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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.

Early detection and monitoring of the internal aspects of Bactrocera zonata infestation in fruits and vegetables are important for sustainable agriculture. The present study depends on the non-destructive detection of B. zonata damage in peach fruits using a high-resolution spectroradiometer to characterize the spectral reflectance pattern of peach fruits in healthy and infested fruits with different pest stages, including egg stage and larval instars. Additionally, five vegetation indices were used to detect infestation. Laboratory trials were carried out to investigate the entomopathogenic nematodes (EPNs) pathogenicity, gamma-irradiated and unirradiated Steinernema carpocapsae, and Heterorhabditis bacteriophora against B. zonata larvae and pupae. The spectral reflectance pattern of healthy peach fruit samples was higher than that of all infested samples. The peak level of light reflection for a peach fruit in a healthy state was observed at 750 nm. Conversely, at 1050 nm, the reflectance was low, and it reached its minimum level at 2150 nm for infested peach fruit. Green spectral zones achieved the highest level of discrimination between healthy and infested peach fruit. There was no noticeable distinction between the blue and SWIR-1 zones. However, SWIR-2, red, and NIR spectral zones exhibited a significant difference as they could differentiate between healthy and infested peach fruit. The normalized pigment chlorophyll index (NPCI) was the best plant index employed in pest identification. As the concentration of EPNs increased, the proportion of mortality additionally increased. Furthermore, this study revealed that irradiation of S. carpocapsae juveniles boosted their pathogenicity toward larvae. The LC50 value decreased from 569.39 infective juveniles (IJs)/larva to 433.43 IJs/larva. There was no significant difference in pupae. However, irradiation of H. bacteriophora juveniles negatively impacted larvae, increasing the LC50 value from 1608.04 IJs/ larvae to 2295.73 IJs/larvae by 1.4 fold. Additionally, it significantly affected pupae, as it caused the lowest LC50 value of 402.66 IJs/pupae. The results of this study confirmed hyperspectral data’s utility in the early prediction of fruit infestation and differentiated between different stages of B. zonata infestation. Similarly, applying irradiation to EPNs significantly impacts the control of B. zonata. [ABSTRACT FROM AUTHOR]

Abstract Ctenocephalides felis felis is a relevant and widely distributed ectoparasite that acts as a vector of disease-causing pathogens. Moreover, it is responsible for economic losses due the use of harmful chemicals to the environment and that favor the emergence of insecticide-resistant populations. Research on entomopathogenic nematodes may open up an alternative route to the insect chemical control. The present study aimed to evaluate the killing efficacy of Heterorhabditis bacteriophora (HP88) against C. felis larvae in 400 μL, 600 μL and 1000 μL of suspension containing 120, 160 and 200 infective juveniles/larva and 600 μL of suspension containing the same concentrations of Heterorhabditis indica (LPP30), divided into two groups (absence and presence of diet) and a control group with three replications containing only distilled water. In the bioassay with H. bacteriophora, the groups in 600 μL of suspension showed higher mortality rates than those in the other tested volumes, which were above 80% at all concentrations. On the other hand, H. indica achieved mortality rates above 70% at all concentrations used. Results indicate that flea larvae are susceptible to in vitro infection by H. bacteriophora and H. indica.

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

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

The weevil Scyphophorus acupunctatus Gyllenhal causes damage and losses in agave crops and has traditionally been controlled using contact and systemic agrochemicals. Implementing microbial control strategies is proposed as an alternative to mitigate the environmental impact associated with agrochemicals. The objective of this study was to determine the survival of entomopathogenic nematodes in oil emulsions for the control of adult S. acupunctatus. Three species of entomopathogenic nematodes were evaluated: Steinernema carpocapsae, S. glaseri, and Heterorhabditis bacteriophora. We used two concentrations (50 ± 5 and 100 ± 10 infectious juvenile nematodes), and oil emulsions derived from Salvia hispanica, Triticum vulgare, and Olea europea with oil purity of 20% and 40%. The effectiveness of these treatments was assessed by determining the mortality rate of S. acupunctatus. The results indicate that the combination of S. glaseri and H. bacteriophora, at concentrations of 50 ± 5 and 100 ± 10 nematodes, respectively, with T. vulgare and O. europea oils, achieved a mortality rate of 85.76% in S. acupunctatus adults at 24 h. At 120 h, a mortality rate of 100% was achieved with specific formulations, such as S. glaseri with 100 ± 10 nematodes + O. europea, and H. bacteriophora with 100 ± 10 nematodes + O. europea. Consequently, we conclude that oil formulations combined with nematodes show potential as an effective and environmentally friendly alternative for the control and management of 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]

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

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: Two consecutive field trials using a blend of entomopathogens in combination with a new chemistry insecticide were conducted to determine treatment effects on onion thrips (Thrips tabaci Lindeman) populations, crop damage, plant development, crop yield and impact on natural enemies. Products were tested in an onion cropping system and included the insect pathogenic fungus Beauveria bassiana (isolate WG‐11), an entomopathogenic nematode Heterorhabditis bacteriophora (strain VS) and the new‐chemistry chemical insecticide spinetoram. RESULTS: In all treatments, a significant decrease in thrips per plant population was detected in both trials. Overall, dual application of entomopathogens and insecticide was more effective than singly applied treatments. The lowest number of thrips larvae (1.96 and 3.85) and adults (0.00 and 0.00) were recorded when treated with dual application of B. bassiana and spinetoram at 7 days post application (DPA) after the second spray application in 2017and 2018, respectively. Damage on onion plants was considerably decreased in all treatments relative to the control. The lowest damage was observed on onion plants treated with B. bassiana + spinetoram at 7 DPA after the second spray application during both years. A significant decrease in the number of natural enemies (beetles, spiders, mites, lacewings, ants and bugs) on onion plants was recorded during both years. Insect pathogens when applied alone and in combination with each other considerably protected arthropod natural enemies compared to insecticide application applied alone. Significant increase in plant agronomic traits was observed compared to the control. Among all the treatments, B. bassiana + spinetoram produced maximum leaf length, leaf weight, total leaves, neck diameter, bulb diameter, number of rings per bulb, bulb weight, dry matter and plant yield following the 2017and 2018 applications, respectively. CONCLUSION: The findings of the study reveal the potential of using insect pathogens and insecticide for control of T. tabaci. However, combinations containing spinetoram are harmful to nontarget organisms, whereas biological control agents help in protecting biodiversity in onion agroecosystems. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Abstract Background Potato tuber worm (PTM) [Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)] is one of the most significant and widespread pests of potato. PTM damages potatoes both in the field and in potato storage areas. Control of the pest is getting harder as it is developing resistance to pesticides. Several entomopathogenic nematode (EPN) species have been reported to successfully control numerous agricultural pests worldwide. The main aim of the study was to isolate native nematode/s as a biological control agent against P. operculella. Morphometric measurements of the infective juvenile (IJ) and sequencing and characterization of the internal transcribed spacer (ITS) region was used to identify the nematode isolate to species level. The efficacy of EPN isolate Z-1 obtained from Zonguldak province, Turkey was tested against different life stages of the pest. Experiments were conducted in 150 ml plastic pots containing sterile soil mixture. Four EPN concentrations (i.e., 0, 250, 500 and 1000 IJs/ml) were applied to the soil. Data relating to the mortality of different life stages were collected daily till 6 days after inoculation. Results Molecular analyses based on the ITS sequence and morphometric data revealed that isolate Z-1 was Heterorhabditis bacteriophora. Mortality rates of PTM larvae exposed to 250, 500, and 1000 IJs/ml concentrations of native EPN were 62.9 ± 9.8, 74.0 ± 3.7, and 92.5 ± 3.7%, respectively. There were non-significant differences among tested EPN concentrations for pupal mortality and the highest concentration (i.e., 1000 IJs/ml) caused 25.6% mortality. Conclusions The results revealed that the native H. bacteriophora isolate was effective against late-stage larvae of PTM under laboratory conditions. Therefore, it can be used as an alternative management option of the pest.

Abstract Background The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an endemic destructive pest for several cultivars in America and recently in Africa and Asia. Due to the development of pesticide resistance as well as environmental contamination, chemical control of the fall armyworm is ineffective. Alternatively, entomopathogenic nematodes (EPNs) provide a successful biological control tool sustainably. This study was designed to estimate the virulence of 2 isolates (Steinernema carpocapsae (All) and Heterorhabditis bacteriophora (HP88)) on 3rd and 5th larval instars of FAW under laboratory conditions. As well, the effect of gamma radiation (with 2 Gy) on the nematodes’ pathogenicity was studied. Results The results revealed that S. frugiperda larvae were sensitive to the 2 tested nematodes which were more apparent to S. carpocapsae. The mortality rates presented a significant elevation with the increase in un-irradiated and irradiated nematode concentrations. The highest recorded mortality for the 3rd and 5th larval instars was 100% after 3 and 4 days of treatment at concentration (80 IJs/ml) irradiated S. carpocapsae and the recorded death rate for un-irradiated S. carpocapsae was 72.2 and 77.8% for the two treated larval instars, respectively, after 4 days of the treatment with the same concentration. However, H. bacteriophora caused mortality of 88.9 and 61.1% at irradiated concentration (80 IJs/ml) and 66.7 and 50% at un-irradiated concentration (80 IJs/ml) for the 3rd and 5th larval instars, respectively, after 6 days of treatment. Based on the LC50 values, the 3rd instar larvae was more susceptible than the 5th instar larvae. In addition, juveniles’ irradiation increased their virulence. Conclusions Laboratory studies indicated that S. carpocapsae had a high potency among S. frugiperda larvae, especially the irradiated juveniles. Therefore, they have the potential to be developed as a biological control agent for S. frugiperda after further field studies.

Wireworms, the soil-borne larvae of click beetles (Coleoptera: Elateridae), are important crop pests throughout the world. In the eastern U.S., Melanotus communis larvae attack grain, root/ tuber, and vegetable crops. Our objectives were to characterize the pathogenicity and virulence of fungal and nematode entomopathogens on M. communis wireworms, and determine if wireworm size affected virulence. Pathogens tested included five entomopathogenic nematodes, Steinernema carpocapsae (All strain), S. feltiae (SN strain), S. riobrave (355 strain), Heterorhabditis bacteriophora (VS strain), and H. indica (HiHom1 strain); and two entomopathogenic fungi, Beauveria bassiana (GHA strain) and Cordyceps javanica (WF-GA17 strain). None of the pathogens tested caused >15% mortality at 7 or 14 days post-inoculation. Mortality was highest in S. carpocapsae (All strain); the other entomopathogens did not cause higher mortality than the untreated control. Overall, smaller wireworms were more susceptible than larger wireworms. Our results suggested that M. communis wireworms have defenses that limit the ability of the entomopathogens we tested to infect the wireworms. Conceivably, other entomopathogen strains or species may be more effective. Natural populations of entomopathogens may contribute to wireworm population reduction, but further studies are warranted before entomopathogens can be used for M. communis management.

Abstract Background Entomopathogenic nematodes (EPNs) have been regarded as the most convenient strategy for insect pest management. The native strains of EPNs: Heterorhabditis bacteriophora EUPT-SD, H. bacteriophora EUPT-R, H. bacteriophora EUPT-KN, H. bacteriophora EUPT-K and H. bacteriophora EUPT-H isolated from mid-Himalayan region of Himachal Pradesh were tested in laboratory for their multiplication and virulence against 3rd and 4th larval instars of the tobacco cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae), the serious polyphagous pest affecting a wide range of agricultural crops worldwide. Results All the EPN strains were effective against 3rd and 4th larval instars of S. litura. Insect mortality reached 90–96% after 96 h at nematode concentrations of 150 infective juveniles (IJs)/ml. The insect mortality was also recorded at low concentrations of IJs, but the most exposure period was required. High virulence was shown by H. bacteriophora EUPT-SD 96 and 94%, followed by H. bacteriophora EUPT-R 92 and 90%, H. bacteriophora EUPT-KN 92 and 90%, H. bacteriophora EUPT-K 92 and 90% and H. bacteriophora EUPT-H 92 and 90%, respectively, against 3rd and 4th larval instars in terms of reproductive potential and killing. All the insects were alive in the absolute control. Conclusion Utilization of EPNs for the management of S. litura may be the best method to overcome the insect resistance problems and to manage the population of this insect pest. It may be an effective method and may be a partial substitute of synthetic insecticides, thus minimizing the excessive use of synthetic chemicals. The results demonstrated the potential of indigenous EPNs isolates against S. litura, but before further recommendation, multiplication field trials need to be conducted to confirm their efficacy at farm level.

Entomopathogenic nematodes (EPNs) are promising as biocontrol agents for the most economically important insect pest attacking a wide range of host plants. Therefore, the aim of this work was to study the impact of four artificial diets and one natural food on numbers, weights, and total lipid content of the greater wax moth larvae, Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae) as well as the impact of these diets on the ability of nematode species Heterorhabditis bacteriophora and Steinernema carpocapsae to infect insects and multiply inside an insect host which had been reared on one of five different diets (D1, D2, D3, D4 and D5). The correlation between larvae weight and total lipid content, pathogenicity or multiplication of nematodes was also studied. The obtained results indicated that D2, D5 and D3 gave the highest growth or weights of larvae. The larvae produced weighed 3.71, 3.67 and 3.25 g from 50 g media, respectively. Statistically, larvae weights had a positive and significant correlation with the lipid content in larvae where r = 0.732. On the other hand, infective juveniles (IJs) of nematodes produced from insect hosts reared on D2 and D5 revealed more pathogenicity on larvae, since they caused the highest percent of mortality, 53.33 and 50.0% for H. bacteriophora, and 56.67 and 53.33% for S. carpocapsae, respectively. The total lipid content had a positive and highly significant correlation with the pathogenicity of the two nematode species where r = 0.97 and 0.971, respectively. Ultimately, the supplied foods of the artificial diets D2, D3 and natural beeswax (D5) gave the most suitable chance for developing insect growth and increasing the EPN quality and enhancing the potential of EPNs as biological control agents against different insect pests.

Background: Potato tuber worm (PTM) [Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)] is one of the most significant and widespread pests of potato. PTM damages potatoes both in the field and in potato storage areas. Control of the pest is getting harder as it is developing resistance to pesticides. Several entomopathogenic nematode (EPN) species have been reported to successfully control numerous agricultural pests worldwide. The main aim of the study was to isolate native nematode/s as a biological control agent against P. operculella. Morphometric measurements of the infective juvenile (IJ) and sequencing and characterization of the internal transcribed spacer (ITS) region was used to identify the nematode isolate to species level. The efficacy of EPN isolate Z-1 obtained from Zonguldak province, Turkey was tested against different life stages of the pest. Experiments were conducted in 150 ml plastic pots containing sterile soil mixture. Four EPN concentrations (i.e., 0, 250, 500 and 1000 IJs/ml) were applied to the soil. Data relating to the mortality of different life stages were collected daily till 6 days after inoculation. Results: Molecular analyses based on the ITS sequence and morphometric data revealed that isolate Z-1 was Heterorhabditis bacteriophora. Mortality rates of PTM larvae exposed to 250, 500, and 1000 IJs/ml concentrations of native EPN were 62.9 ± 9.8, 74.0 ± 3.7, and 92.5 ± 3.7%, respectively. There were non-significant differences among tested EPN concentrations for pupal mortality and the highest concentration (i.e., 1000 IJs/ml) caused 25.6% mortality. Conclusions: The results revealed that the native H. bacteriophora isolate was effective against late-stage larvae of PTM under laboratory conditions. Therefore, it can be used as an alternative management option of the pest. [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 European truffle beetle Leiodes cinnamomeus is the most important pest in black truffle (Tuber melanosporum) plantations. Current control methods against it are inefficient, so entomopathogenic nematodes (EPNs) could play an important role in their population regulation due to their efficacy against many soil-dwelling insect pests. A survey of EPNs and Pristionchus nematodes was conducted in truffle soils of Spain, considering environmental and physical–chemical soil factors. A total of 164 soil samples were collected from forests, productive plantations and null-low productive plantations, representing three distinct black truffle-growing habitat types. EPNs were isolated from seven soil samples (4.3%); four nematodes were identified as Steinernema feltiae and three as Heterorhabditis bacteriophora. Both species were sampled in three types of soil texture (loam, sandy loam or sandy clay loam), characterized by alkaline pH (7.5 to 8.5) and high organic matter (2.1–11.04%). The presence of these EPNs was influenced by habitat type and organic matter content. Pristionchus nematodes were isolated from truffle soil, around truffle fruit bodies and under the elytra of L. cinnamomeus, with Pristionchus maupasi being the most commonly identified species. No significant associations were found between environmental and soil factors and the occurrence of Pristionchus nematodes. These nematodes were found in alkaline soils (pH 7.75 to 8.7), across all seven sampled soil textures, with variable organic matter content (0.73%–5.92%). The ecological trends and the presence of Pristionchus may affect the occurrence of EPNs and their prospective use as biological control agents against L. cinnamomeus in black truffle plantations. [ABSTRACT FROM AUTHOR]

The tomato leafminer, Tuta absoluta (Meyrick) a key pest of tomato both in greenhouses and open-fields, has spread rapidly throughout Iran. The efficiency of native isolates of three species of entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora) was evaluated against the tomato leafminer, T. absoluta larvae (outside leaf and inside galleries), and pupae at various concentrations and times in laboratory conditions. Experiments were conducted at 25 ± 2ºC, 65 ± 5% RH, and 16L:8D h photoperiod. S. feltiae nematode caused the highest mortality for larvae outside the gallery (53.61%), followed by 45% mortality for larvae inside galleries, and lowest mortality for pupae (3.88%). The effect of infective juveniles (IJ) and exposure time (ET) on larval mortality in different treatments showed a significant (P< 0.01) relationship between IJ and ET and their interactions. Mortality of the T. absoluta larvae and pupae rose with more IJ and longer exposure time. The LC50 for, S. feltiae, S. carpocapsae and H. bacteriophora were 156.01, 225.13, and 317.66 IJs/ml for the second instar larvae of T. absoluta (outside the gallery), 296.31, 305.23 and 320.66 IJs/ml for inside gallery, respectively. Therefore, S. feltiae was a more effective species and can be suggested for complementary studies for finding a suitable biocontrol agent of the pest. [ABSTRACT FROM AUTHOR]

The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora infects a wide range of insect hosts with the aid of its mutualistic bacteria Photorhabdus luminescens. While the mutualistic relationship between H. bacteriophora and P. luminescens and the infectivity of the nematodebacteria complex have been characterized, how nematode fitness is affected by entomopathogenic bacteria existing in association with other EPN species remains poorly understood. In this study, the survival of H. bacteriophora infective juveniles containing or lacking P. luminescens was tested against the entomopathogenic bacteria Xenorhabdus nematophila and Photorhabdus asymbiotica as well as the non-pathogenic Escherichia coli. While X. nematophila and E. coli did not significantly affect the survival of H. bacteriophora, P. asymbiotica exerted a significant effect on nematode survival, particularly on those lacking P. luminescens. These results imply that P. asymbiotica encodes factors that are pathogenic to EPNs. Future efforts will focus on the identification of the bacterial molecular components that induce these effects. This study makes an important contribution to a growing body of research aimed at exploiting the full potential of nematodebacterial complexes for eliminating noxious insect pests and treating infectious diseases caused by parasitic nematodes. [ABSTRACT FROM AUTHOR]

BACKGROUND: The control of ticks is challenged by the resistance of tick populations to chemical acaricides. In this study, we evaluated, under laboratory conditions, the efficacy of Heterorhabditis bacteriophora against Rhipicephalus (Boophilus) microplus engorged females with varying body weights (150, 200, 250, 300 or 350 mg per female) or from eight different geographical populations. We also determined the efficacy of H. bacteriophora for tick control under field conditions. RESULTS: R. microplus engorged females with varying body weights exposed to 150 juveniles of H. bacteriophora resulted in a high control efficacy (97.5% to 98.4%). Tests with females from different geographical populations comprised eight tick strains treated with H. bacteriophora and their respective control groups. The biological parameters of females exposed to nematode treatments did not differ significantly and resulted in 89% to 99% of control efficacy. Trials conducted under field conditions were performed in field plots with Megathyrsus maximus grass. Treatment groups received eight cadavers of Tenebrio molitor fully colonized with H. bacteriophora at 1 week prior to the release of female ticks, whereas control groups were untreated. On the first day of the experiment, six engorged females were distributed in each plot. On day 42 and day 63, the apical portion of the grasses with R. microplus larvae were collected and quantified. The population of R. microplus larvae was reduced up to 73.1% in plots treated with H. bacteriophora at day 63 after treatment. CONCLUSION: R. microplus engorged females with varying body weights or from different geographical populations were highly susceptible to H. bacteriophora. The field test demonstrated the efficacy of H. bacteriophora in reducing R. microplus larvae in infested pastures. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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Abstract Background Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) and their symbiotic bacteria are pathogenic for a wide range of insect pests and have been used successfully as a biological control agent. Although EPNs are well studied against many agricultural insect pests, the efficacy of their symbiotic bacteria still remains unclear for many insect pests of agricultural importance. In the present study, the virulence of native EPN isolates and their cell-free supernatants of symbiotic bacteria were tested against the 3rd and 4th larval instars of Agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae) under laboratory conditions (25 ± 1 °C and R.H. 60%). Results The 4th instar larvae were more susceptible to infective juveniles (IJs) and mortalities over (95%) were achieved by all tested EPN isolates at the concentration of 100 IJs/cm2 after 72 hrs of exposure. The cell-free supernatants were more effective against the 3rd instar larvae and the highest mortalities were recorded as 42 and 60% in the contact and leaf disc bioassays, respectively. Conclusion The results indicated that the cell-free supernatants can be an ideal application for young larval stages of A. segetum. However, further studies are required to test the effectiveness of both EPNs and the cell-free supernatants of their symbiotic bacteria in field conditions.

Abstract Background Entomopathogens such as nematodes, bacteria and fungi are well recognized for their biocontrol potential. This study was carried out to examine the insecticidal properties of the Heterorhabditis bacteriophora Poinar, Beauveria bassiana Balsamo-Crivelli, Bacillus thuringiensis Berliner, individually and in combination against 3rd instar larvae of Spodoptera litura Fabricius (Noctuidae: Lepidoptera) under controlled laboratory and greenhouse conditions at Eternal University, Baru Sahib, Sirmaur, Himachal Pradesh. Results The results demonstrated that the combined applications of the tested entomopathogens resulted in 100% insect mortality under the laboratory conditions. Among the individual concentrations, applications of 200 IJs/ml were noticed highly virulent with (98%) mortality, followed by B. thuringiensis (96%) and then by B. bassiana (92%). However, single treatments were also evaluated that further showed a highest mortality in the target pest by H. bacteriophora, followed by B. thuringiensis. Among the combined treatments by H. bacteriophora plus B. thuringiensis (200 IJs + 1 × 1012 CFU/cm2) more effective caused (100%) mortality were noticed in the laboratory and (28%) under the greenhouse conditions than H. bacteriophora plus B. bassiana (200 IJs + 1 × 1010 conidia/cm2) that caused (100%) mortality and (34%) damage under both, laboratory and greenhouse conditions. Conclusion Laboratory bioassay and greenhouse evaluation tests demonstrated that the combined sprayed treatments showed reliable and fast synergism. This study could be recommended to the farmers to control the pest.

Abstract Background Cabbage butterfly, Pieris brassicae Linnaeus (Lepidoptera: Pieridae), is a major insect pest affecting cole crops worldwide. Excessive applications of chemical-based insecticides have a devastating impression over the organisms and environment. Results In this study, entomopathogenic nematode (EPN) Heterorhabditis bacteriophora Poinar strain EUPT-S26 (local isolate) was evaluated for Pieris brassicae control under polyhouse and field conditions. Under the polyhouse conditions, the highest insect mortality 91.6 and 94.0% was observed in the plots treated with the nematodes suspension 1500 IJs/ml and 2000 IJs/ml, respectively. Based on the highest cabbage plant protection under polyhouse conditions, H. bacteriophora EUPT-S26 was also applied for field assays in the course of the crop’s productive phase. Data demonstrated from the field treatments signify the highest concentration (2000 IJs/ml) showed the maximum larval mortality and least damage percentage 45 ± 1.07% that remained constant until harvesting; this resulted in the highest productivity in polyhouse and under field conditions. Conclusion According to assessed field conditions, it was suggested to perform 3 applications of EPNs during the vegetative phase and at the time of head formation to increase productivity and to reduce damage. The results approved that EPNs are an effective alternative of chemical-based insecticides to control the cabbage butterfly.

Abstract Background The bollworm complex consisting of Helicoverpa armigera and Earias vittella is a major threat in cotton production globally. The habit of developing resistance to many insecticides including Bt transgenic cotton necessitates the exploration of an alternate strategy to manage bollworms. The entomopathogenic nematodes (EPN) Steinernema carpocapsae strain APKS2 and Heterorhabditis bacteriophora strains KKMH1 and TRYH1 at different concentrations of 1 × 109 infective juveniles (IJs)·hm−2, 2 × 109 IJs·hm−2, and 3 × 109 IJs·hm−2 in 500 L of water were evaluated as a foliar spray in fields naturally infested with H. armigera and E. vittella located at Eastern Block and and Cotton Research Farm of Tamil Nadu Agricultural University, Coimbaotre, India during October 2010–February 2011 and October 2011–February 2012, respectively. Results In general, all three tested EPN strains reduced the larval population of H. armigera and E. vittella; reduced square and boll damage; and subsequently increased cotton yield compared with the untreated control. The S. carpocapsae APKS2 is most effective against H. armigera whereas both S. carpocapsae APKS2 and H. bacteriophora KKMH1 were equally effective against E. vittella. The higher dose of 3 × 109 IJs·hm−2 was highly significant in the reduction of H. armigera larvae. However, the doses 2 × 109 IJs·hm−2 and 3 × 109 IJs·hm−2 were equally effective for E. vittella control. The S. carpocapsae APKS2 at 3 × 109 IJs·hm−2 caused a 62.2% reduction of H. armigera larvae, 34% reduction of square damage, 58.5% reduction of boll damage, and yielded 45.5% more seed cotton than the untreated control plots. In E. vittella infested field, S. carpocapsae strain APKS2 and H. bacteriophora strain KKMH1 at 2 × 109 IJs·hm−2 resulted in 60.6%~62.4% larva reduction, 68.4%~70.7% square damage reduction, 66.6%~69.9% boll damage reduction and 45.9% yield increase over the untreated control. The effective EPN treatments were comparable to the chemical insecticide chlorpyriphos 20% emulsifiable concentrate spraying at 2 mL·L−1. Conclusions This study has shown that EPN have great potential in the management of the bollworm complex in cotton. Foliar spraying EPN strain S. carpocapsae (APKS2) at 3 × 109 IJs·hm−2 and S. carpocapsae (APKS2) or H. bacteriophora (KKMH1) at 2 × 109 IJs·hm−2 five times at10 days intervals are the best for the management of H. armigera and E. vittella, respectively.

The black cutworm (BCW), Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is an economically significant pest affecting numerous crops and turf grasses. Despite employing various methods, such as chemical and biological control, to mitigate this pest, the efficacy of these methods often fails to reach the desired level. Hence, the integration of diverse strategies is a key to sustainable management. In this study, we assessed the toxicity of four insecticides (indoxacarb, pyridalyl, lufenuron, and methoxyfenozide) and three local EPN isolates (two isolates of Heterorhabditis indica and one of Heterorhabditis bacteriophora) in targeting the fifth instar larval (L5) and pupal stages of BCW. After demonstrating their potential use in BCW control, we explored the combined use of sublethal concentrations of insecticides (LC 15 or LC 30) alongside the LC 20 values of EPNs. The findings revealed that lufenuron and methoxyfenozide, when combined with EPNs, exhibited a synergistic effect on the L5 stage of BCW, whereas the same combination displayed antagonism on pupae. On the other hand, the combination of indoxacarb and pyridalyl with EPNs demonstrated a synergistic effect on the pupal stage of BCW. These results highlight the potential of employing a combination of insecticides and EPNs at sublethal concentrations to control BCW effectively. This approach shows promise for designing sustainable pest management strategies within the framework of integrated pest management (IPM). [Display omitted] • The potential of indoxacarb, pyridalyl, lufenuron, and methoxyfenozide, was shown in managing A. ipsilon. • Entomopathogenic nematodes (EPNs), particularly Heterorhabditis bacteriophora , have shown virulence against A. ipsilon. • Synergistic effects were observed when H. indica isolates were combined with lufenuron or methoxyfenozide. • Variations in the efficacy of these combinations were observed between the larval and pupal stages of A. ipsilon. • Integrating EPNs with insecticides presents a promising and sustainable approach for managing A. ipsilon populations. [ABSTRACT FROM AUTHOR]

The weevil Scyphophorus acupunctatus Gyllenhal causes damage and losses in agave crops and has traditionally been controlled using contact and systemic agrochemicals. Implementing microbial control strategies is proposed as an alternative to mitigate the environmental impact associated with agrochemicals. The objective of this study was to determine the survival of entomopathogenic nematodes in oil emulsions for the control of adult S. acupunctatus. Three species of entomopathogenic nematodes were evaluated: Steinernema carpocapsae, S. glaseri, and Heterorhabditis bacteriophora. We used two concentrations (50 ± 5 and 100 ± 10 infectious juvenile nematodes), and oil emulsions derived from Salvia hispanica, Triticum vulgare, and Olea europea with oil purity of 20% and 40%. The effectiveness of these treatments was assessed by determining the mortality rate of S. acupunctatus. The results indicate that the combination of S. glaseri and H. bacteriophora, at concentrations of 50 ± 5 and 100 ± 10 nematodes, respectively, with T. vulgare and O. europea oils, achieved a mortality rate of 85.76% in S. acupunctatus adults at 24 h. At 120 h, a mortality rate of 100% was achieved with specific formulations, such as S. glaseri with 100 ± 10 nematodes + O. europea, and H. bacteriophora with 100 ± 10 nematodes + O. europea. Consequently, we conclude that oil formulations combined with nematodes show potential as an effective and environmentally friendly alternative for the control and management of S. acupunctatus.

Background: The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an endemic destructive pest for several cultivars in America and recently in Africa and Asia. Due to the development of pesticide resistance as well as environmental contamination, chemical control of the fall armyworm is ineffective. Alternatively, entomopathogenic nematodes (EPNs) provide a successful biological control tool sustainably. This study was designed to estimate the virulence of 2 isolates (Steinernema carpocapsae (All) and Heterorhabditis bacteriophora (HP88)) on 3rd and 5th larval instars of FAW under laboratory conditions. As well, the effect of gamma radiation (with 2 Gy) on the nematodes' pathogenicity was studied. Results: The results revealed that S. frugiperda larvae were sensitive to the 2 tested nematodes which were more apparent to S. carpocapsae. The mortality rates presented a significant elevation with the increase in un-irradiated and irradiated nematode concentrations. The highest recorded mortality for the 3rd and 5th larval instars was 100% after 3 and 4 days of treatment at concentration (80 IJs/ml) irradiated S. carpocapsae and the recorded death rate for un-irradiated S. carpocapsae was 72.2 and 77.8% for the two treated larval instars, respectively, after 4 days of the treatment with the same concentration. However, H. bacteriophora caused mortality of 88.9 and 61.1% at irradiated concentration (80 IJs/ml) and 66.7 and 50% at un-irradiated concentration (80 IJs/ml) for the 3rd and 5th larval instars, respectively, after 6 days of treatment. Based on the LC50 values, the 3rd instar larvae was more susceptible than the 5th instar larvae. In addition, juveniles' irradiation increased their virulence. Conclusions: Laboratory studies indicated that S. carpocapsae had a high potency among S. frugiperda larvae, especially the irradiated juveniles. Therefore, they have the potential to be developed as a biological control agent for S. frugiperda after further field studies. [ABSTRACT FROM AUTHOR]

Background: Entomopathogenic nematodes (EPNs) have been regarded as the most convenient strategy for insect pest management. The native strains of EPNs: Heterorhabditis bacteriophora EUPT-SD, H. bacteriophora EUPT-R, H. bacteriophora EUPT-KN, H. bacteriophora EUPT-K and H. bacteriophora EUPT-H isolated from mid-Himalayan region of Himachal Pradesh were tested in laboratory for their multiplication and virulence against 3rd and 4th larval instars of the tobacco cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae), the serious polyphagous pest affecting a wide range of agricultural crops worldwide. Results: All the EPN strains were effective against 3rd and 4th larval instars of S. litura. Insect mortality reached 90–96% after 96 h at nematode concentrations of 150 infective juveniles (IJs)/ml. The insect mortality was also recorded at low concentrations of IJs, but the most exposure period was required. High virulence was shown by H. bacteriophora EUPT-SD 96 and 94%, followed by H. bacteriophora EUPT-R 92 and 90%, H. bacteriophora EUPT-KN 92 and 90%, H. bacteriophora EUPT-K 92 and 90% and H. bacteriophora EUPT-H 92 and 90%, respectively, against 3rd and 4th larval instars in terms of reproductive potential and killing. All the insects were alive in the absolute control. Conclusion: Utilization of EPNs for the management of S. litura may be the best method to overcome the insect resistance problems and to manage the population of this insect pest. It may be an effective method and may be a partial substitute of synthetic insecticides, thus minimizing the excessive use of synthetic chemicals. The results demonstrated the potential of indigenous EPNs isolates against S. litura, but before further recommendation, multiplication field trials need to be conducted to confirm their efficacy at farm level. [ABSTRACT FROM AUTHOR]

Plants attacked by insects commonly mobilize various defense mechanisms, including the biosynthesis and release of so-called herbivore-induced plant volatiles (HIPVs). Entomopathogenic nematodes (EPNs) can be attracted to these belowground HIPVs, which can enhance biocontrol services from EPNs. However, recent research has also demonstrated that HIPVs can induce and initiate insect immune responses, decreasing the insect's susceptibility to pathogens and parasites. Therefore, experiments were conducted to test the impact of HIPVs on insects and EPNs during the initial stage of EPN infection. Compounds that can impact EPN attraction and infectivity such as pregeijerene, β-caryophyllene, and α-pinene, and compounds that have been determined to increase or decrease susceptibility of insects to pathogens, such as (Z)-3- hexenyl acetate, linalool, and β-ocimene, were selected. Exposure of Galleria mellonella larvae to pregeijerene, linalool, β-ocimene and α-pinene during invasion significantly increased mortality of Steinernema diaprepesi and Heterorhabditis bacteriophora after 48 h. Larval treatment with βcaryophyllene only increased mortality for Heterorhabditis bacteriophora. (Z)-3-hexenyl acetate did not cause differential mortality from the controls for either nematode species. In additional experiments, we found that EPNs exposed to α-pinene and linalool were more readily recognized by the insects' immune cells compared to the control treatment, thus the observed increased mortality was likely due to HIPVs-EPN interactions with the insect's immune system. These results show that the presence of HIPVs can impact EPN survival in the model host, G. mellonella. [ABSTRACT FROM AUTHOR]

The white grub, Temnorhynchus baal, is a major pest of the strawberry crop in many Asian and African countries. The white grabs cause significant economic losses in the yield. The present study aims to evaluate the effectiveness of entomopathogenic nematodes (EPNs) on the third larval instar of T. baal under laboratory conditions. The study extended to compare the efficacy of a combination of EPNs (Steinernema glaseri+Heterorhabditis bacteriophora) against a natural infestation of T. baal with an organophosphorus insecticide (Diazinon) in an Egyptian strawberry field. In the laboratory, five larvae of T. baal were placed in soil and infected with EPNs. At the highest concentration of 4000 IJs/larva, the larvae were more susceptible to infection with S. glaseri than H. bacteriophora, with mortality percentages of 96 and 88%, respectively. The LC50 of S. glaseri and H. bacteriophora was 937.44 and 1026.58 IJs/larvae, respectively. The mortality percentage was 96% and 100% when treated for five larvae/cup and one larva/cup, respectively, after being infected with a combination of S. glaseri+ H. bacteriophora. The mortality percentage was higher in the mixture than for each species studied individually. In the field, throughout the seasons, the percentage of wilted plants was 17.64, 66.09, and 83.95% in 2020 and 12.56, 67.87, and 75.62% in 2021, for the plots treated with a combination of EPNs, insecticides, and control, respectively. Present findings indicate that entomopathogenic nematodes are good alternatives to control the white grub, T. baal, in strawberry fields. [ABSTRACT FROM AUTHOR]

Summary: Dispersal is an important behaviour for nematodes. Entomopathogenic nematodes (EPN) are able to regulate plant-parasitic nematodes in the field. However, the mechanism for the interactions between two types of nematodes is not clearly known. The effects of 12 synthesised ascarosides, three EPN species (Steinernema carpocapsae All, Heterorhabditis bacteriophora H06 and H. indica LN2), and 15 symbiotic bacterial isolates from EPN on the dispersal of Meloidogyne incognita were investigated. The results revealed that M. incognita juveniles were repelled, to various degrees, by most of the tested ascarosides (especially ascr#9), three species of EPN, and by bacterial isolates (especially TT01 from H. bacteriophora TT01 and H06 from H. bacteriophora H06), compared with the controls. Ascr#9 was abundant in M. incognita juvenile-conditioned supernatant. This provides useful cues for elucidating the interaction mechanism between two nematode groups and establishing alternative techniques for the safe and effective control of root-knot nematodes. [ABSTRACT FROM AUTHOR]

Entomopathogenic Xenorhabdus spp. bacteria, symbiont of the nematode Steinernema spp., shows potential for mitigating agricultural pests and diseases through bioactive compound production. The plant-parasitic nematode (PPN) Meloidogyne incognita affects the yield and quality of numerous crops, causing significant economic losses. We speculate that Cell-Free Supernatants (CFS) from Xenorhabdus spp. could reduce the impact of the root-knot nematode (RKN) M. incognita without negatively affecting entomopathogenic nematodes (EPNs), which are considered beneficial organisms. This study explored the activity of seven CFS against M. incognita (two populations, AL05 and Chipiona) and their possible effects on EPNs. The in vitro impact of CFS at 10 %, 40 %, and 90 % concentrations on nematode motility at four and 24 h were tested on the PPN M. incognita and two EPNs, S. feltiae and H. bacteriophora. Additionally, EPN viability and virulence were evaluated at two and five days. On the other hand, tomato plant-mesocosm experiments examined the activity of four CFS on M. incognita reproductive capacity and EPN virulence. In vitro exposure of M. incognita to 90 % concentration of CFS resulted in reductions of activity over 60 % after four hours of expossure in four out of seven CFS. In the in vitro evaluation of two species of EPNs, none of the CFS affected the activity across any tested doses after four hours of exposure nor after 24 h. Plant-mesocosm experiments showed that CFS application significantly reduced RKN galls, egg masses, and galling index. However, the virulence of both EPN species decreased 15 days after application, with a significant impact on S. feltiae. Overall, these findings suggest that CFS could be used as a bio-tool against M. incognita in tomato crops, mitigating its impact on plant growth. However, this study also highlights the necessity of investigating the effects of CFS on non-target organisms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Abstract Background The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is a serious threat to date palms across the globe, causing heavy yield losses. The pest inflicts damage to palms stem and destroys vascular system; resultantly lower the vigor and affect the growth and yield. For ecological farming system, biological control of the pest is gaining increased interest due to hosts’ specificity, safety to human, animal and non-target organisms, and their compatibility to environment. Results In laboratory assay, Beauveria bassiana, Heterorhabditis bacteriophora and Bacillus thuringiensis var. kurstaki (Bt-k) alone and in combination against sixth instar larvae and adults of four distinct populations of RPW were applied. H. bacteriophora was more effective, followed by B. bassiana and Bt-k in alone treatments. While in combined treatments, the highest mortality was recorded for H. bacteriophora + B. bassiana combination (100% for both stages), followed by H. bacteriophora + Bt-k, (larvae 100%; adults 94.24%) and B. bassiana + Bt-k treatments (larvae: 87.01%; adults: 80.53%). Maximum rate of mycosis (larvae 85.74%; adults 69.07%), sporulation (larvae 189.22 conidia ml−1; adults 164.56 conidia ml−1), cadavers affected by nematodes (larvae 92.4%; adults 81.29%) and nematode production (larvae 178.78 IJs ml−1; adults 153.44 IJs ml−1) was observed where B. bassiana or H. bacteriophora was applied alone and the lowest (larvae 122.78 IJs ml−1; adults: 103.22 IJs ml−1) was recorded for H. bacteriophora + B. bassiana combination. Conclusions Entomopathogens can be effectively used alone and/or in integration to control RPW populations. Natural capability of entomopathogens to infect and disseminate into other hosts makes them excellent biocontrol agents to be incorporated in the IPM plan of RPW and to make palm growers confident with the use of the most promising microbial control agents.

Abstract Background Entomopathogenic nematodes (EPNs) have the potential to supersede larvicidal activity for the management of various insect pests. Result Lab experiments were conducted to test the pathogenicity of 2 EPNs local species; Steinernema feltiae and Heterorhabditis bacteriophora at different (IJs/cm2) concentrations against the cabbage butterfly, Pieris brassicae (L.). The native isolate was obtained from soil samples, collected from Rajgarh, Hamachi Pradesh, India. Petri dish bioassay used the EPNs species (S. feltiae HR1 and H. bacteriophora HR2) at the concentrations (0, 10, 20, 40, 80, 160 IJs/cm2). Based on the pathogenicity of the strains, only 2 isolates effectively showed larvicidal activity. The highest (%) (72.08 and 67.42%), at the 2nd instar larval mortality was recorded in the treatments with H. bacteriophora and S. feltiae at160 IJs/cm2, respectively. At the 4th instar larvae, respective larval mortality (85.38, 69.50%) was recorded in treatment with H. bacteriophora, and S. feltiae, respectively, at160 IJs/cm2. In case of pupae, the mortality rates were (62.12, 58.58%) for H. bacteriophora and S. feltiae, respectively, at 160 IJs/cm2; (74 and 12%) for both the tested EPNs, respectively, at 80 IJs/cm2. Percent of P. brassicae larval mortality treated with the tested EPN isolates was significantly higher than the untreated control. Results revealed that the percent of larval mortality significantly increased with the increase in time periods, being maximum at 72 h. S. feltiae and H. bacteriophora, strains showed potent larvicidal activity at low concentration even at 48 and 72 h of exposure. Conclusion This study revealed that the local strains of EPNs (S. feltiae HR1 and H. bacteriophora HR2) were found as a biocontrol agent against P. brassicae.

Plants attacked by insects commonly mobilize various defense mechanisms, including the biosynthesis and release of so-called herbivore-induced plant volatiles (HIPVs). Entomopathogenic nematodes (EPNs) can be attracted to these belowground HIPVs, which can enhance biocontrol services from EPNs. However, recent research has also demonstrated that HIPVs can induce and initiate insect immune responses, decreasing the insect’s susceptibility to pathogens and parasites. Therefore, experiments were conducted to test the impact of HIPVs on insects and EPNs during the initial stage of EPN infection. Compounds that can impact EPN attraction and infectivity such as pregeijerene, β-caryophyllene, and α-pinene, and compounds that have been determined to increase or decrease susceptibility of insects to pathogens, such as (Z)-3-hexenyl acetate, linalool, and β-ocimene, were selected. Exposure of Galleria mellonella larvae to pregeijerene, linalool, β-ocimene and α-pinene during invasion significantly increased mortality of Steinernema diaprepesi and Heterorhabditis bacteriophora after 48 h. Larval treatment with β-caryophyllene only increased mortality for Heterorhabditis bacteriophora. (Z)-3-hexenyl acetate did not cause differential mortality from the controls for either nematode species. In additional experiments, we found that EPNs exposed to α-pinene and linalool were more readily recognized by the insects’ immune cells compared to the control treatment, thus the observed increased mortality was likely due to HIPVs-EPN interactions with the insect’s immune system. These results show that the presence of HIPVs can impact EPN survival in the model host, G. mellonella.

Eubulus cf. elongatus was recently recorded as one of the most destructive pests of cassava in the Brazilian Cerrado. In this study, we evaluate the susceptibility of E. cf. elongatus to entomopathogenic fungi and nematodes in laboratory. Adults and larvae of E. cf. elongatus were first collected in the field to assess the natural occurrence of fungi and nematodes. Seven nematode species within Heterorhabditis and Steinernema genera were tested in direct applications onto the larvae or indirectly through soil inoculation (2000 infective juveniles per group of 10 larvae). Bioassays with 16 strains of entomopathogenic fungi (beauveria and metarhizium species) were conducted by immersion (108 conidia per mL), direct spray or by exposing adults to soil sprayed with conidial suspensions (6 × 104 conidia per cm2). In all bioassays insects were kept at 24–25 °C and 75-90% RH for 16 days. Nematodes were not found naturally occurring in E. cf. elongatus larvae collected in field. Of the adults collected, 1.76% and 0.04% were infected with B. bassiana and Metarhizium sp., respectively. In the laboratory trials, the highest mortality of larvae was caused by H. bacteriophora (95.0% for application on larvae and 60% for soil application). Entomopathogenic fungi caused low mortality rates in adults of E. cf. elongatus, being less than 11% in direct and soil applications and reaching a maximum of 16.07% when insects were treated by immersion. Our results show the potential of nematodes, such as H. bacteriophora, in controlling the larvae of E. cf. elongatus in soil. [ABSTRACT FROM AUTHOR]

The black cutworm (BCW), Agrotis ipsilon (Hufnagel, 1766) (Lepidoptera: Noctuidae), is one of the major pests of potato, and its outbreaks frequently occur in potato-growing areas of Turkey. Entomopathogenic nematodes (EPNs) in the families of Steinernematidae and Heterorhabditidae are known as an important biocontrol agent to many insects including BCW. In 2020 and 2021, surveys of EPNs were conducted in major potato-growing areas of seven provinces of Turkey, including Afyonkarahisar, Konya, İzmir, Sivas, Bolu, Kayseri, and Niğde, in the sake to find a new sustainable biological control option for BCW. Out of the 400 collected soil samples, 48 samples (12%) consisted of EPNs. Based on the morphological, morphometric, and sequence analysis of the internal transcribed spacer (ITS), 34 isolates were identified as Steinernema feltiae Filipjev, 1934 (Rhabditida: Steinernematidae), 13 isolates as Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae), 1 one isolate as Oscheius tipulae Lam and Webster, 1971 (Rhabditida: Rhabditidae). The virulence of EPN isolates was assessed on the larvae of Galleria mellonella L. (Lepidoptera: Pyralidae), and the most pathogenic isolates were further tested for their biocontrol potential against the 3rd/4th larval instar of BCW larvae at two concentrations of 50 and 100 IJs/cm2 under laboratory conditions. All selected isolates were highly effective against the larvae of BCW, and larval mortality ranged between 70 and 100% for both concentrations after 3 days of exposure time. The maximum mortality (100%) was achieved only by two isolates (H. bacteriophora AF-12 and S. feltiae KAY-4) at the higher concentration of 100 IJs/cm2. The results indicate that EPNs are abundantly present in potato-growing areas of Turkey and have the potential to be used in the biocontrol of BCW. To our knowledge, this is the first report of the presence of Oscheius tipulae in Turkey. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs) are promising as biocontrol agents for the most economically important insect pest attacking a wide range of host plants. Therefore, the aim of this work was to study the impact of four artificial diets and one natural food on numbers, weights, and total lipid content of the greater wax moth larvae, Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae) as well as the impact of these diets on the ability of nematode species Heterorhabditis bacteriophora and Steinernema carpocapsae to infect insects and multiply inside an insect host which had been reared on one of five different diets (D1, D2, D3, D4 and D5). The correlation between larvae weight and total lipid content, pathogenicity or multiplication of nematodes was also studied. The obtained results indicated that D2, D5 and D3 gave the highest growth or weights of larvae. The larvae produced weighed 3.71, 3.67 and 3.25 g from 50 g media, respectively. Statistically, larvae weights had a positive and significant correlation with the lipid content in larvae where r = 0.732. On the other hand, infective juveniles (IJs) of nematodes produced from insect hosts reared on D2 and D5 revealed more pathogenicity on larvae, since they caused the highest percent of mortality, 53.33 and 50.0% for H. bacteriophora, and 56.67 and 53.33% for S. carpocapsae, respectively. The total lipid content had a positive and highly significant correlation with the pathogenicity of the two nematode species where r = 0.97 and 0.971, respectively. Ultimately, the supplied foods of the artificial diets D2, D3 and natural beeswax (D5) gave the most suitable chance for developing insect growth and increasing the EPN quality and enhancing the potential of EPNs as biological control agents against different insect pests. [ABSTRACT FROM AUTHOR]

The Baermann filter method is a long-standing, simple technique for recovering nematodes from soil and charcoal coprocultures. Material containing the nematodes is placed on a mesh screen lined with several layers of tissue paper or cheesecloth, and the screen is placed in the mouth of the funnel. Rubber tubing attached to the funnel stem is clamped, and water is added to submerge the material. The filtration material allows the nematodes to swim through while holding back the substrate. Over time the nematodes settle at the clamp in the tubing. After several hours, the clamp is opened and water containing the nematodes is collected. Although recovery of the nematodes is efficient, they are often contaminated with soil or charcoal debris, requiring a secondary cleaning by sedimentation or filtration. Described here is a small, simplified version of the Baermann apparatus that can be used as a secondary cleaning device. The ‘‘mini-Baermann’’ is constructed from materials commonly found in the laboratory. Experiments using infective larvae of 3 nematode species demonstrated that the majority of the larvae applied to the device are collected within 2 hr, and nearly all by 4 hr. Dead larvae fail to pass through the filter and do not significantly impact the passage of living larvae. In addition to removing debris from nematode suspensions, this device can rapidly and efficiently separate living, motile larvae from dead larvae. [ABSTRACT FROM AUTHOR]

Abstract 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.

[Display omitted] • Turfgrass has many insect pests which are typically managed preventively with synthetic insecticides. • We studied the potential of fresh field isolate mixes of endemic entomopathogenic nematodes for multi-year suppression of turfgrass insect pests. • Steinernema carpocapsae , Heterorhabditis bacteriophora , and their combination were applied inoculatively to golf course fairways and roughs. • The nematodes persisted throughout most of the 3 years of the study. • The nematodes suppressed white grubs, annual bluegrass weevil, sod webworms, and cutworms throughout the study. Entomopathogenic nematodes (EPNs) can control several important turfgrass insect pests including white grubs, weevils, cutworms, and sod webworms. But most of the research has focused on inundative releases in a biopesticide strategy using EPN strains that may have lost some of their ability to persist effectively over years of lab maintenance and / or selection for virulence and efficient mass-production. Our study examined the potential of fresh field isolate mixes of endemic EPNs to provide multi-year suppression of turfgrass insect pests. In early June 2020, we applied isolate mixes from golf courses of the EPNs Steinernema carpocapsae , Heterorhabditis bacteriophora , and their combination to plots straddling fairway and rough on two golf courses in central New Jersey, USA. Populations of EPNs and insect pests were sampled on the fairway and rough side of the plots from just before EPN application until October 2022. EPN populations increased initially in plots treated with the respective species. Steinernema carpocapsae densities stayed high for most of the experiment. Heterorhabditis bacteriophora densities decreased after 6 months and stabilized at lower levels. Several insect pests were reduced across the entire experimental period. In the fairway, the combination treatment reduced annual bluegrass weevil larvae (59 % reduction) and adults (74 %); S. carpocapsae reduced only adults (42 %). White grubs were reduced by H. bacteriophora (67 %) and the combination (63 %). Black turfgrass ataenius adults were reduced in all EPN treatments (43–62 %) in rough and fairway. Sod webworm larvae were reduced by S. carpocapsae in the fairway (75 %) and the rough (100 %) and by H. bacteriophora in the rough (75 %). Cutworm larvae were reduced in the fairway by S. carpocapsae (88 %) and the combination (75 %). Overall, our observations suggest that inoculative applications of fresh field isolate mixes of endemic EPNs may be a feasible approach to long-term suppression of insect pests in turfgrass but may require periodic reapplications. [ABSTRACT FROM AUTHOR]