Target pest: Epiphyas postvittana (Lepidoptera: Tortricidae), light brown apple moth
Agent introduced: Trigonospila brevifacies (Diptera: Tachinidae)
Cameron et al. (1989) - parasitised E. postvittana larvae and pupae were collected in eastern Australia and Tasmania in 1967 and 1969 and imported into quarantine at Nelson. Forty-one T. brevifacies emerged in 1967, of which 39 were directly released; 49 emerged in 1969, of which 20 were directly released. It was cultured successfully and reared individuals were also released.
Cameron et al. (1989) - 39 (1967) and 20 (1969) adults were released into tree cages enclosing E. postvittana infestations at Appleby, Nelson. Subsequent releases were made until 1972 at Kerikeri, Hamilton, Tauranga, Nelson and Christchurch. It was redistributed to Havelock North, Christchurch and Nelson in 1981-82 and Christchurch in 1987.
Cameron et al. (1989) - adults of a new generation were observed in September 1967 at Appleby, but the parasitoid failed to become established at this locality. First reported established in Kerikeri in 1972. Since then it has spread to many regions in the North Island and is found as far south as Levin.
Munro (1998) - Trigonospila brevifacies has established throughout the North Island. There were no records of it having established at South Island sites by 1997. However, in the summer of 1997/98 several were collected at Nelson. Because there were no post-release records of T. brevifacies in the South Island it is assumed that it has recently colonised the South Island from the North Island. Trigonospila brevifacies is also present on the Alderman Islands, Three Kings Island, Poor Knights Island, the Mercury Islands and Kapiti Island.
Impacts on target:
Cameron et al. (1989) - a PhD study by C.J.Green in 1984 showed little interaction of the introduced parasitoids T. brevifacies, Xanthopimpla rhopaloceros and Glabridorsum stokesii with hosts on apple trees in Auckland. The study failed to show any regulatory role of these parasitoids, except perhaps for parasitism of Cydia molesta (oriental fruit moth) by G. stokesii. The circumstantial evidence of reduction in archipine tortricid populations in orchards has not been quantified.
Lo et al. (2018) - a study to measure changes in the abundance and pest status of three leafroller species, the introduced Epiphyas postvittana and the endemic Planotortrix octo (greenheaded leafroller) and Ctenopseustis obliquana (brownheaded leafroller), in fruit growing areas of Hawke's Bay between 1976 and 2016, showed populations of all three species decreased substantially; however, P. octo and C. obliquana declined to a much greater extent than E. postvittana. Leafrollers damaged over 20% of apples receiving no insecticides during the 1980s but, subsequent to 2000, damage has been below 2%. Between 1994 and 1999 and 2008-2011, the numbers of immature leafrollers in searches on fruit crop and non-crop hosts decreased by 55% and the mean percentage of leafrollers parasitised per sample increased from 51% to 70%. The reduction in leafroller populations can be attributed to two key factors: increased biological control and the replacement of broad-spectrum insecticides with selective insecticides. In 1974-75, parasitism of leafroller larvae on fruit crops was 13%; in the 2000s, 69%. The decline in importance of leafrollers as pests has occurred on managed and unmanaged orchards, vineyards, and on non-crop shelter plants. In the 1970s and 1980s, leafrollers and their associated damage were highly visible on Hawke's Bay orchards, whereas, currently, they are difficult to find, even on unsprayed trees. From the 1994-1999 and 2008-2011 leafroller larvae collections, 4% of parasitoids reared from three fruit crops (apple, grape, boysenberry), and 62% from oak trees in shelter belts, were T. brevifacies.
Impacts on non-targets:
Green (1984) - T. brevifacies is recorded from the endemic tortricids Ctenopseustis obliquana (Walker), "Cnephasia" jactatana (Walker) and Epalxiphora axenana Meyrick, as well as the natives Platyptilia falcatalis Walker [syn. Amblyptilia falcatalis] (Lepidoptera: Pterophoridae), Hierodoris atychioides (Butler) (Lepidoptera: Oecophoridae), Staphmopoda "skelloni" (Butler) (Lepidoptera: Staphmopodidae) and an identified species of Lepidoptera: Psychidae. It has also been reared from a mixed collection of larvae including the natives Pasiphila lunata (Philpott) (Lepidoptera: Geometridae) and the pterophorid Aciptilia monospilalis Walker [syn. Pterophorus monospilalis]. These records show that T. brevifacies is by no means restricted to tortricid hosts from orchard habitats in New Zealand [for impacts in orchards see Lo et al. (2018) entry in 'Impacts on target' section, and Cameron et al. (1993) entry in 'General comments' section]. Adult T. brevifacies have been found in native forest in Northland and Auckland.
Roberts (1986) - hard data are lacking, but the spread of T. brevifacies seems to be associated with a decline in abundance of some native leafrollers. For example, the leafroller species which was previously common on mangroves is now very hard to find, and of those which are found, a very high percentage are parasitised by T. brevifacies. In addition, the increase in T. brevifacies seems to have been associated with a decline in abundance of the parasitoid Xanthopimpla rhopalocerus [introduced as a biocontrol agent for E. postvittana] in Auckland gardens, though there is no reason to believe it has been completely replaced.
Cameron et al. (1989) - the native oecophorid Stathmopoda horticola is also reported as a host of T. brevifacies. It was known from the outset that this parasitoid accepted a range of archipine tortricids as hosts but it has adapted to an additional range of hosts in other lepidopteran families. Concern has been expressed at the broad host range of introduced Australian parasitoids like T. brevifacies. It is very unlikely that any host species will become extinct as a result of their activities, but some species in some habitats have probably been reduced in abundance during the early "explosive" phase of parasitoid establishment. Native hosts affected in this way will probably increase in numbers again as parasitoid numbers decline. There is no evidence that native host population dynamics have been affected, though no detailed studies have been undertaken.
Berry (1990) - the parasitoid complex reared from field-collected specimens of the native oecophorid moth Hierodoris atychioides was dominated by the introduced parasitoids Trigonospila brevifacies and Xanthopimpla rhopaloceros.
Cameron et al. (1993) - in New Zealand, T. brevifacies is the only parasitoid introduced for biocontrol recorded attacking non-pest native species in an unpredicted manner and the only introduced biocontrol agent that is thought to have negative effects on non-target non-pest species. It has been reared from six lepidopteran families [see the Green (1984) entry above in this section] in a wide range of arboreal habitats. Its impact has not been assessed but suggestions that it affects populations of a mangrove tortricid Planotortrix avicenniae [see the Roberts (1986) entry above in this section] support the need for an evaluation. Although it is commonly reared from alternative native hosts, it is unknown whether this parasitism has any effect on their abundance.
Munro (1997) - Eutorna phaulocosma Meyrick (Lepidoptera: Oecophoridae) (an accidentally introduced Australian moth and a minor pest of cane fruit crops) is identified as a new host of T. brevifacies. This parasitoid is found throughout the North Island in a range of habitats including orchards, urban gardens, exotic forest, farmland and native forest, where it has acquired a wide host range. Records to March 1996 indicate that it parasitises 14 species (10 of which are pests) from five families (Oecophoridae, Tortricidae, Pterophoridae, Geometridae and Stathmopodidae). In Australia five species from three families (Tortricidae, Pyralidae and Gelechiidae) are parasitised.
Munro (1998) - since many offshore islands in New Zealand function as conservation areas for native plants and animals, it is of concern that T. brevifacies has established on some of these islands.
Mauchline & Withers (2000), Withers (2001) - Trigonospila brevifacies heavily parasitises Strepsicrates macropetana (Eucalyptus leafroller) in New Zealand; parasitism of leafroller pupae can be as high as 45%. Strepsicrates macropetana is a pest in New Zealand; T. brevifacies and other natural enemies moderate its populations and reduce its pest status.
Munro & Henderson (2002) - the parasitoid guild attacking tortricids in native broadleaf/podocarp forests was studied in the central North Island. Trigonospila brevifacies shared its host range with 12 native and one introduced parasitoid species and all these parasitoid species were less abundant than T. brevifacies. Trigonospila brevifacies attacked the most species of host, was the dominant parasitoid species on all but two host species and had the highest level of parasitism across the host guild, constituting between 15.6 and 79.5% of parasitism occurring on hosts sampled. In forest habitats T. brevifacies may be having undesirable effects on native fauna by displacing native parasitoids through direct competition. Hosts species parasitised, in addition to those mentioned previously in this section, were Planotortrix octo, P. excessana, P. notophaea, Apoctena flavescens and Strepsicrates ejectana.
Cameron et al. (1993) - native tortricid pest species were included as targets in the 1967-69 programme against E. postvittana. By 1984, changing attitudes to conflicts between conservation and biological control were recognized and more specific consideration was given to the preservation of non-target native species.
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