Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with...Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.展开更多
Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and...Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and cost-effective control methods.This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes(EPNs),Heterorhabditis indica,namely CICR-HI-CL and CICR-HI-MN,against PBW larvae and pupae under in-vitro conditions.Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd,3rd,and 4thinstar larvae,with median lethal dose(LD50)values of 5.45,4.45,and 4.60 infective juveniles(IJs)per larva,respectively.In case of pupal bioassay,both EPN strains demonstrated greater virulence when applied directly(LD50values:29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN,respectively)compared to soil application(147.84 and 272.38 IJs per pupa).Both EPN strains successfully penetrated and reproduced on 4thinstar larvae,resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H.indica(CICR-HI-CL and CICR-HI-MN)against PBW,a dreaded pest of cotton.Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply,sustain and perpetuate on larval and pupal stages of PBW.The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate.The soil-dwelling life stages viz.,last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H.indica for sustainable management of PBW in the cotton ecosystem.However,before taking these EPN strains to field for managing PBW,detailed studies investigating their biocontrol potential against PBW under field conditions are needed.展开更多
<span style="text-align:justify;white-space:normal;">The objective of this review article is to clarify the different interactions between entomopathogenic nematodes, as bio-control agents, against oth...<span style="text-align:justify;white-space:normal;">The objective of this review article is to clarify the different interactions between entomopathogenic nematodes, as bio-control agents, against other bio-control agents (parasitoids and predators) proposed by the researchers. Thus, it gives clear information concerning the potential of combining them as a part of Integrated Pest Management (IPM) programs against insect pests. Some laboratory studies showed that the treatment of predacious insects by entomopathogenic nematodes (EPNs) at different concentrations can infect and kill the treated larva, nymphs and adults of predators. The percentages of mortality were found to be high (up to 100%), moderate (15%</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">-</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">35%) or low (3%</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">-</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">7%). Other studies revealed the resistant of treated predators to nematode-infection. Some predators that were offered infected prey avoid feeding on such prey and, in contrast, the soil predators (ants and mites) consumed the offered cadavers as well as the infective juvenile of the nematodes and did not show any detrimental effects. Mostly, parasitoids cannot complete their development inside or on nematode-infected hosts if parasitism occurs before or early after infection. The parasitoid females may avoid laying eggs in the infected hosts or cannot discriminate between healthy and infected hosts. A field study demonstrated that applying EPNs combined with the predator, </span><i style="text-align:justify;white-space:normal;">Labidura riparia</i><span style="text-align:justify;white-space:normal;"> significantly reduced the population of the target pest compared to the nematode or the predator alone. Also, two field experiments indicated that the combination of parasitoids and nematodes can be successful for insect pest management.</span>展开更多
文摘Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.
基金the Indian Council of Agricultural Research,New Delhi for the grant in aid through ICAR-Central Institute for Cotton Research,Nagpur Institutional Project。
文摘Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and cost-effective control methods.This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes(EPNs),Heterorhabditis indica,namely CICR-HI-CL and CICR-HI-MN,against PBW larvae and pupae under in-vitro conditions.Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd,3rd,and 4thinstar larvae,with median lethal dose(LD50)values of 5.45,4.45,and 4.60 infective juveniles(IJs)per larva,respectively.In case of pupal bioassay,both EPN strains demonstrated greater virulence when applied directly(LD50values:29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN,respectively)compared to soil application(147.84 and 272.38 IJs per pupa).Both EPN strains successfully penetrated and reproduced on 4thinstar larvae,resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H.indica(CICR-HI-CL and CICR-HI-MN)against PBW,a dreaded pest of cotton.Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply,sustain and perpetuate on larval and pupal stages of PBW.The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate.The soil-dwelling life stages viz.,last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H.indica for sustainable management of PBW in the cotton ecosystem.However,before taking these EPN strains to field for managing PBW,detailed studies investigating their biocontrol potential against PBW under field conditions are needed.
文摘<span style="text-align:justify;white-space:normal;">The objective of this review article is to clarify the different interactions between entomopathogenic nematodes, as bio-control agents, against other bio-control agents (parasitoids and predators) proposed by the researchers. Thus, it gives clear information concerning the potential of combining them as a part of Integrated Pest Management (IPM) programs against insect pests. Some laboratory studies showed that the treatment of predacious insects by entomopathogenic nematodes (EPNs) at different concentrations can infect and kill the treated larva, nymphs and adults of predators. The percentages of mortality were found to be high (up to 100%), moderate (15%</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">-</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">35%) or low (3%</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">-</span><span style="text-align:justify;white-space:normal;"> </span><span style="text-align:justify;white-space:normal;">7%). Other studies revealed the resistant of treated predators to nematode-infection. Some predators that were offered infected prey avoid feeding on such prey and, in contrast, the soil predators (ants and mites) consumed the offered cadavers as well as the infective juvenile of the nematodes and did not show any detrimental effects. Mostly, parasitoids cannot complete their development inside or on nematode-infected hosts if parasitism occurs before or early after infection. The parasitoid females may avoid laying eggs in the infected hosts or cannot discriminate between healthy and infected hosts. A field study demonstrated that applying EPNs combined with the predator, </span><i style="text-align:justify;white-space:normal;">Labidura riparia</i><span style="text-align:justify;white-space:normal;"> significantly reduced the population of the target pest compared to the nematode or the predator alone. Also, two field experiments indicated that the combination of parasitoids and nematodes can be successful for insect pest management.</span>
