Effectiveness Of Entomopathogenic Nematodes Research Articles

Effect of male parental gamma irradiation on host suitability of its F1 progeny of a lepidopteran tropical pest, Spodoptera litura (Fabr.) towards development and virulence of entomopathogenic nematodes, Steinernema thermophilum

The suitability of F1 progeny insect larvae of the irradiated male parent, Spodoptera litura (Fabr.) for infective juveniles (IJs) of entomopathogenic nematodes (EPN), Steinernema thermophilum was assessed to comprehend the feasibility of combining EPNs with nuclear pest control tactic. As compared to the control, the IJs induced faster host mortality with reduced proliferation in F1 host larvae. IJs derived from F1 host larvae exhibited almost similar proliferation capacity on normal hosts as in control. Further, the molecular basis of EPNs induced mortality in F1 host larvae was evaluated. Dual stress of EPN infection and irradiation induced downregulation of the relative mRNA expression of antimicrobial genes and upregulated expression of antioxidative genes. A pronounced effect of EPNs in association with irradiation stress was apparent on host mortality. Radiation induced sterile F1 insect larvae of S. litura acted as a reasonably suitable host for EPNs and also provided the environment for developing viable EPNs for their potential use as biocontrol agents.

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.

Thiourea as a polyphenol oxidase inhibitor enhances host infection by the entomopathogenic nematode, Heterorhabditis beicherriana

Entomopathogenic nematodes (EPN) are potent microbial biocontrol agents applied commercially against various economically important insect pests. The efficacy of EPN in the field may be partially reduced when compared to chemical insecticides due to its sensitivity to environmental stressors like temperature, desiccation, and UV light. Thus, researchers have developed methods to enhance the effectiveness of EPN, such as screening or breeding stress-resistant strains and creating adjuvants for EPN protection in the field. This study used another strategy to lower the host’s immunity so that the anti-infection ability of the pest wanes, and the virulence of EPN waxes accordingly. In addition to its use as a plant growth regulator, thiourea also functions as an inhibitor of polyphenol oxidase (PO) in insects. Thiourea can inhibit a key interaction in the humoral immunity of insects, so we utilized it to enhance the efficacy of EPN. To investigate the effects of thiourea on PO activity inhibition and EPN pathogenesis, we studied the effects of thiourea on survival, infectivity, reproduction, and host searching ability of the EPN, Heterorhabditis beicherriana, and monitored in vivo and in vitro polyphenol oxidase activity of the model insect host, Galleria mellonella. The survival of H. beicherriana infective juveniles (IJs) was barely affected after exposure to 0.5 mM and 1 mM thiourea solution, and the reproductive output of H. beicherriana IJs (after applying 50, 100 and 200 IJs per host) in 0.5 mM and 1 mM thiourea was not different compared to the control. However, the LD50 of G. mellonella larvae caused by H. beicherriana without thiourea was significantly higher than H. beicherriana IJs in thiourea. Moreover, thiourea inhibited in vivo and in vitro polyphenol oxidase activity of G. mellonella infected by EPNs at different concentrations. Thus, thiourea can improve the biological control efficacy of EPNs, and the enhanced environmentally friendly approach may apply to diverse cropping systems.

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.

Optimizing Entomopathogenic Nematode Genetics and Applications for the Integrated Management of Horticultural Pests

Entomopathogenic nematodes (EPNs) can kill and recycle in their host populations, which bodes well for EPNs’ exploitation in long-term and safe pest management. However, EPNs’ cost and efficacy need transformational technology to supplant less expensive and more effective but toxic/unhealthy pesticides. A technology that allows for the significant uptake of commercial EPNs should both boost their market suitability and provide genetic improvements. This review provides brief overviews of EPNs’ biology and ecology from the standpoint of pest/pathogen management as a prerequisite for EPN improvements. Understanding the biology and ecology of EPNs, particularly their symbiotic relationships with bacteria, is crucial to their effective use in pest management. This review provides relevant insights into EPN-symbiotic bacteria and the EPN–symbiont complex. The symbiotic relationship between EPNs and bacteria plays a key role in IPM, providing unique advantages. Either of them can be included in mechanisms underlying the various positive sides of plant–insect interactions in emerging integrated pest management (IPM) systems. Recent approaches, in which EPNs can act additively or synergistically with other production inputs in IPM programs, are discussed for further expansion. The simultaneous favorable effects of EPNs and/or their mutualistic bacteria on several pest/pathogen species of crops should be identified. Merits, such as the rapid killing of insect pests, ease of EPN/the symbiont’s mass production and a broad host range, are presented in order to widely disseminate the conditions under which EPN usage can offer a cost-effective and/or value-added technique for IPM. To maximize the effectiveness of EPNs in IPM, various genetic improvement techniques are being explored. Such techniques, along with their merits/demerits and related tools, are reviewed to optimize the common biocontrol usage of EPNs. Examples of genetic improvements to EPNs that allow for their use in transformational technology, such as a cost-effective application technique, increased infectivity, and toleration of unfavorable settings, are given. Proper production practices and genetic techniques should be applied carefully to avoid undesirable results; it is suggested that these are considered on a case-by-case basis. This will enable us to optimize EPN performance based on the given variables.

Entomopathogenic nematodes for control of the cotton cutworm Spodoptera litura in marigolds

AbstractSpodoptera 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.

Investigation of the Effectiveness of Some Entomopathogenic Nematodes (Steinernema feltiae-Balıkesir İsolate and Heterorhabditis bacteriophora-Çanakkale İsolate) Against Potato Moth [Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) by Green

(Zeller) (Lepidoptera: Gelechiidae) (PTM) is the most destructive pest. One of the most successful groups of biological control agents against soil insect pests are the entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae. This study assessed the effects of EPNs (Nematoda: Steinernematidae) species [

The effect of organic compost and soil texture on the survival and infectivity of entomopathogenic nematode species

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

Comparison between the Effectiveness of Certain Insecticides and Entomopathogenic Nematodes Against Tortoise Beetle, Cassida vittata (Vill.) in Sugar Beet Fields and Their Side Effects on Coccinella undecimpunctata

The tortoise beetle, Cassida vittata (Vill.) (Coleoptera: Chrysomelidae), is considered the most serious pest on Sugar beet, Beta vulgaris L. (Chenopodiaceae), in Egypt. Field evaluation of eight insecticides: chlorantraniliprole, thiamethoxam, lufenuron, methomyl, carbosulfan, chlorpyrifos,spinetoram and abamectin comparing with two strains of entomopathogenic nematodes, (EPNs): Heterorhabditis bacteriophora (H88) and Steinernema carpocapsae (S2) against larvae and adults of the C. vittata and their side effects onCoccinella undecimpunctatawas the main goal of this wark, inhabiting sugar beet fields during 2017 and 2018 sugar beet growing seasons at a field in Biyala, Kafr El Sheikh Governorate, Egypt. Data obtained revealed that chlorpyrifos, carbosulfan and thiamethoxam were the most efficient compounds against larvae and adults of C. vittata. However, chlorantraniliprole, spinetoram, abamectin and methomyl demonstrated a moderate toxic effect. Moreover, lufenuron was nontoxic. Also, data showed that a low effect of entomopathogenic nematodes against C. vittata and safe on C. undecimpunctata. Whereas, all tested insecticides significantly reduced the populationof C. undecimpunctata except lufenuron.

Desiccation stress tolerance of Steinernema australe and Heterorhabditis bacteriophora

South African entomopathogenic nematodes (EPNs), Steinernema australe and Heterorhabditis bacteriophora were used for studying the responses of infective juveniles (IJs) to soil desiccation and soil rehydration. The capacity to infect larvae of Galleria mellonella was used to assess the viability of EPNs after their exposure to desiccation. All the samples were initially hydrated to 10% moisture and moisture loss was recorded daily before rehydrating the soil. Desiccation tolerance results revealed that both species were able to withstand desiccated conditions or continuous dehydration for 20 days in sandy loam soil. H. bacteriophora caused 80% larval mortality after day 15 on rehydration of soil, whereas S. australe caused only 60% larval mortality. All the controls, with coarse river sand, gave zero larval mortality by day 21, indicating that the soil texture is also important for EPNs recovery from dehydrated soils. It may be concluded that coarse sand is not ideal for survival and effectiveness of EPNs, because of its incompetence to retain water.

The effect of entomopathogenic nematodes and fungi against four xylophagous pests

ABSTRACT The effects of entomopathogenic nematodes EPN (Steinernematidae and Heterorhabditidae) and fungi EPF (Beauveria bassiana) strains were evaluated in laboratory assays against larvae of four xylophagous pests: the Asparagus moth Parahypopta caestrum, the European goat moth Cossus cossus, the pine longhorn Arhopalus syriacus and the black Buprestid Capnodis tenebrionis. Due to their biology and ethology, these insects may be included in the category of pests residing in cryptic habitats. The control of these species is considered difficult, due to the inability of chemical pesticides to penetrate the cryptic habitats and reach the targets. The pathogenicity of the entomopathogenic nematodes and fungi was tested in vitro against the pests. Two experimental models were considered and aimed to imitate the natural environment of the pests, in Petri dishes filled with plant material and inside wood galleries respectively. Main results showed that the majority of the tested strains of nematodes and fungi affected the insects’ survival rate. Steinernema feltiae and B. bassiana caused the highest percentage of larval mortality (80–100%). Considering the lack of effective chemical control means, the microbial control of the xylophagous pests by EPN and EPF reveals promising perspectives. Nematodes and fungi are able to penetrate the cryptic habitats because they are living organisms and may be horizontally transmitted by infected hosts. The distribution of EPF as preventive control method and the injection of EPN suspensions to reach and infect the larvae inside the wood galleries can be a combined sustainable control system.

Effectiveness of Entomopathogenic Nematodes against the African White Rice Stem Borer Maliarpha separatella Rag

The efficacy of three entomopathogenic nematodes (EPN) species Steinernema carpocapsae Weiser, Steinernema karii Waturu, Hunt & Reid, Heterorhabdtids indica Poinar, Karunaka & David and two EPN isolates collected from Coastal Kenya (EX MOMBASA) and Rift valley (EX NAKURU) was evaluated against larvae of African white rice stem borer, Maliarpha separatella Rag. The experiment was carried out using no- choice modified filter paper bioassay at KARI-Mwea. Whatman filter paper was substituted with white cotton cloth discs. The activity of the biological agents under study was determined at 25℃ and 65% relative humidity, with concentrations of 50, 100 and 200 infective juveniles (IJs) per one M. separatella third instar larva. The larvae were confined in 60mm plastic petri dishes in darkness as the larvae spend their entire life inside the rice stems. The mortality rate was determined at 24, 48, 72 and 96 hours after application of the nematode suspension. Significant virulence was obtained with all the nematode species at 200 infective juveniles (IJs). There was low mortality at 50 and 100 concentration rates. All the EPNs significantly reduced M. separatella larvae after 48 hours in the following order H. indica> EX NAKURU> S. carpocapsae> EX MOMBASA >S. karii. The number of nematodes from the infected cadavers after 48 hours post infection was H. indica (553), EX –MSA (294), EX-NKU (242), S. karii (168) and S. carpocapsae (157). S. karii took the longest time (96 hours) to kill all the test insects. In conclusion, the study shows that EPNs are effective against M. separatella and could be used within an integrated pest management strategy for the pest. There is need to carry out further studies to determine effective dosages under field conditions.

Reproduction of entomopathogenic nematodes (Steinernema feltiae) on different insect hosts under laboratory conditions

Goal. To identify the effectiveness of entomopathogenic nematodes (Steinernema feltiae isolate with a biological product «Entonem» ™ Copert) on the larvae and adults of different insect pests at various ways of their infection, and to explore the possibility of generating a significant amount of the invasive larvae of entomopathogenic nematodes (EPN).
 Research methods. The material for our study is the 7 types of test insects: larvae of the large and the small wax moth, castaneum flour, gyroscope, common cabbage butterfly, Kovalik pilosula, as well as the may beetle, which was used stage larvae, as well as individuals of adult beetles (imago). All the studied insects infected with EPN (pathogen — Steinernema feltiae with biopreparation «Entonem» (™Koppert)) in the laboratory on filter paper or in sterile soil. Recorded date of infection and death of insects and counted the number of allocated of each type of insect infective larvae of nematodes. Estimated duration of migration and reproductive potential of different test insects.
 Results. The use of different methods of infection (dry contact parasite and insect hosts on filter paper or by making a dose in sterile soil, which was placed insect-host) at a dose of 50 larvae per one insect, showed that in half of the cases a significant difference between them is not detected. However, castaneum flour, Kovalik pilosula and ordinary spinning top, the best was the method of contamination in the Petri dishes, and adults of the may beetle — in groundwater samples. The duration of the process of migration of larvae of the entomopathogenic nematodes from the cadavers of insect hosts ranged from 27—51 day and were more dependent on the insect host than from its method of infection. A short period of migration of the larvae of large and small wax moth (27—36 days), long (35—45) from larvae of a top common and castaneum flour, the longest period of time (48—51 hours) — larvae of cabbage butterflies and a beetle may. Performance in relation to the amount of the newly formed infective larvae determines the insect host. Among the investigated 7-insects-the home of highest performance was observed in the may beetle (115980—120060 larvae) and the cabbage (93440—97880 larvae). Less productive was the great wax moth, the flour castaneum and the grasshopper pelousy (respectively 26880 ± 420; 34500 ± 430; 32400 ± 673).Less productive are the common top, the May beetle (imago) and the small wax moth, in which from 15640 to 26880 invasive larvae were formed.
 Findings. In laboratory conditions, without significant material costs, you can get a sufficient number of entomopathogenic nematodes. The method of directly introducing entomopathogenic nematodes onto test insects in Petri dishes proved to be the best compared to soil invasion. The duration and volume of migration of larvae of entomopathogenic nematodes is determined mainly by the species of host insects. The shortest migration period was recorded in wax moth larvae (small and large), significantly longer (almost 1.5 times) in the larvae of May beetle and cabbage. The most productive in relation to juvenile larvae of EPN were the cabbage and the larvae of the May beetle, and the least productive ones were the common top, May beetle (imago) and small wax moth.

Elevated atmospheric carbon dioxide concentrations alter root morphology and reduce the effectiveness of entomopathogenic nematodes

The effects of increasing atmospheric carbon dioxide (CO2) concentrations on beneficial soil fauna, such as entomopathogenic nematodes (EPNs), are poorly understood. We hence aimed to characterize how elevated CO2 (eCO2) affects maize plant (Zea mays) growth, root morphology and the effectiveness of the EPN Heterorhabditis bacteriophora. We grew plants under ambient CO2 (aCO2; 400 μmol mol-1) and eCO2 (640 μmol mol-1) and quantified shoot growth and six root traits. We simultaneously quantified the effectiveness of EPNs (mortality of insect hosts (Galleria mellonella) and EPN density within hosts) when foraging in planted and plant-free environments. Structural equation modeling (SEM) was used to model direct and indirect relationships between atmospheric CO2, root morphology and EPN effectiveness. Root systems of plants grown under eCO2 grew faster, longer, denser, and larger than plants grown under aCO2. This in turn reduced EPN effectiveness as, despite no significant difference between aCO2 and eCO2 in host mortality, significantly more nematodes were recovered from hosts in the vicinity of plants grown in aCO2 environment. The SEM model revealed that this impact was indirect and mediated by the increased root morphological traits. We provide the first example of how changes in atmospheric CO2 indirectly reduce the effectiveness of an EPN used globally for crop protection. Other factors (e.g. plant volatile emissions) may moderate or exacerbate these patterns but our findings suggest that modifications in root traits at eCO2 negatively impact EPN effectiveness and therefore soil-dwelling insect pest management.

Survival and Effectiveness of Entomopathogenic Nematodes in Oil Emulsions Against Scyphophorus acupunctatus Gyllenhal in a Laboratory

Survival of the nematodes Heterorhabditis bacteriophora Poinar and Steinernema glaseri (Steiner) Wouts, Mracek, Gerdin & Bedding formulated in oil emulsions of avocado (Persea americana Mill.), castor bean (Ricinus communis L.), chia seed (Salvia hispanica L.), and mamey (Mammea Americana L.), in concentrations of 30 and 50% with 50 ± 5 and 100 ± 10 infective juveniles per milliliter were evaluated. H. bacteriophora and Steinernema websteri (Cutler & Stock) in P. americana to 30% were applied to adults of Scyphophorus acupunctatus Gyllenhal in doses of 500 and 1,000 ± 10 infective juveniles per insect. Most H. bacteriophora in oil emulsions of 30 and 50% of P. americana survived for 96 hours, 41.5 and 25.5%, respectively. In bioassays, the dose of 1,000 ± 10 infective juveniles of H. bacteriophora in oil emulsion of P. americana to 30% was 100% effective in killing S. acupunctatus 72 hours after being applied. S. websteri survived 120 hours. Formulation of entomopathogenic nematodes in vegetable oils improved survival and effectiveness over S. acupunctatus in a laboratory.

Entomopathogenic Nematodes Survey, Persistence in Soil, Reproductive Potential and their Effects on Meloidogyne incognita

The increasing cost of nematicides and environmental deterioration are the great challenges to agriculture. Entomopathogenic nematodes (EPNs) could be a choice as biocontrol agent in suppressing the root knot nematode, Meloidogyne incognita on tomato and other crops. A total number of 75 soil samples were collected from different locations of Vehari and Faisalabad, Pakistan. In Vehari out of 14 sites, 13 sites were found positive for EPNs, Nematodes were recovered from 19 (54 %) of 35 soil samples obtained from ecologically diverse habitats. From University of Agriculture Faisalabad, EPNs were recovered from 6 (40 %) of 15 soil samples. While, out of 25 samples collected from Ayub Agriculture Research Institute 9(36%) were found positive for EPNs. Both Steinernema and Heterorhabditis species were found in these locations. The soil samples were also analyzed to indicate the effect of soil texture. Maximum EPNs (36 %) were recovered from sandy loam soil followed by loamy soil. A series of experiments was carried out to unearth EPNs’ soil persistence, reproductive potential and their effects on root knot nematodes. All species and strains of EPNs had potential to persist in almost all type of soils. Persistence was observed in sterilized soil sand and clay (1:1). Maximum persistence was found in S. glaseri (29.11 %) followed by S. pakistanese (28.41 %), H. indica (26.93 %), S. asiaticum (24.42 %), S. feltiae (21.52 %) and H. bacteriophora (21.11 %) which showed the least persistence in sterilized soil. All species of both the families Heterorhabditidae and Steinernematidae did not persist more than 30 % in sterilized soil. Reproductive potential of three EPNs was recorded using the greater wax moth Galleria mellonella larvae. H. indica showed very high reproductive potential within wax moth followed by S. asiaticum and S. pakistanese. On the other hand, maximum emerged infective juveniles per day were recovered from H. indica followed by S. pakistanese and S. asiaticum. Suppressive effect of EPNs against root knot nematodes was observed on susceptible tomato cultivars at different concentration. S. pakistanese suppress M. incognita population more efficiently than H. indica at all the levelsi.e. 1250, 2500 and 5000 nematodes pot-1 . After 35days egg masses (EM) recovered from S. pakistanese treated pots at level 1250 were 232/pot, at level 2500 were 207 and at level 5000 were 135 respectively. Similarly, egg masses recovered from H. indica treated plants at level 1250 were 276, at level 2500 were 212 and at level 5000 were 154 EM pot-1 respectively. No EM were recovered from clean plants on contrary328 EM were recovered from plants with root knot nematodes only.

Compost as a carrier medium for entomopathogenic nematodes – The influence of compost maturity on their virulence and survival

The effectiveness of entomopathogenic nematodes (EPN) against pest insects is largely dependent on the method of application and nematode survival under field conditions. Nematodes must persist long enough to control pest populations, despite sensitivity to abiotic factors such as desiccation and UV light. Here we investigate the use of compost as a carrier medium for the entomopathogenic nematode Steinernema feltiae, since co-application with compost could potentially mitigate some of the negative environmental constraints of EPN application. We tested three application methods in combination with six composts of different biological maturity (defined using the Nematode Index of Compost Maturity (NICM). EPN in composts were applied to a soil and incubated in 1L pots for 12 weeks. The application methods used were aqueous application (AA), non-formulated infected host cadavers (NFC) and formulated infected host cadavers (FC). Destructive sampling was used at 4, 6, 9 and 12 weeks to test for entomopathogenic nematode survival (via extraction and enumerations) and nematode virulence based on Galleria mellonella mortality. After 12 weeks of incubation, survival ranged from 3.2% in control pots with AA, to 62% found in a mature compost applied with formulated cadavers. FC and NFC application and the use of more mature composts resulted in an improved survival. Application method had significant effects on virulence, NFC and AA had higher G. mellonella mortality than FC. A NICM immature compost significantly decreased virulence compared to a NICM mature compost, although neither were significantly better than the control. These results suggest that both application method and biological quality of a compost have to be considered for co-application of compost and EPN. Thus, the use of compost enriched with host cadavers may be an environmentally friendly way to suppress pest insects on farms while simultaneously improving soils through compost application, though economic viability would still need assessment.

Laboratory and semi-field evaluation of three entomopathogenic nematode species on two non-target insect predators, Coccinella septumpunctata (Coleoptera: Coccinellidae) and Chrysoperla carnea (Neuroptera: Chrysopidae)

Biocontrol potential of the entomopathogenic nematodes (EPNs) on the second-instar larvae of the non-target insect predators, Coccinella septumpunctata and Chrysoperla carnea as compared to Spodoptera littoralis (Boisd.) was evaluated. The pathogenicity of EPNs, namely, Heterorhabditis bacteriophora, Steinernema feltiae and Steinernema carpocapsae at concentrations 100, 200, 400, 800 and 1600 IJs/cup) were tested at 2, 4 and 6 days’ post-inoculation. Laboratory results showed significant differences among the mortality rates of different tested larvae, for each concentration at different time intervals. H. bacteriophora induced the highest mortality followed by S. carpocapsae treatment. However, S. feltiae was found to be more safety on predators as it causes less mortality at 6 days of treatment. The values of half lethal concentrations (LC50) were 614.06, 3797.43 and 676.47 IJs/cup for C. Carnea and 390.60, 1209.88 and 503.65 IJs/cup for C. septumpunctata treated by H. bacteriophora, S. feltiae and S. carpocapsae, respectively. In semi-field experiments, there were non-significant differences among mortality of each predator indicated at concentrations of the different EPNs after 2 days or 6 days’ post-inoculation. The study revealed a lethal pathogenic effect of EPNs against insect pests but caused low mortality on the non-target ones.

Effect of entomopathogenic nematodes on different developmental stages of Drosophila suzukii in and outside fruits

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is a harmful invasive fruit pest, which is currently spreading in Europe. Since its arrival in 2008, the spotted wing drosophila has caused major losses in several soft-skinned fruit crops. This critical situation urgently requires efficient practices of residue-free pest control. In the present laboratory study, entomopathogenic nematodes (EPNs) were investigated for their ability to infect larvae and pupae of D. suzukii within directly sprayed fruit, fruit placed on soil, and soil. Steinernema feltiae Filipjev (Rhabditida: Steinernematidae), and Steinernema carpocapsae Weiser (Rhabditida: Steinernematidae) were more efficient at infecting soil-pupating host larvae than Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) at application rates ranging from 25 to 400 EPN cm−2. Applied as a soil drench, S. feltiae and S. carpocapsae were able to infect D. suzukii larvae in the soil as well as hidden inside fruit. Direct application of EPNs on the fruit was less successful, although emergence of flies was significantly reduced.

Effects of Entomopathogenic Nematodes on the Predator Calosoma granulatum in the Laboratory

Entomopathogenic nematodes (EPNs) are used in inundative biological control of pests, such as Spodoptera frugiperda, which is targeted primarily when it enters the soil to form pupae. Within insects, EPNs require 7–15 days to form new infective juveniles (IJs); however, if the insect carcass is predated during this period, the population dynamics of nematodes and predators in the soil may be affected. In the soil, S. frugiperda is predated by carabid beetle Calosoma granulatum, which feeds on carcasses and living insects. The aim of the study was to analyze the direct effects of EPN contact with the predator and the effects of EPNs parasitizing prey on predator feeding. The predator C. granulatum and EPN H. amazonensis isolates RSC 5 and JPM 4, which have activity against S. frugiperda, were used. Laboratory experiments were conducted with topical application of IJs on the predator, as were experiments with and without choice using S. frugiperda larvae that were either healthy or infected by EPNs as prey. It was found that only the first instar predator larvae are susceptible to EPNs when applied topically at concentrations greater than 150 IJs/mL. The third instar larvae and adults avoid feeding on infected larvae, but the repulsion occurs only after symbiotic bacteria are released by EPNs inside the host. When predator only had access to infected carcasses as food, most larvae died during the 6 days of feeding. The results obtained shown that in general, these two native isolates of H. amazonensis, are safe for the native predator C. granulatum.