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.

Manage insect pests of Strawberries with entomopathogenic nematodes

Strawberries are one of the most economically grown crops throughout the world and in North America with annual yields ranging from 4-20 tons per acre and average monitory values between $2,800 to $14000 per acre.  There are several kinds of insect pests have been reported that attack and cause significant economic losses (over 60%) to this crop.   Different species of entomopathogenic have been used as biological control agents against different  insect pests of strawberries. It has been demonstrated that  the entomopathogenic nematode, Steinernema kraussei can reduce over 81%  population of black vine weevil (Ansari et al., 2010; Susurluk and Ehlers, 2008; Willmott et al., 2002). Entomopathogenic nematodes, Heterorhabditis megidis and H. downesi also can reduce 93 and 51% population of black vine weevil, respectively (Boff et al., 2001, 2002; Lola-Luz et al., 2005; Fitters et al., 2001). Populations of black vine weevils were also reduced by application of infective juveniles of Steinernema carpocapsae and S. glaseri (Booth et la., 2002). Steinernema carpocapsae can reduce 51% population of strawberry crown moth (Bruck et al., 2008).

Please read following literature for more information on interaction between insect pests of strawberries and different species entomopathogenic nematodes.

Ansari, M.A., Shah, F.A. and Butt, T.M. 2010.  The entomopathogenic nematode Steinernema 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.

Berry, R.E., Liu, J. and Groth, E. 1997.  Efficacy and persistence of Heterorhabditis marelatus (Rhabditida: Heterorhabditidae) against root weevils (Coleoptera: Curculionidae) in strawberry. Environmental Entomology. 26: 465-470.

Boff, M.I.C., van Tol, R.H.W.M. and Smits, P.H. 2002.  Behavioural response of Heterorhabditis megidis towards plant roots and insect larvae. Biocontrol. 47: 67-83.

Boff, M.I.C., Wiegers, G.L. and Smits, P.H. 2001.  Influence of insect larvae and plant roots on the host-finding behaviour of Heterorhabditis megidis. Biocontrol Science and Technology. 11: 493-504.

Boff, M.I.C., Zoon, F.C. and Smits, P.H. 2001.  Orientation of Heterorhabditis megidis to insect hosts and plant roots in a Y-tube sand olfactometer. Entomologia Experimentalis et Applicata. 98: 329-337.

Booth, S.R., Tanigoshi, L.K., Shanks, C.H. 2002.  Evaluation of entomopathogenic nematodes to manage root weevil larvae in Washington state cranberry, strawberry, and red raspberry. Environmental Entomology. 31: 895-902.

Bruck, D.J., Edwards, D.L. and Donahue, K.M. 2008.  Susceptibility of the strawberry crown moth (Lepidoptera : Sesiidae) to entomopathogenic nematodes. Journal of Economic Entomology. 101: 251-255.

Curran, J. 1992. Influence of application method and pest population-size on the field efficacy of entomopathogenic nematodes. Journal of Nematology. 24: 631-636.

Fitters, P.F.L., Dunne, R. and Griffin, C.T. 2001.  Vine weevil control in Ireland with entomopathogenic nematodes: optimal time of application. Irish Journal of Agricultural and Food Research. 40: 199-213.

KakouliDuarte, T., Labuschagne, L. and Hague, N.G.M. 1997.  Biological control of the black vine weevil, Otiorhynchus sulcatus (Coleoptera: Curculionidae) with entomopathogenic nematodes (Nematoda: Rhabditida). Annals of Applied Biology. 131: 11-27.

Lola-Luz, T. and Downes, M. 2007.  Biological control of black vine weevil Otiorhynchus sulcatus in Ireland using Heterorhabditis megidis. Biological Control. 40: 314-319.

Lola-Luz, T., Downes, M. and Dunne, R. 2005.  Control of black vine weevil larvae Otiorhynchus sulcatus (Fabricius) (Coleoptera : Curculionidae) in grow bags outdoors with nematodes. Agricultural and Forest Entomology. 7: 121-126.

Simser, D. and Roberts, S. 1994.  Suppression of strawberry root weevil, Otiorhynchus-ovatus, in cranberries by entomopathogenic nematodes (Nematoda, Steinernematidae and Heterorhabditidae). Nematologica. 40: 456-462.

Susurluk, A. and Ehlers, R.U. 2008.  Sustainable control of black vine weevil larvae, Otiorhynchus sulcatus (Coleoptera: Curculionidae) with Heterorhabditis bacteriophora in strawberry. Biocontrol Science and Technology. 18: 635-640.

Vainio, A. and Hokkanen, H.M.T. 1993.  The potential of entomopathogenic fungi and nematodes against Otiorhynchus-ovatus L and O. dubius strom (Col, Curculionidae) in the field. Journal of Applied Entomology-Zeitschrift fur Angewandte Entomologie. 115: 379-387.

Willmott, D.M., Hart, A.J., Long, S.J., Edmondson, R.N. and Richardson, P.N. 2002.  Use of a cold-active entomopathogenic nematode Steinernema kraussei to control overwintering larvae of the black vine weevil Otiorhynchus sulcatus (Coleoptera: Curculionidae) in outdoor strawberry plants. Nematology. 4: 925-932.

Wilson, M., Nitzsche, P. and Shearer, P.W. 1999.  Entomopathogenic nematodes to control black vine weevil (Coleoptera : Curculionidae) on strawberry. Journal of Economic Entomology. 92: 651-657.

Biological Control of Black Vine Weevil using Insect Parasitic Nematodes

• Black vine weevil, Otiorhynchus sulcatus is a common insect pest of over 150 plant species that grown in the greenhouses and nurseries.

• Some of the plant species damaged by black vine weevils include Azalea, Cyclamen, Euonymus, Fuxia, Rosa, Rhododendron and Taxus.

• Grubs (Larvae) of these weevils generally girdle the main stem, and feed and damage roots leading to nutrient deficiencies.

• Adults feed on leaves and flowers by notching their edges thus reducing aesthetic value of plants.

• The entomopathogenic nematodes species including Heterorhabditis bacteriophora, H. megidis and Steinernema carpocapase, S. feltiae and S. glaseri have been found to be effective alternatives to chemical insecticides such as chlorpyrifos (Dursban) in controlling black vine weevils.

• Susceptibility of black vine weevil to nematodes is species and strain specific.

• The rate of application of the nematode species/strains that tested against black vine weevil varies (5,000- 60,000 infective juveniles/pot) among different studies but nematodes applied at the rate of 5000- 20,000 infective juveniles/pot can cause up to 100% grub mortality.

• Nematodes can be easily applied in water suspension as spray applications to the surface of plant growing medium but if nematodes are injected at depths deeper than 5 cm i.e. near to grubs they can cause highest mortality of grubs (70-93%) than those nematodes applied to the surface.

• All the four larval stages (instars) and pupae of black vine weevil are susceptible to all entomopathogenic nematode species.

• However, Heterorhabdtis bacteriophora can cause higher mortality of first and second instars than S. carpocapase and S. glaseri.

• Also, all the three nematodes species are equally effective against third and fourth instars of black vine weevil.

How Entomopathogenic Nematodes Kill Black Vine Weevil

• When the infective juveniles are applied to the surface of plant growing medium or injected in the potting medium, they start searching for their hosts, in this case black vine weevil grubs and pupae.

• Once a grub/pupa has been located, the nematode infective juveniles penetrate into the grub or pupa body cavity via natural openings (mouth, anus and spiracles).

• Infective juveniles of Heterorhabditis also enter through the intersegmental members of the grub/pupa 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 grub blood.

• Multiplying nematode-bacterium complex in the blood causes septicemia and kills the grub 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 grubs or pupae in the potting medium/soil.