(excretory pore/neck length) × 100]. Other morphological differences include anterior end to the nerve ring distance (77–100 vs. 121–130 μm), V% [(anterior end of vulva/body length) × 100] (46–57 vs. 41–47) in hermaphroditic females; rectum size (slightly longer than the anal body diameter vs. about three times longer), phasmids (smaller vs. inconspicuous), body length (0.13–2.0 vs. 0.32–0.39 mm), body diameter (73–150 vs. 160–220 μm), anterior end to the excretory pore distance (135–157 vs. 174–214 μm), and demanian ratios in amphimictic females. Morphological differences with H. ruandica and H. zacatecana were also observed. Furthermore, H. casmirica n. sp. did not mate or produce fertile progeny with other Heterorhabditis nematodes reported from India. It was also discovered that H. casmirica n. sp. is associated with Photorhabdus luminescence subsp. clarkei symbiotic bacteria. Conclusions: The discovery of H. casmirica n. sp. provides novel insights into the diversity and evolution of Heterorhabditis nematodes and their symbiotic bacteria. This new species adds to the catalog of entomopathogenic nematodes in India. [ABSTRACT FROM AUTHOR]

Combining different biocontrol agents (BCA) is an approach to increase efficacy and reliability of biological control. If several BCA are applied together, they have to be compatible and ideally work together. We studied the interaction of a previously selected BCA consortium of entomopathogenic pseudomonads (Pseudomonas chlororaphis), nematodes (Steinernema feltiae associated with Xenorhabdus bovienii), and fungi (Metarhizium brunneum). We monitored the infection course in a leaf- (Pieris brassicae) and a root-feeding (Diabrotica balteata) pest insect after simultaneous application of the three BCA as well as their interactions inside the larvae in a laboratory setting. The triple combination caused the highest mortality and increased killing speed compared to single applications against both pests. Improved efficacy against P. brassicae was mainly caused by the pseudomonad-nematode combination, whereas the nematode-fungus combination accelerated killing of D. balteata. Co-monitoring of the three BCA and the nematode-associated Xenorhabdus symbionts revealed that the four organisms are able to co-infect the same larva. However, with advancing decay of the cadaver there is increasing competition and cadaver colonization is clearly dominated by the pseudomonads, which are known for their high competitivity in the plant rhizosphere. Altogether, the combination of the three BCA increased killing efficacy against a Coleopteran and a Lepidopteran pest which indicates that this consortium could be applied successfully against a variety of insect pests. [ABSTRACT FROM AUTHOR]

The integration of chemical insecticides with the biocontrol agent, entomopathogenic nematodes (EPNs) belonging to the Heterorhabditidae family, necessitates an understanding of the potential adverse effects of these insecticides on the biocontrol agent. Therefore, the primary objective of this research was to investigate the impact of two organophosphates (profenofos and chlorpyrifos), a carbamate (methomyl), and two pyrethroids (lambda-cyhalothrin and deltamethrin) on the viability and virulence of three strains of EPNs: Heterorhabditis sp. NEM 08, Heterorhabditis sp. NEM 15, and Heterorhabditis bacteriophora HP88. This investigation involved assessing their action on viability and infectivity toward the last instar larvae of Galleria mellonella upon exposure to recommended field rates for varying durations: 6 hours, 24 hours, and 48 hours. The results concerning EPN viability revealed that profenofos caused the most significant reduction in EPN viability, ranging from 44.9% to 65.9% after 48 hours of exposure. Additionally, the EPN strains exhibited varying levels of tolerance. Profenofos also had the highest adverse impact on infectivity, resulting in reductions ranging from 65.9% to 82.2% after 48 hours of exposure. Chlorpyrifos followed, which causing reductions in infectivity ranging from 25% to 55.6% after 48 hours of exposure. In contrast, Lambda-cyhalothrin had the least adverse effect on EPN viability and infectivity. Furthermore, it was observed that prolonged exposure time intensified the adverse effects on EPN viability and infectivity. These findings provide valuable insights for the integrated use of these neurotoxic insecticides with EPNs in insect control programs, helping in the selection of the most tolerant EPN strains for this purpose. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes have been used in biological control for some time and are an alternative for the control of insect pests, but during their implementation, situations have arisen that can be improved. These vary with each species and include their production and storage. Oscheius myriophila, an entomopathogenic nematode (EPN), was monitored for its performance when produced in vivo, as well as its development using Galleria mellonella larvae, using the MC5-2014 strain isolated from soil samples in the municipality of Tepalcingo, Morelos, México. For a study with native strains of EPNs, a wide range of tests must be conducted because the required conditions can be very specific. In vivo production was quantified at initial infective juvenile (IJ) inocula of 50, 100 and 500, and we obtained the same production for the three inocula. The life cycle of the EPNs lasted 12 days, and two generations were observed in which adults were found at days 5 and 9. Both evaluations were performed at a temperature of 27 °C in G. mellonella larvae. In addition, the temperatures of 8, 12, 20 and 24 °C were evaluated for their storage, and we observed that the EPNs can be kept for at least 6 months, maintaining a survival rate of 58.67% and a good infective capacity at a temperature of 12 °C, remaining above 60%. [ABSTRACT FROM AUTHOR]

Steinernema glaseri is a potential biocontrol agent against white grubs of the Phyllophaga spp. complex; however, its suitability for in vitro multiplication has been scarcely investigated. In this study, the effects of the surface culture of NJ-43 strain with its symbiotic bacteria Xenorhabdus poinarii on egg-yolk agar (P2), chicken-liver agar and nutrient meat-peptone (MP) agar on infective juvenile (IJ) productivity and their virulence against Galleria mellonella larvae were investigated. The bacteria on the surface of the agar were first incubated in darkness at 30 °C for 54-102 h, and then 100 surface-sterilised IJs were added. After two harvests, the accumulated productivity was higher on chicken-liver agar (536 × 103 IJs/m2 day) and P2 agar (534 × 103 IJs/m2 day) than on nutrient MP agar (58 × 103 IJs/m2 day). The mean virulence of the in vitro produced IJs was 46-60% and showed no statistically significant difference among the three culture media. In conclusion, the maximum multiplication factor of S. glaseri NJ-43 on solid media was 385, and its original virulence was retained.

Secondary metabolites, bioactive compounds produced by living organisms, can unveil symbiotic relationships in nature. In this study, soilborne entomopathogenic nematodes associated with symbiotic bacteria (Xenorhabdus stockiae and Photorhabdus luminescens) were extracted from solvent supernatant containing secondary metabolites, demonstrating significant inhibitory effects against E. coli, S. aureus, B. subtilus, P. mirabilis, E. faecalis, and P. stutzeri. The characterization of these secondary metabolites by Fourier transforms infrared spectroscopy revealed amine groups of proteins, hydroxyl and carboxyl groups of polyphenols, hydroxyl groups of polysaccharides, and carboxyl groups of organic acids. Furthermore, the obtained crude extracts were analyzed by high-performance liquid chromatography for the basic identification of potential bioactive peptides. Gas chromatography–mass spectrometry analysis of ethyl acetate extracts from Xenorhabdus stockiae identified major compounds including nonanoic acid derivatives, proline, paromycin, octodecanal derivatives, trioxa-5-aza-1-silabicyclo, 4-octadecenal, methyl ester, oleic acid, and 1,2-benzenedicarboxylicacid. Additional extraction from Photorhabdus luminescens yielded functional compounds such as indole-3-acetic acid, phthalic acid, 1-tetradecanol, nemorosonol, 1-eicosanol, and unsaturated fatty acids. These findings support the potential development of novel natural antimicrobial agents for future pathogen suppression.