Target pest: Phyllonorycter messaniella (Lepidoptera: Gracillariidae) = Lithocolletis messaniella, oak leaf-miner
Agent introduced: Pholetesor circumscriptus group (Hymenoptera: Braconidae) = Apanteles circumscriptus group
Cameron et al. (1989) - from a 1955-57 investigation of parasitoids of P. messaniella in Europe, two parasitoid species, P. circumscriptus [then Apanteles circumscriptus] and Achrysocharoides splendens [see the A. splendens introduction entry], were selected for importation into New Zealand as biocontrol agents. Nine hundred and fifty-four pupal cocoons, labelled as A. circumscriptus (though better referred to as A. circumscriptus group [or now, Pholetesor circumscriptus group]) [see Cameron et al. (1989) and Valentine & Walker (1991) entries in ‚ÄėGeneral comments‚Äô section], collected in Italy were imported in March/April 1957, from which 806 females and five males emerged.
Cameron et al. (1989) - Pholestesor circumscriptus group adults emerging from imported pupae were released in autumn 1957 in Nelson, South Island into field cages containing P. messaniella-infested oak leaf clusters. Cages were removed after four to five days, at which time parasitism levels of up to 50% were recorded. A comprehensive distribution programme followed during the next two years, with large numbers sent to many districts in New Zealand.
Cameron et al. (1989) - sampling in the winter and spring of 1957 following the autumn releases in Nelson confirmed the establishment and slow spread of P. circumscriptus group.
Impacts on target:
Cameron et al. (1989) - in Nelson, population levels of P. messaniella declined rapidly in the years following the successful establishment of Achrysocharoides splendens [also released against P. messaniella around the same time as P. circumscriptus group - see the A. splendens introduction entry] and especially Pholetesor circumscriptus group. 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 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 Pholetesor 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) - Pholetesor circumscriptus group, in conjunction with Achrysocharoides splendens [see the A. splendens 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.
Cameron et al. (1989) - since the 1957 importation of what was considered at the time to be Apanteles circumscriptus, the circumscriptus group of Apanteles has been revised (by Nixon in 1973) [and has subsequently been placed in the genus Pholetesor]. In 1978, two consignments totalling 200 field-collected Apanteles [now Pholetesor] spp. cocoons were sent from New Zealand to Canada for the biocontrol of Phyllonorycter blancardella. Subsequent identification indicated the first shipment contained only A. arisba and the second only A. bicolor [now Pholetesor arisba and P. bicolor]. If these identifications are correct, the consignments imported to New Zealand from Europe in 1957 presumably contained a mixture of Apanteles [Pholetesor] spp. The true identity of the parasitoids attacking P. messaniella in New Zealand remains to be resolved; until then they should be referred to as A. circumscriptus [P. circumscriptus] group.
Valentine & Walker (1991) - Pholetesor bicolor and P. arisba were introduced into New Zealand from Italy in 1957 (to control P. messaniella) as Apanteles circumscriptus [now Pholetesor circumscriptus]. When ‚Äúcircumscriptus‚ÄĚ was introduced from New Zealand to Canada in 1978 the consignments were identified as Apanteles pedias and A. arisba [now Pholetesor bicolor and P. arisba, respectively], the latter described by Nixon from Europe in 1973 and very similar in structure to circumscriptus. Until New Zealand Pholetesor are examined in more detail, the presence of circumscriptus in this country is open to question.
Taxonomic note (22 July 2023) - Fernandez-Triana et al. (2019) indicate that the question of which Pholetesor spp. are present in New Zealand is unresolved at the time of their publication.
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
Fernandez-Triana J, Shaw MR, Boudreault C, Beaudin M, Broad GR (2020). Annotated and illustrated world checklist of Microgastrinae parasitoid wasps (Hymenoptera, Braconidae). ZooKeys 920: 1-1089 https://doi.org/10.3897/zookeys.920.39128
Valentine EW, Walker AK (1991). Annotated catalogue of New Zealand Hymenoptera. New Zealand Dept. of Scientific and Industrial Research, Plant Protection Report No. 4