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Biocontrol introduction

Target pest: Phyllonorycter messaniella (Lepidoptera: Gracillariidae) = Lithocolletis messaniella, oak leaf-miner

Agent introduced: Achrysocharoides splendens (Hymenoptera: Eulophidae) = Enaysma splendens

Imported:

1957

Import source:

Switzerland

Import notes:

Cameron et al. (1989) - from a 1955-57 investigation of parasitoids of P. messaniella in Europe, two parasitoid species, A. splendens (then called Enaysma splendens) and Apanteles circumscriptus group [subsequently renamed Pholetesor circumscriptus - see the P. circumscriptus group introduction entry], were selected for importation into New Zealand as biocontrol agents. Six hundred and twenty-six A. splendens pupae collected in Switzerland were imported in October/November 1957, from which 352 adults emerged.

Released:

1957-58

Release details:

Cameron et al. (1989) - adult A. splendens emerging from imported pupae were released in Nelson, South Island into field cages containing P. messaniella-infested oak leaf clusters. Cages were removed after four to five days. Leaves containing diapausing pupae were transferred from the field cage site to an oak plantation at Stoke (Nelson) in the winter of 1958. A large number of adults emerging from infested leaf clusters in the laboratory were further distributed to many districts in New Zealand during the next two years.

Establishment:

Cameron et al. (1989) - a sampling programme confirmed that A. splendens established soon after its initial release.

Impacts on target:

Cameron et al. (1989) - in Nelson, population levels of P. messaniella declined rapidly in the years following the successful establishment of A. splendens and especially Apanteles circumscriptus group [subsequently renamed Pholetesor circumscriptus, also released against P. messaniella around the same time as A. splendens - see the P. circumscriptus group introduction entry]. By the mid-1960s the host range of P. messaniella had also reduced and the species could not be found in Nelson on native beech Nothofagus spp. [since 2013 placed in the genera Fuscospora and Lophozonia] or apple trees. A 1973 publication reported total parasitism of 30-80% in P. messaniella populations on deciduous oaks in Christchurch, Canterbury. Pholetesor circumscriptus group was the most abundant parasitoid although A. splendens was of almost equal importance where low host populations occurred. The same publication reported a decline in P. messaniella mines on Quercus robur [English oak] in Nelson from more than 40 per leaf prior to the release of the parastoids to around 2.3 per leaf in 1969-70. The introduction of P. circumscriptus group and A. splendens is probably one of the best examples of successful classical biocontrol in New Zealand. The parasitoids rapidly reduced P. messaniella to insignificant levels and have provided effective control until the present day.

Cameron et al. (1993) - Achrysocharoides splendens, in conjunction with Apanteles circumscriptus group, [subsequently renamed Pholetesor circumscriptus - see the P. circumscriptus group introduction entry] is categorised as exerting ‚Äúcomplete‚ÄĚ control (defined as ‚Äúcontrol of the target over an extensive area so that pest outbreaks are rare or other control treatments are rarely necessary‚ÄĚ) over P. messaniella.

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