Entomopathogenic Nematodes as excellent biocontrol agents

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.

List of insects susceptible to various species of entomopathogenic nematodes

Insect Species: Entomopathogenic nematode species

Ø Apopka weevil (Diaprepes abbreviatus): S. carpocapsae All strain

Ø Armyworm (Heliothis armigera): S. carpocapsae All strain

Ø Billbugs (Sphenophorus purvulus): H. bacteriophora & S. carpocapsae All strain

Ø Black vine weevil (Otiorhynchus salcatus): S. carpocapsae All & UK strains, S. feltiae, S. glaseri & H. megidis UK 211 strain

Ø Blue grass weevil (Listronotus maculicollis): H. bacteriophora & S. carpocapsae

Ø Carpenter worms (Cossus cossus): S. carpocapsae

Ø Carrot weevil (Listronotus oregonensis): S. feltiae

Ø Cat fleas (Ctenocephalides felis): S. carpocapsae

Ø Citrus root weevil (Pachnaeus litus): S. carpocapsae All strain

Ø Clover root weevil (Sitona hispidulus): S. feltiae & H. bacteriophora

Ø Codling moth (Cydia pomonella): S. carpocapsae

Ø Crane flies (Tipula spp.): S. carpocapsae & H. megidis

Ø Cutworms (Agrotis ipsilon, A. segetum): S. carpocapsae All strain

Ø Dog fleas (Ctenocephalides cannis): S. carpocapsae

Ø Face fly (Musca autumnalis): S. carpocapsae, H. bacteriophora & S. feltiae

Ø Fall web worms (Hyphantria cunea): S. carpocapsae

Ø Flea beetles (Phyllotreta spp.): S. carpocapsae

Ø Fungus gnats (Bradysis spp.): H. bacteriophora, H. indica, H. zealandica, S. anomali, S. carpocapsae, S. feltiae SN strain & S. riobrave

Ø House flies (Musca domestica): S. carpocapsae, H. bacteriophora & S. feltiae

Ø Hunting billbug (Sphenophorus venatus venatus): S. carpocapsae All strain

Ø Japanese beetle (Popillia japonica): H. bacteriophora, H. indica, H. marelata, H. megidis, H. zealandica, S. anomali, S. carpocapsae, S. feltiae, S. glaseri, S. kushidai, S. riobrave, S. scapterisci & S. scarabae

Ø Leaf minors (Liriomyza trifolii): S. carpocapsae & S. feltiae

Ø Leopard moth (Zeuzera pyrina): S. carpocapsae

Ø Mole crickets (Gryllotapla gryllotapla): S. riobravis & S. scapterisci

Ø Peach borer moth (Synanthedon exitiosa): S. carpocapsae

Ø Pecan weevil (Curculio caryae): H. bacteriophora

Ø Pine weevil (Hylobius abietis): S. carpocapsae, S. feltiae & H. downesi

Ø Plum weevil (Conotrachelus nenuphar): S. riobrave 355 strain

Ø Shore flies (Scatella stagnalis): H. megidis, S. carpocapsae, S. feltiae & S. anomaly

Ø Sod webworm (Herpetogramma phaeopteralis): S. carpocapsae All strain

Ø Stable fly (Stomoxys calcitrans): S. carpocapsae, H. bacteriophora & S. feltiae

Ø Strawberry root borer (Nemocestes incomptus): S. carpocapsae

Ø Sugarcane borer (Diaprepes abbreviatus): S. carpocapsae All strain

Ø Sweet potato weevil (Cylasformicarius elegantulus): S. carpocapsae All strain & H. bacteriophora HP88 strain

Ø Western flower thrips (Frankliniella occidentalis): H. bacteriophora, H. indica, H. marelata, S. abassi, S. arenarium, S. bicornutum, S. carpocapsae, S. feltiae

Ø White grubs (Amphimallon solstitiale): S. glaseri

Ø White grubs (Anomala orientalis): H. bacteriophora, H. megidis, H. zealandica, S. carpocapsae, S. glaseri, S. longicaudum, S. scarabae

Ø White grubs (Ataenius spretulus): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Costelytra zealandica): H. bacteriophora & S. glaseri

Ø White grubs (Cotinus nitida): H. bacteriophora, S. carpocapsae, S. feltiae, S. glaseri & S. scarabae

Ø White grubs (Cyclocephala borealis): H. bacteriophora, H. indica, H. marelata, H. megidis, H. zealandica, S. glaseri & S. scarabae

Ø White grubs (Cyclocephala hirta): H. bacteriophora, H. megidis, S. carpocapsae, S. feltiae, S. glaseri, S. kushidai, S. riobrave & S. scarabae

Ø White grubs (Cyclocephala lurida): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Cyclocephala pasadenae): H. bacteriophora, S. glaseri, S. kushidai & S. scarabae

Ø White grubs (Hoplia philanthus): H. megidis, S. feltiae & S. glaseri

Ø White grubs (Maladera castanea): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Melolontha melolontha): H. bacteriophora, H. marelata, H. megidis, S. arenaria, S. feltiae, S. glaseri & S. riobrave

Ø White grubs (Phyllophaga congrua): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Phyllophaga crinita): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Phyllophaga georgiana): H. bacteriophora, S. glaseri & S. scarabae

Ø White grubs (Rhizotrogus majalis): H. bacteriophora, H. megidis, H. zealandica, S. carpocapsae, S. feltiae, S. glaseri & S. scarabae

For more information on insect pathogenic nematodes read following books:

Ø Nematodes As Biocontrol Agents by Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon.

Ø Entomopathogenic Nematodes in Biological Control by Gaugler, R. and Kaya, H. K. (eds.), CRC Press, Boca Raton

Ø Entomopathogenic Nematology by Gaugler, R. (Ed.), CABI

Use entomopathogenic nematodes to manage plant-parasitic nematodes

• For the last several decades, entomopathogenic nematodes have been successfully used for the management of insect pests of many economically important crops (Grewal et al., 2005).
• As an additional benefit, several researchers including Fallon et al. (2002), Gouge et al. (1997), Grewal et al. (1997; 1999), Jagdale et al. (2002), Jagdale and Grewal (2008), LaMondia and Cowles (2002), Lewis et al. (2001), Lewis and Grewal (2005), Molina et al. (2007), Nyczepir et al. (2004), Perez and Lewis (2002), Perry et al. (1998) and Shapiro et al. (2006) have demonstrated that entomopathogenic nematodes can also be used as biological control agents to control plant-parasitic nematodes infesting different crops in the fields and greenhouses .
• To control plant- parasitic nematodes, entomopathogenic nematodes can be applied using standard spraying equipments used for application of chemical pesticides.
• Entomopathogenic nematodes are generally applied against plant-parasitic nematodes at the rate of 1 billion infective juveniles per acre but this rate can vary with both entomopathogenic nematode and plant- parasitic nematode species,
• Following are the examples of different species of entomopathogenic nematode that found to be successful in suppressing the population of different species of plant- parasitic nematodes.
• Steinernema carpocapsae can reduce the population of ring nematodes (Mesocriconema spp., Criconemoides spp.) by 65%.
• S. carpocapsae can reduce the population of stubby root nematodes (Paratrichodorus spp.) by 60%.
• S. carpocapsae can reduce the population of potato cyst nematodes (Globodera rostochiensis).
• S. carpocapsae can reduce the populations of foliar nematode Aphelenchoides fragariae
• Steinernema riobrave can reduce the population of stunt nematodes (Tylenchorynchu spp.) by 85%.
• S. riobrave can reduce the population of lance nematodes (Hoplolaimus spp.).
• S. riobrave can reduce the population of root-knot nematodes (Meloidogyne spp.) by 83%.
• S. riobrave reduced egg masses of root-knot nematodes (Meloidogyne spp.)
• S. riobrave can reduce the population of sting nematodes (Belonolaimus longocaudatus).
• Steinernema feltiae can inhibit hatching root-knot nematode eggs and infection by hatched infective juveniles of root-knot nematodes (Meloidogyne spp.).
• S. feltiae reduced egg masses of root-knot nematodes (Meloidogyne spp.) .
• S. feltiae can reduce the population of root-knot nematodes (Meloidogyne spp.).
• Steinernema glaseri reduced egg masses of root-knot nematodes (Meloidogyne spp.)
• Heterorhabditis bacteriophora can reduce the population of ring nematodes (Mesocriconema spp., Criconemoides spp.) by 80%.
• H. bacteriophora can reduce the population of stunt nematodes (Tylenchorynchus spp.) by 60%.
• H. bacteriophora can reduce the population of lesion nematodes (Pratylenchus pratensis).
• H. baujardi can inhibit hatching root-knot nematode eggs and infection by hatched infective juveniles of root-knot nematodes (Meloidogyne mayaguensis).

e Read following literature for more information on interaction between entomopathogenic nematodes and plant- parasitic nematodes:

1. Fallon, D.J., Kaya, H.K., Gaugler, R., Sipes, B.S., 2002. Effects of entomopathogenic nematodes on Meloidogyne javanica on tomatoes and soybeans. Journal of Nematology 34, 239-245.

2. Fallon, D.J., Kaya, H.K., Sipes, B.S., 2006. Enhancing Steinernema spp. suppression of Meloidogyne javanica. Journal of Nematology 38, 270-271.

3. Grewal, P.S., Ehlers, R.-U., Shapiro-Ilan, D.I. (Eds.), 2005. Nematodes As Biocontrol Agents. CABI Publishing, CAB International, Oxon, U.K.,

4. Grewal, P.S., Lewis, E.E., Venkatachari, S., 1999. Allelopathy: a possible mechanism of suppression of plant-parasitic nematodes by entomopathogenic nematodes. Nematology. 1, 735-743.

5. Grewal, P.S., Martin, W.R., Miller, R.W., Lewis E.E., 1997. Suppression of plant-parasitic nematode populations in turfgrass by application of entomopathogenic nematodes. Biocontrol Science and Technology 7, 393-399.

6. Jagdale, G.B., Grewal, P.S., 2008. Influence of the entomopathogenic nematode Steinernema carpocapsae in host cadavers or extracts from cadavers on the foliar nematode Aphelenchoides fragariae on Hosta. Biological Control 44, 13-23.

7. Jagdale, G.B., Somasekhar, N., Grewal, P.S., Klein, M.G., 2002. Suppression of plant parasitic nematodes by application of live and dead entomopathogenic nematodes on Boxwood (Buxus spp). Biological Control. 24, 42-49.

8. Lewis, E.E., Grewal, P.S., 2005. Interactions with plant-parasitic nematodes. In: Grewal, P.S., Ehlers, R.-U., Shapiro-Ilan, D.I. (Eds.), Nematodes As Biocontrol Agents. CABI Publishing, CAB International, Oxon, U.K., pp. 349-362.

9. Perry, R.N., Homonick, W.M., Beane, J., Briscose, B., 1998. Effects of the entomopathogenic nematodes, Steinernema feltiae and S. carpocapsae, on the potato cyst nematode, Globodera rostochiensis, in pot trials. Biocontrol Science and Technology 8:175 – 180.

10. Shapiro, D.I., Nyczepir, A.P., Lewis, E.E., 2006. Entomopathogenic nematodes and bacteria applications for control of the pecan root-knot nematode, Meloidogyne partityla in the greenhouse. Journal of Nematology 38, 449-454.

Kill slugs and snails with parasitic nematode, Phasmarhabditis hermaprodita

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.

White grub species susceptible to entomopathogenic nematodes

Species of white grubs : Species of entompathogenic nematodes

1. Asiatic garden beetle (Maladera castanea): H. bacteriophora, S. glaseri, S. scarabae
2. Black turfgrass ataenius (Ataenius spretulus): H. bacteriophora, S. glaseri, S. scarabae
3. Cockchafer (Melolontha melolontha): H. bacteriophora, H. marelata, H. megidis, S arenaria, S. feltiae, S. glaseri, S. riobrave
4. Cranberry root grub (Phyllophaga Georgiana): H. bacteriophora, S. glaseri, S. scarabae
5. European chafer (Rhizotrogus majalis): H. bacteriophora, H. megidis, H. zealandica, S. carpocapsae, S. feltiae, S. glaseri, S. scarabae
6. Grass grub beetle (Costelytra zealandica): H. bacteriophora, S. glaseri
7. Green June beetle (Cotinus nitida): H. bacteriophora, S. carpocapsae, S. feltiae, S. glaseri, S. scarabae
8. Japanese beetle (Popillia japonica): H. bacteriophora, H. indica, H. marelata, H. megidis, H. zealandica, S. anomali, S. carpocapsae, S. feltiae, S. glaseri, S. kushidai, S. riobrave, S. scapterisci, S. scarabae
9. Masked Chafer (Cyclocephala pasadenae): H. bacteriophora, S. glaseri, S. kushidai, S. scarabae
10. Northern Masked Chafer (Cyclocephala borealis): H. bacteriophora, H. indica, H. marelata, H. megidis, H. zealandica, S. glaseri, S. scarabae
11. Oriental beetle (Anomala orientalis): H. bacteriophora, H. megidis, H. zealandica, S. carpocapsae, S. glaseri, S. longicaudum, S. scarabae
12. Southern Masked Chafer (Cyclocephala lurida): H. bacteriophora, S. glaseri, S. scarabae
13. Southwestern Masked Chafer (Cyclocephala hirta): H. bacteriophora, H. megidis, S. carpocapsae, S. feltiae, S. glaseri, S. kushidai, S. riobrave, S. scarabae
14. Summer chafer (Amphimallon solstitiale): S. glaseri
15. White grub (Hoplia philanthus): H. megidis, S. feltiae, S. glaseri
16. White grub (Phyllophaga crinita): H. bacteriophora, S. glaseri, S. scarabae
17. White grub (Phyllophaga congrua): H. bacteriophora, S. glaseri, S. scarabae

For more information on insect pathogenic nematodes read 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

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.

Kill leaf beetles (Altica quercetorum, Agelastica alni and Xanthogaleruka luteola) with Entomopathogenic Nematodes

• The leaf beetles, Altica quercetorum and Agelastica alni are serious pests of urban trees including Quercus sp and Alnus sp, respectively.
• The elm leaf beetle Xanthogaleruka luteola is a serious pest that causes defoliation of eml trees (Ulmus spp.) in North America.
• Adults of these beetles generally feed on leaves by chewing holes through the leaf tissue.
• Larvae skelotonize leaves by feeding on leaf tissues leaving veins and upper epidermis intact.
• Entomopathogenice nematodes including Heterorhabditis megidis, Steinernema carpocapsae and S. feltiae can be used as potential biocontrol agents against different species leaf beetles (read Grewal et al., 2005 for more information).
• It has been shown that both the pre-pupal and pupal stages of A. quercetorum and A. alni are very susceptible to H. megidis when applied in the soil.
• The last instar larvae of X. luteola are highle susceptible to S. carpocapsae when applied to the mulch.

How Entomopathogenic Nematodes kill leaf beetles

• When the infective juveniles are applied to the soil surface or mulch, they start searching for their hosts, in this case leaf beetles grubs.
• Once a beetle grub has been located, the nematode infective juveniles penetrate into the grub body cavity via natural openings such as mouth, anus and spiracles.
• Infective juveniles of Heterorhabditis also enter through the intersegmental members of the grub cuticle.
• Once in the body cavity, infective juveniles release symbiotic bacteria (Xenorhabdus spp. for Steinernematidae and Photorhabdus spp. for Heterorhabditidae) from their gut in grub blood.
• In the blood, multiplying nematode-bacterium complex causes septicemia and kills grubs usually within 48 h after infection.
• Nematodes feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the cadaver to seek new larvae in the soil.

References: Refer following book to read more about efficacy of entomopathogenic nematodes against leaf beetles

1. Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). Nematodes As Biocontrol Agents. CAB publishing, CAB International, Oxon

Kill Japanese beetles (Popillia japonica) with Entomopathogenic Nematodes

• The Japanese beetle, Popillia japonica, is a most economically important pest of many ornamental plants and turf grasses.

• Larvae of these beetles are called white grubs that generally feed on roots of over 300 plants but their primary food source is grass roots. Severe damage caused by these grubs can result in dead patches of turf that can be picked up like a loose carpet.

• Adults mostly feed on leaves and flowers by chewing the tissue between the veins, a type of feeding called skeletonizing.

• Chemical insecticides including Imidacloprid (Merit), Chlorpyrifos, Isofenphos, and Diazinon are generally used to manage white grubs but due to human health and environment pollution concerns their use is restricted.

• Currently, environmentally safe biological control agents including a milky disease causing bacterium Bacillus popilliae (Milky spores) and entomopathogenic nematodes have been used to control this pest.

• Three entomopathogenic nematodes including Heterorhabditis bacteriophora GPS11 and TF strains, H. zealandica X1 strain and Steinernema scarabaei have been considered to be the most effective species against Japanese beetle grubs.

• It has been demonstrated that the application of H. bacteriophora GPS11 and TF strains, H. zealandica X1 strain and S. scarabaei at rate of 2.5 billion infective juveniles per hectare can cause about 96, 98 and 100%, respectively control of Japanese beetle grubs infesting turfgrass (for more information read Grewal et a., 2005).

• Nematodes can be applied using traditional sprayers that are used for the application of insecticides.

• Nematodes perform better when they are applied to target small stages of grubs.

• Nematodes also survive better and remain efficacious when field/lawns are irrigated before and after nematode applications.

How Entomopathogenic Nematodes kill Japanese beetles

• When the infective juveniles are applied to the soil surface or thatch layer, they start searching for their hosts, in this case Japanese beetle grubs.

• Once a Japanese beetle grub has been located, the nematode infective juveniles penetrate into the Japanese beetle grub body cavity via natural openings such as mouth, anus and spiracles.

• Infective juveniles of Heterorhabditis also enter through the intersegmental members of the grub cuticle.

• Once in the body cavity, infective juveniles release symbiotic bacteria (Xenorhabdus spp. for Steinernematidae and Photorhabdus spp. for Heterorhabditidae) from their gut in grub blood.

• In the blood, multiplying nematode-bacterium complex causes septicemia and kills Japanese beetle grubs usually within 48 h after infection.

• Nematodes feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the cadaver to seek new larvae in the soil.

References

1. Grewal, P.S., Koppenhofer, A.M., and Choo, H.Y., 2005. Lawn, turfgrass and Pasture applications. In: Nematodes As Biocontrol Agents. Grewal, P.S. Ehlers, R.-U., Shapiro-Ilan, D. (eds.). CAB publishing, CAB International, Oxon. Pp 147-166.

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

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.

Kill black cutworms (Agrotis ipsilon Hufnagel) with Entomopathogenic Nematodes

• The black cutworm, Agrotis ipsilon (Hufnagel), is a polyphagous pest, feeding on almost all vegetables, many grain crops, ornamentals, turf grasses and weeds.
• The plants damaged by black cutworms include beans, broccoli, cabbage, carrot, Chinese broccoli, Chinese cabbage, Chinese spinach, clover, corn, cotton, eggplant, flowering white cabbage, green beans, head cabbage, lettuce, mustard, potato, spinach, sugarcane, sweet potato, tomato, turnip, alfalfa, rice, sorghum, strawberry, sugarbeet, tobacco, bluegrass (Poa pratensis), curled dock (Rumex crispus); lambsquarters (Chenopodium album), yellow rocket (Barbarea vulgaris) and redroot pigweed (Amaranthus retroflexus).
• There are five to nine larval instars that generally feed on seedlings at ground level by cutting off the stem causing a significant damage especially in newly planted fields. They also feed on roots and the below ground stem.
• They can damage turfgrass by clipping off their blades and shoots.
• The biological control agents including a bacterium Bacillus thuringiensis var. kurstaki, and entomopathogenic nematodes have a great potential against black cutworms.
• Bacillus thuringiensis var. kurstaki produces a toxin that paralyzes the gut of the caterpillar.  This toxin does not kill the caterpillars quickly, but it does cause the caterpillars to stop feeding, which in turn reducing the intensity of the damage.
• Since caterpillars of cutworms are highly mobile insects, the entomopathogenic nematodes with ambush type of foraging strategy can be used very effectively for the management of cutworms.
• For example, Steinernema carpocapsae, is an ambusher nematode species that can control black cutworms very effectively if applied at a rate of 1 billion nematodes/acre on golf course greens.

How Entomopathogenic Nematodes Kill Black Cutworms

• When the infective juveniles are applied to the soil surface or thatch layer, they start searching for their hosts, in this case caterpillares.
• Once a caterpillar has been located, the nematode infective juveniles penetrate into the caterpillar body cavity via natural openings such as mouth, anus and spiracles.
• Once in the body cavity, infective juveniles release symbiotic bacteria (Xenorhabdus spp. for Steinernematidae) from their gut in the caterpillar blood.
• In the blood, multiplying nematode-bacterium complex causes septicemia and kills shore fly larvae usually within 48 h after infection.
• Nematodes feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the cadaver to seek new larvae in the potting medium/soil.

How entomopathogenic nematodes find their insect hosts (Foraging Strategies)

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.

Kill leafminers (Liriomyza spp.) with Entomopathogenic Nematodes

• Leafminers (Liriomyza spp.) are considered as economically important polyphagous pests of many indoor vegetable crops and flowering plants.

• Vegetable host crops included beans, beet, carrots, celery, cucumbers, eggplants, lettuce, melons, onions, peas, peppers, potatoes, squash and tomatoes.

• Flowering host plants included ageratum, aster, calendula, chrysanthemum, dahlia, gerbera, gypsophila, marigold, petunia, snapdragon, and zinnia.

• Leafminer maggots generally feed on leaf parenchyma tissues by tunneling/mining between the upper and lower epidermal leaf surfaces.

• Adults generally feed on sap exuding from the punctures caused by maggots during mining.

• Infested leaves appear stippled due to the punctures made by leafminers while feeding, mining and oviposition especially at the leaf tip and along the leaf margins.

• Widespread mining and stippling on the leaves generally decreases the level of photosynthesis in the plant leading towards the premature leaf drop reducing the amount of shade, which in turn causes sun scalding of fruits.

• Injuries caused by maggots on the foliage also allow entry of bacterial and fungal disease causing pathogens.

• Life cycle of leafminers contains four stages including egg, maggot, pupa and adult.

• Life cycle can be completed within 15-21 days depending upon the host and temperature.

• Adult females lay eggs in leaf tissues, eggs hatch within 2-3 days into maggots, hatched maggots starts feeding immediately and become mature within 3-4 days. Mature larvae eventually cut through the leaf epidermis and move to the soil for pupation and adults emerge within 3 weeks of pupation in the summer.

• Although, chemical insecticides are generally used to protect foliage from injury caused by leafminers, but development of insecticide resistance among leafminer populations is a major problem.

• Insecticides also are highly disruptive to naturally occurring biological control agents, particularly parasitoids.

• Therefore, biological control agents including Bacillus thuringiensis var. thuringiensis (Bt), parasitic wasps (Diglyphus begina, D. intermedius, D. pulchripes and Chrysocharis parksi) and entomopathogenic nematodes (Heterorhabditis spp, Steinernema carpocapase and S. feltiae) have been considered as alternatives to chemical pesticides.

• For successful control of leafminers, entomopathogenic nematodes can be easily applied in water suspension as spray application on plant foliage.

• Entomopathogenice nematodes including S. carpocapase and S. feltiae when applied at the rate of 5.3 X 108 nematodes/ha can cause over 64% mortality of leafminers but need at least 92% relative humidity.

How Entomopathogenic Nematodes kill leafminers

• When the infective juveniles are applied as spray to plant foliage, they enter the leaf mines through the leaf miner feeding punctures or exit holes made by the adults.

• Once inside the mine the nematodes swim to find a leafminer maggot, nematodes then penetrate into the maggot body cavity via natural openings such as mouth, anus and spiracles.

• Infective juveniles of Heterorhabditis also enter through the intersegmental members of the larval cuticle.

• Once in the body cavity, infective juveniles release symbiotic bacteria (Xenorhabdus spp. for Steinernematidae and Photorhabdus spp. for Heterorhabditidae) from their gut in the maggot blood.

• In the blood, multiplying nematode-bacterium complex causes septicemia and kills maggots usually within 48 h after infection.

For more information on the interaction between entomopathogenic nematodes and leafminers, please read following research and extension publications.

• Hara, A.H., Kaya, H.K., Gaugler, R., Lebeck, L.M. and Mello, C.L. 1993. Entomopathogenic nematodes for biological control of the leafminer, Liriomyza trifolii (Dipt.: Agromyzidae). Entomophaga 38, 359-369.

• Head, J. and Walters, K.F.A. 2003. Augmentation biological control utilising the entomopathogenic nematode, Steinernema feltiae, against the South American Leafminer, Liriomyza huidobrensis. Proceedings of the 1st International Symposium on Biological Control, (Hawaii, USA, 13-18 January 2002). USDA Forest Service, FHTET-03-05, 136-140.

• Olthof, T.H.A. and Broadbent, A.B. 1992. Evaluation of steinernematid nematodes for control of a leafminer, Liriomyza trifolii, in greenhouse chrysanthemums. Journal of Nematology 24, 612.

• Tong-Xian Liu, Le Kang, K.M.Heinz, J.Trumble. 2008. Biological control of Liriomyza leafminers: progress and perspective. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2009, 4, No. 004, 16 pp.

• Williams, E.C. and Walters, K.F.A. 1994. Nematode control of leafminers: Efficacy, temperature and timing. Brighton Crop Protection Conference - Pests and Disease. 1079-1084.

• Williams, E.C. and MacDonald, O.C., 1995. Critical factors required by the nematode Steinernema feltiae for the control of the leafminers Liriomyza huidobrensis, Liriomyza bryoniae and Chromatomyia syngenesiae. Annals of Applied Biology. 127, 329-341.

• Williams, E.C. and Walters, K.F.A. 2000. Foliar application of the entomopathogenic nematode Steinernema feltiae against leafminers on vegetables. Biocontrol Science and Technology 10, 61-70.