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Biological Control : A Guide to Natural Enemies in North America Anthony Shelton, Ph.D., Professor of Entomology, Cornell University

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Ibalia leucospoides ensiger

Hymenoptera: Ibaliidae

by Derek J. Robertson and Kamal J.K. Gandhi, University of Georgia

Ibalia leucospoides ensiger (Hymenoptera: Ibaliidae) is a solitary parasitoid wasp of egg and early instar larvae of woodwasps (Hymenoptera: Siricidae) in the Nearctic Region (Smith and Schiff 2002).  This species has been introduced into pine (Pinus spp.) plantations in the Southern Hemisphere to assist with controlling pest populations of Sirex noctilio, an introduced woodwasp from Eurasia and North Africa (Taylor 1976, Cameron 2012).  Ibalia leucospoides ensiger presumably also attacks Sirex noctilio populations introduced to the Great Lakes region in North America, as they have been reared from the same trees (Long et al. 2009, Eager et al. 2011).



Ibalia leucospoides ensiger is a small wasp (~15 mm) with a black head, thorax, and legs, and reddish abdomen (Weld 1952, Norton 1963). Antennae are filiform. Males and females have 13 and 11 antennal segments (in addition to scape and pedicel), respectively. The last antennal segment is rounded in females and pointed in males, while the first segment in males has a sinuous excavation. The wings are clear with semitransparent apical ends. As typical of ibaliid wasps, the abdomen is rectangular and laterally compressed.  Females have a triangular appendage on the ventral portion of abdomen used for guiding the ovipositor into wood. The last tergite of the female is triangular, and that of the male is more rectangular in shape (Norton 1963).



This ibaliid wasp is found in conifer-dominated forests in North America. Ibalia leucospoides ensiger has been associated with trees in the following genera: Abies, Cupressus, Libocedrus, Picea, Pinus, and Tsuga (Champlain 1922, Weld 1952, Cameron 1962, Yoshimoto 1970, Ryan et al. 2012).  It is one of the most widely distributed parasitoids of woodwasps in North America (Liu and Nordlander 1992, Coyle and Gandhi 2012).


Pests Attacked (Host Range)

Ibalia leucospoides ensiger has been reported to either parasitize or is reared from the same trees as at least 11 species of woodwasps within the following genera: Sirex, Urocerus,and Xeris (Schiff et al. 2012).


Life Cycle

Adults of Ibalia leucospoides ensiger have been found during April-October in the mid-Atlantic states (Smith and Schiff 2002).  The wasp has been reared from Pinus taeda logs infested with Sirex nigricornis during October-December in Louisiana (Meeker and Johnson, pers. comm.).  Females will locate an oviposition site of siricids presumably through olfactory cues.  Eggs are laid on either the egg or first instar larvae of siricids. The parasitoid remains endoparasitic until the third instar when it emerges and consumes the remains of the woodwasp and enters pupation.  The life cycle usually lasts one year and typically coincides with host emergence.


Relative Effectiveness

Ibalia leucospoides ensiger has been introduced widely to the Southern Hemisphere where non-native pines are planted and have experienced damage by Sirex noctilio (Cameron 2012).  Parasitism rates both in the introduced and native ranges on Sirex spp. are highly variable, depending upon site and year.  However, parasitism of up to 21% in New York (Long et al. 2009) and 49% in Louisiana (Meeker and Johnson, pers. comm.) has been reported.  In North America, Ibalia leucospoides ensiger is the most common parasitoid reared from logs infested with Sirex spp. (Long et al. 2009, Ryan et al. 2012).  Hence, this species has the potential to exert the greatest biological control pressure on Sirex noctilio.


Pesticide Susceptibility

No information is available concerning pesticides and Ibalia leucospoides ensiger.

Commercial Availability

Ibalia leucospoides ensiger is not available commercially.


We are grateful to R. Hoebeke (University of Georgia), and W. Johnson, J. Meeker, and N. Schiff (USDA Forest Service) for providing constructive comments on this paper.  Many thanks also to H. Goulet (Agriculture and Agri-Food Canada) for allowing us to use his wasp image.


Cameron, E. A. (1962) North American survey for natural enemies of the Siricidae, May-October, 1962. CBIC Report, California Station, Fontana, CA. 21 pp.

Cameron, E. A. (2012) Parasitoids in the management of Sirex: looking back and looking ahead, Ch. 8. In B. Slippers, P. de Groot, and M. J. Wingfield (eds.), The Sirex Woodwasp and its Fungal Symbiont: Research and Management of a Worldwide Invasive Pest. Springer, New York, NY.

Champlain, A. B. (1922) Records of hymenopterous parasites in Pennsylvania. Psyche 29: 95-100.

Coyle, D. R., and K. J. K. Gandhi.  (2012) The ecology and biological control potential of hymenopteran parasitoids of woodwasps (Hymenoptera: Siricidae) in North America. Environ. Entomol.  41: 731-749.

Eager, P. T., D. C. Allen, J. L. Frair, and M. K. Fierke. (2011) Within-tree distributions of the Sirex noctilio Fabricius (Hymenoptera: Siricidae) - parasitoid complex and development of an optimal sampling scheme. Environ. Entomol. 40: 1266-1275.

Liu, Z., and G. Nordlander.  (1992)  Ibaliid parasitoids of siricids woodwasps in North America: two new Ibalia species and a key to species (Hymenoptera: Cynipoidea).  Proc. Entomol. Soc. Wash. 94: 500-507.

Long, S. J., D. W. Williams, and A. E. Hajek. (2009) Sirex species (Hymenoptera: Siricidae) and their parasitoids in Pinus sylvestris in eastern North America. Can. Entomol. 141: 153-157.
Norton, E.  (1963)  A description of several new Hymenoptera.  Proceedings of the Entomological Society of Philadelphia 1: 198-200.

Ryan, K., P. de Groot, R. W. Nott, S. Drabble, I. Ochoa, C. Davis, S. M. Smith, and J. J. Turgeon. (2012) Natural enemies associated with Sirex noctilio (Hymenoptera: Siricidae) and S. nigricornis in Ontario, Canada. Environ. Entomol. 41: 289-297.

Schiff, N. M., H. Goulet, D. R. Smith, C. Boudreault, A. D. Wilson, and B. E. Scheffler. (2012) Siricidae (Hymenoptera: Symphyta: Siricoidea) of the Western Hemisphere. Can. J.  Arthropod Ident. 21: 1-305.

Smith, D. R., and N. M. Schiff. (2002) A review of the siricid woodwasps and their ibaliid parasitoids (Hymenoptera: Siricidae, Ibaliidae) in the eastern United States, with emphasis on the mid-Atlantic region. Proc. Entomol. Soc. Wash. 104: 174-194.

Taylor, K. L. (1976) The introduction and establishment of insect parasitoids to control Sirex noctilio in Australia. Entomophaga 21: 429-440.

Weld, L. H. (1952) Cynipoidea (Hym.) 1905-1950.  Privately printed, Ann Arbor, MI. 351 pp.

Yoshimoto, C. M. (1970) A new ibaliid wasp from North America (Hymenoptera: Cynipoidea, Ibaliidae). Can. Entomol. 102: 1196-1198.


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Ibalia leucospoides ensiger.

Photo: Henri Goulet (Agriculture and Agri-Food Canada)








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