Biocontrol introduction

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

Agent introduced: Neopolycystus insectifurax (Hymenoptera: Pteromalidae)

Imported:

1934, 1987 [the 1934 importation was identified only at the genus level and the 1987 importation subsequently determined to be N. sp., not N. insectifurax - see Cameron et al. (1989) and Berry (2003) in 'Import Notes' section]

Import source:

Australia

Import notes:

Cameron et al. (1989) - in March 1934 a small consignment of field-collected Paropsis atomaria eggs was imported from Australia; five Neopolycystus adults emerged and one of the females successfully parasitised P. Charybdis eggs in the laboratory. No releases were made. In June 1987 approximately 400 adult N. neopolycystus were received from Perth, Western Australia. These were successfully cultured in quarantine and the progeny released.

Berry (2003) - comparison of 1987-imported specimens with 2003 New Zealand field specimens [see Jones & Withers (2003) in 'Establishment' section] showed the former were N. sp., the latter N. insectifurax. It is possible that N. insectifurax has established accidentally, the most probable route being inside eggs of its host on plant material.

Released:

1987

Release details:

Cameron et al. (1989) - between November 1987 and March 1988, approximately 650 were released at each of three sites in Nelson, South Island (Collingwood, Golden Downs and Richmond), approximately 1,000 at Chertsey (Canterbury, South Island), approximately 1,500 at each of two Bay of Plenty, North Island sites (Kaingaroa and Maketu) and approximately 2,300 near Tokoroa (Waikato, North Island) [NB: subsequent identification - see Berry (2003) in 'Import Notes' section - showed these were N. sp., not N. insectifurax].

Jones and Withers (2003) - following the discovery of N. insectifurax in the field in New Zealand in 2008, they were mass-reared and released in the central North Island over the summer of 2002/03 in an attempt to increase distribution.

Establishment:

Cameron et al. (1989) - so far no recoveries of Neopolycystis have been made.

Jones & Withers (2003) - Neopolycystsus insectifurax has been found parasitising P. charybdis in New Zealand; these are the result of a probably accidental self-introduction [see Berry (2003) in 'Import Notes' section].

Mansfield et al. (2011) - Neopolycystus insectifurax has been reared from field-collected eggs of P. charybdis in both the North and South Islands.

Toni Withers (Scion, pers. comm. 2014) - extensive monitoring of P. charybdis eggs through the 1990s failed to find Neopolycystus parasitism, supporting the conclusion that the Neopolycystus sp. released 1987-88 [see Berry (2003) in 'Import Notes' section] did not establish and the N. insectifurax field specimens collected in 2003 [see Jones & Withers (2003) above] represented a recent self-introduction.

Impacts on target:

Jones and Withers (2003) - Neopolycystus insectifurax i.e. the self-introduced population [see Berry (2003) in 'Import Notes' section], parasitised 35-100% of eggs in late summer in central North Island, and thus appears to be an effective second post-winter generation egg parasitoid.

Mansfield et al. (2011) - field parasitism rates of P. charybdis eggs monitored over three summers (2002-2005) in the Bay of Plenty and Taupo regions of the central North Island showed N. insectifurax the dominant parasitoid by late summer for two of the summers. On average the parasitoid Enoggera nassaui appeared first, Baeoanusia albifunicle (a hyperparasitoid of E. nassaui) a month later, and N. insectifurax after another month. P. charybdis egg parasitism was highest towards the end of summer (usually >70%) with all three parasitoids present. However, prior to the establishment of N. insectifurax in New Zealand, parasitism by E. nassaui alone was at a similar level (>80%) at the same point in time (Murphy and Kay, 2000). Therefore, there is no strong evidence that the accidental arrival of N. insectifurax has improved biological control of P. charybdis beyond the levels achieved by E. nassaui alone because N. insectifurax has not increased parasitism during the first host generation. However the introduction of N. insectifurax was fortuitous in that it compensates for the negative effect of the hyperparasitoid's arrival (around the same time N. insectifurax arrived in New Zealand) on E. nassaui populations during the second host generation.

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

Pugh et al. (2020) - Paropsis charybdis egg parasitism was monitored at two Eucalyptus nitens plantations in the central North Island between November 2016 and April 2017. 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. Neopolycytus insectifurax, as well as the P. charybdis parasitoid Enoggera nassaui and its hyperparasitoid Baeoanusia albifunicle, 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 appeared later and became the primary egg parasitoid in the second generation of P. charybdis, providing a very useful level of control over that generation.

References

Berry JA. (2003). Neopolycystus insectifurax Girault (Hymenoptera: Pteromalidae) is established in New Zealand, but how did it get here? New Zealand Entomologist 26: 113-114

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

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, 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