Biocontrol introduction
Target pest: Sirex noctilio (Hymenoptera: Siricidae), sirex wood wasp
Agent introduced: Ibalia leucospoides ensiger (Hymenoptera: Ibaliidae)
Imported:
1963, 1966-1968
Import source:
California (1963), USA via Tasmania (1966-68)
Import notes:
Cameron et al. (1989) - in 1963, 19 male and 24 female adults were received from CIBC station in California. Many were carrying mites which were removed with a fine brush dipped in alcohol. The wasps were sluggish, oviposition was not observed and no progeny were obtained. In 1966 (110 males, 100 females), 1967 (188 males, 186 females) and 1968 (99 males, 98 females) were received from CSIRO, Tasmania, from cultures sent there from USA in 1963. All 1966 specimens were used for insectary culture, although 33 females were released after oviposition. Fifty of each sex received in 1967, and 23 males and 24 females received in 1968, were retained for insectary culture and the rest released. Culturing ceased in 1970.
Released:
1966
Release details:
Cameron et al. (1989) - not released from the 1963 importation. In 1966, 33 imported females (after oviposition in insectary) were released at Berwick (Otago, South Island). In 1967, releases were made at Omihi (North Canterbury, South Island) and in the North Island at Kaingaroa (Bay of Plenty), and Tahorakuri (near Taupo), and in 1968 in the Otago Coast Forest (south of Dunedin) and at Ashley (North Canterbury). The 1967 and 1968 releases comprised a mix of imported adults and insectary emergents. Liberation of reared specimens continued to 1971 when the last release was made at Motueka (Nelson). In total 1,883 males and 1,729 females were released in 14 forests.
Establishment:
Cameron et al. (1989) - first recovered in 1968. Recoveries have been made from 6 of the 14 forests it was released in but because of inbreeding with Ibalia leucospoides leucospoides it has not been recognised in collections since 1976. [But see Hurley et al. (2020) entries below and in 'General comments' section.]
Hurley et al. (2020) - an investigation of I. leucospoides in its native and introduced ranges found no evidence that the subspecies I. leucospoides ensiger has established (or hybridised with I. l. leucospoides) outside its native range. [Note though, that specimens from the introduced range used in the study did not include insects from New Zealand; only South Africa, Chile, Argentina and Australia.]
Impacts on target:
Cameron et al. (1989) - the presence of successfully introduced parasitoids [including I. l. ensiger], together with the accidentally introduced nematode Deladenus siricidicola [subsequently reclassified as Beddingia siricidicola] and good forest management has been effective in keeping losses caused by S. noctilio at a low level. The combined effect of the introduced parasitoids may kill over 70% of S. noctilio larvae in a particular forest. [But see the Hurley et al. (2020) entries in the ‘Establishment’ and ‘General comments’ section relating to the possibility that I. l. ensiger is not established in New Zealand.]
Cameron et al. (1993) - Ibalia leucospoides ensiger, in conjunction with Rhyssa persuasoria persuasoria, Ibalia leucospoides leucospoides and Megarhyssa nortoni nortoni [see the R. p. persuasoria, I. l. leucospoides and M. n. nortoni introduction entries], is categorised as exerting “partial” control (defined as “additional control remains commonly necessary but…pest outbreaks occur less frequently”) over Sirex noctilio. [But see the Hurley et al. (2020) entries in the ‘Establishment’ and ‘General comments’ section relating to the possibility that I. l. ensiger is not established in New Zealand.]
General comments:
Cameron et al. (1989) - Ibalia leucospoides ensiger is known to interbreed with the well established I. l. leucospoides [also introduced against S. noctilio] and separate populations in New Zealand cannot be recognised. [But see the Hurley et al. (2020) entry below.]
Hurley et al. (2020) - two sub-species of the parasitoid I. leucospoides (I. l. leucospoides and I. l. ensiger) have been introduced to the southern hemisphere as a biological control agent for Sirex noctilio and are reported to have hybridised. However, an investigation of the genetic variation of I. leucospoides in its native and introduced ranges using mitochondrial (COI) and nuclear (ITS) markers found no evidence of hybridisation between the two sub-species of the parasitoid in its introduced range. [Note though, that specimens from the introduced range used in the study did not include insects from New Zealand, only South Africa, Chile, Argentina and Australia.]
References
Cameron PJ, Hill RL, Bain J, Thomas WP (1989). A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424p.
Cameron PJ, Hill RL, Bain J, Thomas WP (1993). Analysis of importations for biological control of insect pests and weeds in New Zealand. Biocontrol Science and Technology 3(4): 387-404
Hurley BP, Fitza KNE, Wingfield MJ, Slippers B. (2020). Sequence data reflect the introduction pathways of the Sirex woodwasp parasitoid, Ibalia leucospoides (Ibaliidae, Hymenoptera). Agricultural and Forest Entomology 22(2): 129-135 https://doi.org/10.1111/afe.12367
