Target pest: Epiphyas postvittana (Lepidoptera: Tortricidae), light brown apple moth
Agent introduced: Glabridorsum stokesii (Hymenoptera: Ichneumonidae) = Gambrus stokesii, Ischnus stokesii
Cameron et al. (1989) - parasitised E. postvittana pupae were collected in eastern Australia and Tasmania in 1967 and 1969 and imported into quarantine at Nelson. Eight G. stokesii emerged in 1967; 34 emerged in 1969, of which 11 were directly released. It was cultured successfully and reared individuals were also released.
Cameron et al. (1989) - in 1969, 11 adults were released into field cages at Nelson. Releases were made in 1967-73 at Kerikeri, Hamilton, Kaingaroa Forest, Rotorua, Nelson and Christchurch. In 1972, 1979-80 and 1985 it was redistributed to Christchurch.
Cameron et al. (1989) - established in Nelson 1969-70, and is established in Northland, Auckland, Hamilton and Hawkes Bay. The redistribution to Christchurch in 1972 and 1979-80 failed to achieve establishment. Late-spring releases in Christchurch in 1985 led to at least two field generations in the summer of 1985-86, but there is no recent evidence of establishment in Canterbury.
Sandanayaka et al. (2017), Charles et al. (2019) - found parasitising codling moth (Cydia pomonella) [another target pest for G. stokesii] in Nelson, Central Otago and Hawke's Bay while monitoring for the codling moth biocontrol agent Mastrus ridens.
Impacts on target:
C.J.Green (1984, in Cameron et al. 1989) - little interaction of the introduced parasitoids G. stokesii, Trigonospila brevifacies and Xanthopimpla rhopaloceros with hosts on apple trees in Auckland. No evidence of 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, with increased biological control considered a key contributing factor. From the 1994-1999 and 2008-2011 leafroller larvae collections, G. stokesii was not reported as a component of the parasitoid guild reared from three fruit crops (apple, grape, boysenberry), but was a minor component (5%) of the parasitoids reared from oak trees in shelter belts.
Impacts on non-targets:
Cameron et al. (1989) - G. stokesii has been recorded from the New Zealand native torticids Ctenopseustis obliquana in the Bay of Plenty, and Ctenopseustis obliquana sensu latu and Planotortrix excessana sensu latu in Nelson. [These leafrollers are significant orchard pests.] Glabridorsum stokesii is the most common introduced parasitoid of leafroller pupae in Nelson. However, while native hosts are parasitised, at least in some habitats, there is no evidence that this is affecting the population dynamics of these species.
Lo et al. (2018) - the New Zealand endemic leafrollers Planotortrix octo (greenheaded leafroller) and Ctenopseustis obliquana (brownheaded leafroller) have declined in orchards, vineyards and shelterbelts (where they are pests), at least partly as a result of introduced biological control agents [see Lo et al. (2018) entry in 'Impact on target' section, and Cameron et al. (1993) entry in 'General comments' section]. G. stokesii was recorded as a minor component (5%) of the parasitoids reared from leafroller larvae of these species (and Epiphyas postvittana) collected from oak trees in shelter belts in Hawke's Bay, though was not reported from larvae collected from fruit crops.
Cameron et al. (1993) - native pest species were included as targets in the 1967-69 programme against E. postvittana. In this programme, alternative tortricid hosts (including E. postvittana outside orchards) were considered to provide overwinter reservoirs from which G. stokesii may reinvade orchards. 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.
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
Charles JG, Sandanayaka WRM, Walker JTS, Shaw PW, Chhagan A, Cole LM, Colhoun K, Davis VA, Wallis DR (2019). Establishment and seasonal activity in New Zealand of Mastrus ridens, a gregarious ectoparasitoid of codling moth Cydia pomonella. BioControl 64: 291â€“301 https://doi.org/10.1007/s10526-019-09939-z
Lo PL, Walker JTS, Hedderley DI, Cole LM. (2018). Reduction in leafroller (Lepidoptera: Tortricidae) abundance in orchards and vineyards 1976-2016, in Hawke's Bay, New Zealand. Agricultural and Forest Entomology 20 (4): 505-513
Sandanayaka M, Charles J, Davis V, Chhagan A, Shaw P, Wallis R, Lo P, Cole L, Walker J, Colhoun K. (2017). Establishment of Mastrus ridens (Hymenoptera: Ichneumonidae), an ectoparasitoid of codling moth, in New Zealand. Proceedings of the 5th International Symposium on Biological Control of Arthropods, Langkawi, Malaysia, September 11-15, 2017: 85-87 https://www.cabi.org/cabebooks/FullTextPDF/2017/20173267456.pdf