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Sixteen isolates of bacteria obtained from the entomopathogenic nematode (Heterorhabditis sp.) infected cadavers of Galleria mellonella larvae were identified following phenotypic characterization and molecular analysis of 16S rRNA. Two isolates were identified as the symbiotic bacterium, Photothabdus luminescens, while 14 other isolates were represented by nine species of nonsymbiotic bacteria viz., Stenotrophomonas maltophilia, Alcaligenes aquatilis, Brevundimonas diminuta, Brucella pseudointermedia, Ochrobactrum sp., Brucella pseudogrignonensis, Brucella anthropic, Pseudomonas azatoformans and Pseudomonas lactis. The phylogenetic analysis confirmed the evolutionary relationship between P. luminescens and Pseudomonas spp. The study also found a close relationship among the nonsymbiotic bacteria such as A. aquatilis, B. diminuta, Ochrobactrum sp., and Brucella spp. P. luminescens has been documented for its insecticidal effects against a wide range of insects. The two local isolates obtained in this study may be explored for their biocontrol potential against major pests of the region. Further, the association of nonsymbiotic bacteria with the EPN may be investigated. [ABSTRACT FROM AUTHOR]

Efficacy of two Indian isolates of entomopathogenic nematodes (EPNs) viz., Heterorhabditis bacteriophora MK256358 and Steinernema feltiae MK256355 were tested in laboratory against the larvae of cabbage butterfly, Pieris brassicae. Larval mortality was found directly proportional to initial inoculum level of infective juveniles (IJs). Susceptibility of larvae varied with respect to their variable size. H. bacteriophora MK256358 @ 25 IJs/larva caused 100% mortality to 3rd instar larvae at 72 h but @ 75 IJs/larva, the same mortality was achieved in 48 h. S. feltiae MK256355 @ 100 IJs/larva caused 100% mortality to 3rd instar larvae of P. brassicae at 48 h. H. bacteriophora MK256358 @ 25 and 100 IJs/larva resulted in 100% mortality to 4th and 5th instar larvae, respectively at 72 h, however S. feltiae MK256355 was unable to cause 100% mortality to either 4th or 5th instar larvae at any inoculum level or time period used in the study. LD50 and LT50 values of H. bacteriophora MK256358 were lower than S. feltiae MK256355 indicating that less nematode dose and time is required to kill 50% pest population. Reproduction capacity of nematode within the host was directly proportional to individual larval size and nematode inoculum level and for H. bacteriophora MK256358, it was higher and statistically significant (P ≤ 0.05) from S. feltiae MK256355. Our experimental findings open new avenues for utilization of EPNs against P. brassicae and set the basis for safe insect pest management programme. [ABSTRACT FROM AUTHOR]

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]

Cole crops, the most important and attractive vegetables, belonging to the family Cruciferae are widely grown all over the world. In India, their annual production has been reported to be about 191.77 million metric tons, so chips into the economy by a huge amount. Pieris brassicae, one of the dreaded insect pests incur damage to different vegetables to a tune of 40%. To curb this pest damage various synthetic insecticides are applied, albeit showing promising results yet posing drastic negative imprints on non-target organisms, environment and pest resistance. These drawbacks demand a perfect alternative which seals all the glitches created by the chemical insecticides. For this Infective Juveniles (IJs) of Entomopathogenic Nematodes (EPNs) act as perfect biocontrol agents. So, work done in these lines has been reviewed to facilitate students and researchers for advanced research related to entomopathogenic nematodes and P. brassicae. [ABSTRACT FROM AUTHOR]

Despite impressive advances in the broad field of innate immunity, our understanding of the molecules and signaling pathways that control the host immune response to nematode infection remains incomplete. We have shown recently that Transforming Growth Factor-β (TGF-β) signaling in the fruit fly Drosophila melanogaster is activated by nematode infection and certain TGF-β superfamily members regulate the D. melanogaster anti-nematode immune response. Here, we investigate the effect of an entomopathogenic nematode infection factor on host TGF-β pathway regulation and immune function. We find that Heterorhabditis bacteriophora serine carboxypeptidase activates the Activin branch in D. melanogaster adults and the immune deficiency pathway in Activin-deficient flies, it affects hemocyte numbers and survival in flies deficient for Activin signaling, and causes increased intestinal steatosis in Activin-deficient flies. Thus, insights into the D. melanogaster signaling pathways and metabolic processes interacting with H. bacteriophora pathogenicity factors will be applicable to entomopathogenic nematode infection of important agricultural insect pests and vectors of disease. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes of the genera Steinernema and Heterorhabditis, along with their bacterial symbionts from the genera Xenorhabdus and Photorhabdus, respectively, are important biological control agents against agricultural pests. Rapid progress in the development of genomic tools has catalyzed a transformation of the systematics of these organisms, reshaping our understanding of their phylogenetic and cophlylogenetic relationships. In this review, we discuss the major historical events in the taxonomy and systematics of this group of organisms, highlighting the latest advancements in these fields. Additionally, we synthesize information on nematode–bacteria associations and assess the existing evidence regarding their cophylogenetic relationships. [ABSTRACT FROM AUTHOR]

Background: The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a polyphagous insect pest species that travel great distances every summer to disperse. They mostly feed on maize and over 350 other crops. In this investigation, two entomopathogens: Beauveria bassiana and Heterorhabditis taysearae, were utilized to test the efficacy of each against S. frugiperda separately and then as a group by inoculating H. taysearae two days after fungal infection. Results: Evaluations were done on mortality percentage, infective juvenile (IJ) production, and conidia production. The LT50 continually reduced with increases in nematode and fungus concentrations. For the LC50 value, the H. taysearae isolate was 289 IJs/larva after 96 h of treatment, while for B. bassiana isolate, it was 106 CFU/ml after 144 h of treatment. Dual infections with B. bassiana and H. taysearae had a beneficial effect on pest mortality, resulting in 83% mortality, and caused a significant increase in conidia production while utilizing the nematode or fungal separately caused decrease in mortality (63 and 73%, respectively). Conclusions: The study's findings indicated a quicker time to death and suggested that combining a moderately pathogenic fungal isolate with nematodes could raise the mortality rate. The mutually beneficial relationship between B. bassiana and H. taysearae controls S. frugiperda. [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]

AbstractThe box tree moth (BTM), Cydalima perspectalis, and the fall webworm (FWW), Hyphantria cunea are two invasive forest pests in northern Iran. Entomopathogenic nematodes (EPNs) are usually compatible with integrated pest management programs. In this study, the efficacy of five isolates of EPNs was evaluated against the two pests in laboratory and field conditions. LC50 values of Steinernema carpocapsae (IRTabriz), S. feltiae (IRTabriz), S. feltiae (Entonem), Oscheius rugaoensis and Heterorhabditis bacteriophora (IRTabriz) were as follow: 44.8, 66.5, 113.8, 190.7 and 515.9 infective juveniles (IJs) larva−1 on the fifth instar larvae of BTM; and 75.2, 96.6, 131.0, 258.0 and 292.5 IJs larva−1 on fifth instar larvae of FWW, respectively in the laboratory tests 48 h post-treatment at 25 °C and 60% relative humidity. Under field conditions, the foliar applications of S. carpocapsae (IRTabriz), S. feltiae (IRTabriz), and S. feltiae (Entonem) at the rate of 106 IJs L−1 resulted in 36–58% mortality after 48 h against BTM and 15–52% mortality against FWW, respectively. The results demonstrate that EPNs are promising candidates for biocontrol of BTW and FWW. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of biostimulants derived from Streptomyces avermitilis metabolites on entomopathogenic nematodes: Steinernema carpocapsae, Steinernema feltiae, and Heterorhabditis bacteriophora, obtained from the soil of several Miscanthus × giganteus plantations in 2020–2023. The nematodes were isolated, identified, and cultured using live insects (the greater wax moth Galleria mellonella). Three preparations containing biostimulants – Charkor, Stimpo, and Regoplant, were tested for compatibility with entomopathogenic and plant parasitic nematodes. Their effect on nematode survival was evaluated using the Petri dish test. The study showed that the effect of biostimulants on the survival of nematodes depended on the concentration of aversectin contained in the evaluated preparations. Stimpo and Regoplant had an adverse effect on plant parasitic nematodes. The highest G. mellonella mortality was observed at the higher dose of Charkor (0.4%), and the lowest at the lower dose of Regoplant (1.22%). The study showed that the virulence of the nematodes decreased after 48 hours of incubation in Regoplant and Stimpo solutions containing aversectin. The degree of interaction between nematodes depended on the nematode species, trophic preferences, and the concentration of active ingredients in the preparations. This conclusion is crucial for the selection of appropriate types of entomopathogenic nematodes and the application rate of plant parasitic nematodes in the assessment of their short- and long-term spread, persistence, and recycling in field conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: The red palm weevil, Rhynchophorus ferrugineus, is a major problem for palm plantations worldwide. While chemical pesticides are known to be effective, their environmental impact and insecticide resistance pose serious concerns. Biological control approaches, such as employing entomopathogenic nematodes, can mitigate these challenges by focusing on pests while avoiding harm to the environment or non-target organisms. Our findings show that indigenous and commercial EPNs have the ability to manage red palm weevils. As a result, alternate methods, such as the use of entomopathogenic nematodes, are critical for the sustainable control of red palm weevils. The red palm weevil (RPW) is a significant threat to date palms. Conventional pest control has been ineffective. This study aims to evaluate entomopathogenic nematodes (EPNs) indigenous to Saudi Arabia and commercial against RPW. We used 33 soil samples collected from four areas of Saudi Arabia. The indigenous EPNs were isolated and cultured using an insect baiting method to obtain infective juveniles. Pathogenicity bioassays were conducted against different stages of RPW, including eggs, larvae, and adults. The bioassay was performed using all the isolates at 1 × 106 IJ/mL. Distilled water was used as a control. The results revealed that only 9.09% of soil samples contained positive EPNs. Through DNA sequencing analysis, the positive samples were identified as indigenous isolates belonging to Heterorhabditis indica and Steinernema carpocapsae EPN species. In pathogenicity tests, 90% mortality of RPW eggs was observed after five days. Similar mortality trends were seen in RPW larvae and adults, with 90% mortality recorded after ten days for all the EPN treatments. Mortality increased with the duration of post-EPN inoculation exposure. The 1 × 106 IJ/mL concentrations of EPN effectively killed various stages of RPW in the laboratory. More research is needed to test EPNs against RPW in the field. [ABSTRACT FROM AUTHOR]

The entomopathogenic nematode Heterorhabditis bacteriophora, symbiotically associated with enterobacteria of the genus Photorhabdus, is a biological control agent against many insect pests. Dauer Juveniles (DJ) of this nematode are produced in industrial-scale bioreactors up to 100 m3 in liquid culture processes lasting approximately 11 days. A high DJ yield (> 200,000 DJ·mL−1) determines the success of the process. To start the mass production, a DJ inoculum proceeding from a previous monoxenic culture is added to pre-cultured (24 h) Photorhabdus bacteria. Within minutes after contact with the bacteria, DJ are expected to perceive signals that trigger their further development (DJ recovery) to reproductive hermaphrodites. A rapid, synchronized, and high DJ recovery is a key factor for an efficient culture process. In case of low percentage of DJ recovery, the final DJ yield is drastically reduced, and the amount of non-desired stages (males and non-fertilized females) hinders the DJ harvest. In a preliminary work, a huge DJ recovery phenotypic variability in H. bacteriophora ethyl methanesulphonate (EMS) mutants was determined. In the present study, two EMS-mutant lines (M31 and M88) with high and low recovery phenotypes were analyzed concerning their differences in gene expression during the first hours of contact with Photorhabdus supernatant containing food signals triggering recovery. A snapshot (RNA-seq analysis) of their transcriptome was captured at 0.5, 1, 3 and 6 h after exposure. Transcripts (3060) with significant regulation changes were identified in the two lines. To analyze the RNA-seq data over time, we (1) divided the expression profiles into clusters of similar regulation, (2) identified over and under-represented gene ontology categories for each cluster, (3) identified Caenorhabditis elegans homologous genes with recovery-related function, and (4) combined the information with available single nucleotide polymorphism (SNP) data. We observed that the expression dynamics of the contrasting mutants (M31 and M88) differ the most within the first 3 h after Photorhabdus supernatant exposure, and during this time, genes related to changes in the DJ cuticle and molting are more active in the high-recovery line (M31). Comparing the gene expression of DJ exposed to the insect food signal in the haemolymph, genes related to host immunosuppressive factors were not found in DJ upon bacterial supernatant exposure. No link between the position of SNPs associated with high recovery and changes in gene expression was determined for genes with high differential expression. Concerning specific transcripts, nine H. bacteriophora gene models with differential expression are provided as candidate genes for further studies. [ABSTRACT FROM AUTHOR]

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This study examines the impact of Heterorhabditis indica entomopathogenic nematodes on mature larvae of the peach fruit fly, Bactrocera zonata (Saunders), and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), both of which are highly detrimental species in the Tephritidae family. The investigation is conducted in a laboratory setting using two types of soil: sandy loam and sand. The research focuses on the virulence and biochemical effects of the nematodes. The results indicate that H. indica is more effective in sandy loam soil than sandy soil. This is supported by the LC50 values (the lethal concentration that kills 50% of the tested organisms) of 566.656 Infective Juveniles/ml for B. zonata and 250.53 Infective Juveniles/ml for C. capitata in sandy loam soil, whereas the corresponding values in sandy soil were 1149.051 and 701.839 Infective Juveniles/ml, respectively. Consequently, C. capitata larvae are more susceptible to entomopathogenic nematodes than B. zonata larvae. The infection by the nematodes also leads to changes in specific enzymatic activities of the larvae. This includes significant reductions in amylase, trehalase, and acetylcholine esterase, alongside an increase in invertase activity. Moreover, varying decreases are observed in chitinase, acid phosphatase, and alkaline phosphatase activities. In conclusion, the nematodes effectively reduce the emergence of adult flies by targeting the final stages of insect development. Furthermore, they offer an eco-friendly alternative to chemical pesticides. Entomopathogenic nematodes is an alternative biological control for fruit flies. H. indica is a soil control agent and adapted well to field situations. H. indica suppressed fruit fly larvae and could restrict their population expansion. Individuals of C. capitata were more comparatively susceptible than B. zonata ones. H. indica caused disturbance in specific enzymatic systems of both species larvae. [ABSTRACT FROM AUTHOR]

Summary: The entomopathogenic nematode (EPN), Heterorhabditis bacteriophora , is an efficient biological control agent against several economically important insect pests. Recent research has assessed the possibility to correlate desired beneficial traits with genotype data to pave a way for marker-assisted breeding approaches. A collection of H. bacteriophora WT inbred lines has been phenotyped in this framework for stress- and virulence-related traits. However, these traits are rarely combined in a single line. Thus, unifying these traits in commercial strains is of high priority. This investigation unified beneficial traits in hybrid pools through marker-assisted breeding using single nucleotide polymorphisms (SNPs) associated with reproductive potential, longevity, virulence and cold tolerance. Recombinant inbred lines (RILs) generated from a cross between a stress tolerant WT inbred line (XX21) and a line high in in vitro reproduction potential (IL3) were genotyped via SeqSNP and screened for SNP markers associated with beneficial traits. Thereafter, a genotypic pool (X21L3) comprising 22 ILs was formed. The X21L3 pool was subsequently evaluated for the target traits in comparison with the cross parents and a commercial strain HB4. An improvement of oxidative stress tolerance at 2°C (cold tolerance) was recorded with X21L3 surviving 1 day longer than the best performing parent (XX21). The hybrid pool also survived 1 day longer than the least performing parent IL3 for the trait longevity at 25°C under oxidative stress conditions. A higher dauer juvenile (DJ) recovery (58%) and DJ yield (209 000 DJ ml−1) than the least performing parent XX21 was recorded for the pool. The storage stability in diatomaceous earth formulation at 2°C and 7.5°C was also improved by 2 and 5 days, respectively, in comparison to the least performing parent XX21. This study depicts the potential of precision marker-assisted breeding for beneficial trait improvement of H. bacteriophora. [ABSTRACT FROM AUTHOR]

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]

The spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a pest that reduces the productivity of small fruits. Entomopathogenic nematodes (EPNs) and chemical insecticides can suppress this pest, but the compatibility of the two approaches together requires further examination. This laboratory study evaluated the compatibility of Steinernema brazilense IBCBn 06, S. carpocapsae IBCBn 02, Heterorhabditis amazonensis IBCBn 24, and H. bacteriophora HB with ten chemical insecticides registered for managing D. suzukii pupae. In the first study, most insecticides at the recommended rate did not reduce the viability (% of living infective juveniles (IJs)) of S. braziliense and both Heterorhabditis species. The viability of S. carpocapsae was lowered by exposure to spinetoram, malathion, abamectin, azadirachtin, deltamethrin, lambda-cyhalothrin, malathion, and spinetoram after 48 h. During infectivity bioassays, phosmet was compatible with all the EPNs, causing minimal changes in infectivity (% pupal mortality) and efficiency relative to EPN-only controls, whereas lambda-cyhalothrin generally reduced infectivity of EPNs on D. suzukii pupae the most, with a 53, 75, 57, and 13% reduction in infectivity efficiency among H. bacteriophora, H. amazonensis, S. carpocapsae, and S. brazilense, respectively. The second study compared pupal mortality caused by the two most compatible nematode species and five insecticides in various combinations. Both Heterorhabditis species caused 78–79% mortality among D. suzukii pupae when used alone, and were tested in combination with spinetoram, malathion, azadirachtin, phosmet, or novaluron at a one-quarter rate. Notably, H. bacteriophora caused 79% mortality on D. suzukii pupae when used alone, and 89% mortality when combined with spinetoram, showing an additive effect. Novaluron drastically reduced the number of progeny IJs when combined with H. amazonensis by 270 IJs and H. bacteriophora by 218. Any adult flies that emerged from EPN–insecticide-treated pupae had a shorter lifespan than from untreated pupae. The combined use of Heterorhabditis and compatible chemical insecticides was promising, except for novaluron. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs) can be applied using drip irrigation systems. However, the choice of driplines and types of drippers significantly impacts the efficacy of field applications. This study investigated the performance of EPN applications using two common dripper types (katif and cylindrical drippers) under both pot and field conditions. The primary objective of the study was to optimize EPN applications and create a modular system in which driplines and drippers can be selected based on the target pest or plant. In our modular system, driplines were connected to a battery-powered backpack sprayer rather than an irrigation system. The efficacy of EPN applications was assessed on Galleria mellonella L. (Lepidoptera: Pyralidae) larvae at a commercial dose of approximately 50 IJs cm-2 . The results revealed that only 60% of the nematodes were discharged from the cylindrical drippers, with 40% becoming trapped in the irrigation system. In contrast, over 90% of the nematodes were successfully discharged from the katif dripper. As a result, the katif dripper exhibited significantly higher larval mortality compared to all other application methods. These findings emphasize the substantial impact of the dripper type on EPN discharge, while also highlighting the applicability of the modular method for EPN applications. [ABSTRACT FROM AUTHOR]

ABSTRACT The cornstalk borer, Elasmopalpus lignosellus (Lepidoptera: Pyralidae), reduces the productive potential of maize crops and is a difficult pest to manage. A management program using different methods could improve the control of E. lignosellus. Considering the potential of entomopathogenic nematodes (EPN) in reducing insect pest populations in soil, the objective of this study was to evaluate the virulence of these EPN and adjust their concentration for controlling E. lignosellus larvae under laboratory and greenhouse conditions. In the laboratory, the virulence of five EPN populations was tested; then, Heterorhabditis amazonensis MC01 was tested at four concentrations. In the greenhouse, H. amazonensis MC01 was tested at four concentrations and was applied to vessels containing maize plants and six larvae. After five days, mortality was evaluated, and means were compared using Tukey’s test (p-value < 0.05). Heterorhabditis amazonensis MC01 and S. carpocapsae All were equally virulent, reducing the larva population by more than 90%. The concentration of H. amazonensis MC01 that caused the highest mortality of larvae in the laboratory was 182 infective juveniles (IJ) larva-1. In the greenhouse, the nematode was also considered virulent to E. lignosellus since all concentrations tested caused larval mortality greater than 70%.

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]

Fungal diseases such as Fusarium head blight (FHB) are significant biotic stressors, negatively affecting wheat production and quality. This study explored the antifungal activity of the metabolites produced by the bacterial symbionts of entomopathogenic nematodes (EPNs) against FHB-causing Fusarium sp. Fusarium graminearum. To achieve this, the symbiotic bacteria of nine EPN isolates from the EPN collection at the Agricultural Research Council-Small Grains (ARC-SG) were isolated from the cadavers of Galleria mellonella (Lepidoptera: Pyralidae) larvae after infection with EPNs. Broth cultures (crude) and their supernatants (filtered and autoclaved) of each bacterial isolate were used as bacterial metabolite treatments to test their inhibitory effect on the mycelial growth and spore germination of F. graminearum. Mycelial growth inhibition rates varied among both bacterial isolates and treatments. Crude metabolite treatments proved to be more effective than filtered and autoclaved metabolite treatments, with an overall inhibition rate of 75.25% compared to 23.93% and 13.32%, respectively. From the crude metabolite treatments, the Xenorhabdus khoisanae SGI 197 bacterial isolate from Steinernema beitlechemi SGI 197 had the highest mean inhibition rate of 96.25%, followed by Photorhabdus luminescens SGI 170 bacteria isolated from Heterorhabditis bacteriophora SGI 170 with a 95.79% mean inhibition rate. The filtered metabolite treatments of all bacterial isolates were tested for their inhibitory activity against Fusarium graminearum spore germination. Mean spore germination inhibition rates from Xenorhabdus spp. bacterial isolates were higher (83.91 to 96.29%) than those from Photorhabdus spp. (6.05 to 14.74%). The results obtained from this study suggest that EPN symbiotic bacterial metabolites have potential use as biological control agents of FHB. Although field efficacy against FHB was not studied, the significant inhibition of mycelial growth and spore germination suggest that the application of these metabolites at the flowering stage may provide protection to plants against infection with or spread of F. graminearum. These metabolites have the potential to be employed as part of integrated pest management (IPM) to inhibit/delay conidia germination until the anthesis (flowering stage) of wheat seedlings has passed. [ABSTRACT FROM AUTHOR]

Photorhabdus spp. are the only known terrestrial bioluminescent bacteria. We show that the bioluminescence produced by these bacteria reduces scavenging activity on the insect cadavers they colonize. Photorhabdus spp. are the symbiont of the insect pathogenic nematodes Heterorhabditis spp. Together they kill insects and colonize the cadaver. The function of their bioluminescence has been the subject of debate, but here for the first time we demonstrate an ecological benefit. In our experiments, fewer Photorhabdus temperata -infected cadavers than uninfected cadavers were scavenged, but only in dark conditions where their bioluminescence would be visible. This was the case both in the field and in laboratory experiments with Lehmannia valentiana slugs (the primary scavengers found in our field tests). We also show that L. valentiana is innately deterred from scavenging on uninfected cadavers in proximity to light imitating the bioluminescence of Photorhabdus, indicating that luminescence can be a deterrent independent of chemical cues. We propose a multimodal defence where bioluminescence works together with the chemical defences also produced by Photorhabdus to deter scavengers, such as slugs, from feeding on the host cadaver, with the potential for aposematism. [ABSTRACT FROM AUTHOR]

Xenorhabdus and Photorhabdus, bacterial symbionts of entomopathogenic nematodes Steinernema and Heterorhabditis, respectively, have several biological activities including insecticidal and antimicrobial activities. Thus, XnChi, XhChi, and PtChi, chitinases of X. nematophila, X. hominickii, and P. temperata isolated from Korean indigenous EPNs S. carpocapsae GJ1-2, S. monticolum GJ11-1, and H. megidis GJ1-2 were cloned and expressed in Escherichia coli BL21 to compare their biological activities. Chitinase proteins of these bacterial symbionts purified using the Ni-NTA system showed different chitobiosidase and endochitinase activities, but N-acetylglucosamidinase activities were not shown in the measuring of chitinolytic activity through N-acetyl-D-glucosarmine oligomers. In addition, the proteins showed different insecticidal and antifungal activities. XnChi showed the highest insecticidal activity against Galleria mellonella, followed by PtChi and XhChi. In antifungal activity, XhChi showed the highest half-maximal inhibitory concentration (IC50) against Fusarium oxysporum with 0.031 mg/mL, followed by PtChi with 0.046 mg/mL, and XnChi with 0.072 mg/mL. XhChi also showed the highest IC50 against F. graminearum with 0.040 mg/mL, but XnChi was more toxic than PtChi with 0.055 mg/mL and 0.133 mg/mL, respectively. This study provides an innovative approach to the biological control of insect pests and fungal diseases of plants with the biological activity of symbiotic bacterial chitinases of entomopathogenic nematodes. [ABSTRACT FROM AUTHOR]

Summary: Limited shelf life is a major constraint to successful commercialisation of entomopathogenic nematodes (EPN), and to extend shelf life, dauer juveniles (DJ) are formulated and stored at low temperatures (4-8°C). We evaluated the cold storage potential of strains of Heterorhabditis bacteriophora formulated in diatomaceous earth at storage temperatures between 5 and 9°C. When assessing DJ decline to reach 75% survival (MT75) in the formulation for the respective temperatures, H. bacteriophora strain HB4 had the highest survival of 25 days at 9°C, while strain D2D6 survived longest at 8°C for 28 days. A set of 22 H. bacteriophora wild type inbred lines was then phenotyped for cold tolerance in water under oxidative stress in 70 mM H2O2 at 2°C. The MT50 (time to 50% survival) ranged from 11 to 23 days. The phenotypic data were correlated with the respective genotypic data, identifying four single nucleotide polymorphic (SNP) markers associated with cold tolerance. The survival of two lines (PT11 and IR11) with opposite extreme cold tolerance pheno- and genotypes was evaluated in diatomaceous earth formulation at 2°C with the cold tolerant IR11 surviving 3 days longer than PT11. Our study yields a set of valuable SNP markers employable in rapid genotyping of cold tolerance and tracking this trait during the breeding process. [ABSTRACT FROM AUTHOR]

The entomopathogenic nematode Heterorhabditis bacteriophora (Nematoda: Rhabditidae) is used in biological insect control. Their dauer juveniles (DJs) are free-living and developmentally arrested, invading host insects. They carry cells of their bacterial symbiont Photorhabdus spp. in the intestine. Once inside the insect´s hemolymph the DJs perceive a food signal, triggering them to exit the DJ stage and regurgitate the Photorhabdus cells into the insect's haemocoel, which kill the host and later provide essential nutrients for nematode reproduction. The exit from the DJ stage is called "recovery". For commercial pest control, nematodes are industrially produced in monoxenic liquid cultures. Artificial media are incubated with Photorhabdus before DJs are added. In absence of the insect's food signal, DJs depend on unknown bacterial food signals to trigger exit of the DJ stage. A synchronized and high DJ recovery determines the success of the industrial in vitro production and can significantly vary between nematode strains, inbred lines and mutants. In this study, fourteen bacterial strains from H. bacteriophora were isolated and identified as P. laumondii, P. kayaii and P. thracensis. Although the influence of bacterial supernatants on the DJ recovery of three inbred lines and two mutants differed significantly, the bacterial impact on recovery has a subordinate role whereas nematode factors have a superior influence. Recovery of inbred lines decreased with age of the DJs. One mutant (M31) had very high recovery in bacterial supernatant and spontaneous recovery in Ringer solution. Another mutant (M88) was recovery defective. [ABSTRACT FROM AUTHOR]

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]

Extensive surveys of entomopathogenic nematodes (EPNs) have been conducted globally to identify native species. In Africa, EPN-related research has gained much attention over the past two decades, with several surveys having been undertaken in different countries, including Benin, Cameroon, Egypt, Ethiopia, Kenya, Morocco, Nigeria, Rwanda, South Africa and Tanzania. Such surveys have led to the description of 37 EPN species and 16 species of symbiotically associated bacteria being documented from Africa. Whereas South Africa and Egypt have made significant progress in the discovery and identification of EPN, in terms of their symbiotic bacteria and pathogenicity testing against pest insects, in many other African countries, the research is still in its early stages, or is else non-existent. Most research conducted so far has focused on laboratory bioassays, while research on the use of nematodes in more natural environments is scant. The present review provides a comprehensive overview of EPNs and their associated symbiotic bacteria from the African continent. The biological control potential of local EPN isolates against various economically important insect pests in Africa is also discussed. [ABSTRACT FROM AUTHOR]

Biological control of agave weevil, Scyphophorus acupunctatus Gyllenhal, includes use of entomopathogenic nematodes of the genus Heterorhabditis, which have potential for managing pests with cryptic habits. Virulence of two native isolates of Heterorhabditis indica Poinar, Karunakar & David (A14 and X1) and commercial isolate Heterorhabditis bacteriophora were evaluated on a population of adult agave weevils. Isolates of larvae and pupae of sugarcane weevil, Scyphophorus incurrens, were collected in the State of Morelos, Mexico. Virulence of each isolate was determined by laboratory bioassays to calculate lethal concentration (LC50) and lethal time 50 (LT50) required to eliminate 50% of a population of adult agave weevils. The adult agave weevils were collected at Jalisco, Mexico. For the three isolates evaluated, LC50 ranged from 1,183 to 1,913 infective juveniles, with no significant differences between the isolates evaluated; however, A14 required a lesser LC50. The isolate was statistically different from X1 in terms of LT50 to eliminate 50% of the test population. Based on results of the study, native isolates had potential as biological control agents against S. acupunctatus. [ABSTRACT FROM AUTHOR]

The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora is an effective biological-control agent of insect pests. The dauer juveniles (DJs) seek for, infect insects, and release cells of the carried symbiotic bacterium of the genus Photorhabdus. Inside the host, the DJs perceive signals from the insect's haemolymph that trigger the exit from the arrested stage and the further development to mature adults. This developmental step is called DJ recovery. In commercial production, a high and synchronous DJ recovery determines the success of liquid-culture mass production. To enhance the understanding about genetic components regulating DJ recovery, more than 160 mutant- and 25 wild type inbred lines (WT ILs) were characterized for DJ recovery induced by cell-free bacterial supernatant. The mutant lines exhibited a broader DJ recovery range than WT ILs (4.6–67.2% vs 1.6–35.7%). A subset of mutant lines presented high variability of virulence against mealworm (Tenebrio molitor) (from 22 to 78% mortality) and mean time survival under oxidative stress (70 mM H2O2; from 10 to 151 h). Genotyping by sequencing of 96 mutant lines resulted in more than 150 single nucleotide polymorphisms (SNPs), of which four results are strongly associated with the DJ recovery trait. The present results are the basis for future approaches in improving DJ recovery by breeding under in vitro liquid-culture mass production in H. bacteriophora. This generated platform of EMS-mutants is as well a versatile tool for the investigation of many further traits of interest in EPNs. Keypoints: • Exposure to bacterial supernatants of Photorhabdus laumondii induces the recovery of Heterorhabditis bacteriophora dauer juveniles (DJs). Both, the bacteria and the nematode partner, influence this response. However, the complete identity of its regulators is not known. • We dissected the genetic component of DJ recovery regulation in H. bacteriophora nematodes by generating a large array of EMS mutant lines and characterizing their recovery pheno- and genotypes. • We determined sets of mutants with contrasting DJ recovery and genotyped a subset of the EMS-mutant lines via genotyping by sequencing (GBS) and identified SNPs with significant correlation to the recovery trait. [ABSTRACT FROM AUTHOR]

Protecting stands of Scots pine (Pinus sylvestris) from the larvae of the pine lappet moth (Dendrolimus pini) has been a problem for many years in Central Europe. The feeding habits of the larvae of D. pini often result in more than 50 per cent defoliation, which weakens trees and increases their susceptibility to unfavourable environmental conditions. The aim of this study was to evaluate the effectiveness of native isolates of the entomopathogenic nematodes Steinernema feltiae (Filipjev, 1934) and Heterorhabditis megidis (Poinar, Jackson and Klein, 1987), as well as of the commercial preparations Nemamax (Heterorhabditis downesi) (Stock, Griffin and Burnell), Entonem (S. feltiae) and E-nema GmbH (S. carpocapsae) in greenhouse experiments and field trials. The highest extensity of infection (>80 per cent) of the pine lappet moth with nematodes in the greenhouse experiments studies was found for the strain S. feltiae ZAG15. In field trials, a greater effectiveness was obtained using commercial preparations of S. feltiae (Entonem), which led to approximately a twofold reduction in the number of wintering D. pini larvae. The results of this study indicate that entomopathogenic nematodes can be considered a potential biological control agent for reducing the damage caused by D. pini larvae. [ABSTRACT FROM AUTHOR]

A survey was conducted in some northern regions of Iraq between 2021 and 2022 to evaluate the diversity of entomopathogenic nematodes in these areas. Entomopathogenic nematodes were isolated from soil using the Galleria trap technique. Molecular identification illustrated that these isolates belong to two genera of entomopathogenic nematodes, Heterorhabditis, and Steinernema. The results of the molecular analysis also showed the presence of Steinernema isolates in the Al-Rashidiyah region in Mosul, Iraq. Heterorhabditis nematodes were isolated from Salah Al-Din, Samarra, and Al-Jadriya, Baghdad. Some collected soil samples were negative and had no nematode species such as Dohuk, Sulaymaniyah, Erbil, and Anbar cities. Molecular analyses using 28S genes confirmed that the isolated nematodes were Heterorhabditis indica (OQ653109.1), Heterorhabditis bacteriophora (OR243201.1), and Steinernema carpocapsae (OR243196.1). [ABSTRACT FROM AUTHOR]

The occurrence and distribution of entomopathogenic nematodes (EPNs) in the Syrian coast regions remain relatively uncharted. To address this gap in our knowledge, an extensive survey of these ecosystems was essential. This study aims to isolate and identify EPNs from diverse ecosystems within the coastal regions. The distribution of EPNs in cultivated and natural environments was analyzed according to habitat, altitude, and sampling season factors. Between 2017 and 2020, EPNs were recovered from 27 out of 821 soil samples (3.28%) and collected from 24 out of 375 sampling sites (6.4%). Based on morphological, morphometric, and molecular (ITS) characteristics, four EPN species were identified: Heterorhabditis indica (51.85%), representing the first report of its occurrence in the coastal regions, H. bacteriophora (33.33%), H. pakistanense (7.4%), which is also reported for the first time in Syria, and Steinernema affine (7.4%). There were statistical differences in the abundance and recovery frequency of EPNs in each type of habitat. Additionally, there were statistical differences in the altitude and sampling season recovery frequency.

BackgroundNematodes are a major group of soil inhabiting organisms. Heterorhabditis nematodes are insect-pathogenic nematodes and live in a close symbiotic association with Photorhabdus bacteria. Heterorhabditis-Photorhabdus pair offers a powerful and genetically tractable model to study animal-microbe symbiosis. It is possible to generate symbiont bacteria free (axenic) stages in Heterorhabditis. Here, we compared the transcriptome of symbiotic early-adult stage Heterorhabditis nematodes with axenic early-adult nematodes to determine the nematode genes and pathways involved in symbiosis with Photorhabdus bacteria.ResultsA de-novo reference transcriptome assembly of 95.7 Mb was created for H. bacteriophora by using all the reads. The assembly contained 46,599 transcripts with N50 value of 2,681 bp and the average transcript length was 2,054 bp. The differentially expressed transcripts were identified by mapping reads from symbiotic and axenic nematodes to the reference assembly. A total of 754 differentially expressed transcripts were identified in symbiotic nematodes as compared to the axenic nematodes. The ribosomal pathway was identified as the most affected among the differentially expressed transcripts. Additionally, 12,151 transcripts were unique to symbiotic nematodes. Endocytosis, cAMP signalling and focal adhesion were the top three enriched pathways in symbiotic nematodes, while a large number of transcripts coding for various responses against bacteria, such as bacterial recognition, canonical immune signalling pathways, and antimicrobial effectors could also be identified.ConclusionsThe symbiotic Heterorhabditis nematodes respond to the presence of symbiotic bacteria by expressing various transcripts involved in a multi-layered immune response which might represent non-systemic and evolved localized responses to maintain mutualistic bacteria at non-threatening levels. Subject to further functional validation of the identified transcripts, our findings suggest that Heterorhabditis nematode immune system plays a critical role in maintenance of symbiosis with Photorhabdus bacteria.

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]

Despite impressive advances in the broad field of innate immunity, our understanding of the molecules and signaling pathways that control the host immune response to nematode infection remains incomplete. We have shown recently that Transforming Growth Factor-β (TGF-β) signaling in the fruit fly Drosophila melanogaster is activated by nematode infection and certain TGF-β superfamily members regulate the D. melanogaster anti-nematode immune response. Here, we investigate the effect of an entomopathogenic nematode infection factor on host TGF-β pathway regulation and immune function. We find that Heterorhabditis bacteriophora serine carboxypeptidase activates the Activin branch in D. melanogaster adults and the immune deficiency pathway in Activin-deficient flies, it affects hemocyte numbers and survival in flies deficient for Activin signaling, and causes increased intestinal steatosis in Activin-deficient flies. Thus, insights into the D. melanogaster signaling pathways and metabolic processes interacting with H. bacteriophora pathogenicity factors will be applicable to entomopathogenic nematode infection of important agricultural insect pests and vectors of disease.

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]

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]

In the present study, infective capabilities of two entomopathogenic nematode species including Heterorhabditis bacteriophora and Steinernema carpocapsae were evaluated against red palm weevil, under laboratory and field conditions. Bioassay experiments took place to estimate theLC50, LC90, LT50 and LT90 values. By H. bacteriophora treatment, theLC50's against the 2nd, 4th, 8th and 12th larval instars of R. ferrugineus were 909.48, 1623.00, 1771.08 and 2897.44 IJs/ml, respectively. The correspondent LC90 values were 3389.86, 6586.00, 8096.61 and 22548.21 IJs/ml, respectively after 15 days of treatment. Also, the LT50 values after using the concentration 2500 IJs/ml were 7.43, 9.54, 10.83 and 16.28 days, respectively, while those of LT90 were 21.81, 41.33, 52.68 and 116.40 days, respectively. By S. carpocapsae treatment, theLC50's were 728.97, 1370.00, 1547.21 and 2771.84 IJs/ml, respectively. LC90 values were 3507.36, 6784.74, 9293.00 and 18916.27 IJs/ml, respectively for the 2nd, 4th, 8th and 12th instars after 15 days of treatment. Also, the LT50 values after using the concentration 2500 IJs/ml were 7.04, 7.13, 10.16 and 14.62 days, respectively, while those of LT90 were 19.05, 22.57, 43.46 and 96.78 days, respectively. Whereas, the two species of EPN (H. bacteriophora and S. carpocapsae) by 2500 IJs/ml concentration caused 90 & 95% mortality for 2nd instar, 70 & 75% for 4th instar, 65 & 70% for 8th instar and 50 & 50% for 12th instar, respectively, 15 days after treatment. The field study showed that infested date palm trees injected by H. bacteriophora and S. carpocapsae by concentration 2 x 107 IJs/liter at the infestation site by the red palm weevil caused 60 and 80% recovery, respectively, recovery from infestation after 25 days of treatment. The study recommends using of S. carpocapsae to control the red palm weevil. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPN) are well-established plant protection tools for the control of insect pests. The release of EPN species is often limited to species that are endemic in the country. Therefore, surveys to check for the presence of EPN species in the country are necessary. Here, a sampling and baiting method based on the in situ attraction of EPN to insects contained in a plastic tube is described. Heterorhabditis downesi was isolated from overgrown dunes at the Baltic coast and Steinernema feltiae from chromic luvisol further inland. This is the first report of the presence of H. downesi in Germany. [ABSTRACT FROM AUTHOR]

The Neotropical brown stink bug, Euschistus heros (Fabricius), is considered a pest in soybean that is difficult to control and leads to deterioration of grains and reduced production. Entomopathogenic nematodes can be used to control insect pests and can also be a complementary tool in the management of the Neotropical brown stink bug. They also exhibit significant compatibility with chemical phytosanitary products. Thus, this study aimed to determine the virulence, production, and concentration of entomopathogenic nematodes in the Neotropical brown stink bug, as well as their compatibility with chemical phytosanitary products. Six nematode isolates, administered in the concentration of 100 Infective Juveniles (IJs) adult-1, were evaluated. Subsequently, Heterorhabditis amazonensis MC01 was evaluated at concentrations of 50, 100, 150, 200, and 250 IJs adult-1. The evaluations were carried out by determining Neotropical brown stink bug mortality and the production of IJs. The compatibility tests consisted of evaluating the viability and infectivity of two nematode isolates incubated in contact with 11 phytosanitary products for 48 hours. The virulence test showed up to 48% Neotropical brown stink bug mortality after 7 days. A greater concentration of IJs was produced for H. amazonensis MC01, compared to Steinernema feltiae, reaching 101,000 and 97,800 IJs adult-1, respectively. The application of 150 IJs adult-1 was associated with the highest mortality of E. heros and the highest production of IJs. Methomyl and profenofos were incompatible with both tested nematodes and chlorpyrifos was incompatible with H. amazonensis MC01. The compatibility of the chemical products with nematodes highlights the possibility of application in association with entomopathogenic nematodes to control E. heros. Products considered incompatible should be avoided, and further tests should be performed to confirm the results in field conditions. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes in the genera Steinernema and Heterorhabditis , produced through in vitro or in vivo methods, are effective insect biological control agents. In vivo production yields good-quality nematodes, but the costs associated with obtaining insects and labor make this production system have a low economy of scale. Conceivably, if growers can produce their own nematodes, then the cost could be reduced. Grower-based production systems described to-date are not sustainable because they rely on outside sources to obtain or calibrate inoculum. Here, we describe a self-sufficient grower-based system where the grower can produce in-house nematodes after obtaining the initial inoculum from a reliable source. We validated our approach in 2 experiments comparing in vivo nematode production from standard White traps and a grower-based approach using polyacrylamide gel. For both tested species, Steinernema carpocapsae (Weiser) and Heterorhabditis bacteriophora Poinar, the grower-based approach produced equal to or more nematodes than the standard method. For example, when comparing the average yield of S. carpocapsae -infective juveniles per Galleria mellonella cadaver (n = 30), the standard White trap method produced 159,114 ± 9,669, whereas the grower-based approach produced 244,029 ± 16,241. The sustainable system described herein has promise for wide adoption by growers. [ABSTRACT FROM AUTHOR]

Black soldier fly Hermetia illucens (L.) larvae can serve many uses, of which potential exists for its use as a host for mass production of entomopathogenic nematodes. This study evaluates its larval instars for their suitability for rearing of Heterorhabditis bacteriophora (Poinar) and Steinernema carpocapsae (Weiser). The results revealed that 4th instar larvae is economical and effective, and this can be used at farm level. Thus, it can be popularized for mass production of entomopathogenic nematodes. The nematodes/ cadaver was found to be half as that from Galleria, and hence two 4th instar cadavers can be recommended in place of a single Galleria cadaver. The results also showed that H. illucens is unsuitable for mass multiplication of S. carpocapsae. [ABSTRACT FROM AUTHOR]

An alternative to chemical control, entomopathogenic nematodes are very effective against insect pests. Native isolates of Steinernema siamkayai, S. carpocapsae, Heterorhabditis indica, H. bacteriophora, Heterorhabditis sp. and Oscheius sp. have been evaluated for their virulence against white grubs. Under laboratory conditions, S. glaseri was more susceptible to A. communis in potato. S. glaseri @ 2.5 x109 IJ/ ha showed the highest grub mortality of 83.33% and 19.04% tuber damage. The same dosage of Heterorhabditis sp. in pot culture caused 18.66% tuber damage and 74.05% larval mortality. Steirnernema glaseri and Heterorhabditis sp. effectiveness against the coleopteran insect pests of Anomala communis in potato was conducted under field conditions. The maximum grub mortality with S. glaseri at 2.5 x109 IJ/ ha was 71.33%. With Heterorhabditis sp. at 2.5 x109 IJ/ ha, the yield increased by 14.14 t/ ha while tuber damage was 24.99%. However, the nematode S. glaseri and Heterorhabditis sp. has its best ability to live at the lowest temperature in the field trial, Anomala communis was successfully managed by S. glaseri followed Heterorhabditis sp. in potato. The natural distribution of the native isolates of EPNs may be used for local insect pest management. [ABSTRACT FROM AUTHOR]

The red palm weevil (RPW) is a significant threat to date palms. Conventional pest control has been ineffective. This study aims to evaluate entomopathogenic nematodes (EPNs) indigenous to Saudi Arabia and commercial against RPW. We used 33 soil samples collected from four areas of Saudi Arabia. The indigenous EPNs were isolated and cultured using an insect baiting method to obtain infective juveniles. Pathogenicity bioassays were conducted against different stages of RPW, including eggs, larvae, and adults. The bioassay was performed using all the isolates at 1 × 106 IJ/mL. Distilled water was used as a control. The results revealed that only 9.09% of soil samples contained positive EPNs. Through DNA sequencing analysis, the positive samples were identified as indigenous isolates belonging to Heterorhabditis indica and Steinernema carpocapsae EPN species. In pathogenicity tests, 90% mortality of RPW eggs was observed after five days. Similar mortality trends were seen in RPW larvae and adults, with 90% mortality recorded after ten days for all the EPN treatments. Mortality increased with the duration of post-EPN inoculation exposure. The 1 × 106 IJ/mL concentrations of EPN effectively killed various stages of RPW in the laboratory. More research is needed to test EPNs against RPW in the field.

Summary: The entomopathogenic nematode (EPN), Heterorhabditis bacteriophora , is a biocontrol agent with almost world-wide distribution, thus providing a huge source of biodiversity available for exploitation in breeding programmes to improve beneficial traits. For management of economically important insect pests, the nematode is mass-produced in liquid culture, formulated with inert carriers, and transported under controlled temperature conditions to maintain its quality. The biocontrol potential of nematode materials is defined by their genetic background. Previous reports have assessed the phenotypic plasticity of H. bacteriophora. Major beneficial traits are field efficacy influenced by their virulence, longevity and field persistence and tolerance to abiotic stresses like oxidative stress, desiccation and extreme low and high temperatures. For several of these traits high heritability values (h 2) have been reported, providing a platform for trait improvement by selection. Modern breeding uses molecular markers to track beneficial traits. Recent studies reported hundreds of single nucleotide polymorphisms (SNPs) in H. bacteriophora. This investigation revived a large set of cryopreserved wild types, hybrids and phenotyped materials of H. bacteriophora. Additional phenotypic data on the virulence (LC50) of H. bacteriophora strains against mealworm (Tenebrio molitor) were produced ranging from 1.4 ± 0.3 to 8.0 ± 3.6 nematodes per insect. Markers linked to beneficial traits were used for a comprehensive genotype analysis transferring reported SNP sequence information into the multiplex platform SeqSNP. Specific alleles associated to beneficial traits were identified and 65 materials were classified for the presence of relevant SNPs associated to beneficial traits. This information provides a valuable platform for exploitation of the nematode's biodiversity for future breeding and selection approaches. [ABSTRACT FROM AUTHOR]

The use of entomopathogenic nematodes (families: Heterorhabditidae and Steinernematidae) against various insect pests has grown rapidly in recent years and around 100 valid species of entomopathogenic nematodes have been identified from different countries of the world. In this context, the present study aimed to isolate and identify entomopathogenic nematodes from local soil in Uttar Pradesh, India; and have been evaluated for their efficacy against lepidopteran and coleopteran larvae. Totally 28 samples were found positive (14 %) from 200 soil samples collected for entomopathogenic nematodes isolation and on the basis of molecular characterization, three were identified as Heterorhabditis indica, Steinernema abbasi, and Steinernema siamkayai. In controlled conditions, they were evaluated against the fifth instar larva of Galleria mellonella and the first and second instar grubs of Holotrichia serrata. The lowest ED50 (IJs/larva) value was recorded at 48 h for H. indica (ED50 4.603) followed by Steinernema abbasi (ED50 7.118) and S. siamkayai (ED50 10.663) against G. mellonella. Further, the most effective strain of H. indica was tested against 1st and 2nd stage grubs H. serrata and ED50 of 130.798 and 263.104 were recorded, respectively. In the present study, the native strains of entomopathogenic nematodes evaluated against the larval stage of lepidopteran and coleopteran pests and found more suitable against local pests because of adaptation to local climate; these confined bioagents may serve as a viable option for pest control in organic farming. [ABSTRACT FROM AUTHOR]

Heterorhabditis indica from genera Heterorhabditis is an efficient biological control agent, due to their ease of culture, their high fatality against key soil insect pests, and their safety in use. However, their commercial utilization is limited by their limited shelf life in storage. Thus, efficient storage is essential so as to attain successful use of them alone including a part of integrated insect pest management strategies. Heterorhabditis indica isolated from soil in Uttar Pradesh, India (GPS location 28.6691°N, 77.4537°E) was characterized in terms of storage in different media including de-ionized water; at different temperatures and infectivity of their infective juveniles (IJs). After the primary screening of several media alone and in different combinations; a set of six media viz., de-ionized water (S1), cocopeat (S2), vermicompost (S3), earth (S4), potter's clay, talcum powder & earth (S5) and potter's clay, talcum powder, earth & cocopeat (S6) were selected and the survival and infectivity of H. indica IJs were studied at, 15±2 °C, 20±2 °C and 25±2 °C, for a period of 120 days. The effectiveness of H. indica IJs was ascertained on the basis of the establishment of IJs, using Galleria mellonella larval mortality tests in Petridish using baiting method technique at 15 days intervals. The results of this study revealed that storage media markedly affects the survival as well as the establishment of H. indica IJs. At all three test temperatures viz., 15±2 °C, 20±2 °C and 25±2 °C, a comparatively higher survival rate of H. indica IJs was observed in S2 and S6 media for 120 and 90 days, respectively, but the same reduced drastically in other media. Heterorhabditis indica IJs stored in S2 media showed comparatively better establishment following S6 than those stored in others at all temperatures for different storage durations as compared to de-ionized water. Present studies indicate that the storage stability of H. indica IJs enhances up to 120 days in S2 at all ranges of the temperature of 15-25 °C. In conclusion, our study adds further valuable information about the effect of storage media and temperature on the survival and infectivity of H. indica which appears to be promising biocontrol agents of major soil arthropod pests. [ABSTRACT FROM AUTHOR]

Epilachna beetle (Henosepilachna septima Dieke) and melon fruit fly (Zeugodacus cucurbitae Coquillett) are serious pests of bitter gourd in Kerala. Studies were conducted to evaluate pathogenicity of Entomopathogenic nematodes (EPNs) against H. septima and Z. cucurbitae under laboratory conditions. NBAIR isolates of EPNs viz. Heterorhabditis indica Poinar and Steinernema carpocapsae Weiser were tested for their pathogenicity against 3rd instar larvae of H. septima. Among EPN species, H. indica @100 IJs recorded highest percentage mortality (100.00) followed by S. carpocapsae (90.00) at 48 hours after treatment (HAT). Three different formulations viz. sponge, talc and alginate gel of effective EPN strain was prepared and stored for 11 weeks. Infective juveniles stored in alginate gel formulation showed more than 50.00 per cent survival upto eight weeks after storage and recorded 72.22 per cent mortality of H. septima larvae at 72 HAT. Results of laboratory experiment on the effect of EPN formulation on adult emergence of fruit fly revealed that both alginate gel and talc based formulations of H. indica is equally effective to chemical. The study highlighted the efficacy of H. indica formulations as soil application for the management of Z. cucurbitae. [ABSTRACT FROM AUTHOR]