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Biocontrol introduction

Target pest: Cydia pomonella (Lepidoptera: Tortricidae), codling moth

Agent introduced: Mastrus ridens (Hymenoptera: Ichneumonidae) = Mastrus ridibundus


2009, 2018

Import source:

Kazakhstan (via USA and Argentina) 2009, Kazakhstan (via Chile) 2018

Import notes:

Sandanayaka et al. (2018) - since the importation of M. ridens from Argentina in 2009 a laboratory population had been maintained at the New Zealand Institute for Plant and Food Research Limited in Auckland on diapausing codling moth cocoons.

Sandanayaka et al. (2022) - the 2009 importation descended from parasitoids that were field-collected in Kazakhstan from 1993 to 1998 and subsequently reared in laboratories in the USA (California) and then Argentina. The colony originating from this importation has been maintained at a laboratory at the New Zealand Institute for Plant and Food Research Limited for over 130 generations since its importation. In November 2018, 125 pupae were imported into New Zealand from a Chilean colony descended from parasitoids collected from two different field locations in Almaty, Kazakhstan, in September 2015 and subsequently maintained at a laboratory in Chile (Fruit Crops Entomology, Pontificia Universidad de Chile, Santiago) for approximately 40 generations. Crossing trials between the Argentina- and Chile-sourced populations were undertaken to see if genetic diversity of the current M. ridens population in New Zealand could be improved. No indication of improved trait values in mixed populations of was found, although a maternal effect was detected, with females of the population formed with individuals collected from their place of origin more recently (i.e. the Chile population) having better trait values (e.g. female longevity, reproductive output).


2012 (from Argentine importation), 2020 (from Chilean importation)

Release details:

Vicky Davis (Plant and Food Research, pers. comm. 2014) - numbers and locations released: Oct 2012 - Mar 2013: Hawke's Bay 8,500; Apr 2013: Gisborne 1,600; Jan-May 2014: Hawke's Bay 36,000, Nelson 32,000, Central Otago 16,000.

Sandanayaka et al. (2017) - in addition to the releases noted in the entry above: Jan - May 2015: Hawke's Bay 22,500, Gisborne 14,000, Nelson/Motueka 5,240, Central Otago 28,000, Waikato 970, Wairarapa 1,500; Jan - May 2016: Auckland 39,000; Feb - Mar 2017: Waikato 22,800.

Sandanayaka et al. (2018) - over a period of 5 years from 2012 to 2017 nearly 243,000 adult M. ridens (from the 44th to the 80th generations of the parasitoid reared in culture in New Zealand since 2009) were released into 35 sites across Hawke’s Bay, Gisborne, Nelson, Central Otago, Waikato, Wairarapa and 17 sites in greater Auckland [see previous entries for details]. Release sites were abandoned or poorly managed commercial blocks of apples, or ‘home-garden’ orchards, without insecticide sprays. Most releases were made during the period between January and March when there was an abundance of flowering plants (mostly weeds) present, providing a local source of nutrition for the adult parasitoids, and cocooning codling moth larvae were likely to be present.

Mano Sandanayaka (Plant and Food Research, pers. comm. 2022) - individuals from the Chile-sourced population were released January-February 2020 at Nelson (South Island) (3,520 parasitised codling moth larvae over eight sites) and Hawke's Bay (North Island) (2,830 parasitised codling moth larvae at one large site); populations from the Argentina-sourced importation were already established in both regions. An average of four parasitoid adults were expected to emerge from each parasitised codling moth larva.


Sandanayaka et al. (2017), Charles et al. (2019) - monitoring in 2016 at release sites in Hawke's Bay, Gisborne, Nelson/Motueka, Central Otago and Waikato has confirmed M. ridens is established in all these regions except Waikato, where relatively low numbers were released. In 2017 M. ridens was recovered up to 300 m from the original release site, and more recently, in Hawke’s Bay, about 1.5 km from the nearest release site. Monitoring in Waikato and Auckland is continuing in 2017 to confirm establishment.

Impacts on target:

Sandanayaka et al. (2017), Charles et al. (2019) - monitoring between 2014 and 2016 showed M. ridens females attacked hosts from at least September (early spring) until May (autumn). This seasonal activity indicates that they may complete several generations per year (compared with only one or two of its host codling moth), signalling a potentially effective parasitoid. Four other codling moth parasitoids were also recovered during the monitoring (including the extremely polyphagous Dibrachys microgastri, which was found parasitising both codling moth and its parasitoids); the extent to which they may disrupt or enhance biocontrol by M. ridens remains to be investigated.

Charles et al. (2019) - after only 2-5 years since the first releases, M. ridens is not expected to have reached an equilibrium with its host at any release site, and so any impact of the parasitoid on codling moth populations has yet to be determined.

Impacts on non-targets:

Charles & Dugdale (2011), Pipfruit New Zealand Inc. (2011), Charles et al. (2013a & b) - codling moth is the only known host of M. ridens in its native Kazakhstan and in its introduced range in North and Central America, strong field evidence that it will only attack codling moth in New Zealand as well. Based on a combination of taxonomic relatedness and ecological similarity to codling moth, and ‘safeguard’ or socioeconomic criteria, five potential host species were chosen for host range tests in quarantine in New Zealand. In these trials, M. ridens did lay some eggs on non-target cocoons, but few parasitoids survived on these hosts and those that did were small and ecologically unfit. The host range tests suggest New Zealand natives are generally not at risk because they will not be recognised as possible hosts, and that the chances of M. ridens establishing self-sustaining populations on non-target species in New Zealand are very low and they may, for all practical purposes, be regarded as non-hosts.

Sandanayaka et al. (2016) - M. ridens could potentially compete with Liotryphon caudatus (also released in New Zealand as a biological control of codling moth) for resources because they oviposit and develop on the same life-stage of C.pomonella (cocooned larvae). Competition experiments in the laboratory showed L. caudatus out-competed M. ridens in an enclosed space, but that ability in a natural ecosystem remains to be investigated.

EPA Applications:

EPA (2012b) - 8 Mar 2012: application by Pipfruit New Zealand Inc. to release Mastrus ridens from containment into New Zealand for the biological control of codling moth. EPA Application # APP201151 - approved without controls 26 Jun 2012.


Charles JG, Dugdale JS (2011). Non-target species selection for host-range testing of Mastrus ridens. New Zealand Entomologist 34: 45-51

Charles JG, Sandanayaka WRM, Chhagan A and Page-Weir NEM (2013a). Host selection behaviour in Mastrus ridens, a gregarious ectoparasitoid of codling moth, Cydia pomonella. BioControl 58: 493-503

Charles JG, Sandanayaka WRM, Chhagan A and Page-Weir NEM (2013b). Survival of the gregarious ectoparasitoid Mastrus ridens on codling moth, Cydia pomonella, and non-target species. BioControl 58: 505-513

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: 291–301 https://doi.org/10.1007/s10526-019-09939-z

EPA (2012b). Application to EPA (APP201151) to import for release the parasitoid wasp Mastrus ridens into New Zealand for the biological control of codling moth, Cydia pomonella. Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/APP201151

Pipfruit New Zealand Inc. (2011). Application to EPA (APP201151) to import for release, or release from containment, a new organism [Mastris ridens]. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/APP201151/0e7e570eb3/APP201151-APP201151-Application.pdf

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

Sandanayaka MWR, Jenkins HK, Davis VA, Page-Weir NEM, Chhagan A, Blin A, Zaviezo T (2022). Assessment of fitness traits of pure and mixed crosses of Mastrus ridens populations to improve classical biological control of codling moth. Biological Control, Volume 169, June 2022, 104899 https://doi.org/10.1016/j.biocontrol.2022.104899

Sandanayaka WRM, Charles JG, Davis VA, Chhaganj A, Shaw PW, Cole LM, Colhoun K, Wallis DR (2018). Mass rearing and release of Mastrus ridens (Hym: Ichneumonidae) a parasitoid for the biological control of codling moth Cydia pomonella. New Zealand Entomologist: 41(2): 37-45

Sandanayaka WRM, Davis VA, and Charles JG (2016). Interspecific competition between Mastrus ridens and Liotryphon caudatus, ectoparasitoids of codling moth Cydia pomonella. New Zealand Plant Protection 69: 310-317 https://www.journal.nzpps.org/index.php/nzpp/article/view/5902/5730