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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]

A key aspect of parasitic nematode infection is the nematodes' ability to evade and/or suppress host immunity. This immunomodulatory ability is likely driven by the release of hundreds of excretory/secretory proteins (ESPs) during infection. While ESPs have been shown to display immunosuppressive effects on various hosts, our understanding of the molecular interactions between individual proteins released and host immunity requires further study. We have recently identified a secreted phospholipase A2 (sPLA2) released from the entomopathogenic nematode (EPN) Steinernema carpocapsae we have named Sc-sPLA2. We report that Sc-sPLA2 increased mortality of Drosophila melanogaster infected with Streptococcus pneumoniae and promoted increased bacterial growth. Furthermore, our data showed that Sc-sPLA2 was able to downregulate both Toll and Imd pathway-associated antimicrobial peptides (AMPs) including drosomycin and defensin, in addition to suppressing phagocytosis in the hemolymph. Sc-sPLA2 was also found to be toxic to D. melanogaster with the severity being both dose- and time-dependent. Collectively, our data highlighted that Sc-sPLA2 possessed both toxic and immunosuppressive capabilities.

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.

Copyright of Arab Journal of Plant Protection is the property of Arab Society for Plant Protection 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 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]

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

Diamond back Moth (DBM), Plutella xylostella L. is one of the economically important insect pests that destroy cabbage crops in most countries of the world. The target of the present study was to examine the potency of gamma radiated nematodes, normal nematode Steinernema carpocapsae BA2, and insect growth regulator, Match 5%EC as alternative control methods for P. xylostella larvae compared with conventional insecticides (radiant and radiant mixture with match), as well as to examine their safety on P. xylostella predators inhibiting cabbage plants. This experiment was carried out at El-Riad District, Kafr El-Sheikh Province in 2020 and 2021 seasons. The results revealed that plants treated with irradiated nematode in rate of 120 IJ's +2 Gy / ml hosted the fewest number of P. xylostella larvae compared to the untreated plants with a significant reduction of 98.05% and 98.81% during 2020 and 2021, season. Further, 2 Gy irradiated S. carpocapsae BA2 was more potency in reducing numbers of insect larvae than normal nematodes and other treatments. Gamma irradiated nematodes at rate of 120 IJ's +2 Gy / ml seems to be the most auspiciously agents against P. xylostella. While insect growth regulator Match 5% gave overall average of 76.52 and 76.42% mortality in the two seasons, respectively. The 2 Gy irradiated S. carpocapsae BA2 and normal nematode were safe on P. xylostella predators on cabbage plants, whereas chemical insecticides reduced numbers of predators.

Males of many species compete over access to females by physical contests. Previous experience of mating and the opportunity to mate with a female may influence the motivation of males to engage in contests and the outcome of such contests. Often, prior mating results in increased aggression and probability of success. This is mediated by the effects on the male's subjective evaluation of both the resource value (RV) and his own ability to acquire the resource (resource-holding potential, RHP). Moreover, having mated may also affect a male's actual fighting ability. In Steinernema nematodes, mated males paired with naïve males are more likely to win contests. Here we show that this advantage in mated males of Steinernema carpocapsae cannot be explained solely by the physical changes brought about by prior female contact, since males exposed to female pheromone alone developed sperm and increased in size like mated males but did not have the same advantage as them in contests with naïve males. Effects of mating on other components of RHP, such as skill or motivation, or on RV may explain the greater probability of mated males winning. We also show that mating had differential effects on the probability of a male initiating attack, depending on whether the opponent was a mated male (and thus ready to mate again) or naïve, consistent with the relative threat of the opponent as a competitor for copulations. • Mating status affected contest behaviour in male Steinernema nematodes. • In contest with naïve males, mated males were more likely to win, but naïve initiated. • Males exposed to females or their pheromones developed sperm and increased in size. • Larger size did not explain the fighting advantage of mated males. • Mated males' advantage must be due to elements of RHP other than size or to RV. [ABSTRACT FROM AUTHOR]

Nematode–microbe symbiosis plays a key role in determining pathogenesis against pests. The modulation of symbiotic bacteria may affect the virulence of entomopathogenic nematodes (EPNs) and the biological management of pests. We tested the influence of asafoetida (ASF) extract on the virulence of Steinernema carpocapsae and its symbiotic bacterium, Xenorhabdus nematophila, in Pyrrhocoris apterus. A total of 100 mg of ASF killed 30% of EPNs in 48 h, while P. apterus remained unaffected. The EPNs pre-treated with 100 mg of ASF influenced P. apterus's mortality by 24–91.4% during a period of 24 to 72 h. The topical application of ASF acted as a deterrent to S. carpocapsae, lowering host invasion to 70% and delaying infectivity with 30% mortality for 168 h. Interestingly, Steinernema's symbiotic bacterium, Xenorhabdus, remained unaffected by ASF. An in vitro turbidity test containing 100 mg of ASF in a medium increased the growth rate of Xenorhabdus compared to a control. A disc diffusion assay confirmed the non-susceptibility of Xenorhabdus to ASF compared to a positive control, streptomycin. Pro-phenol oxidase (PPO) and phenol oxidase (PO) upregulation showed that ASF influences immunity, while EPN/ASF showed a combined immunomodulatory effect in P. apterus. We report that ASF modulated the virulence of S. carpocapsae but not that of its symbiotic bacterium, X. nematophila, against P. apterus. [ABSTRACT FROM AUTHOR]

Aim of study: The green vegetable bug Nezara viridula L. is a polyphage that is spread all over the world, but in the last 10 years it has entered the territory of the Russian Federation. The use of biological protection against this pest is an important task in the country. We used the entomopathogenic nematodes (EPN) Steinernema feltiae and Steinernema carpocapsae to control N. viridula. Area of study: Federal Research Center of Biological Plant Protection (FRCBPP), Krasnodar Krai, Russia, 2019-2020. Material and methods: A laboratory test was carried out with adults and nymphs of N. viridula. Each species of EPN (S. carpocapsae and S. feltiae) was used at doses of 50, 75 and 100 individuals infective larvae per insect. The initial material for analysis was collected on soybean crops in the crop rotation of the FRCBPP. The experimental results were assessed using ANOVA. Main results: Laboratory tests of the EPN S. carpocapsae and S. feltiae caused the death of up to 98.0% of nymphs and up to 91.4% of adults of N. viridula. The species S. feltiae turned out to be the most effective, as allowed the pathogen to develop in shorter periods of time, and caused the death of 81.9-91.4% adults and of 92.0-98.0% nymphs. Research highlights: This study showed that during the period of growth and development of larvae, the use of EPN is more effective in nymphs than on adults.

The 5th instar larvae of each of the four insect species were assayed about their capability to play as host for mass propagation of juveniles of two beneficial entomopathogenic nematodes (EPN) species; Heterorabditis bacteriophora and Steinernema carpocapsae in the laboratory at 25 °C and 65±5 % R.H. After exposure of larvae at the rate of 1000 IJs/5 larvae, daily microscope inspections were carried out until larval mortality and penetration of the new IJs out from the host larvae. Counts of the newly emerged juveniles were carried out periodically and successively (3, 6, 9, 12, 15, 20, 25 and 30 days after starting emergence). Larvae of Galleria mellonella manifested the shortest period from exposure to IJs until larval mortality (2 days), as opposed to 2.33 days in the case of Spodoptera frugiperda, 2.33 and 3 days after infection of Spodoptera littoralis larvae by H. bacteriophora and S. carpocapsae IJs, respectively, and 4.33 and 2.33 days, respectively for T. molitor larvae indicating the longest period after infection to mortality. As for the period from the time of exposure until starting of IJs emergence, that was the shortest (7 days) in the case of S. frugiperda infected by either of the two EPN species and G. mellonella (by S. carpocapsae), while this period was the longest for T. molitor infested by H. bacteriophora and S. carpocapsae (12 and 14 days, respectively). After 30 days of starting emergence out of host larvae, the highest mean of the total number of H. bacteriophora juveniles (364767 IJs) resulted from T. molitor larvae, followed by 284680 IJs/S. frugiperda larvae and 259817 IJs from G. mellonella larvae. While, in the case of S. carpocapsae; the highest number of harvested juveniles (341790 IJs) was produced from G. mellonella larvae, followed by 258363 IJs/a S. frugiperda larvae and 246633 IJs/a S. littoralis larvae. As a general conclusion, for mass - propagation of H. bacteriophora, rearing on T. molitor larvae is recommended, followed by G. mellonella. On the same target for S. carpocapsae; to obtain the highest production of juveniles, rearing on G. mellonella larvae is the best followed by S. littoralis, then S. frugiperda larvae. [ABSTRACT FROM AUTHOR]

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.

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.

A key aspect of parasitic nematode infection is the nematodes' ability to evade and/or suppress host immunity. This immunomodulatory ability is likely driven by the release of hundreds of excretory/secretory proteins (ESPs) during infection. While ESPs have been shown to display immunosuppressive effects on various hosts, our understanding of the molecular interactions between individual proteins released and host immunity requires further study. We have recently identified a secreted phospholipase A2 (sPLA2) released from the entomopathogenic nematode (EPN) Steinernema carpocapsae we have named Sc-sPLA2. We report that Sc-sPLA2 increased mortality of Drosophila melanogaster infected with Streptococcus pneumoniae and promoted increased bacterial growth. Furthermore, our data showed that Sc-sPLA2 was able to downregulate both Toll and Imd pathwayassociated antimicrobial peptides (AMPs) including drosomycin and defensin, in addition to suppressing phagocytosis in the hemolymph. Sc-sPLA2 was also found to be toxic to D.melanogaster with the severity being both dose- and time-dependent. Collectively, our data highlighted that Sc-sPLA2 possessed both toxic and immunosuppressive capabilities. [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 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]

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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 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.

A key aspect of parasitic nematode infection is the nematodes’ ability to evade and/or suppress host immunity. This immunomodulatory ability is likely driven by the release of hundreds of excretory/secretory proteins (ESPs) during infection. While ESPs have been shown to display immunosuppressive effects on various hosts, our understanding of the molecular interactions between individual proteins released and host immunity requires further study. We have recently identified a secreted phospholipase A2 (sPLA2) released from the entomopathogenic nematode (EPN) Steinernema carpocapsae we have named Sc-sPLA2. We report that Sc-sPLA2 increased mortality of Drosophila melanogaster infected with Streptococcus pneumoniae and promoted increased bacterial growth. Furthermore, our data showed that Sc-sPLA2 was able to downregulate both Toll and Imd pathway-associated antimicrobial peptides (AMPs) including drosomycin and defensin, in addition to suppressing phagocytosis in the hemolymph. Sc-sPLA2 was also found to be toxic to D. melanogaster with the severity being both dose- and time-dependent. Collectively, our data highlighted that Sc-sPLA2 possessed both toxic and immunosuppressive capabilities.

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]

Highlights We developed an improved capsule formulation named as Capsule-C supplemented with glucose, which can obviously increase the larva feeding amount of Agrotis ipsilon. The nematodes of Steinernema carpocapsae HB310 in Capsule-C survived well and maintained high pathogenicity against Galleria mellonella after storage for 180 days. Under laboratory conditions, Capsule-C could be released into the rhizosphere directly and effectively reduced maize seedlings damage by A.ipsilon.

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]

Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae) is an insect pest in poultry production systems. This insect has developed resistance to many chemical insecticides. As an alternative to chemicals, entomopathogenic nematodes (EPNs) are one of the most commonly used agents against several pest arthropods. The pathogenicity of the EPN Steinernema carpocapsae Weiser on four field strains of lesser mealworm, A. diaperinus, from Turkey was studied. In the experiments, larvae of A. diaperinus were found to be more sensitive than adults to S. carpocapsae infection. In terms of LC50 values in both larval and adult insects, Balikesir strain was found to be the most susceptible, Manisa strain the most resistant. The calculated LC50 values for adults were 85.9, 205.6, 135.4, and 418.8 IJs/ml, and for larvae 31.2, 39.8, 34.8, and 70.9 IJs/ml for the Balikesir, Canakkale, İzmir, and Manisa strains, respectively. This is the first report about the pathogenicity of EPNs against larvae and adults of lesser mealworm A. diaperinus strains from Turkey. We conclude that S. carpocapsae can be used as a control agent for lesser mealworms. [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]

Attempts were made to evaluate the purified bioactive compounds of Xenorhabdus nematophila against Meloidogyne incognita. In order to extract the purified compounds, a solid-supported liquid-liquid extraction system with a flow rate (1 mL/min) was used to purify bioactive molecules. Compounds were individually collected concentrated and evaluated against M. incognita. Among 25 fractions the L19 fraction, exhibited 98% inhibition in egg hatching and mortality of juveniles. The biomolecules were identified through Liquid Chromatography- Mass Spectroscopy (LC-MS) technique. To decipher the mode of action of compounds, molecular docking studies were performed with potential protein targets such as acetylcholinesterase, β-1,4-endoglucanase, glutathione S-transferase-1, cytochrome c oxidase, G-protein coupled receptor and Fatty acid and retinol-binding proteins of M. incognita. The results revealed that among eight compounds from the L19 fraction, malonate and pidopidon exhibited greater binding affinity towards the selected protein targets of M. incognita. In vitro studies with malonate and pidopidon against M. incognita showcased a 99% reduction in egg hatching and juvenile mortality. Moreover, greenhouse experiments revealed that malonate compounds not only reduced 94% of the M. incognita population but also enhanced the plant growth parameters in tomato by 60%. Hence the present study stands novel in exploiting the nematicidal compounds from X. nematophila giving limelight to explore pidopidon and malonate as novel nematicidal compounds for the management of M. incognita., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

An entomopathogenic nematode, Oscheius tipulae, was isolated from a soil sample. The identification of this species was supported by morphological and molecular markers. The nematode isolate exhibited pathogenicity against different target insects including lepidopteran, coleopteran, and dipteran insects. The virulence of this nematode was similar to that of a well-known entomopathogenic nematode, Steinernema carpocapsae, against the same insect targets. A comparative metagenomics analysis of these two nematode species predicted the existence of a combined total of 272 bacterial species in their intestines, of which 51 bacterial species were shared between the two nematode species. In particular, the common gut bacteria included several entomopathogenic bacteria including Xenorhabdus nematophila, which is known as a symbiotic bacterium to S. carpocapsae. The nematode virulence of O. tipulae to insects was enhanced by an addition of dexamethasone but suppressed by an addition of arachidonic acid, suggesting that the immune defenses of the target insects against the nematode infection is mediated by eicosanoids, which would be manipulated by the symbiotic bacteria of the nematode. Unlike S. carpocapsae, O. tipulae showed high virulence against dipteran insects including fruit flies, onion flies, and mosquitoes. O. tipulae showed particularly high control efficacies against the onion maggot, Delia platura, infesting the Welsh onion in the rhizosphere in both pot and field assays., (© 2024 Wiley Periodicals LLC.)

Nematode–microbe symbiosis plays a key role in determining pathogenesis against pests. The modulation of symbiotic bacteria may affect the virulence of entomopathogenic nematodes (EPNs) and the biological management of pests. We tested the influence of asafoetida (ASF) extract on the virulence of Steinernema carpocapsae and its symbiotic bacterium, Xenorhabdus nematophila, in Pyrrhocoris apterus. A total of 100 mg of ASF killed 30% of EPNs in 48 h, while P. apterus remained unaffected. The EPNs pre-treated with 100 mg of ASF influenced P. apterus’s mortality by 24–91.4% during a period of 24 to 72 h. The topical application of ASF acted as a deterrent to S. carpocapsae, lowering host invasion to 70% and delaying infectivity with 30% mortality for 168 h. Interestingly, Steinernema’s symbiotic bacterium, Xenorhabdus, remained unaffected by ASF. An in vitro turbidity test containing 100 mg of ASF in a medium increased the growth rate of Xenorhabdus compared to a control. A disc diffusion assay confirmed the non-susceptibility of Xenorhabdus to ASF compared to a positive control, streptomycin. Pro-phenol oxidase (PPO) and phenol oxidase (PO) upregulation showed that ASF influences immunity, while EPN/ASF showed a combined immunomodulatory effect in P. apterus. We report that ASF modulated the virulence of S. carpocapsae but not that of its symbiotic bacterium, X. nematophila, against P. apterus.

Spodoptera litura Fabricius (Lepidoptera: Noctuidae) is a major pest of marigolds in Thailand. It causes severe damage to flower quantity and quality. The most common control method is synthetic insecticides, although this method struggles to control hidden larvae inside flowers or buds and underground pupae. Entomopathogenic nematodes (EPNs) are widely used as biocontrol agents against many foliage and cryptic insects. The virulence of two commercial EPNs strains, Steinernema siamkayai (Stock, Somsook and Reid) and S. carpocapsae (Weiser), isolated in Thailand, were assessed against different developmental stages of S. litura. The younger larvae of first and third instar were more susceptible to S. siamkayai with the LD50 of 15.84 and 40.34 dauer juveniles (DJs) per host, whereas S. carpocapsae caused higher mortality in older larvae. Against the fifth instar larvae and pupae, the LD50 ranged between 54.37 and 607.97 DJs/host. Field experiments compared the effect of EPNs with farmer's practice (insecticides). EPNs treatments with S. siamkayai and S. carpocapsae significantly reduced the percentage of damaged flowers to 2.53 ± 1.2% and 2.97 ± 1.5%, respectively, compared with insecticide treatment at 4.21 ± 2.1% in the first trial. In trial 2, the insecticide treatment had the highest percentage of damaged flowers of 5.02 ± 5.7%. The benefit–cost ratio (BCR) of EPNs treatments ranged from 2.42 to 2.53 in the first trial and 1.24–1.50 in the second trial and was superior to insecticide treatments with 2.21 and 1.16 in the two trials. [ABSTRACT FROM AUTHOR]

[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]

• Two novel behaviorally active compounds for EPN IJs were revealed. • The two species tested (Steinernema feltiae and S. carpocapsae) responded differently to the behaviorally active compounds. • Within the blend of volatiles emitted by EPN-infected insect cadavers, 1-nonene plays a behavior-active role. • Ethanol is a novel attractant for S. feltiae IJs. • The differences in the responses to the compounds support known data on scavenging trends of the EPNs tested. Entomopathogenic nematodes (EPNs) parasitize insects in the soil and are applied as environmentally friendly means for pest control in agriculture. Knowledge of how EPN infective juveniles (IJs) find their prey can be used to increase their effectiveness. Chemical signals in the soil are undoubtedly important but exactly which ones is little known. We hypothesized that volatile compounds emitted by EPN-infected larval cadavers could act as such signals. The objective of the study was to test the behavioral effects of 1-nonene which is known as a volatile compound emitted by several EPN-infected insect cadavers. Behavioral tests revealed that 1-nonene was attractive to IJs of both Steinernema feltiae and S. carpocapsae. High concentrations of the compound were repellent to S. feltiae and attractive to S. carpocapsae IJs. Low concentrations were attractive to S. feltiae (those from 104 to 106 times lower than the repellent concentrations) but did not affect the behavior of S. carpocapsae. Ethanol (solvent used for control tests) was attractive to S. feltiae IJs and not to those of S. carpocapsae. Both compounds are new agents involved in the behavior control of these EPN species. Different responses of IJs of two taxonomically closely related EPN species to chemical compounds could indicate interspecific difference in foraging. Behavioral reactions of S. carpocapsae IJs are more in line with the strategy of the scavenger. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs) are widely used as a biological control agent in pest management. The purpose of this study was to determine the effectiveness and penetration rates of certain EPNs. Three different EPN species were utilized in the study: Heterorhabditis bacteriophora HBH hybrid strain, Steinernema carpocapsae TUR-S4 isolate, Steinernema feltiae TUR-S3 and S-Bilecik isolates. These isolates were applied at different doses (50, 100, 150, 200, 250, 300, 350, and 400 Infective Juveniles (IJs)/Petri) on larvae of Tenebrio molitor and adults of Rhyzopertha dominica. Additionally, the penetration rates of the mentioned EPN species on T. molitor larvae and R. dominica adults were determined. As a result, the highest mortality rate observed in R. dominica adults was 93.33% when treated with the HBH isolate at the dose of 400 IJs/Petri dishes. For T. molitor larvae, the highest mortality rate was 100% at doses of 8.85 IJs/cm2, 10.60 IJs/cm2, 12.40 IJs/cm2, 14.15 IJs/cm2 for HBH and TUR-S3, 10.60 IJs/cm2, 12.40 IJs/cm2, 14.15 IJs/cm2 for TUR-S4, and 7.10 IJs/cm2, 8.85 IJs/cm2, 10.60 IJs/cm2, 12.40 IJs/cm2, 14.15 IJs/cm2 for S-Bilecik. When examining the penetration rates, the highest rate of 23.33% was observed in R. dominica adults treated with HBH, while for T. molitor , this rate was 22.67% in individuals treated with HBH. These findings underscore the importance of continued investigation into the potential of these EPNs for sustainable pest management strategies. • Entomopathogenic nematodes (EPNs) play a crucial role as biological control agents in controlling agricultural pests. • The HBH isolate of Heterorhabditis bacteriophora showed high mortality rates of 93.33% in Rhyzopertha dominica adults. • Specific doses for each EPN species resulted in a 100% mortality rate for Tenebrio molitor larvae. • The HBH isolate demonstrated the highest penetration rates, with 23.33% observed in R. dominica and 22.67% in T. molitor. [ABSTRACT FROM AUTHOR]

Parasitic nematodes infect a variety of organisms including insects and vertebrates. To survive, they evade host immune responses to cause morbidity and mortality. Despite the vast clinical knowledge regarding nematode infections and their biological makeup, molecular understanding of the interactions between host and parasite remains poorly understood. The utilization of model systems has thus been employed to help elucidate the molecular interactions of the host immune response during parasitic nematode infection. Using model systems, it has been well established that parasitic nematodes evade host immunity by releasing excretory/secretory proteins (ESPs), which are involved in immunomodulation. Model systems have enabled researchers to characterize further the underlying mechanisms ESPs use to facilitate evasion and modulation of the host immune response. This review assessed notable ESPs from parasitic nematodes that infect vertebrates or insects and have been studied in mechanistic detail. Being able to characterize how ESPs affect the immune systems of hosts on a molecular level increases our understanding of host–parasite interactions and could lead to the identification of novel therapeutic targets and important molecular pathways. [ABSTRACT FROM AUTHOR]

Background: Entomopathogenic nematodes (EPNs) have long been used for controlling soil-dwelling insects. Steinernema carpocapsae HB310, previously showed a high virulence against many pests including Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae). Due to the lack of durable formulations, up until now, S. carpocapsae HB310 has thus far been prevented from use in large-scale farming. The present study aimed to get a better EPNs capsule formulation suitable for long-term storage and effective application. Results: An improved EPNs capsule formulation, herein named: Capsule-C was prepared by the following composition: Solution I: 18% glycerol, 0.075% formaldehyde, 1% sodium alginate, 0.2% xanthan gum, 0.5% potassium sorbate, 9% glucose, 2% fructose, 2% sucrose, and the remainder was distilled water. The nematodes suspension was added to the alginate mixture in 2 × 104 IJs/mL; Solution II: 18% glycerol, 0.075% formaldehyde, 0.5% calcium chloride, 0.5% potassium sorbate, with the remainder being distilled water. After storage for 180 days at 16 °C and 100% RH, the survival rate of nematodes in Capsule-C was 75.68 ± 0.48% and the nematodes caused 82.33 ± 1.45% mortality in the 5th instar larvae of Galleria mellonella. A. ipsilon larvae preferred to chew and ingest Capsule-C due to the addition of the glucose compound. The feeding rate of A. ipsilon larvae on Capsule-C reached to 100% within 24 h and the larval mortality of A. ipsilon was 90.48 ± 6.35%. Conclusion: EPNs-containing capsules were as effective as sprayed EPNs in water solution at killing A. ipsilon. These results will provide ideas to acquire a stable and efficient EPNs capsule formulation and further promote the application of environmental friendly biological pesticides. Highlights: We developed an improved capsule formulation named as Capsule-C supplemented with glucose, which can obviously increase the larva feeding amount of Agrotis ipsilon. The nematodes of Steinernema carpocapsae HB310 in Capsule-C survived well and maintained high pathogenicity against Galleria mellonella after storage for 180 days. Under laboratory conditions, Capsule-C could be released into the rhizosphere directly and effectively reduced maize seedlings damage by A.ipsilon. [ABSTRACT FROM AUTHOR]

Abstract Combined effect of substerilizing doses of gamma radiation (40 and 100 Gy) and different concentrations of the entomopathogenic nematode, Steinernema carpocapsae BA2 (20 and 40 IJs/ml) on the hemocyte count of the greater wax moth, Galleria mellonella (L.) larvae was studied. Eight types of hemocytes were described in the hemolymph of the normal larvae of G. mellonella. Prohemocytes were the predominant type, while the cystocytes were the rare ones. Morphological malformations and changes in the number of each hemocyte type were observed in F1 larvae (of irradiated male parent pupae with 40 or 100 Gy) or larvae treated with different concentrations of the S. carpocapsae BA2 (normal or F1 larvae); these alterations were increased by increasing the radiation dose or the nematode concentration that led to increase the susceptibility of the larvae to the nematode. Therefore, it could be concluded that integration of entomopathogenic nematodes and gamma radiation may serve as integrated control program for G. mellonella.

The entomopathogenic nematode, Steinernema carpocapsae, was evaluated for control of the potato tuber moth, Phthorimaea operculella, under laboratory conditions. We evaluated different concentrations of S. carpocapsae for control of 2nd, 3rd, and 4th instar P. operculella. The median lethal concentration (LC50) of S. carpocapsae infective juveniles (IJs) to 2nd, 3rd and 4th instar larvae of P. operculella was 200, 363, 181 IJs mL−1, respectively. With the extension of treatment time, the cumulative mortality increased for 2nd, 3rd, and 4th instar larvae and pupae of P. operculella. Fourth instars were the most susceptible for all observation periods. Therefore, our results suggest that S. carpocapsae could be an effective biological control agent for P. operculella.

Abstract During a survey of entomopathogenic nematodes (EPNs) in Moghan region of Iran in 2015, a steinernematid species was isolated, using the Galleria-baiting method. Based on its morphological and phylogenetic analysis of molecular data, the isolate was identified as Steinernema carpocapsae. The ITS rDNA sequence was deposited in NCBI (National Center for Biotechnology Information) with accession number of MF187616.1. Nucleotide row data was edited, using MEGA 6.0 software, and homologous sequences were involved in analysis, using Blast software. Sequences were aligned using Clustal W. Bootstrap analysis. The phylogenetic tree was constructed by the maximum likelihood method, using MEGA 6.0 software, and Steinernema feltiae was used as out-group. The turnip moth, Agrotis segetum Denis and Schiffermuller (Lepidoptera: Noctuidae), is one of the most important and destructive cutworm pests in Moghan. Therefore, the lethal effect of S. carpocapsae isolate Moghan (IRMoghan) was evaluated in a soil assay against the last instar larvae of A. segetum under laboratory conditions. The bioassay results showed high susceptibility of the larvae to S. carpocapsae. The LC10, LC50, and LC90 values were 9.9, 54.13, and 246.2 IJs (infective juveniles) per larva of the pest, respectively (χ 2 = 7.36; df = 3, P value = 0.061). Reproduction of the EPNs within the dissected cadavers was observed. The bioassay results indicated that the new isolate is a promising biocontrol agent against A. segetum larvae with success recycling through them.

BACKGROUND Entomopathogenic nematodes (EPN) show potential in controlling larvae of the Mediterranean fruit fly (medfly) Ceratitis capitate, but previous studies mainly concern species and strains that are not commercially available. The use of EPN for control of Mediterranean fruit fly is further hampered by the cost of using nematodes. In this study, the efficacy and residual activity of commercial strains of three EPN species, Steinernema carpοcapsae, S. feltiae and Heterοrhabditis bacteriοphοra medfly) C. capitata, in the soil substrate and inside fruits were evaluated. RESULTS: Suspensions of these species were applied at a dose of 1.5 mi m−2 on a soil substrate wherein medfly larvae were added sequentially for a period of 4 weeks post application at 20 °C. S. feltiae provided the highest suppression up to 50% as assessed by adult medfly emergence because it had the highest immediate activity and long residual activity. Furthermore, S. feltiae, and to a lesser degree S. carpocapsae, were able to move and infect medfly larvae inside infested apples and oranges left in the surface of the substrate wherein EPN were applied, reducing significantly adult medfly emergence (60–78%). CONCLUSION: These results support the efficacy and feasibility of applying a single, relatively low dose of S. feltiae in autumn, off‐season, targeting overwintering medfly larvae with the scope of reducing the number of adult medflies emerging later in the new season. [ABSTRACT FROM AUTHOR]

Non-native pests are often responsible for serious crop damage. Since Drosophila suzukii has invaded North America and Europe, the global production of soft, thin-skinned fruits has suffered severe losses. The control of this dipteran by pesticides, although commonly used, is not recommended because of the negative impact on the environment and human health. A possible alternative is the use of bio-insecticides, including Bacillus thuringiensis and entomopathogenic nematodes, such as Steinernema carpocapsae. These biological control agents have a fair effectiveness when used individually on D. suzukii, but both have limits related to different environmental, methodological, and physiological factors. In this work, we tested various concentrations of B. thuringiensis and S. carpocapsae to evaluate their efficacy on D. suzukii larvae, when administered individually or in combination by using agar traps. In the combined trials, we added the nematodes after 16 h or concurrently to the bacteria, and assessed larvae lethality from 16 to 48 h. The assays demonstrated a higher efficacy of the combined administration, both time-shifted and concurrent; the obtained data also showed a relevant decrease of the time needed to kill the larvae. Particularly, the maximum mortality rate, corresponding to 79% already at 16 h, was observed with the highest concentrations (0.564 µg/mL of B. thuringiensis and 8 × 102 IJs of S. carpocapsae) in the concurrent trials. This study, conducted by laboratory tests under controlled conditions, is a good starting point to develop a further application step through field studies for the control of D. suzukii. [ABSTRACT FROM AUTHOR]

[Display omitted] • Plant volatiles (z)‑3‑hexenol and carvone exhibited strong attraction to Steinernema carpocapsae IJs. • Transcriptome analysis revealed 721 differentially expressed genes (DEGs) between carvone-treated and control groups, and the responsive DEGs to carvone attraction were mainly involved in locomotion, localization, behavior, response to stimulus, and olfactory transduction. • Four upregulated genes of chemoreceptor and response to stimulus that were involved in the response of IJs to carvone attraction. Entomopathogenic nematodes (EPNs) use the chemical cues emitted by insects and insect-damaged plants to locate their hosts. Steinernema carpocapsae , a species of EPN, is an established biocontrol agent used against insect pests. Despite its promising potential, the molecular mechanisms underlying its ability to detect plant volatiles remain poorly understood. In this study, we investigated the response of S. carpocapsae infective juveniles (IJs) to 8 different plant volatiles. Among these, carvone was found to be the most attractive volatile compound. To understand the molecular basis of the response of IJs to carvone, we used RNA-Seq technology to identify gene expression changes in response to carvone treatment. Transcriptome analysis revealed 721 differentially expressed genes (DEGs) between carvone-treated and control groups, with 403 genes being significantly upregulated and 318 genes downregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the responsive DEGs to carvone attraction were mainly involved in locomotion, localization, behavior, response to stimulus, and olfactory transduction. We also identified four upregulated genes of chemoreceptor and response to stimulus that were involved in the response of IJs to carvone attraction. Our results provide insights into the potential transcriptional mechanisms underlying the response of S. carpocapsae to carvone, which can be utilized to develop environmentally friendly strategies for attracting EPNs. [ABSTRACT FROM AUTHOR]

• Allium sativum EO increased EPN mortality and reduced their infective capacity. • Satureja montana EO caused low mortality rates but exhibited repellency towards EPNs. • Mentha suaveolens EO minimally affected EPNs survival, infectivity and reproduction. • M. suaveolens EO is suggested as the most compatible oil for field use with EPNs. • Field validation is essential to confirm the practical applicability of these findings. The European truffle beetle, Leiodes cinnamomeus , is the most important pest in black truffle (Tuber melanosporum) plantations. Entomopathogenic nematodes (EPNs) are promising biological control agents against L. cinnamomeus. Essential oils (EOs) are also recently being investigated for the control of the adults of this pest. Therefore, both control methods could be combined in Integrated Pest Management (IPM) programs to enhance their efficacy. However, limited information exists regarding the effects of the EOs on EPNs and so their compatibility. The aims of our work were to study the effects of three previously described insecticidal and nematicidal essential oils, Allium sativum , Mentha suaveolens , and Satureja montana, on the survival, infectivity, reproduction, and attraction behaviour of three EPN species: Steinernema feltiae , Steinernema carpocapsae and Heterorhabditis bacteriophora. Therefore, we conducted three experiments under laboratory conditions to observe the lethal and sublethal effects by direct contact, the lethal effect by fumigation, and the chemotaxis response. Allium sativum caused the highest mortality rates in all three EPN species at 24 and 72 h post application whether by direct contact (97–99%) or fumigation (40–42%), and it also reduced their infective capacity on Galleria mellonella. Satureja montana EO caused low mortality rates compared to A. sativum , but it was significantly more lethal (6–8%) than the control (0–3%) at 72 h in the direct contact assay. It also displayed repellent properties against S. feltiae and H. bacteriohora in the chemotaxis assay. In contrast, M. suaveolens EO exhibited minimal impact on the survival, infectivity and reproduction of all three EPN species. Therefore, our results suggest M. suaveolens oil may be the most compatible EO for use integrated with EPNs. Further validation under field conditions and in the presence of L. cinnamomeus is necessary to confirm the practical applicability of these findings. [ABSTRACT FROM AUTHOR]