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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)

Import notes:

Cameron et al. (1989) – approximately 80 E. nassaui adults were imported from Perth, Western Australia in August 1987. They were successfully cultured for field releases.

Murphy et al. (2004) - Enoggera nassaui were collected from paropsine eggs in Tasmania during 1999/2000 and reared on Paropsis aegrota var. elliottii. Live adults and parasitised P. aegrota eggs were sent to New Zealand in May 2000, but only two strains, from the Florentine Valley and Evandale, were established in culture.

Released:

1987 (Western Australia strain), 2000 (Tasmania strains)

Release details:

Cameron et al. (1989) - in 1987-88 approximately 650 E. nassaui were released at each of Collingwood, Golden Downs and Richmond (Nelson, South Island), Longwoods (Southland, South Island), Tapanui and Kaitangata (Otago, South Island), approximately 1,000 at each of Chertsey and Rolleston (Canterbury, South Island), approximately 1,500 at each of Kaingaroa and Maketu (Bay of Plenty, North Island) and approximately 2,300 near Tokoroa (Waikato, North Island).

Kay (1990 - in Murray et al. 2008) - over 100,000 were reared and sold to forest managers throughout the country for release.

Murphy et al. (2004) - Tasmanian E. nassaui were released at four central North Island sites during November 2000 as follows: Kinleith Forest (Waikato) 1,000 Florentine Valley strain, 100 Evandale strain; Poronui Station (near Taupo, Waikato) 1,000 Florentine Valley, 1,000 Evandale; Kaingaroa Forest (Waikato/Bay of Plenty) 1,200 Florentine Valley, 800 Evandale; Rotorua (Bay of Plenty) 300 Florentine Valley, 300 Evandale. Releases consisted of approximately equal numbers of free adults and parasitised eggs hung in plastic containers from foliage.

Establishment:

Cameron et al. (1989) - Enoggera nassaui has been recovered from Maketu (Bay of Plenty, North Island) and Collingwood (Nelson, South Island). In October 1988 adults were observed ovipositing in P. charybdis eggs at Colllingwood, so the parasitoid has definitely established at least in this area.

Kay (1990 - in Murray et al. 2008) - with over 100,000 sold to forest managers throughout the country E. nassaui spread quickly.

Murphy et al. (2004) - of Tasmanian strains released in 2000, the Florentine Valley strain was detected 2001, but not the Evandale strain. However, samples sizes were small.

Murray et al. (2008) - Enoggera nassaui is well established throughout New Zealand.

Withers et al. (2011) - sampling in 2010 at the Poronui (Taupo, North Island) release site indicates the Florentine Valley strain has established there; the Evandale strain was not detected and it is still unclear if latter is established. Hybrids between the Florentine Valley and the Western Australia strains were also found.

Mansfield et al. (2011) - we do not know to what extent the Tasmanian biotype has been able to establish or spread within the population of E. nassaui that is widespread throughout New Zealand. Until shown otherwise we assume that the original Perth biotype remains the dominant biotype and is still responsible for the majority of parasitism recorded on P. charybdis.

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) - severe problems with P. Charybdis defoliation can still occur in the Central North Island region of New Zealand. Enoggera nassaui may be inadequately adapted to conditions in some parts of New Zealand due to introductions originating from frost-free areas in Western Australia. Paropsis Charybdis outbreaks seen in problem sites appear to result from poor spring parasitism by E. nassaui, with low parasitism (<20%) of P. Charybdis eggs early in the first post-winter generation. However, high parasitism rates in the late season period (at least 80% by March) prevent a second period of larval defoliation that would otherwise occur.

Withers (2001) - the control of P. charybdis achieved by E. nassaui has been impressive, particularly throughout warmer regions of New Zealand.

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) - the apparent dominance of the Florentine Valley strain at Poronui Station (Taupo), only 10 years after release, could suggest this strain has some ecological advantage over the Western Australian strain. If so, this might benefit the biocontrol of P. charybdis elsewhere in New Zealand. It is not known if hybridisation of Florentine Valley and Western Australia strains (seen at Poronui) will improve or hinder biocontrol of P. charybdis.

Mansfield et al. (2011) - field parasitism rates monitored over three summers (2002-2005) in the Bay of Plenty and Taupo regions of the central North Island showed suppression of P. charybdis was still not consistent across both host generations although in two of the three seasons total parasitism (dominated by E. nassaui) in December was higher (up to 50%) than that reported previously (<20%, Murphy and Kay, 2000). This increase in early parasitism may reflect the introduction of the cool-adapted (Tasmanian) strain of E. nassaui or local adaptation of the parasitoid population to the prevailing climate.

Withers, Todoroki et al. (2020) - current biological control agents (mainly the egg parasitoids E. nassaui and Neopolycystus insectifurax) have proven to be inadequate in controlling the first (spring) of two generations that P. charybdis undergoes.

Pugh et al. (2020) - P. charybdis egg parasitism was monitored at two Eucalyptus nitens plantations in the central North Island between November 2016 and April 2017. P. charybdis egg production peaked in mid‐late November and again in early February at both sites. The spring generation of P. charybdis escaped egg parasitism entirely. Levels of egg parasitism increased substantially from January onwards, peaking at 50–68% in March/April. Enoggera nassaui and its hyperparasitoid Baeoanusia albifunicle, as well as the P. charybdis parasitoid Neopolycytus insectifurax, were active at both sites. Enoggera nassaui was the first parasitoid to appear and remained present intermittently at low densities throughout the monitoring period. Neopolycytus insectifurax was the primary egg parasitoid in the second generation of P. charybdis.

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.

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

Mansfield S, Murray TJ, Withers TM. (2011). Will the accidental introduction of Neopolycystus insectifurax improve biological control of the eucalyptus tortoise beetle, Paropsis charybdis, in New Zealand? Biological Control 56: 30-35 https://doi.org/10.1016/j.biocontrol.2010.09.008

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

Pugh AR, Withers TM, Peters EM, Allen GR, Phillips CB. (2020). Why introducing a parasitoid of Paropsis charybdis Stål, 1860 (Coleoptera: Chrysomelidae) larvae is expected to enhance biological control of this Eucalyptus pest in New Zealand. Austral Entomology 59(4): 829-837 https://doi.org/10.1111/aen.12492

Withers TM (2001). Colonization of eucalypts in New Zealand by Australian insects. Austral Ecology 26: 467-476 https://doi.org/10.1046/j.1442-9993.2001.01140.x

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

Withers TM, Todoroki CL, Allen GR, Pugh AR, Gresham BA. (2020). Host testing of Eadya daenerys, a potential biological control agent for the invasive chrysomelid pest Paropsis charybdis, predicts host specificity to eucalypt-leaf feeding Paropsina. BioControl 65(1): 25-36. Published online: 02 November 2019. https://doi.org/10.1007/s10526-019-09978-6