Beneficial nematodes

Entomopathogenic Nematodes as excellent biocontrol agents by Ganpati Jagdale

Both Steinernematid and Heterorhabditid nematodes are considered as excellent biocontrol agents against soil dwelling insect pests of many economically important crops.  This is because they have a broad host range, the ability to search actively for hosts, the ability to kill their hosts rapidly within 24-48 hours, the potential to recycle in the soil environment, no deleterious effects on humans, other vertebrate animals, non-target organisms and plants and no negative effects on environment.  In addition these insect parasitic nematodes can be easily mass produced using both in vivo and in vitro methods and applied using traditional insecticide spraying equipments.  Since these nematodes are compatible with many chemical insecticides and biopesticides, they are easily included in IPM programs. Entomopatogenic nematodes also been been exempted from registration and regulation requirement by US Environmental Protection Agency (EPA) and similar agencies in many other countries.

    Kill slugs and snails with parasitic nematode, Phasmarhabditis hermaprodita by Ganpati Jagdale

    Biological control of slugs and snails with parasitic nematode, Phasmarhabditis hermaprodita

    • Slugs (Mollusca: Gastropoda) are considered as important pests of many agricultural and horticultural crops throughout the world.
    • Recently, a slug parasitic nematode, P. hermaprodita has been commercialized as a biological molluscicide by MicroBio Ltd, UK and sold under the trade name "Nemaslug".
    • Phasmarhabditis hermaprodita as been found to be associated with several different bacteria rather than one particular species but the association with a bacterium, Moraxella oslensis proved to be highly pathogenic to gray garden slug (Deroceras reticulatum) and preferred bacterium for mass production of this nematode in monoxenic culture.
    • Like entomopathogenic nematodes, slug parasitic nematode infective juveniles or dauer juveniles move through soil, locate slugs and infect.  They penetrate slugs through a natural opening at the backside of the mantle. Once inside, the dauer juveniles release bacterial cells, start feeding on multiplying bacteria and develop into self-fertilizing hermaphrodites. Nematode- bacteria complex can cause the death of the slug within 7-21 days after infection.
    • Phasmarhabditis hermaprodita can attack and kill several species of slugs including Arion ater, A. intermedius, A. distinctus, A. silvaticus, D. reticulatum, D. caruanae, Tandonia budapestensis and T. sowerbyi.
    • Phasmarhabditis hermaprodita can also parasitize several species of snails including Cernuella virgata, Cochlicella acuta, Helis aspersa, Monacha cantiana, Lymnaea stagnalis and Theba pisana.
    • It has been demonstrated that slug parasitic nematodes when applied at the rate of 3x 109 infective juveniles/hectare can give better control of slugs than standard chemical molluscicide, Methiocarb pellets.
    • For more information on insect and slug parasitic nematodes read a book "Nematodes As Biocontrol Agents" by Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon.

    Entomopathogenic Nematodes are considered as excellent biocontrol agents by Ganpati Jagdale

    Why do entomopathogenic nematodes are considered as excellent biocontrol agents? Because they......

    1. have a broad host range.
    2. have the ability to search actively for hosts.
    3. have the ability to kill their hosts rapidly within 24-48 hours.
    4. have the potential to recycle in the soil environment.
    5. have no deleterious effects on humans, other vertebrate animals, non-target organisms and plants.
    6. have no negative effects on environment.
    7. can be easily mass produced using both in vivo and in vitro methods.
    8. can be easily applied using traditional insecticide spraying equipments.
    9. are compatible with many chemical insecticides and biopesticides.
    10. have been exempted from registration and regulation requirement by US Environmental Protection Agency (EPA) and similar agencies in many other countries.

    Why entomopathogenic nematodes are safe to use as biological control agents against insect pests? by Ganpati Jagdale

    Because....... 1. Entomopathogenic nematodes and their symbiotic bacterium have no detrimental effects on animals and plants. 2. Both nematodes and their symbiotic bacteria do not cause any harm to the personnel involved in their production and application. 3. Entomopathogenic nematode treated agriculture products are safe to handle and eat. 4. Entomopathogenic nematodes and symbiotic bacteria do not have any pathogenic effects on humans or animals. 5. When applied in the soil, entomopathogenic nematodes have also no negative effect on beneficial nematodes (bacteriovore, fungivore, omnivore and predatory) and other microbial communities. 6. Finally, entomopathogenic nematodes are non-polluting and thus environmentally safe.

    How entomopathogenic nematodes find their insect hosts (Foraging Strategies) by Ganpati Jagdale

    Infective juveniles of entomopathogenic nematodes use three different strategies to find their insect hosts.1. Ambush foraging: Ambushers such as Steinernema carpocapsae and S. scapterisci have adapted "sit and wait" strategy to attack highly mobile insects (billbugs, sod webworms, cutworms, mole-crickets and armyworms) when they come in contact at the surface of the soil.  These nematodes do not respond to host released cues but infective juveniles of some Steinernema spp can stand on their tails (nictate) and easily infect passing insect hosts by jumping on them.  Since highly mobile insects live in the upper soil or thatch layer, ambushers are generally effective in infecting more insects on the surface than deep in the soil. 2. Cruise foraging: Cruiser nematodes such as Heterorhabditis bacteriophora, H. megidis, Steinernema glaseri and S. kraussei generally move actively in search of hosts and therefore, they are distributed throughout the soil profile and more effective against less mobile hosts such as white grubs and black vine weevils.  Cruisers never nictate but respond to carbon dioxide released by insects as cues. 3. Intermediate foraging: Some nematode species such as Steinernema feltiae and S.riobrave have adapted a strategy in between ambush and cruise strategies called an intermediate strategy to attack both the mobile and sedentary/less mobile insects at the surface or deep in the soil.  Steinernema feltiae is highly effective against fungus gnats and mushroom flies whereas S.riobrave is effective against corn earworms, citrus root weevils and mole crickets.

    Symbiotic bacteria of Heterorhabdits nematodes- Photorhabdus species by Ganpati Jagdale

    1. Heterorhabditis amazonensis- undescribed
    2. H. argentinensis- P. temperata
    3. H. bacteriophora- Photorhabdus luminescens subsp. laumondii TT01, P. luminescens kayaii subsp. nov., P. luminescens thracensis subsp. nov., P. temperate
    4. H. baujardi- undescribed
    5. H. brevicaudis- P. luminescens
    6. H. downesi- Photorhabdus sp
    7. H. floridensis- undescribed
    8. H. georgiana- undescribed
    9. H. hambletoni- undescribed
    10. H. hawaiiensis- P. luminescens
    11. H. heliothidis- undescribed
    12. H. hepialius- P. luminescens
    13. H. hoptha- undescribed
    14. H. indica- P. luminescens
    15. H. marelata- P. luminescens
    16. H. megidis- P. temperata subsp. temperata XlNach
    17. H. mexicana- undescribed
    18. H. poinari- Photorhabdus sp
    19. H. safricana- undescribed
    20. H. taysearae- undescribed
    21. H. zealandica- P. temperata

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    Symbiotic bacteria of Steinernematid nematodes- Xenorhabdus species by Ganpati Jagdale

    1. Steinernema abbasi- undescribed
    2. S. aciari- undescribed
    3. S. affine-Xenorhabdus bovienii
    4. S. akhursti- undescribed
    5. S. anatoliense- undescribed
    6. S. apuliae- undescribed
    7. S. arenarium- X. kozodoii
    8. S. ashiuense- undescribed
    9. S. asiaticum- undescribed
    10. S. australe- X. magdalenensis
    11. S. backanense- undescribed
    12. S. beddingi- undescribed
    13. S. bicornutum- X. budapestensis
    14. S. carpocapsae- X. nematophila
    15. S. caudatum- undescribed
    16. S. ceratophorum- undescribed
    17. S. cholashanense- undescribed
    18. S. cubanum- X. poinarii
    19. S. cumgarense- undescribed
    20. S. diaprepesi- undescribed
    21. S. eapokense- undescribed
    22. S. feltiae- X. bovienii
    23. S. glaseri- X. poinarii
    24. S. guangdongense- undescribed
    25. S. hebeiense- undescribed
    26. S. hermaphroditum- undescribed
    27. S. intermedium - X. bovienii
    28. S. jollieti-undescribed
    29. S. karii- undescribed
    30. S. khoisanae- undescribed
    31. S. kraussei- X. bovienii
    32. S. kushidai- X. japonica
    33. S. leizhouense- undescribed
    34. S. litorale- undescribed
    35. S. loci- undescribed
    36. S. longicaudum- undescribed
    37. S. monticolum- undescribed
    38. S. neocurtillae- undescribed
    39. S. oregonense- undescribed
    40. S. pakistanense- undescribed
    41. S. puertoricense- X. romanii
    42. S. rarum- X. szentirmaii
    43. S. riobrave- Xenorhabdus sp
    44. S. ritteri- Xenorhabdus sp
    45. S. robustispiculum- undescribed
    46. S. sangi- undescribed
    47. S. sasonense- undescribed
    48. S. scapterisci- X. innexi
    49. S. scarabaei- X. koppenhoeferi
    50. S. serratum- X. ehlersii
    51. S. siamkayai- X. stockiae
    52. S. sichuanense- X. bovienii
    53. S. silvaticum- undescribed
    54. S. tami- Xenorhabdus sp
    55. S. texanum- undescribed
    56. S. thanhi- undescribed
    57. S. thermophilum- X. indica
    58. S. websteri- undescribed
    59. S. weiseri- undescribed
    60. S. yirgalemense- undescribed

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    Beneficial Nematodes: Steinernema and Heterorhabditis species by Ganpati Jagdale

    Entomopathogenic nematodes in the genera Steinernema and Heterorhabditis are recognized as insect-parasitic nematodes, beneficial nematodes, biocontrol agents, biological control agents, biological insecticides or biopesticides. These nematodes are also recognized as pathogens or microbial control agents because of their symbiotic association with bacteria (Xenorhabdus and Photorhabdus spp.) that are mainly pathogenic to insects. Because of mutualistic relationship with pathogenic bacteria these nematodes are named as entomopathogenic nematodes.

    These beneficial nematodes contribute to the regulation of natural populations of insects.  However, the population of naturally occurring entomopathogenic nematodes is normally not high enough to manages soil dwelling plant pests. Therefore, during last 3-4 decades, these live nematodes have been commercially mass produced and inundatively applied to control many garden insects, turfgrass insects, nursery insects, greenhouse insects and insects that feed on different field crops.

    Use of this natural control of insects is beneficial for both the environment and humans because it reduces use of chemical insecticides/pesticides.

    These biopesticides (entomopathogenic nematodes and their symbiotic bacteria) are safe to produce and not harmful to users, application personnel, mammals, most beneficial insects or plants.

    Since entomopathogenic nematodes do not cause any health risk to the consumers of nematode treated agricultural produce and damage to the environment, they are exempted from registration requirements in most countries.

    These biological control agents have also no detrimental effect on other benefical nematodes including bacterial feeders, some fungal feeders (Aphelenchus sp.), predatory nematodes and other soil microbial communities.

    But entomopathogenic nematodes can be detrimental to plant-parasitic nematodes that are responsible for causing a tremendous economic loss to our agriculture industry throughout world. It has been demonstrated that entomopathogenic nematodes can suppress the populations of many economically important plant-parasitic nematodes including foliar nematodes, potato cyst nematodes, ring nematodes, root-knot nematodes,  root lesion nematodes, sting nematodes, stubby root nematodes and stunt nematodes.

    Symbiotic bacterial genus, Photorhabdus by Ganpati Jagdale

    known species of symbiotic bacterial genus Photorhabdus associated with a nematode genus Heterorhabditis. Identification based on colony morphology and molecular techniques

    1. Photorhabdus luminescens (Thomas and Poinar 1979) Boemare et al. 1993
    2. P. temperata
    3. P. luminescens subsp. luminescens subsp. nov., Fischer-Le Saux, Viallard, Brunel, Normand & Boemare, 1999
    4. P. luminescens subsp. akhurstii subsp. nov., Fischer-Le Saux, Viallard, Brunel, Normand & Boemare, 1999
    5. P. luminescens subsp. kayaii subsp. nov., Hazir, Stackebrandt, Lang, Schumann, Ehlers & Keskin, 2004
    6. P. luminescens subsp. laumondii subsp. nov., Fischer-Le Saux, Viallard, Brunel, Normand & Boemare, 1999
    7. P.luminescens subsp. sonorensis, Orozco, Hill & Stock, 2013
    8. P. temperata sp. nov., Fischer-Le Saux, Viallard, Brunel, Normand & Boemare, 1999
    9. P. temperata subsp. temperata subsp. nov., Fischer-Le Saux, Viallard, Brunel, Normand & Boemare, 1999
    10. P. luminescens subsp. thracensis subsp. nov., Hazir, Stackebrandt, Lang, Schumann, Ehlers & Keskin, 2004

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    Symbiotic bacterial genus, Xenorhabdus Thomas and Poinar 1979 by Ganpati Jagdale

    known species of symbiotic bacterial genus Xenorhabdus Thomas and Poinar 1979 associated with a nematode genus Steinernema. Identification based on colony morphology and molecular techniques

    1. Xenorhabdus beddingii (Akhurst 1986) Akhurst and Boemare 1993
    2. X. bovienii (Akhurst 1983) Akhurst and Boemare 1993
    3. X. budapestensis Lengyel, Lang, Fodor, Szállás, Schumann, Stackebrandt, 2005
    4. X. cabanillasii Tailliez, Pagès, Ginibre & Boemare, 2006
    5. X. doucetiae Tailliez, Pagès, Ginibre & Boemare, 2006
    6. X. ehlersii Lengyel, Lang, Fodor, Szállás, Schumann, Stackebrandt, 2005
    7. X. griffiniae Tailliez, Pagès, Ginibre & Boemare, 2006
    8. X. hominickii Tailliez, Pagès, Ginibre & Boemare, 2006
    9. X. indica Somvanshi, Lang, Ganguly, Swiderski, Saxena, & Stackebrandt 2006
    10. X. innexi Lengyel, Lang, Fodor, Szállás, Schumann, Stackebrandt, 2005
    11. X. japonica Nishimura et al. 1995
    12. X. koppenhoeferi Tailliez, Pagès, Ginibre & Boemare, 2006
    13. X. kozodoii Tailliez, Pagès, Ginibre & Boemare, 2006
    14. X. magdalenensis, Tailliez, Pages, Edgington, Tymo, & Buddie, 2012
    15. X. mauleonii Tailliez, Pagès, Ginibre & Boemare, 2006
    16. X. miraniensis Tailliez, Pagès, Ginibre & Boemare, 2006
    17. X. nematophila (Poinar and Thomas 1965) Thomas and Poinar 1979
    18. X. poinarii (Akhurst 1983) Akhurst and Boemare 1993
    19. X. romanii Tailliez, Pagès, Ginibre & Boemare, 2006
    20. X. stockiae Tailliez, Pagès, Ginibre & Boemare, 2006
    21. X. szentirmaii Lengyel, Lang, Fodor, Szállás, Schumann, Stackebrandt, 2005

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    Life cycle of entomopathogenic nematodes (EPNs) by Ganpati Jagdale

     

    Entomopathogenic nematode life cycle

    • EPNs complete most of their life cycle in insects with an exception of infective juveniles, the only free-living stage found in soil.
    • Infective juveniles of both Steinernema and Heterorhabditis locate a host and enter through its natural body openings such as mouth, anus or spiracles.
    • Infective juveniles of Heterorhabditis also enter through the intersegmental members of the host cuticle.
    • Infective juveniles then actively penetrate through the midgut wall or tracheae into the insect body cavity (hemocoel) containing insect blood (haemolymph).
    • Once in the body cavity, infective juvenile releases symbiotic bacteria from its intestine in the insect haemolymph.
    • Bacteria start multiplying in the nutrient-rich haemolymph and infective juveniles recover from their arrested state (dauer stage) and start feeding on multiplying bacteria and disintegrated host tissues.
    • Toxins produced by the developing nematodes and multiplying bacteria in the body cavity kill the insect host usually within 48 hours.
    • These bacteria also produce a plethora of metabolites, toxins and antibiotics with bactericidal, fungicidal and nematicidal properties, which ensures monoxenic conditions for nematode development and reproduction in insect cadaver.
    • Heterorhabditid and Steinernematid nematodes differ in their mode of reproduction. For example, in heterorhabditid nematodes, the first generation individuals are produced by self-fertile hermaphrodites (hermaphroditic) but subsequent generation individuals are produced by cross fertilization involving males and females (amphimictic). In Steinernematid nematodes with an exception of one species, all generations are produced by cross fertilization involving males and females (amphimictic).
    • Depending on availability of food resource, both heterorhabditid and steinernematid nematodes generally complete 2-3 generations within insect cadaver and emerge as infective juveniles to seek new hosts.
    • Generally, life cycle of entomopathogenic nematodes (from infective juvenile penetration to infective juvenile emergence) is completed within 12- 15 days at room temperature. The optimum temperature for growth and reproduction of nematodes is between 25 and 300C.

    Species of the genus Heterorhabditis Poinar, 1976 by Ganpati Jagdale

    Known species of Heterorhabditis Poinar, 1976 with a biocontrol potential- Identification based on morphological and molecular techniques

    1. Heterorhabditis amazonensis Andalo, Nguyen, & Moino, 2006
    2. H. argentinensis Stock, 1993
    3. H. atacamensis, Edgington, Buddie, Moore, France, Merino, & Hunt, 2011
    4. H. bacteriophora Poinar, 1976
    5. H. baujardi Phan, Subbotin, Nguyen & Moens, 2003
    6. H. brevicaudis Liu, 1994
    7. H. downesi Stock, Griffin & Burnell, 2002
    8. H. floridensis Nguyen, Gozel, Koppenhofer, & Adams, 2006
    9. H. georgiana Nguyen, Shapiro-Ilan, & Mbata, 2008
    10. Heterorhabditis gerrardi, Plichta, Joyce, Clarke, Waterfield, & Stock, 2009
    11. H. hambletoni (Pereira, 1937) Poinar, 1976
    12. H. hawaiiensis Gardner, Stock & Kaya, 1994
    13. H. heliothidis (Khan, Brooks & Hirschman, 1976) Poinar, Thomas & Hess, 1977
    14. H. hepialius Stock, Strong & Gardner, 1996
    15. H. hoptha (Turco, 1970), Poinar, 1979
    16. H. indica Poinar, Karunakar & David, 1992
    17. H. marelata Liu & Berry, 1996
    18. H. megidis Poinar, Jackson & Klein, 1988
    19. H. mexicana Nguyen, Shapiro-Ilan, Stuart, MCCoy, James & Adams, 2004
    20. H. poinari Kakulia & Mikaia, 1997
    21. H. safricana Malan, Nguyen, deWaal, & Tiedt, 2008
    22. Heterorhabditis sonorensis, Stock, Rivera-Orduno, & Flores-Lara, 2009
    23. H. taysearae Shamseldean, El-Sooud, Abd-Elgawad & Saleh, 1996
    24. H. zealandica Poinar, 1990

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    Species of the genus Steinernema Travassos, 1927 by Ganpati Jagdale

    Known species of Steinernema Travassos, 1927 with a biocontrol potential- Identification was based on morphological and molecular techniques

    1. Steinernema abbasi Elawad, Ahma & Reid, 1997
    2. S. aciari Qiu, Yan, Zhou, Nguyen & Pang, 2004
    3. S. affine (Bovien, 1937) Wouts, Mrácek, Gerdin & Bedding, 1982
    4. S. akhursti Qiu, Hu, Zhou, Mei, Nguyen, & Pang, 2005
    5. S. anatoliense Hazir, Stock & Keskin, 2003
    6. S. apuliae Triggiani, Mracek & Reid, 2004
    7. S. arenarium (Artyukhovsky, 1967) Wouts, Mrácek, Gerdin & Bedding, 1982
    8. S. ashiuense Phan, Takemoto & Futai, 2006
    9. S. asiaticum Shahina, Reid & Rowe, 2002
    10. S. australe, Edgington, Buddie, Tymo, Hunt, Nguyen, France, Merino, & Moore, 2009
    11. S. backanense Phan, Spiridonov, Subbotin & Moens, 2006
    12. S. balochiense Fayyaz, Khanum, Ali, Solangi, Gulsher & Javed, 2015
    13. S. beddingi Qiu, Hu, Zhou, Pang & Nguyen, 2005
    14. S. bicornutum Tallosi, Peters & Ehlers 1995
    15. S. brazilense, Nguyen, Ginarte, Leite, dos Santos, & Harakava, 2010
    16. S. carpocapsae (Weiser, 1955) Wouts, Mrácek, Gerdin & Bedding, 1982
    17. S. caudatum Xu, Wang & Li, 1991
    18. S. ceratophorum Jian, Reid & Hunt 1997
    19. S. cholashanense Nguyen, Puža & Mrácek, 2008
    20. S. citrae Stokwe, Malan, Nguyen, Knoetze, & Tiedt, 2011
    21. S. costaricense Uribe, Mora & Stock, 2007
    22. S. cubanum Mrá¡cek, Hernandez & Boemare, 1994
    23. S. cumgarense Phan, Spiridonov, Subbotin & Moens, 2006
    24. S. dharanaii , Kulkarni, Rizvi, Kumar, Paunikar& Mishra, 2012
    25. S. diaprepesi Nguyen, & Duncan, 2002
    26. S. eapokense Phan, Spiridonov, Subbotin & Moens, 2006
    27.  S. fabii Abate, Malan, Tiedt, Wingfield, Slippers, Hurley, 2016. 
    28. S. feltiae (Filipjev, 1934) Wouts, Mrácek, Gerdin & Bedding, 1982
    29. S. glaseri (Steiner, 1929) Wouts, Mracek, Gerdin & Bedding, 1982
    30. S. guangdongense Qiu, Fang, Zhou, Pang, & Nguyen, 2004
    31. S. hebeiense Chen, Li, Yan, Spiridonov & Moens, 2006
    32. S. hermaphroditum Stock, Griffin, & Chaerani, 2004
    33. S.  innovation Cimen, Lee, Hatting, Hazir, Stock 2015
    34. S. intermedium (Poinar, 1985) Mamiya, 1988
    35. S. jeffreyense Malan, Knoetze & Tiedt, 2016
    36. S. jollieti Spiridonov, Krasomil-Osterfeld & Moens, 2004
    37. S. karii Waturu, Hunt & Reid, 1997
    38. S. khoisanae Nguyen, Malan, & Gozel, 2006
    39. S. kraussei (Steiner, 1923) Travassos, 1927
    40. S. kushidai Mamiya, 1988
    41. S. leizhouense Nguyen, Qiu, Zhou, & Pang, 2006
    42. S. litorale Yoshida, 2004
    43. S. loci Phan, Nguyen & Moens, 2001
    44. S. longicaudum Shen & Wang, 1992
    45. S. monticolum Stock, Choo & Kaya, 1997
    46. S. neocurtillae Nguyen & Smart, 1992
    47. S. oregonense Liu & Berry, 1996
    48. S. pakistanense Shahina, Anis, Reid, Rowe & Maqbool, 2001
    49. S. papillatum  San-Blas, Portillo, Nermut, Puza, & Morales-Montero 2015
    50. S. phyllophagae Nguyen and Buss, 2011
    51. S. puertoricense Roman & Figueroa, 1994
    52. S. puntauvense Uribe, Mora & Stock, 2007
    53. S. rarum (Doucet, 1986) Mamiya, 1988
    54. S. riobrave Cabanillas, Poinar & Raulston, 1994
    55. S. ritteri de Doucet & Doucet, 1992
    56. S. robustispiculum Phan, Subbotin, Waeyenberge, & Moens, 2005
    57. S. sangi Phan, Nguyen & Moens, 2001
    58. S. sasonense Phan, Spiridonov, Subbotin & Moens, 2006
    59. S. scapterisci Nguyen & Smart, 1992
    60. S. scarabaei Stock & Koppenhöfer 2003
    61. S. serratum Liu, 1992
    62. S. siamkayai Stock, Somsook & Kaya, 1998
    63. S. sichuanense Mrácek, Nguyen, Tailliez, Boemare & Chen, 2006
    64. S. silvaticum Sturhan, Spiridonov & Mracek, 2005
    65. S. tami Luc, Nguyen, Reid & Spiridonov, 2000
    66. S. texanum Nguyen, Stuart, Andalo, Gozel, & Roger, 2007
    67. S. thanhi Phan, Nguyen & Moens, 2001
    68. S. thermophilum Ganguly & Singh, 2000
    69. S. websteri Cutler & Stock, 2003
    70. S. weiseri Mrácek, Sturhan & Reid, 2003
    71. S. xinbinense Ma, Chen, De Clercq, Waeyenberge, Han & Moens, 2012
    72. S. xueshanense, Mracek, Liu, & Nguyen, 2009
    73. S. yirgalemense Nguyen, Tesfamariam, Gozel, Gaugler, & Adams, 2005

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    Entomopathogenic Nematode Facts by Ganpati Jagdale

    Entomopathogenic nematodes (EPNs) of the two genera Steinernema Travassos, 1927 and Heterorhabditis Poinar, 1976 in the order Rhabdita kill most insects but they are harmless to some beneficial insects (e.g. honey bees), higher animals and environment. Third-stage juvenile is the only free-living stage in the life cycle of the nematode known as the infective juvenile or dauer juvenile that found in soil and can seek, infect and kill their insect hosts.

    These infective juveniles are mutualistically associated with symbiotic bacteria (Xenorhabdus spp. or Photorhabdus spp.) in the family Enterobacteriaceae, which are capable of causing disease in insect pests and killing them.

    Species of genus, Xenorhabdus are specifically assocaited with the members of the nematode genusSteinernema and Photorhabdus species are associated with the members of nematode genusHeterorhabditis.

    In this mutualistic relationship, the nematode infective juveniles provides protection for bacterium outside the insect host (as bacterium is unable to survive in the outside environment i.e. soil or water) and a means of transmission to new hosts and in return bacteria provides nutrients required for the nematode development and reproduction.

    Infective juveniles are adapted to remain in the soil environment without feeding until they find a suitable host.

    They are also resistant to unfavorable environmental conditions such as desiccation, heat and freezing.

    EPNs can infect soil dwelling stages of butterflies, moths, beetles, flies, crickets and grasshoppers.

    Infective juveniles of different nematode species employ different foraging strategy to find and infect their insect hosts. For example, Heterorhabditis bacteriophora is a cruiser forager meaning that it actively finds out or hunts its prey, Steinernema carpocapsae is an ambusher forager that sits and wait for a pray to pass by and S. feltiae and S. rivobrave are intermediate foragers.

    EPNs are now commercially produced using both in vivo (in living host) and in vitro (in artificial medium) techniques.

    Since EPNs have a wide host range, they are currently used as potential biological control agents to manage insect pests of many field crops, greenhouse and nursery plants, horticultural crops, turfgrass, and in some instances insect pests of animals and humans.

    EPNs also have a potential to use as biocontrol agents against plant-parasitic nematodes.

    Commercially produced nematode infective juveniles can be stored for extended periods and easily applied in aqueous suspensions in the field using traditional sprayers.

    Also, EPNs are compatible with several chemical fungicides, insecticides, nematicides and herbicides, and therefore, they can be easily included in IPM programs.

    Under current pesticide regulations, the U.S. Environmental Protection Agency has exempted these biological control agents from registration.