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Biocontrol introduction

Target pest: Paropsis charybdis (Coleoptera: Chrysomelidae), eucalyptus tortoise beetle

Agent introduced: Enoggera nassaui (Hymenoptera: Pteromalidae)

Imported: 1987, 2000

Import source: Australia (Western Australia 1987, Tasmania 2000)

Released: 1987-88 (Western Australia strain), 2000 (Tasmania strains)

Release details: Cameron et al. (1989) - in 1987-88 approximately 650 were released at each of Collingwood, Golden Downs and Richmond (Nelson), Longwoods (Southland), Tapanui and Kaitangata (Otago), 1,000 each at Chertsey and Rolleston (Canterbury) 1,500 at Kaingaroa and Maketu (Bay of Plenty) and 2,300 near Tokoroa (Waikato). Kay (1990 - in Murray et al. 2008) - over 100,000 reared and sold to forest managers throughout the country. Withers et al. (2011) - in 2000 two Tasmanian strains (Florentine Valley, Evandale) released in the North Island, including 1000 at Poronui near Taupo.

Establishment: Cameron et al. (1989) - recovered from Maketu and Collingwood. Kay (1990 - in Murray et al. 2008) - with over 100,000 sold to forest managers throughout the country spread quickly. Murphy et al. (2004) - of Tasmanian strains released 2000, Florentine Valley strain detected 2001, but not Evandale strain. However, samples sizes small. Murray et al. (2008) - E. nassaui well established throughout New Zealand. Withers et al. (2011) - Florentine Valley strain established at Poronui (Taupo), Evandale strain not detected, still unclear if latter is established. Hybrids between Florentine Valley and Western Australia strains also found.

Impacts on target: Kay (1990 - in Murray et al. 2008) - E. nassaui spread quickly to provide effective control of P. charybdis in many regions. Murphy and Kay (2000) - low parasitism (<20%) of P. charybdis eggs early in the season (first post-winter generation) but at least 80% parasitism achieved by March. Jones and Withers (2003) - in 2003 in central North Island there was a 50% parasitism rate in early summer, dropping later in the season to 10% as a result of hyperparasitism by Baeoanusia albifunicle. This obligate hyperparasitoid, first detected in New Zealand in 2001, puts effective biological control of P. charybdis by E. nassaui in doubt. Murphy et al. (2004) - erratic control by Western Australia strain of E. nassaui in inland regions of New Zealand led to release in 2000 of two Tasmanian strains to attempt expansion of the climatic range of biocontrol. Withers et al. (2011) - not known if hybridisation of Florentine Valley and Western Australia strains (seen at Poronui) will improve or hinder biocontrol of P. charybdis.

References

Cameron PJ, Hill RL, Bain J and 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.

Jones DC and Withers TM. (2003). The seasonal abundance of the newly established parasitoid complex of the eucalyptus tortoise beetle (Paropsis charybdis). New Zealand Plant Protection 56: 51-55

Murphy BD and Kay MK. (2000). Paropsis charybdis defoliation of Eucalyptus stands in New Zealand's Central North Island. New Zealand Plant Protection 53: 334-338

Murphy BD, Kay MK and Allen GR. (2004). Detection of a Tasmanian strain of the biological control agent Enoggera nassaui Girault (Hymenoptera: Pteromalidae) using mitochondrial COI. New Zealand Plant Protection 57: 252-256

Murray TJ, Withers TM, Mansfield S and Bain J. (2008). Distribution and current status of natural enemies of Paropsis charybdis in New Zealand. New Zealand Plant Protection 61: 185-190

Withers TM, Phillips LD, Bates TEM and Ganley RJ. (2011). Hybridisation between populations of Enoggera nassaui in New Zealand. New Zealand Plant Protection 64: 44-48