Target pest: Cydia molesta (Lepidoptera: Tortricidae) = Grapholita molesta, oriental fruit moth
Agent introduced: Glabridorsum stokesii (Hymenoptera: Ichneumonidae) = Gambrus stokesii, Ischnus stokesii
Cameron et al. (1989) - 11 released at Nelson in 1969. 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 at Appleby, Nelson in 1969-70 and since then in Northland, Auckland, Hamilton and Hawkes Bay. Collected in Christchurch in 1985-86 but its establishment there is uncertain.
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.
Russell (1986, 1987, in Cameron et al. 1989) - G. stokesii parasitises C. molesta in Auckland, but has not been recovered from C. molesta in Hawke's Bay. Parasitism in Auckland varied from 21-73% per generation over the 1982-4 seasons; individual weekly percentage parasitism reached 100% in February 1984. Most common as a parasitoid of C. molesta in the second summer generation of the host; levels of parasitism can be high late in the season but host/parasitoid synchrony is limited by their overwintering habits.
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. G. stokesii was recorded as a minor component (5%) of the parasitoids reared from leafroller larvae of these species collected from oak trees in shelter belts in Hawke's Bay, though was not reported from larvae collected from fruit crops.
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.
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