Entomopathogenic nematodes for the biological control of Colorado potato beetles- Nematode information

Entomopathogenic nematodes and Colorado potato beetle

• Colorado potato beetles (Leptinotarsa decemlineata) are a most damaging pest of potatoes but they can also cause a significant damage to tomatoes and eggplants.
• Generally, both adults and larvae feed voraciously on leaves causing hundreds of millions dollars in yield loss each year in the United States.
• Many chemical insecticides have been recommended to control these beetles but unfortunately beetles have an ability to develop resistance to insecticides.
• Entomopathogenic nematodes as biological control agents could provide an alternative to chemical pesticides in management of Colorado potato beetles.
• As entomopathogenic nematodes naturally found soil, they are very effective against soil dwelling stages of host insect pests.  For example, mature larvae of Colorado potato beetle that moves in the soil for pupation can be a very good target for entomopathogenic nematodes.
• Commercially available entomopathogenic nematode species including Steinernema carpocapsae, Steinernema feltiae, Heterorhabditis megidis, Heterorhabditis marelata and Heterorhabditis bacteriophora have showed a very high efficacy against adult, larval and prepupal stages of Colorado potato beetles when tested in soil under laboratory conditions.

Publications:

1. Ebrahimi, L., Niknam, G. and Lewis, E. E. 2011.   Lethal and sublethal effects of Iranian isolates of Steinernema feltiae and Heterorhabditis bacteriophora on the Colorado potato beetle, Leptinotarsa decemlineata.  Biocontrol 56: 781-788.
2. Ebrahimi, L.,Niknam, G.and Dunphy, G.B. 2011. Hemocyte responses of the Colorado potato beetle, Leptinotarsa decemlineata, and the greater wax moth, Galleria mellonella, to the entomopathogenic nematodes, Steinernema feltiae andHeterorhabditis bacteriophora . Journal of Insect Science 11, Article Number: 75.
3. Armer, C.A., Berry, R.E., Reed, G.L. and Jepsen, S.J. 2004.  Colorado potato beetle control by application of the entomopathogenic nematode Heterorhabditis marelata and potato plant alkaloid manipulation. Entomologia Experimentalis et Applicata. 111: 47-58.
4. Berry, R.E., Liu, J. and Reed, G. 1997.  Comparison of endemic and exotic entomopathogenic nematode species for control of Colorado potato beetle (Coleoptera : Chrysomelidae). Journal of Economic Entomology. 90: 1528-1533.
5. Cantelo, W.W. and Nickle, W.R. 1992. Susceptibility of prepupae of the Colorado potato beetle (coleoptera, chrysomelidae) to entomopathogenic nematodes (Rhabditida, Steinernematidae, Heterorhabditidae). Journal of Entomological Science. 27: 37-43.
6. Nickle, W.R., Connick, W.J. and Cantelo, W.W. 1994. Effects of pesta-pelletized Steinernema-carpocapsae (all) on western corn rootworms and colorado potato beetles. Journal of Nematology. 26: 249-250.
7. Trdan, S., Vidrih, M., Andjus, L. and Laznik, Z. 2009. Activity of four entomopathogenic nematode species against different developmental stages of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera, Chrysomelidae. Helminthologia. 46: 14-20.

Influence of potting media on the virulence of entomopathogenic nematodes against black vine weevil, Otiorhynchus sulcatus

It has been demonstrated that five different types of commercial potting media including peat, bark, coir, and peat blended with 10% and 20% compost green waste can influence the virulence of entomopathogenic nematodes against third-instar black vine weevil, Otiorhynchus sulcatus.  For example, Heterorhabditis species including Heterorhabditis bacteriophora UWS1 strain, H. megidis, H. downesi can cause 100% mortality of black vine weevil grubs in all the five types of media but  Steinernema species including Steinernema feltiae, S. carpocapsae, and S. kraussei can cause 100% black vine weevil grub mortality only in the peat blended with 20% compost green waste.  These results suggest that when growers are selecting entomopathogenic nematodes to control black vine weevil, Otiorhynchus sulcatus in their nurseries/greenhouses, they should take into consideration the type of potting media used in growing their plants. Please read following paper for the information on the method of nematode application rates and timings.

Ansari, M. A. and Butt, T. M. 2011.  Effect of potting media on the efficacy and dispersal of entomopathogenic nematodes for the control of black vine weevil, Otiorhynchus sulcatus (Coleoptera: Curculionidae). Biological Control 58: 310-318.

Ansari, M.A., Shah, F.A. and Butt, T.M. 2010.  The entomopathogenic nematodeSteinernema kraussei and Metarhizium anisopliae work synergistically in controlling overwintering larvae of the black vine weevil, Otiorhynchus sulcatus, in strawberry growbags. Biocontrol Science and Technology. 20: 99-105.

Control of the black vine weevil Otiorhynchus sulcatus infesting strawberry fields

It has been reported that entompathogenic nematodes including Heterorhabditis megidis and Steinernema kraussei are effective against the black vine weevil Otiorhynchus sulcatus infesting strawberry fields (Haukeland and Lola-Luz, 2010).  It has been suggested that the soil type and soil temperature plays a significant role in efficacy of these nematodes against the black vine weevil.  It is also noted that H. megidis performs better at soil temperatures above 10oC and S. kraussei at below 10oC. References:

Haukeland, S. and Lola-Luz, T. 2010.  Efficacy of the entomopathogenic nematodes Steinernema kraussei and Heterorhabditis megidis against the black vine weevil Otiorhynchus sulcatus in open field-grown strawberry plants. Agricultural and Forest Entomology.12363-369

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

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 Shore flies (Scatella stagnalis) with Entomopathogenic Nematodes

• The shore fly, Scatella stagnalis (Fallén) (Diptera: Ephydridae) is an important insect pest of greenhouse plants.

• Larvae of these flies mainly feed on blue-green algae grown on the surface of plant growing media, walls, floors, benches, and pots.

• But larvae can also cause a serious damage to tender plant tissues thus reducing quality and productivity of plants.

• The adults are not considered as plant feeders but they are nuisance to people and disseminate pathogens such as Fusarium and Pythium from plant to plant as they disperse through the greenhouse.

• Currently, most growers rely on chemicals that kill host plants such as blue-green algae to reduce the incidence of shore flies. However, this method has not been proved effective in reducing shore fly incidence.

• Biological control agents including Bacillus thuringiensis var. thuringiensis (Bt) and entomopathogenic nematodes have been considered as alternatives to chemical pesticides.

• For successful control of shore flies, entomopathogenic nematodes can be easily applied in water suspension as spray application to the surface of plant growing medium.

• Entomopathogenice nematodes including Heterorhabditis megidis, Steinernema arenarium and Steinernema feltiae when applied at the rate of 50 nematodes/cm2 can cause 94- 100% mortality of shore flies.

How Entomopathogenic Nematodes kill Shore flies

• When the infective juveniles are applied to the surface of plant growing substrate, they start searching for their hosts, in this case shore fly larvae.

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

• Infective juveniles of Heterorhabditis spp 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 larval 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.

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

• Foote, B.A. 1977. Utilization of blue-breen algae by larvae of shore flies. Environmental Entomology 6, 812-814.

• Goldberg, N.P. and Stanghellini, M.E. 1990. Ingestion-egestion and aerial transmission of Pythium aphanidermatum by shore flies (Ephydrinae: Scatella stagnalis). Phytopathology 80, 1244-1246.

• Lindquist, R., Buxton, J. and Piatkowski, J. 1994. Biological control of sciarid flies and shore flies in glasshouses. Brighton Crop Protection Conference, Pests and Diseases, BCPC Publications 3, 1067-1072.

• Morton, A., Garcia del Pino, F., 2007. Susceptibility of shore fly Scatella stagnalis to five entomopathogenic nematode strains in bioassays. Biocontrol 52: 533-545.

• Morton, A. and Garcia del Pino, F. 2003. Potential of entomopathogenic nematodes for the control of shore flies (Scatella stagnalis). Growing Biocontrol Markets Challenge Research and Development. 9th European Meeting IOBC/WPRS Working Group "Insect Pathogens and Entomopathogenic Nematodes", Abstracts, 67.

• Vanninen, I., Koskula, H. 2000. Biological control of the shore fly (Scatella tenuicosta) with steinernematid nematodes and Bacillus thuringiensis var. thuringiensis in peat and rockwool. Biocontrol Sci. Technol.. 13: 47-63.

• Zack, R.S. and Foote, B.A. 1978. Utilization of algal monoculture by larvae of Scatella stagnalis. Environmental Entomology 7, 509-511.