Search

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]

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]

Copyright of Journal of Anatolian Environmental & Animal Science is the property of Bulent Verep and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 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]

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]

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]

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]

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]

The entomopathogenic nematodes (EPNs) Steinernema and Heterorhabditis have long been described as specifically associated with endosymbiotic bacteria, but recent studies have revealed associations with more complex bacterial communities. The endosymbionts Xenorhabdus and Photorhabdus are the first bacterial circle of EPNs. The other associated bacterial taxa, the second bacterial circle, belong to other species, mostly Proteobacteria. Putative first, and a second, bacterial circles have also been described in the entomopathogenic bacterivorous nematodes, Caenorhabditis briggsae and Oscheius sp. The second bacterial circle might play a role in the parasitic cycle, that is, entry into the live insect, causing death, nematode reproduction in the insect cadaver, and EPN transmission and dissemination in soil. Single host–symbiont interactions should be reconsidered from the perspective of the pathobiome. We revisit here the interactions between entomopathogenic nematodes (EPNs) and their microbiota. We first describe the discovery of these EPNs and their bacterial endosymbionts. We also consider EPN-like nematodes and their putative symbionts. Recent high-throughput sequencing studies have shown that EPNs and EPN-like nematodes are also associated with other bacterial communities, referred to here as the second bacterial circle of EPNs. Current findings suggest that some members of this second bacterial circle contribute to the pathogenic success of nematodes. We suggest that the endosymbiont and the second bacterial circle delimit an EPN pathobiome. [ABSTRACT FROM AUTHOR]

The presented study is concerned with infectivity of select entomopathogenic nematode species under different temperature conditions (15, 20 and 25 °C) in the presence of competing species. Two species of nematodes of the genus Steinernema (S. kraussei, S. feltiae) and two of the genus Heterorhabditis (H. bacteriophora and H. megidis) were included in the analysis. Different experimental variants were adopted in which the selected two entomopathogenic nematode species were mixed between Steinernema and Heterorhabditis. The study showed that Heterorhabditis and Steinernema cannot coexist together in a single host and one genus will always prevail. H. megidis, under co-occurrence with S. feltiae separately infected Galleria mellonella larvae most commonly at 15 °C, while H. bacteriophora at 20 °C. The study showed that the main determinant of nematode activity towards the host is not temperature, but the presence of co-existing nematode species. The results of the experiment encourage further research to determine the effects of a variety of concurrent biotic and abiotic factors on entomopathogenic nematodes and their biological activity. [ABSTRACT FROM AUTHOR]

Abstract Background The wheat stink bug, Aelia rostrata Boheman (Hemiptera: Pentatomidae), is one of the harmful insects that caused significant product losses in cereals due to outbreaks. Entomopathogenic nematodes (EPNs) are natural enemies of soil insect pests whose effects as a biocontrol agent against many harmful pests have been demonstrated by many laboratories and field/garden studies in the world. The present laboratory studies, using native EPNs [Steinernema carpocapsae (Black sea isolate), S. feltiae (isolate 09-31) (Aydin isolate) and Heterorhabditis bacteriophora (isolate 09-43) (Aydin isolate)] against the wheat stink bug adults, were carried out. Results In the application of EPNs to the soil in plastic cups, the highest mortality rates (75 and 70%) on wheat stink bug occurred at 200 IJs cm−2 concentration of S. carpocapsae isolate at 15 and 12 °C, respectively. In other tested nematode species, the highest insect mortality was observed at 200 IJs cm−2 concentration of S. feltiae and H. bacteriophora isolates, with mortality rates of 65–35% and 55–25%, at 15 and 12 °C, respectively. S. carpocapsae (Black sea isolate) was the most pathogenic among the three nematodes tested. Conclusions It was concluded that S. carpocapsae had the potential as a biocontrol agent against the wheat stink bug, A. rostrata. The applications of S. carpocapsae were the great potential for the management of the pest. Effective use of EPNs should be evaluated in integrated pest management strategies between other biological control agents. According to EPNs laboratory experiments results, field trials should be conducted in future studies.

Background: The weevils Cosmopolites sordidus (Germar), Metamasius hemipterus (Linnaeus), and M. hebetatus (Gyllenhal) (Coleoptera: Curculionidae) form a complex of important pests of plantain crops, causing crop losses of over 60%. Using synthetic insecticides to control these insects has not been efficient; for this reason, the present study searched for using entomopathogenic fungi (EPF) and nematodes (EPN) as alternative control tools. Results: Compatibility of 74 combinations among 30 native fungal isolates and two EPNs (Steinernema feltiae and Heterorhabditis sp.) through inhibition tests was evaluated. It was found that the bacteria carried by Heterorhabditis sp. inhibited the growth of all fungi. In the biological test with EPF and EPN simultaneously against adults of C. sordidus, antagonistic interactions were observed when Heterorhabditis sp. was applied. Only the combination of the fungus strain B14 (Beauveria bassiana) + the EPN, S. feltiae had synergistic effects with a mortality rate of (93.3%). Conclusions: This study revealed that S. feltiae and B. bassiana (strain B14) showed a synergistic effect against adults of C. sordidus. This combination could be an excellent candidate for developing a highly efficient biopesticide prototype in further trials and, together with other strategies of integrated pest management has the potential to improve control of the banana weevil complex. [ABSTRACT FROM AUTHOR]

The confused flour beetle, Tribolium confusum Jacquelin du Val, 1863 (Coleoptera: Tenebrionidae) is a major pest on stored grains. Chemical pesticides are usually used to control stored grain pests but insecticides residue and other negative effects on human and environmental health are the constrain ones in this concern. The biological control agents such as entomopathogenic nematodes (EPNs), which are used to control different harmful organisms, get attention in the alternative control methods. The aim of this study was carried out to determine biocontrol potential of local entomopathogenic nematode isolates, Steinernema carpocapsae (Tokat-Bakışlı05), S. feltiae (Tokat-Emir), Heterorhabditis bacteriophora (TOK-20), and H. bacteriophora (11KG) against adult beetles of confused flour beetle under controlled conditions. EPNs isolates were applied at four different concentrations i.e., 0.0, 25, 50 and 100 IJs/beetle in 1 ml of distilled water at 15 and 25 ± 1 °C temperatures. The highest mortality rates for H. bacteriophora (11KG) and H. bacteriophora (TOK-20) isolates at 25 ± 1 ºC were determined as 91.0 and 81.2%, respectively. H. bacteriophora (11KG) and H. bacteriophora (TOK-20) were found to be the most effective EPNs at a concentration of 100 IJs/beetle at 15 ºC with a mortality of 57.7 and 55.6%, respectively. Mortality rates for the adult confused flour beetle were increased with an increasing the concentration of all EPNs species and also the degrees of temperature. Results showed that local EPNs isolates may use as an alternative biological control agent for T. confusum. Efforts should be made to develop new formulations that will allow nematodes to survive until they find their hosts, and they also need to be tested under field conditions. [ABSTRACT FROM AUTHOR]

The objective of this research was to identify the most promising formulation variants for entomopathogenic nematodes (EPNs) through a systematic review of the literature and a meta-analysis. The focus was aimed at preformulating a nematode strain of the Heterorhabditis genus. Thus, 81,900 articles within the period 1985-2022 were processed and 404 were selected for the review, of which only 44 were included in the database for the meta-analysis. Two databases were created: VIABILITY and PATHOGENICITY, with 254 and 224 pairs of data, respectively, after purification. The data were processed by the nematode genus (Heterorhabditis or Steinernema) according to the result of a generalized linear model to Proc Mixed of SAS 9.0 and the contrast test of minimal significant difference. The statistical package RStudio version 1.1.463 2018 was used for the meta-analytic study. The statistics Q and I² were evaluated. The effect size and its 95% confidence interval were calculated and a forest-plot graph was used. The meta-analysis showed a high variability of the viability and pathogenicity data. The results confirmed that the solid formulations by using clays and other excipients, were adequate to for the entomopathogenic nematodes of the genus Heterorhabditis. [ABSTRACT FROM AUTHOR]

The current study aims to investigate the residual toxicity and nutritional indices of entomopathogenic nematodes (EPNs), as well as immunological response to an infection in Spodoptera littoralis. Compared to the individual impacts of Steinernema carpocapsae, Heterorhabditis indica and EPNs binary combinations showed a higher pathogenicity to S. littoralis according to mortality, physiological responses, and humoral immune. The anti-feedant activity percentages of H. indica and S. carpocapsae treated larvae had a more potent effect than their binary mixture at LC35, compared to full-feeding activity in the control. The biochemical characteristics of infected hemolymph showed a significant variation, not only in the total protein concentration, but also in the appearance of the new protein bands profile. An additional band, with a molecular weight of ~79 KDa was observed at immunized hemolymph, it has been postulated that it may be the phenoloxidase (PO), which is in close agreement with the significant induction of PO activity after infection. Interestingly, the immunised hemolymph of the larvae infected with binary combinations of EPNs showed a notably increased intensity of the major proteins and a rise in the number of antimicrobial peptides with molecular weights under 30 KDa. However, the significant reduction of total protein count and PO level, which ultimately resulting in larval death, is evidence that the binary mixture of the investigated nematodes is highly suppressed S. Littoralis larval immune system. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agriculture & Nature / Kahramanmaraş Sütçü İmam Üniversitesi Tarım & Doğa Dergisi is the property of Kahramanmaras Sutcu Imam Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a notorious polyphagous pest that has recently invaded India in 2018. Within a short period, this pest has spread throughout the country, causing a significant damage to maize. In order to manage this menace, farmers rely on chemical insecticides, but due to concealed feeding nature of this pest insecticides remain ineffective in reaching the target site. In this context, the present study aimed to isolate, characterize and evaluate the reproductive potential of the native strains of entomopathogenic nematode, Heterorhabditis indica against larval instars of S. frugiperda under laboratory conditions. Results: Two strains of H. indica isolated and characterized from the rhizosphere of mango and curry leaf trees were designated as CICR-HI-MN and CICR-HI-CL, respectively. Both strains, CICR-HI-CL and CICR-HI-MN showed differential mortality against 3rd (LC50 value of 21.65, 48.91 IJs/larva), 4th (LC50 value of 25.46, 52.36 IJs/larva) and 5th (LC50 value of 59.20, 71.04 IJs/larva) instar larvae of S. frugiperda, respectively. The instar-wise mortality of S. frugiperda showed that 3rd instar was relatively more susceptible compared to 4th and 5th instar larvae. In terms of efficacy, CICR-HI-CL was almost twice effective than CICR-HI-MN when LC50 and LC95 values of 3rd instar larvae were compared. However, the reproductive potential of both the strains was significantly higher against 5th instar than the 3rd and 4th instar larvae. Strain CICR-HI-CL was more effective in larval mortality, while nematode reproduction was higher in CICR-HI-MN. Conclusions: Native strains of H. indica evaluated in the present study were found effective against larval instars of fall armyworm, S. frugiperda. Higher reproduction on 5th instar larvae demonstrates the ability of these strains to multiply, sustain and perpetuate on late instars of this polyphagous pest and may serve as viable option in integrated pest management program. [ABSTRACT FROM AUTHOR]

[Display omitted] • EPN symbiotic bacteria and their filtrates have insecticidal effects on T. absoluta. • The bacterium X. nematophila was the most effective against larvae of T. absoluta. • 1st/2nd instar larvae of T. absoluta were more susceptible than 3rd/4th instar. • The EPN, their bacteria and filtrates were also tested on the key predator N. tenuis. • The EPN symbiotic bacteria and their filtrates had low impact on N. tenuis. The use of biocontrol agents, such as predators and entomopathogenic nematodes, is a promising approach for the effective control of the tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidaean), an oligophagous insect feeding mainly on Solanaceae species and a major pest of field- and greenhouse-grown tomatoes globally. In this context, the effects of two entomopathogenic nematode species Steinernema carpocapsae (Weiser) (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora (Poinar) (Rhabditida: Heterorhabditidae), as well as their respective bacterial symbionts, Xenorhabdus nematophila and Photorhabdus luminescens (Enterobacterales: Morganelaceae), which were applied as bacterial cell suspensions and as crude cell-free liquid filtrates on T. absoluta larvae, were investigated. The results showed that of all treatments, the nematodes S. carpocapsae and H. bacteriophora were the most effective, causing up to 98 % mortality of T. absoluta larvae. Regarding bacteria and their filtrates, the bacterium X. nematophila was the most effective (69 % mortality in young larvae), while P. luminescens and both bacterial filtrates showed similar potency (ca. 48–55 % mortality in young larvae). To achieve a holistic approach of controlling this important pest, the impact of these factors on the beneficial predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) was also studied. The results demonstrated that although nematodes and especially S. carpocapsae , caused significant mortality on N. tenuis (87 %), the bacterial cell suspensions of X. nematophila and P. luminescens and crude cell-free liquid filtrates had minimum impact on this beneficial predator (∼11–30 % mortality). [ABSTRACT FROM AUTHOR]

Spodoptera frugiperda has caused serious economic damage to various crops. Entomopathogenic nematodes (EPNs) can be used as biological control agents for many pests, including lepidopteran insects. In this study, 218 soil samples were collected from 46 sites in Guangxi, and EPNs were detected in 15 samples. The ITS region of the rDNA gene was used for the molecular identification of isolated nematodes. In total, four and eleven identified populations belonged to Heterorhabditis and Oscheius, respectively. A series of bioassays were conducted to examine the virulence of EPN isolates from Guangxi to control the larvae and pupae of S. frugiperda. The mortality of the third-instar larvae caused by EPNs was concentration dependent. The same dose of EPNs was used to control the third and sixth-instar larvae of S. frugiperda, and the virulence was lower in the sixth-instar larvae. S. frugiperda pupae were treated with different EPNs strains, and the adult eclosion rate of the treated group was significantly lower than that of the sterile water control group (93.3%). Therefore, EPNs could significantly inhibit the eclosion of S. frugiperda pupae. This study provides important information for the biological control of S. frugiperda with EPNs. [ABSTRACT FROM AUTHOR]

The contributions of soil arthropods to entomopathogenic nematode (EPN) food webs are mainly studied in artificial conditions. We investigated changes in arthropod communities in a citrus orchard following soil inundation with Steinernema feltiae or Heterorhabditis bacteriophora. We hypothesized that arthropod taxa, which decline or increase in response to EPN augmentation, represent potential prey or predators of EPN, respectively. Soil was sampled periodically after nematodes were applied, DNA was extracted from organisms recovered by sucrose centrifugation, libraries were prepared, and the ITS2 and CO1 genes were sequenced using Illumina protocol. Species from 107 microarthropod (mites and collembola) families and 121 insect families were identified. Amplicon sequence variant (ASV) reads for H. bacteriophora were less than 10% of those for S. feltiae three days after inundation, whereas microarthropod ASVs were double in plots with H. bacteriophora compared to those with S. feltiae. Significantly fewer microarthropod and insect reads in S. feltiae compared to untreated plots suggest the possibility that S. feltiae preyed on mites and Collembola in addition to insects. The responses over time of the individual microarthropod species (MOTU) suggest that regulation (up or down) of these EPN resulted from a cumulative response by many species, rather than by a few key species. [ABSTRACT FROM AUTHOR]

The present study on pathogenicity of entomopathogenic nematodes against Spodoptera litura in laboratory conditions was undertaken during 2020-21, with the aim to ascertain the effectiveness of entomopathogenic nematodes, against an obnoxious cosmopolitan pest S. litura. Experiments were conducted by using entomopathogenic nematode (EPN) isolate Heterorhabditis indica (CICRGuava), on filter paper, against Galleria mellonella and S. litura at the treatment dose of 10, 20, 30, 40, 60, 80 and 100 IJs/100µl along with control (Sterile distilled water). The results of our study revealed that, EPN isolate H. indica (CICR-Guava) caused 100% mortality at the treatment dose of 40 IJs/100µl within 72 h of infection in 5th instar larvae of G. mellonella and in case of S. litura, 100% mortality was recorded within 72 h of infection at the treatment dose of 100 IJs/100µl in 3rd instar larvae, which was found more susceptible. The median lethal concentration of H. indica (CICR-Guava) for 5th instar larvae was 2.29 IJs/100µl. The result of reproductive potential of isolates of entomopathogenic nematodes revealed that the highest yield was obtained from 5th instar larvae of G. mellonella at treatment dose of 100 IJs/100µl 278667 IJs per larva. In case of S. litura, the highest yield obtained was 152533 IJs. It could be concluded that, there was a positive correlation between nematode treatment concentration, time of exposure and the insect mortality of the tobacco cut worm and multiplication rate of IJs increased with increase of exposure time and size of larvae. This EPN isolate, H. indica (CICR-Guava) can be suggested as biocontrol agents for the control of S. litura in the Vidarbha region. [ABSTRACT FROM AUTHOR]

Background: The wheat stink bug, Aelia rostrata Boheman (Hemiptera: Pentatomidae), is one of the harmful insects that caused significant product losses in cereals due to outbreaks. Entomopathogenic nematodes (EPNs) are natural enemies of soil insect pests whose effects as a biocontrol agent against many harmful pests have been demonstrated by many laboratories and field/garden studies in the world. The present laboratory studies, using native EPNs [Steinernema carpocapsae (Black sea isolate), S. feltiae (isolate 09-31) (Aydin isolate) and Heterorhabditis bacteriophora (isolate 09-43) (Aydin isolate)] against the wheat stink bug adults, were carried out. Results: In the application of EPNs to the soil in plastic cups, the highest mortality rates (75 and 70%) on wheat stink bug occurred at 200 IJs cm−2 concentration of S. carpocapsae isolate at 15 and 12 °C, respectively. In other tested nematode species, the highest insect mortality was observed at 200 IJs cm−2 concentration of S. feltiae and H. bacteriophora isolates, with mortality rates of 65–35% and 55–25%, at 15 and 12 °C, respectively. S. carpocapsae (Black sea isolate) was the most pathogenic among the three nematodes tested. Conclusions: It was concluded that S. carpocapsae had the potential as a biocontrol agent against the wheat stink bug, A. rostrata. The applications of S. carpocapsae were the great potential for the management of the pest. Effective use of EPNs should be evaluated in integrated pest management strategies between other biological control agents. According to EPNs laboratory experiments results, field trials should be conducted in future studies. [ABSTRACT FROM AUTHOR]

Summary: The entomopathogenic nematode (EPN), Heterorhabditis bacteriophora , is an important biological control agent worldwide. Industrially produced EPN need to meet the climatic requirements for the control of pests in field agriculture in autumn and spring when temperatures are low. For this trait (virulence at low temperature), previous EPN improvement attempts relied on phenotypic selection and the selected trait had low stability. The use of molecular markers can increase the efficacy of EPN breeding by tracking traits associated with specific genotypes. To date, fewer than 200 polymorphic and reproducible sequence-tagged molecular markers in H. bacteriophora have been reported. Here, we enhanced the palette of highly polymorphic genetic markers for this EPN by applying genotyping by sequencing (GBS). By analysing 48 H. bacteriophora homozygous wild-type inbred lines from different origins, we determined 4894 single nucleotide polymorphisms (SNPs) with at least one polymorphism along the tested set. For validation, we designed robust PCR assays for seven SNPs, finding 95% correspondence with the expected genotypes along 294 analysed alleles. We phenotyped all lines for their virulence at low temperature (15°C) against mealworm and observed infectivity ranging from 38 to 80%. Further, we carried out association analyses between genotypic and phenotypic data and determined two SNPs yielding potential association with H. bacteriophora virulence at low temperature. The use of these candidate SNPs as breeding markers will speed up the generation of strains better adapted to low temperature in this species. The generated set of lines and SNP data are a versatile tool applicable for further traits in this EPN. [ABSTRACT FROM AUTHOR]

Background: Entomopathogenic nematodes of the genera Heterorhabditis and Steinernema are widely used as biocontrol agents against diverse insect pests. Their association with symbiont bacteria is found to be the primary cause of insect mortality. The present study reported a comprehensive characterization of a local Philippine EPN isolate using congruent morpho-taxometrical and molecular data and the associated bacterium in the infective dauer juveniles. Results: Using an insect-baiting technique, a nematode isolate labeled F2H was recovered from the sandy soils in the coastal area of southern Philippines. Based on morphology and morpho-taxometrics, the F2H isolate collected from Iligan City was identified as Heterorhabditis indica. Analysis of the ITS region of rDNA revealed the highest sequence match to H. indica. The sequences of the bacterial 16S rDNA gene showed that the symbiont of H. indica presented 100% similitude with the sequences of Ochrobactrum anthropi. Further, pairwise alignment and phylogenetic analysis demonstrated that O. anthropi, O. lupini and O. cytisi shared 100% similarity and form a monophyletic clade. These strains have not presented any differences in the phylogenetic and 16S rDNA data, and O. lupini and O. cytisi should be considered a later heterotypic synonym of O. anthropi. Conclusions: The description of H. indica-O. anthropi association was the first report in the Philippines. This provides additional account and collection of naturally isolated EPN-bacteria, contributing to limited knowledge on its diversity in the Philippines, which can be utilized in the biocontrol of pests after further comprehensive assessments. [ABSTRACT FROM AUTHOR]

Background: Cutworms (Agrotis spp.) are cosmopolitan and polyphagous pests distributed throughout world, which belong to the family Noctuidae, and about 26 species are found associated with agriculturally important crops in India and some other countries of world. The most prominent species belonging to genera Agrotis are Agrotis ipsilon, A. flammatra, A. plecta, A. spinifera and A. segetum. Cutworms cause substantial damage to many agricultural and horticultural crops particularly, at the seedling stage. This pest produces vitiating symptoms with a young stage (larvae) by feeding on the epidermis of leaves and eating away parts of the stem, tubers, etc. Results: This review article is mainly focused on management of cutworm, which is very challenging due to larval hiding behaviour during the day time and feed actively at night. Efficient chemical control of cutworm may be obtained by adequately applying chemicals when young caterpillars are still on the leaves and therefore vulnerable. As per biology of cutworms, these pests remain hidden in cracks and crevices during most of life cycle so chemical control is often ineffective and economic. Sometimes, inadequate application of these chemicals is resulted into the development of resistance in these pests. Moreover, the adverse effects of the chemicals have led researchers to search for new control strategies. Recently, biological control has become a practical option for eco-friendly management of numerous insect pests. Among biological control, entomopathogenic nematodes (EPNs) have broad potential to kill the cutworms in soil itself. Conclusions: Various species of EPNs like Steinernema spp. and Heterorhabditis spp. are found a quite effective and hold considerable potential to manage cutworms. So, the use of EPNs for the management of cutworms is a good alternate to chemical method. [ABSTRACT FROM AUTHOR]

Codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) is the main pest of apple all over the world. Besides the usage of the broad spectrum insecticides being the main control for the C. pomonella, also there is a potential of the usage of the entomapathogen nematodes(EPN) for the same control. In this study, the efficacies of four entomopathogenic nematode species [Steinernema carpocapsae (Tokat Bakisli05), S. feltiae (Tokat-Emir), Heterorhabditis bacteriophora (TOK-20), and H. bacteriophora (11KG)] have been investigated against the last instar of C. pomonella under laboratory conditions (in vitro). Three different EPNs concentrations [250, 500 and 1000 infective juvenile (IJ)/ml-1] of the nematodes and distilled water as a control were used. Dead larvae were counted 48, 72 and 120 h after treatment, and mortality rates were calculated. H. bacteriophora (11KG) isolate was the most effective isolate causing 77.8% larval mortality at the highest concentration (1000 IJs/ml-1) after 120 h. This was followed by S. feltiae (76.4%), S. carpocapsae (69.5%) and H. bacteriophora (TOK-20) (65.3%). The lowest mortality rates (respectively %5.3, 13.5, 2.7 and 10.8) were seen in all nematode species at a concentration of 250 IJs/ml-1. The isolates are found effective on the last instar larvae of C. pomonella but should be supported with detailed field studies. [ABSTRACT FROM AUTHOR]

Background: Biotic and abiotic factors influence survival, infectivity, development, reproduction, and activity of the entomopathogenic nematodes (EPNs). EPNs have been used to suppress the soil-inhabitant insects, which applied as a successful biological control agent against the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera/Noctuidae) larvae, and pupae. Results: Studying the effect of different temperatures 20, 25, and 30°C ± 2, and the soil moisture content at 10, 15, and 25% on the susceptibility of two Heterorhabditis sp. strains, Egyptian strain (TAN5) and imported strain (Hb88) against the A. ipsilon 4th and 6th larval instars and 3-day-old pupae was carried out under laboratory conditions. The tested concentrations of the two strains were 30, 60, 120, 240, and 480 IJs/cm2 of soil surface. The mortality rate of 4th instar A. ipsilon larvae was high after Heterorhabditis strain TAN5 treatments at all concentrations, which ranged between (24 and 100%) and (6–100%) at 25°C and 30°C, respectively. At 20°C, Heterorhabditis strain Hb88 recorded higher mortality percentages for A. ipsilon 4th and 6th larval instars and pupae than the indigenous strain TAN5. The soil moisture content of 25% gave the highest mortality rates for the 4th instar larvae of A. ipsilon after treatments of the two strains. The Egyptian Heterorhabditis strain TAN5 was tolerant to the increase in temperature and more tolerant to the change in the water content of the soil than the imported strain Hb88 at all concentrations tested. In a semi-field experiment, Heterorhabditis strain TAN5 at concentrations between (1000–8000 IJs/cm2 of soil surface) showed mortality rates (27–95%) for 4th instar A. ipsilon larvae and (19–81%) for the 3-day-old pupae, respectively. Conclusions: Heterorhabditis strains TAN5 can was utilized against the black cutworm of A. ipsilon at the temperatures 25 and 30°C. Heterorhabditis strains TAN5 and Hb88 can be utilized against the black cutworm of A. ipsilon at the soil moisture content from 15 to 25%. In the semi-field experiment, Heterorhabditis TAN5 and Hb88 strains were effective against larvae and pupae of A. ipsilon at high concentrations of the nematodes. [ABSTRACT FROM AUTHOR]

Background: Entomopathogenic nematodes (EPNs) are promising alternatives since they have many characteristics as a biological control agent against insect pests. Results: Among indigenous EPN isolated, adapted to local environmental conditions by employing the Galleria baiting strategy, only one sample was positive for the presence of EPNs. The new isolate was identified at the species level using DNA sequencing of the internal transcribed spacer region and the Basic Local Alignment Search Tool search of GenBank showed that the isolate had a high similarity (99%) with that sequence available for Heterorhabditis taysearae. The pathogenicity of the EPN isolate was tested against the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), using different concentrations (60, 90, 120 and 150 IJs/larvae). Data showed that 150 IJs/larvae caused 100% mortality rate, followed by 120 IJs/larvae (90%), while 60 IJs/larvae showed the lowest rate (60%) after 72 h. Conclusions: The present study indicated that the native isolate of EPN could be recommended against S. littoralis as an efficient tool in its control programs. [ABSTRACT FROM AUTHOR]

The efficacy of both botanical pesticides and entomopathogenic nematodes (EPN) is largely dose-dependent and driven by environmental conditions. Combination of the EPNs and botanicals may enhance their efficacy; thus, we investigated the compatibility of the medicinal plants Alepidea amatymbica and Elephantorrhiza elephantina with five locally isolated EPN strains, three Steinernema (S. khoisanae, S. biddulphi and S. innovationi) and two Heterorhabditis (H. bacteriophora and Heterorhabditis sp. SGI 244). The experiments were designed to evaluate EPNs survival in plant extracts extracted using water and ethanol at 1%, 0.75%, 0.50%, 0.25% and 0.125% concentrations and nematode viability post-exposure. A concentration of 1000 IJs/mL in distilled water was used. Incubating extracts of A. amatymbica and E. elephantina with EPNs influenced the survival and virulence of the EPN species examined. The percentage survival of the EPNs post-exposure to the plant extracts was dependent on the plant extraction method and concentration in A. amatymbica but not in E. elephantina. The ethanol extraction method supported high percentage survival both at smaller and larger concentrations. The surviving infective juveniles (IJs) were virulent to Tenebrio molitor in both the aqueous and ethanol extracts of A. amatymbica and E. elephantina. However, virulence was observed to be strain-specific and not IJ concentration-dependent. Percentage mortality (against T. molitor) of strains with low percentage survival in aqueous extract of A. amatymbica compared effectively with those of higher percentage survival. The compatible relationship between extracts of the two plants and the EPN strains may lead to improved pest control in agricultural farming systems relative to either one of them applied individually. [ABSTRACT FROM AUTHOR]

Abstract Three strains of entomopathogenic nematodes, labelled P5, P6 and PH, were isolated during surveys of agricultural soils of Pir Panjal Range, using insect baiting technique. Morpho-taxometrical studies and molecular data confirmed that these isolates belong to Heterorhabditis bacteriophora, making this finding the first report of this species from Jammu and Kashmir, India. Their distribution using a meta-analysis of GenBank records was attempted to assess. The morphology, morphometric studies and molecular data were conspecific to original description with minor deviations. Data analysis of the distribution showed that H. bacteriophora was the most ubiquitous throughout the South Africa subcontinent, but it was rarely found in Indian subcontinent having been isolated from 3 states throughout the country. As these 3 strains of H. bacteriophora are native to the hilly region of Kashmir Valley, they can be exploited for the control of target crop insect pests of the region. However, further studies are required regarding their life cycle, host range, virulence potential and survival capacity under extreme environmental conditions.

To improve the efficacy of entomopathogenic nematodes (EPNs) as biocontrol agents in the field, knowledge about the kinds of impact, which the physical nature of the agricultural soil environment may have on nematode survival, persistence, and host location is important. The study aimed to investigate the effects which the addition of organic soil amendments would have on the duration of infectivity and survivorship of infective juveniles (IJs) belonging to Heterorhabditis bacteriophora in soils undergoing progressive moisture loss. The soil amendments involved mixing commercially available organic compost such as mulch, organic compost, professional potting mix, organic lawn dressing with two soil textural classes, namely loamy soil, and coarse river sand. Using Petri dish-based assays, the mulch soil amendment resulted in the highest Galleria mellonella larval mortality rate across different organic compost application concentrations (mass: mass basis). The type of compost used based on its feedstock composition, the concentration of nutrients, and organic matter mixed with a specific type of soil texture had a significant effect on the tolerance of EPNs to different dehydration periods. Virulence and efficacy decreased over 7 days of progressive dehydration. The use of organic compost did not have any detrimental effect on EPNs. The knowledge obtained could be applied to increase the effectiveness of entomopathogenic nematodes as biocontrol agents. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema kill insects with the help of their symbiotic bacteria. They are widely used as biocontrol agents to manage insect pests of crops. The infective juveniles (IJ) of EPNs are isolated from soil by insect baiting technique, which is labour-intensive, time-consuming, wasteful, and inefficient. Here, we present loop-mediated isothermal amplification (LAMP) assays for rapid detection of Heterorhabditis spp. (Het-LAMP) and Steinernema spp. (Ste-LAMP) from total soil DNA. The primers for Het-LAMP and Ste-LAMP were designed using ITS and 18S rDNA regions of genomic DNA. The LAMP reactions could be completed in 60 min, at 66 °C and 68 °C, respectively, followed by termination at 85 °C for 5 min. The assays were highly sensitive and could detect up to 0.02 picograms of Heterorhabditis DNA and 96 picograms of Steinernema DNA in a 25 μl reaction. Both the assays were specific for the target nematode species and detected the presence of a single IJ in the total DNA extracted from 250 mg of soil. The assays developed in this study would be of immense utility for the efficient detection and identification of native EPNs in large-scale surveys. These assays are amenable to automation and could be used to develop convenient detection kits for point-of-service diagnosis of EPNs in the field without the need for a trained and experienced personnel. [ABSTRACT FROM AUTHOR]

We present the first report of Heterorhabditis bacteriophora entomopathogenic nematodes isolated from sandy loam soil obtained from Walkerville, South of Johannesburg, Gauteng province, South Africa. A survey was conducted to collect soil samples and isolate entomopathogenic nematodes between 2012 and 2016. Entomopathogenic nematodes are insect-killing microscopic worms found in soil and have a symbiotic relationship with insect pathogenic bacteria. Molecular and morphological techniques including genomic DNA extractions, polymerase chain reaction and sequencing of the 18S rDNA, phylogenetic analysis, light microscopy and scanning electron microscopy were used to identify entomopathogenic nematodes from the collected soil samples. H. bacteriophora was recovered in one out of 80 soil samples from an uncultivated grassland and the frequency of its isolation from soil samples in our study was 2%. Phylogenetic tree analysis revealed that the South African isolate was grouped with the strain H. bacteriophora strain 56-C. H. bacteriophora. The body length, body width and tail of the isolate are slightly shorter than the previously described H. bacteriophora. This is the first H. bacteriophora species to be isolated and reported from South African soil and future studies will explore its potential as a biological control agent of problematic insect pests in agricultural industries. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPN) have great potential as biological control agents against root-feeding insects. They have a rapid and long-lasting mode of action, minimal adverse effects on the environment and can be readily mass-produced. However, they have a relatively short shelf-life and are susceptible to desiccation and UV light. These shortcomings may be overcome by encapsulating EPN in Ca2+-alginate hydrogels, which have been shown to provide a humid and UV protective shelter. Yet, current Ca2+-alginate formulations do not keep EPN vigorous and infectious for a prolonged period of time and do not allow for their controlled release upon application. Here, we introduce solid Ca2+-alginate beads which we supplemented with glycerol to better retain the EPN during storage and to ensure a steady release when applied in soil. Glycerol-induced metabolic arrest in EPN (Heterorhabditis bacteriophora) resulting in quiescence and total retainment of EPN when added to beads made with 0.5% sodium alginate and 2% CaCl2·2H2O solutions. More than 4,000 EPN could be embedded in a single 4–5-mm diameter bead, and quiescence could be broken by adding water, after which the EPN readily emerged from the beads. In a field trial, the EPN beads were as effective in reducing root damage by the western corn rootworm (WCR, Diabrotica virgifera virgifera) as EPN that were applied in water. Although further improvements are desirable, we conclude that Ca2+-alginate beads can provide an effective and practical way to apply EPN for the control of WCR larvae. [ABSTRACT FROM AUTHOR]

Spodoptera frugiperda has caused serious economic damage to various crops. Entomopathogenic nematodes (EPNs) can be used as biological control agents for many pests, including lepidopteran insects. In this study, 218 soil samples were collected from 46 sites in Guangxi, and EPNs were detected in 15 samples. The ITS region of the rDNA gene was used for the molecular identification of isolated nematodes. In total, four and eleven identified populations belonged to Heterorhabditis and Oscheius, respectively. A series of bioassays were conducted to examine the virulence of EPN isolates from Guangxi to control the larvae and pupae of S. frugiperda. The mortality of the third-instar larvae caused by EPNs was concentration dependent. The same dose of EPNs was used to control the third and sixth-instar larvae of S. frugiperda, and the virulence was lower in the sixth-instar larvae. S. frugiperda pupae were treated with different EPNs strains, and the adult eclosion rate of the treated group was significantly lower than that of the sterile water control group (93.3%). Therefore, EPNs could significantly inhibit the eclosion of S. frugiperda pupae. This study provides important information for the biological control of S. frugiperda with EPNs.

Background: Entomopathogenic nematodes (EPNs) are one of the widely studied biological control agents. The present study was conducted to evaluate the efficacy of two EPNs species, Heterorhabditis bacteriophora (Poinar) (Rhabditida: Heterorhabditidae) and Steinernema aciari (Qui, Yan, Zhou, Nguyen and Pang) (Rhabditida: Steinernematidae), isolated locally from soils of Majuli river island, Assam, India against two important subterrenean pests; Odontotermes obesus (Rambur) (Isoptera: Termitidae) and Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) under laboratory conditions. Results: In case of O. obesus, mortality percent was recorded by H. bacteriophora after 72 h. at 300 IJs/termite and by S. aciari at 250 and 300 IJs/termite after 96 h. The lowest LD50 and LT50 values obtained for H. bacteriophora were 13.054 IJs/termite and 26.639 h., respectively, while those of S. aciari were 42.040 IJs/termite and 31.761 h., respectively. With respect to A. ipsilon, H. bacteriophora registered a highest mortality rate at 300 IJs/larvae after 144 h. S. aciari showed 100 percent mortality at 300 IJs/larva after 168 h. The lowest values of LD50 and LT50 for H. bacteriophora were 35.711 IJs/larva and 83.050 h., respectively. The lowest values of LD50 and LT50 for S. aciari were 71.192 IJs/larvae and 97.921 h., respectively. Overall, H. bacteriophora displayed more virulence toward O. obesus and A. ipsilon than S. aciari. Conclusion: Both native EPNs were found effective against O. obesus and A. ipsilon. However, H. bacteriophora was more virulent toward O. obesus and A. ipsilon than S. aciari under the laboratory conditions. [ABSTRACT FROM AUTHOR]

The antagonistic activity of four Philippine EPN isolates of Steinernema abbasi Elawad et al. (SaMBLB) and Heterorhabditis indica Poinar et al., (HiPBCB, HiBSDS, and HiMAP) was investigated against Meloidogyne incognita (Kofoid & White) Chitwood. Fourteen days after inoculation, it was demonstrated that concomitant application of 1,000 live infective juveniles (IJ) of each EPN species and 200 M. incognita IJ significantly reduced root penetration consequently affecting juvenile development to the adult stage of M. incognita. The lowest number of M. incognita was found in plants treated with S. abbasi MBLB (1.90 ± 2.20) and H. indica PBCB (2.05 ± 2.61). Externally, formation of well-developed galls was only observed on tomato plants inoculated with RKN alone indicative of the negative effect of EPN to M. incognita root penetration. However, none of the EPN isolates had positive effect on the growth of M. incognita-treated tomato plants measured through plant height. This study provides the first insight on the biological control potential of these local EPN isolates for the management of M. incognita in the Philippines. [ABSTRACT FROM AUTHOR]

• The polyphenol oxidase of G. mellonella is resistant to H. beicherriana. • Use thiourea as an adjuvant for biopesticide to enhance the effectiveness of EPN. • Suppressing host immunity combined with EPN can accelerate host death. Entomopathogenic nematodes (EPN) are potent microbial biocontrol agents applied commercially against various economically important insect pests. The efficacy of EPN in the field may be partially reduced when compared to chemical insecticides due to its sensitivity to environmental stressors like temperature, desiccation, and UV light. Thus, researchers have developed methods to enhance the effectiveness of EPN, such as screening or breeding stress-resistant strains and creating adjuvants for EPN protection in the field. This study used another strategy to lower the host's immunity so that the anti-infection ability of the pest wanes, and the virulence of EPN waxes accordingly. In addition to its use as a plant growth regulator, thiourea also functions as an inhibitor of polyphenol oxidase (PO) in insects. Thiourea can inhibit a key interaction in the humoral immunity of insects, so we utilized it to enhance the efficacy of EPN. To investigate the effects of thiourea on PO activity inhibition and EPN pathogenesis, we studied the effects of thiourea on survival, infectivity, reproduction, and host searching ability of the EPN, Heterorhabditis beicherriana , and monitored in vivo and in vitro polyphenol oxidase activity of the model insect host, Galleria mellonella. The survival of H. beicherriana infective juveniles (IJs) was barely affected after exposure to 0.5 mM and 1 mM thiourea solution, and the reproductive output of H. beicherriana IJs (after applying 50, 100 and 200 IJs per host) in 0.5 mM and 1 mM thiourea was not different compared to the control. However, the LD 50 of G. mellonella larvae caused by H. beicherriana without thiourea was significantly higher than H. beicherriana IJs in thiourea. Moreover, thiourea inhibited in vivo and in vitro polyphenol oxidase activity of G. mellonella infected by EPNs at different concentrations. Thus, thiourea can improve the biological control efficacy of EPNs, and the enhanced environmentally friendly approach may apply to diverse cropping systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantification of Photorhabdus DNA inside Heterorhabditis bacteriophora using qPCR. • Detection of bacteria load directly proportional to H. bacteriophora virulence. • Storage temperatures below 7.5 °C resulted detrimental to Photorhabdus along time. Biological control products based on the entomopathogenic nematode Heterorhabditis bacteriophora can vary in virulence (quality). The influence of their symbiotic bacteria Photorhabdus spp. inside the infective dauer juvenile (DJ) on DJ quality has not received much attention in the past. The presence of the bacteria in the DJ is crucial for its biocontrol potential. This investigation provides a method to quantify the bacterial load inside the DJ based on a qPCR technique. Information from the genome of Photorhabdus laumondii strain DE2 was used to identify single copy genes with no homology to any other bacterial accessions. One gene (hereby named CG2) was selected for primers design and for further qPCR experiments. Cross-amplification tests with P. thracensis and P. kayaii , also symbionts of H. bacteriophora , were positive, whereas no amplicons were produced for P. temperata or Xenorhabdus nematophila. We tested our qPCR system in DJ populations carrying defined proportions of bacteria-free (axenic) vs bacteria-carrying nematodes. With an increasing proportion of axenic DJ in a population, virulence declined, and the virulence was proportional to the amount of bacterial DNA detected in the population by qPCR. Along liquid storage over long time, virulence also decreased, and this factor correlated with the reduction of bacterial DNA on the respective DJ population. We observed that stored DJ kept virulent up to 90 days and thereafter the virulence as well as the amount of bacterial DNA drastically decreased. Storage temperature also influenced the bacterial survival. Inside formulated DJ, the loss of bacterial DNA on the DJ population was accelerated under storage temperatures below 7.5 °C, suggesting that reproduction of the bacterial cells takes place when growth temperature is favorable. The role of bacterial survival inside stored DJ can now be adequately addressed using this molecular quality-control technique. [ABSTRACT FROM AUTHOR]

Abstract Tomato leaf miner, Tuta absoluta (Meyrick), is a major threat to tomato production as it can cause up to 100% yield loss under both greenhouse and open-field conditions. Chemical control, which is associated with several undesirable effects, remains the only option readily available for this pest since its invasion of Rwanda in the year 2015. This study assessed the potential of using local isolates of entomopathogenic nematodes (EPNs) in management of T. absoluta in Rwanda. Six EPNs including four locally isolated strains: Steinernema sp. RW14-M-C2a-3, Steinernema sp. RW14-M-C2b-1, S. carpocapsae RW14-G-R3a-2 and Heterorhabditis bacteriophora RW14-N-C4a, and two exotic species: S. carpocapsae All and H. bacteriophora H06 were evaluated. Three bioassays were conducted in the laboratory, using a tomato leaflet with third instar T. absoluta larva in gallery and 9-cm Petri dishes as bioassay arenas in a completely randomized design with three replications. The EPNs were applied at a volume of 1 ml containing 500 infective juveniles per leaflet, while sterile tap water was used as negative control. Larval mortality was checked continuously for 96 h at 24 h interval. The results revealed that all the tested EPNs were able to find and kill T. absoluta larvae inside the leaf galleries; and their efficacy increased with exposure time. The pathogenicity effects were significantly different (p < 0.05) among EPNs. In the first 24 h after inoculation, the efficacy of local EPN isolates (53.3–96.7%) was significantly higher than the one of exotic species (0.0–26.7%). The efficacy of three Rwandan EPN isolates, Steinernema sp. RW14-M-C2a-3, Steinernema sp. RW14-M-C2b-1, and S. carpocapsae RW14-G-R3a-2 was not significantly different from 24 to 96 h after inoculation, except for S. carpocapsae RW14-G-R3a-2 during 24 h after inoculation in bioassay 3. There was insignificant difference among all the EPN isolates after 96 h of exposure. This is the first study carried out in Rwanda that investigated the potential of locally isolated EPNs against T. absoluta. Field experiments should be conducted to fully explore the possibilities of using local EPN isolates in integrated pest management of T. absoluta in Rwanda.

Abstract A survey was conducted in three main regions of Iraq to isolate and identify entomopathogenic and insect parasitic nematodes. Soil samples were collected from 15 sites across 3 provinces from grassland, date palm, and citrus fields, and tested for the presence of nematodes. Out of 100 samples collected, 2 isolates of nematodes were recognized. The collected specimens were characterized first morphologically and then by molecular studies to characterize and identify the isolates based on ITS and 18S rDNA genes. Both isolates were recovered from soil samples of citrus and palm orchards located in 3 regions in the city of Baghdad. The isolates were identified by analyzing sequenced results and then by DNA sequences that were blasted against the NCBI database in GenBank. The 2 isolates were separated into 2 genera, assigned as IRQ.1 and were identified as Heterorhabditis and IRQ.2, that was identified as Oscheius. Molecular analysis and phylogenetic relationship of both genera were analyzed, using the DNA sequences of 2 loci. The Heterorhabditis species was assigned as Heterorhabditis bacteriophora, while the Oscheius species was identified as Oscheius myriophilus. These species were the first to be reported in Iraq.

Background: Entomopathogenic nematodes (EPNs) are widely used in biological control for soil-dwelling stages of many insect pests that are characterized by their safety to most non-target organisms and to the environment. Results: The objectives of the present study were isolation of EPNs from agricultural soil in Egypt for further use in biological control programs and study the genetic variation among them using the molecular marker inter-simple sequence repeats (ISSR). Three out of 25 soil samples collected from fields cultivated with strawberry, tangerine, and pumpkin were positive for the presence of EPNs, using the Galleria baiting technique. Sequencing of the internal transcribed spacer (ITS) region indicated that the isolates obtained belong to Heterorhabditis sp. The ITS sequences were submitted to the National Center for Biotechnology Information (NCBI) and registered under accession nos. MH553165, MH553168, and MH553169. Six ISSR primers were used. The numbers of polymorphic bands were 42 out of 56, and the polymorphism percentage was 75%. The highest number of bands was 12 bands generated by primer ISSR8 followed by UBC-809 (11 bands) while recorded the lowest band number (4 bands), the percentage of polymorphism ranged from 40% (ISSR1) to 100% (ISSR6). Conclusion: ISSR marker can be considered a good marker to study genetic diversity and detecting the genetic polymorphism among the nematodes species. [ABSTRACT FROM AUTHOR]