Steinernema Carpocapsae Research Articles

A Nematode Isolate, Oscheius Tipulae, Exhibiting a Wide Entomopathogenic Spectrum and its Application to Control Dipteran Insect Pests.

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.

Impacts of Combining Steinernema carpocapsae and Bracon hebetor Parasitism on Galleria mellonella Larvae.

The greater wax moth, Galleria mellonella, is a significant pest in apiculture and a well-established model organism for immunological and ecotoxicological studies. This investigation explores the individual and combined effects of the ectoparasite Bracon hebetor (B.h.) and the entomopathogenic nematode Steinernema carpocapsae (S.c.) on G. mellonella larvae. We evaluated the activity of oxidative stress enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), malondialdehyde (MDA) levels, cytochrome P450 activity, cell viability using Annexin V-FITC, DNA damage via comet assay, and larval morphology through scanning electron microscopy (SEM). Control larvae exhibited higher GPx and GST activities compared to those treated with B.h., S.c., or the B.h. + S.c. combination. Conversely, MDA levels displayed the opposite trend. SOD activity was reduced in the B.h. and S.c. groups but significantly higher in the combined treatment. Cytochrome P450 activity increased in response to parasitism by B. hebetor. The Annexin V-FITC assay revealed decreased cell viability in parasitized groups (B.h. 79.4%, S.c. 77.3%, B.h. + S.c. 70.1%) compared to controls. DNA damage analysis demonstrated significant differences between groups, and SEM observations confirmed severe cuticle abnormalities or malformations in G. mellonella larvae. These findings highlight the complex interactions between B. hebetor, S. carpocapsae, and their host, G. mellonella. Additionally, they illuminate the intricate physiological responses triggered within the host larvae.

Preferences for livestock bedding as a development substrate of the stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), and potential application of entomopathogenic nematodes for controlling stable fly larvae.

The stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), is a significant insect pest with global veterinary implications due to its capacity to both cause nuisance and transmit disease-causing pathogens to livestock. This study aimed to determine the livestock bedding preferred for use as a development substrate by S. calcitrans larvae and field-collected adults. The result showed that S. calcitrans larvae exhibited a preference (26.7%) for 7-day-old cow manure. Gravid females displayed a pronounced preference (55.0%) for fresh cow manure. As there were eight choices, indifference would result in 12.5% for each bedding substrate. Furthermore, the efficacy of four entomopathogenic nematodes (EPNs), namely Heterorhabditis bacteriophora (Poinar), Heterorhabditis indica Poinar, Karunakar & David (Rhabditida: Heterorhabditidae), Steinernema siamkayai Poinar, Karunakar & David and Steinernema carpocapsae (Weiser) (Rhabditida: Steinernematidae), against S. calcitrans larvae and the persistence after application to livestock bedding substrates were evaluated under laboratory conditions. In filter paper bioassays, all four EPNs caused 76.7%-100.0% mortality in the second instar larvae of S. calcitrans when applied at 50 and 100 infective juveniles (IJs)/cm2 within 5 days after exposure. For the third instar larvae of S. calcitrans, only H. indica induced high mortalities of 86.6% when applied at 100 IJs/cm2 within 5 days after exposure, while the other EPNs resulted in mortalities of less than 70%. The data further demonstrated that H. bacteriophora, H. indica and S. siamkayai remained present in the substrates linked to S. calcitrans larvae for as long as 7 days after the application of EPNs. This study demonstrates the potential of EPNs as a biologically based control agent against larvae of S. calcitrans, a serious pest and significant vector for various livestock animals.

DETERMINATION OF ENTOMOPATHOGENIC NEMATODE FAUNA IN ŞIRNAK, TURKIYE

This study focuses on the isolation, identification, and characterization of entomopathogenic nematodes (EPNs) in Şırnak Province, Turkey. Between July and September 2023, we collected 256 soil samples, from which 11 EPN isolates were successfully recovered,representing a 4.3% of the samples. These isolates were identified using morphological examinations and molecular diagnostics, including mitochondrial COI and 18S rDNA gene regions. Our findings revealed a diverse population of EPNs, predominantly Heterorhabditis bacteriophora with five isolates, alongside four Steinernema species (one Steinernema carpocapsae, one Steinernema affine, and two Steinernema sp.). Phylogenetic analysis, employing the mitochondrial cytochrome oxidase subunit I (COXI) and the 18S rDNA gene regions, indicated low genetic variability within H. bacteriophora and greater diversity among Steinernema species. The study contributes significant insights into the EPN biodiversity in Şırnak Province and underscores the potential of these nematodes in biological pest control, offering a sustainable alternative to chemical pesticides. The results highlight the importance of local EPN isolates in the development of effective biological control strategies and the conservation of agricultural biodiversity.

Long-term suppression of turfgrass insect pests with native persistent entomopathogenic nematodes

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.

Comparative Efficacy of Different Biopesticides against the Tobacco Caterpillar [Spodoptera litura (Fabricius)

Tobacco caterpillar, Spodoptera litura (Fabricius) is an economically important polyphagous pestinflicting significant economic damage to numerous field and horticultural crops. Overreliance of chemical insecticides to manage the pest has led to the development of resistance, resurgence and residue problem in the crop ecosystems, in addition to high operating costs. Biopesticides have been reported to be effective for managing this pest in ecofriendly manner. Hence, the present study was conducted to assess the efficacy of different bio pesticides against S. litura under laboratory conditions at Bihar Agricultural College, Sabour, Bhagalpur during the rabi of 2022-23. It was conducted in completely randomized design (CRD) with eight treatments and three replications. Among the various biopesticides evaluated, Steinernema carpocapsae- 500 IJs/Petri Plate and Metarhizium anisopliae 1×108 spores/ml -5g/l were most effective treatments and at par each other with 93.00 and 82.50 per cent larval mortality, respectively. They had performed equally with chemical check, Emmamectin benzoate 5 SG- 0.4 g/l which recorded with 95.63 % larval mortality. Neem oil 1500 ppm- 5 ml/litre and Beauveria bassiana 1×108 @5ml/l were the next best treatments with 78.31 and 59.38 % larval mortality respectively. The order of efficiency was Emamectin benzoate 5 SG (0.4g/l) > EPNs (500 IJs) >Metarhizium anisopliae 1% WP (5g/l) >Neem oil 1500 ppm (5 ml/litre) >Beauveria bassiana1 % WP (5 g/l) >Metarhizium anisopliae 1 % WP (2.5 g/l) >Beauveria bassiana 1 % WP (2.5 g/l).

The Efficacy of Entomopathogenic Nematodes Plus an Adjuvant against Helicoverpa zea and Chrysodeixis includens in Aboveground Applications.

In the southern United States, corn earworm, Helicoverpa zea (Boddie), and soybean looper, Chrysodeixis includens (Walker) are economically important crop pests. Although Bt crops initially provided effective control of target pests such as H. zea, many insect pests have developed resistance to these Bt crops. Alternative approaches are needed, including biological control agents such as entomopathogenic nematodes (EPNs). However, the effectiveness of EPNs for aboveground applications can be limited due to issues such as desiccation and ultraviolet radiation. Effective adjuvants are needed to overcome these problems. Ten strains of EPNs were tested for virulence against eggs, first to fourth instars, fifth instars, and pupae of H. zea and C. includens in the laboratory. These 10 EPN strains were Heterorhabditis bacteriophora (HP88 and VS strains), H. floridensis (K22 strain), Hgkesha (Kesha strain), Steinernema carpocapsae (All and Cxrd strains), S. feltiae (SN strain), S. rarum (17c+e strain), and S. riobrave (355 and 7-12 strains). EPNs could infect eggs of H. zea or C. includens in the laboratory, but the infection was low. The mortality caused by 10 EPN strains in seven days was significantly higher for the first to fourth instars of H. zea compared to the control, as was the fifth instars of H. zea. Similarly, for the first to fourth and fifth instars of C. includens, the mortality was significantly higher compared to the controls, respectively. However, only S. riobrave (355) had significantly higher mortality than the control for the pupae of H. zea. For the pupae of C. includens, except for H. bacteriophora (HP88), S. rarum (17c+e), and H. floridensis (K22), the mortality of the other seven strains was significantly higher than the control. Subsequently, S. carpocapsae (All) and S. riobrave (7-12) were chosen for efficacy testing in the field with an adjuvant 0.066% Southern Ag Surfactant (SAg Surfactant). In field experiments, the SAg Surfactant treatment significantly increased the mortality and EPN infection for S. carpocapsae (All) on first instars of H. zea in corn plant whorls. On soybean plants, with the SAg Surfactant, S. carpocapsae (All) was more effective than S. riobrave (7-12) on fifth instars of C. includens. This study indicates that EPNs can control H. zea and C. includens, and SAg Surfactant can enhance EPN efficacy.

Biocontrol potential of entomopathogenic nematodes against the grey maize weevil Tanymecus dilaticollis (Coleoptera: Curculionidae) adults.

The grey maize weevil, Tanymecus dilaticollis, is a polyphagous species, which is among the most important pests of maize in Southeastern Europe. The efficacy of commercial products with two species of entomopathogenic nematodes (EPNs), Steinernema carpocapsae and Heterorhabditis bacteriophora, was investigated against adults of the grey maize weevil under laboratory conditions. Nemastar®, containing S. carpocapsae was more effective on T. dilaticollis adults than Nematop® containing H. bacteriophora, when applied uniformly to the surface of the soil, on Petri dishes containing T. dilaticollis adults. Results showed that S. carpocapsae rates of 83-333 infective juveniles/adult caused > 94% mortality in T. dilaticollis adults, whereas H. bacteriophora caused 27-61%, adult mortality, after exposure of insects to the commercial products of EPNs for 15days. The infection rates of EPNs increased with concentration applied and ranged from 70-83% and 19-64% for Nemastar® and Nematop®, respectively. Subsequent field and semi-field tests were conducted with Nemastar® (application rate of 50 million S. carpocapsae per 100m2) in maize crops with biological (mycoinsecticide Naturalis®, biofungicides and fertilizers) and chemical seed treatment (Gaucho® FS 600; active ingredient: imidacloprid) in Knezha, Bulgaria. Nematodes were found only in the dead specimens, in open plots and cages sprayed with the commercial nematode product. Nematode sprayings contributed for higher maize yields in the open maize plots in the fields with different seed treatments. We suggest that the use of powder formulation of S. carpocapsae in combination with biologically treated maize seeds can contribute to minimize the use of chemical insecticides against the grey maize weevil. The results obtained can be used as a base to further tests to ascertain the efficacy of EPNs products before they can be recommended for use in the integrated approach to T. dilaticollis management.

The role of drought in the efficacy of some entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) are endoparasitic organisms commonly used in the control of agricultural pests. There are several factors that determine the efficacy of EPNs on hosts, with one of the most significant being soil moisture. The aim of this study is to determine the effectiveness of some EPNs on hosts at different doses and under different soil moisture conditions. The study utilized 1 Hybrid Strain and 3 EPN isolates, Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae) HBH hybrid strain, Steinernema carpocapsae Weiser, 1955 TUR-S4 isolate, and Steinernema feltiae Weiser, 1955 (Rhabditida: Steinernematidae) TUR-S3 and S-Bilecik isolates. These species were applied to Tenebrio molitor L., 1758 (Coleoptera: Tenebrionidae) larvae at 5, 10, and 15 Infective Juveniles (IJs) doses, under 1, 4, 7, 10, and 13% soil moisture conditions. The study was conducted in 2024 at Bursa Uludağ University, Faculty of Agriculture, Department of Plant Protection, Nematology Laboratory. As a result, the highest mortality rates on T. molitor larvae were obtained at 13% soil moisture with 15 IJs, 100% for HBH, 93.33% for TUR-S4, 86.67% for TUR-S3, and 83.33% for S-Bilecik. This study carries important implications for understanding the relationship between EPN efficacy on hosts and soil moisture.

Efficacy of different entomopathogenic nematode isolates, against the peach fruit fly, Bactrocera zonata (Saund.) (Diptera: Tephritidae)

BackgroundThe 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.ResultsData 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.ConclusionAll 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.

The application of entomopathogenic nematode modified microbial communities within nesting mounds of the red imported fire ants, Solenopsis invicta

Entomopathogenic microorganisms (e.g., fungi, bacteria, nematodes) have been widely used in biological control of soil-dwelling pests, including the red imported fire ant (RIFA), Solenopsis invicta, a notorious invasive pest worldwide. The application of large amounts of entomopathogenic microorganisms to soil may affect the indigenous soil microbial communities. However, reports about the effect of entomopathogenic nematodes (EPN) on soil microbial communities are very few. In this study, the effects of EPN on RIFA populations and microbial communities in mounds were investigated. Our results showed that the application of the EPN Steinernema carpocapsae. All strain on mounds efficaciously suppressed RIFA worker populations, without forming significantly more satellite mounds compared with the control treatment. The application of EPN did not impact the bacterial and fungal diversity in soils derived from the RIFA mounds. However, it slightly altered the taxonomic make-up of the bacterial communities, but significantly altered the taxonomic composition of fungal communities at the phylum, family, and genus levels. The abundances of some beneficial bacteria and fungi, such as Streptomyces, decreased, while those of plant and animal pathogenic bacteria and fungi, dramatically increased, after EPN treatment. On the other hand, the abundances of some entomopathogenic fungi, such as Fusicolla, Clonostachys, and Mortierella, increased. Redundancy analysis or canonical correspondence analysis revealed a positive correlation between the efficacious EPN control and the presence of the insect-resistant bacteria, Sinomonas, as well as entomopathogenic fungi Fusicolla and Mortierella. This suggests that the interactions between EPN and entomopathogenic fungi may play a role in the biological control of RIFA. Our discoveries shed light on the interactions among EPN, RIFA, and soil microbial communities, and emphasize a possible mutualistic relationship between EPN and entomopathogenic fungi in the biological control of RIFA.

Çam Kütüklerindeki Monochamus galloprovincialis (Cerambycidae) Populasyonlarına Karşı Steinernema carpocapsae (Steinernematidae)’nin Biyolojik Mücadelede Kullanılması

Aim of study: Pine wilt disease (PWD) is a serious threat to the susceptible pine forests. It is caused by Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) (Steiner and Buhrer 1934), Nickle 1970 and transmitted by Monochamus Dejean beetles. In the recent study, we assessed the effects of entomopathogenic nematode, Steinernema carpocapsae (Nematoda: Steinernematidae) against Monochamus galloprovincialis larvae in Anatolian black pine and Scots pine logs. 
 Area of the study: The experiments were conducted in Duzce University, Faculty of Forestry and in a pine forest at Duzce University campus area. 
 Material and methods: The mean number of eggs per pine logs, and the productivity of S. carpocapsae in M. galloprovincialis larvae were compared under laboratory conditions. The nematode experiments were conducted using oviposited pine logs in the field.
 Main results: The females of M. galloprovincialis oviposited more eggs on Scots pine compared to black pine logs. Both in black pine and in Scots pine, the survival rates of M. galloprovincialis after nematode application was significantly lower than control. 
 Highlihts: As a result of the study, S. carpocapsae can be an efficient biological control agent of this wood-boring insect.

Effects of storage temperature on viability and virulence of entomopathogenic nematodes Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae), Steinernema carpocapsae Weiser, 1955 and Steinernema feltiae Filipjev, 1934 (Rhabditida: Steinernematidae)

Entomopathogenic nematodes (EPN) are a widely used biological control agent. The aim of the study was to detect efficacy and mortalities of some EPN stored at different temperatures and periods. Three EPN species were used in the study. They were Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae) HBH hybrid strain, Steinernema carpocapsae Weiser, 1955 TUR-S4 isolate and Steinernema feltiae Weiser, 1955 (Rhabditida: Steinernematidae) TUR-S3 isolate. The species were kept at 4, 15, 25 and 35°C for 7, 14 and 21 days. Subsequently, these species were applied at a dose of 15 Infective juveniles on Tenebrio molitor L., 1758 (Coleoptera: Tenebrionidae) larvae. The study was carried out in laboratory conditions in 2023. As a result, HBH and TUR-S4 kept at 25°C for 14 days and TUR-S3 for 21 days showed the highest virulence as 93.33%. Mortality rates of the EPN species kept at the specified temperatures were also determined. The results have showed that the highest mortality rates for the HBH, TUR-S4 and TUR-S3 isolates were 11.96% on the 14th day at 35°C, 19.81% on the 21st day at 25°C and 7.39% on the 21st day at 35°C, respectively. This study is an important step in determining suitable temperature conditions for storing and transporting EPN.

Virulence and Reproduction of Entomopathogenic Nematodes Isolated from a Single Mexican Locality

Abstract Entomopathogenic nematodes (EPNs) are important biological control agents of insect pests. Strains or isolates obtained in specific regions and utilized in situ might contribute to the success of EPNs, since they are adapted to local abiotic conditions. We isolated and identified three isolates each of Heterorhabditis bacteriophora Poinar and Steinernema carpocapsae (Weiser) from soils at Saltillo, Coahuila State, Mexico. These six isolates were bioassayed against larvae of Tenebrio molitor L., using six concentrations of infective juveniles (IJs) per larva (0, 10, 25, 50, 100, 200). EPN-induced mortality of the isolates ranged from 15.2% to 100%. The designated M5 isolate of S. carpocapsae caused 100% mortality after 72 h at concentrations ≥25 IJs/larva with a median lethal concentration of 4.99 IJs/larva. Comparison of mortality levels induced at the same concentration of the six EPN isolates indicated that the Steinernema isolates, in general, induced higher mortality levels than the Heterorhabditis isolates. IJ production in T. molitor larvae also was greatest with the M5 isolate of S. carpocapsae following exposure of larvae to a concentration of 100 IJs/larva with a mean of 17,320 IJs/larva. Based on induced mortality and IJ production, the S. carpocapsae M5 isolate appears to be a viable candidate for further study and possible development for use in insect pest management programs. This study indicates that naturally coexisting local nematode isolates possess different attributes critical for their use as biocontrol agents.

A sustainable grower-based method for entomopathogenic nematode production.

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

Natural Warriors against Stored-Grain Pests: The Joint Action of Beauveria bassiana and Steinernema carpocapsae.

Tribolium castaneum, Trogoderma granarium, Oryzaephilus surinamensis, Sitophilus oryzae, Rhyzopertha dominica, and Cryptolestes ferrugineus are all major pests of stored grains. In this study, the efficiency of single and joint applications of the entomopathogenic nematode (EPN) Steinernema carpocapsae at two different doses (50 and 100 IJs cm-2) and the entomopathogenic fungus (EPF) Beauveria bassiana for the management of the aforementioned pests was estimated. At single treatments, both doses of S. carpocapsae caused higher mortality rates to all six pest species compared to B. bassiana. The combined treatment of EPF and EPN resulted in higher mortality compared to single treatments. Mortality was strongly influenced by the exposure interval and the application dose of the EPN at both single and combined treatments. Maximum mortality was observed for the application of the combined treatment at the high dose of S. carpocapsae and B. bassiana. Among the different insect species tested, the maximum mortality rate was observed for R. dominica (96.62%), followed by S. oryzae (90.48%), T. castaneum (87.23%), C. ferrugineus (76.05%), O. surinamensis (70.74%), and T. granarium (57.71%). The outcomes of this study demonstrate the potential of utilizing specific combinations of EPF and EPN as effective natural enemies against stored-grain pests.

Persistence of the entomopathogenic nematode Steinernema carpocapsae on red palm weevil-infested date palm trees in an arid environment

Summary The persistence of the entomopathogenic nematode (EPN), Steinernema carpocapsae, was evaluated following application on date palm (Phoenix dactylifera) trees infested with the red palm weevil (RPW) Rhynchophorus ferrugineus in an arid environment. Live S. carpocapsae were detected in different sections of the tree trunk, including internal parts, in the soil, and from RPW cadavers. EPN third-stage infective juveniles were extracted from the palm stem tissue and soil up to 45 days and 180 days after application, respectively. Results support the high potential of commercial S. carpocapsae application as a useful biological control agent for R. ferrugineus in date palms in arid environments.

Pathogenicity of the Entomopathogenic Nematodes, Steinernema carpocapsae and Heterorhabditis bacteriophora, against the Black Cutworm Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

The black cutworm Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is worldwide in distribution. It is a polyphagous insect attacking nearly all vegetables and many economic field crops in the world. The objective of the present study was to investigate the pathogenicity of two entomopathogenic nematodes (EPNs), Steinernema carpocapsae (Weiser) and Heterorhabditis bacteriophora (Poinar) against 4th and 5th instar larvae of A. ipsilon. The newly moulted larvae were infected with five concentrations of each EPN and the data were recorded at 24, 48, 72 & 96 hr post-infection. The most important results could be summarized as follows. After infection of the 4th or 5th instar larvae with five concentrations of S. carpocapsae or H. bacteriophora, a dose-dependent course of the total mortality rate of infected larvae was recorded. After infection of larvae with S. carpocapsae or H. bacteriophora, the mortality rate of infected larvae increased with the increasing concentration of infective juveniles (IJs), at certain times of exposure. After infection of the 4th or 5th instar larvae with S. carpocapsae, the mortality rate of infected larvae did not increase with the increasing time interval of exposure. On the other hand, infection of the 4th or 5th instar larvae with H. bacteriophora resulted in an increasing mortality rate with the increasing time interval of exposure. After infection of 4th instar larvae, LC50 values were 16 IJs/ml and 48 IJs/ml, for S. carpocapsae and H. bacteriophora, respectively. After infection of 5th instar larvae, LC50 values were 21 IJs/ml and 62 IJs/ml, for S. carpocapsae and H. bacteriophora, respectively. Thus, S. carpocapsae was more pathogenic against A. ipsilon larvae than H. bacteriophora. Also, the 4th instar larvae were more susceptible to the nematode pathogenicity than the 5th instar larvae. A few nematode-infected 4th instar larvae could pupate at the lower two concentrations of S. carpocapsae and H. bacteriophora. A similar result was recorded after infection of 5th instar larvae with S. carpocapsae. Moreover, the infected larvae with H. bacteriophora successfully pupated at all concentrations except the highest one. In conclusion, S. carpocapsae may be an effective microbial control agent in the integrated pest management program against the destructive insect pest, A. ipsilon.

An improved bioassay for the testing of entomopathogenic nematode virulence to the western corn rootworm (Diabrotica virgifera virgifera) (Coleoptera: Chrysomelidae): with focus on neonate insect assessments.

Bioassays involving newly hatched larval insects can be limited by the larvae's feeding state. Assays attempting to monitor mortality effects can be negatively affected by starvation effects on the larvae. Neonate western corn rootworms have significant reductions in viability if not provided food within 24 h post hatch. The recent development of an improved artificial diet for western corn rootworm larvae provides a new bioassay type for evaluating entomopathogenic nematodes that also makes the testing arena easy to observe. Here, we evaluated four species of entomopathogenic nematodes including Heterorhabditis bacteriophora Poinar, Steinernema carpocapsae (Weiser), Steinernema diaprepesi Nguyen & Duncan, and Steinernema rarum (de Doucet) against neonate western corn rootworm, Diabrotica virgifera virgifera LeConte, in 96-well plate diet bioassays. Nematode inoculation levels were 0, 15, 30, 60, and 120 nematodes per larva. Percentage mortality increased for each species as the rate of inoculation increased. Overall, H. bacteriophora and S. carpocapsae caused the greatest amount of larval mortality. The diet-based bioassays were shown to be an effective method for nematode exposure to insect pests. The assays provided adequate moisture to keep nematode from desiccating while also allowing freedom of movement around the arenas. Both rootworm larvae and nematodes were contained within the assay arenas. The addition of nematodes did not cause any significant deterioration of the diet within the three-day period of testing. Overall, the diet bioassays worked well as a measure of entomopathogenic nematode virulence.

Biocontrol Potential of Entomopathogenic Nematodes against Odontotermes obesus (Blattodea: Termitidae) under Laboratory and Field Conditions

Odontotermes obesus (Blattodea: Termitidae) is a prevalent subterranean wood-eating termite species that causes damage to mature trees, saplings and seedlings. The efficacy of most synthetic insecticides against this notorious pest has been compromised primarily because of its enigmatic feeding behavior and development of resistance to a number of insecticides. It has therefore become necessary to explore other alternative biologically sound and low-impact termite control methods, particularly for use in forests. Hence, this study was designed to verify the efficacy of different indigenous EPN isolates (Steinernema carpocapsae, Heterorhabditis bacteriophora and Heterorhabditis indica) against workers of Odontotermes obesus. The pathogenicity of each nematode isolate was assessed in laboratory conditions using filter paper and sawdust bioassay at two different temperatures (16 ± 1 and 26 ± 1 °C). Additionally, the efficacy of the nematode species was also assessed in field conditions. The results of the experiments revealed that the mortality of termite workers was more pronounced in sawdust bioassay in comparison with filter paper bioassay at both the tested temperatures. The mortality response in both bioassays was more pronounced at the higher temperature. A significantly higher mortality was recorded at both tested temperatures for S. carpocapsae followed by H. bacteriophora and H. indica. A dose-dependent positive mortality response was also recorded at both tested temperatures. Similar to the laboratory trials, the field applications of the three tested nematode species showed that maximum mortality was recorded for S. carpocapsae followed by H. bacteriophora and H. indica. It was therefore concluded that indigenous EPNs can provide more effective control of termites, possibly because of their direct interaction with pest species in the soil and the possibility of causing secondary infection through infected cadavers.