Biocontrol introduction
Target pest: Ulex europaeus (Fabales: Fabaceae), gorse
Agent introduced: Cydia ulicetana (Lepidoptera: Tortricidae), gorse pod moth
Imported:
1989, 1992 [Imported as Cydia succedana but subsequently considered likely to be C. ulicetana (see 'General comments' section).]
Import source:
Gourlay (2007b) - first imported from England 1989.
Withers et al. (2008) - Viana do Castello, Portugal 1992
Import notes:
Landcare Research (2005) – moths for initial releases were sourced from Yately Common, Hampshire, UK. Later some moths were also sourced from Portugal in an attempt to increase genetic diversity and improve climate matching.
Released:
Withers et al. (2008) – released 1992.
Release details:
Gourlay (2007b) - released throughout New Zealand in the early 1990s.
Establishment:
Harman et al. (1996) - has established well at a site in Canterbury.
Gourlay (2007b) - now becoming widespread in both North and South Islands.
Hill et al. (2007) - the moth is now abundant throughout gorse-infested areas of New Zealand.
Landcare Research (2014c) - common in many areas.
Impacts on target:
Landcare Research (2005) - gorse pod moths are not having a significant impact on gorse, particularly in the North Island. The reasons for this are not yet known.
Gourlay et al. (2004) - an insecticide exclusion trial in Canterbury, South Island showed that while gorse pod moth has a negative impact on the gorse seed weevil (Epaxion ulicis) the combined effects of the two agents was greater than either alone, with 81% of spring seed destroyed by both agents in combination. Modelling suggests a reduction in the annual seed crop of 75–85% would be sufficient to cause long-term decline in gorse cover. In places where autumn seed production contributes little to the annual seed crop, these two agents may already be contributing to a decline in gorse population density.
Gourlay (2007b) - at a site in Canterbury gorse pod moth and the gorse seed weevil (Epaxion ulicis) were found to be destroying 90-100% of the spring/summer seed crop (about half each) and gorse pod moth was taking about 15-20% of the winter/autumn seed crop. Early indications are that gorse pod moth infestation levels in the autumn are lower than hoped and this may be due to less-than-optimal synchrony between gorse flowering and pod moth activity.
Hill et al. (2007) - the predicted reduction in autumn seed production has not occurred. There appears to be lack of synchrony between the emergence of moths and the peak occurrence of gorse pods in autumn, and infestation rates rarely exceed 10%. As seed set in autumn forms the bulk of seed production in warmer parts of New Zealand, adequate control of seed production has not yet been achieved.
Withers et al. (2008) - in a spring field survey, at North Island sites, where gorse flowered in November and mature pods opened in January, gorse pod moth infestation levels never exceeded 2% of gorse pods. South Island sites, where gorse flowered in October and mature pods opened in December, had much higher infestation levels, up to 90%.
Sixtus et al. (2013) - from Aug 2009 to April 2011, 15 sites in upper South Island and lower North Island were monitored for gorse pod moth damage. Overall 27% of seed was damaged to point of being non-viable, which indicates gorse control by this agent is not successful, primarily because moth population and gorse flowering is not in synchrony.
Landcare Research (2014c) - can destroy many seeds in spring but not as effective in autumn.
Impacts on non-targets:
Paynter et al. (2004), Fowler et al. (2004) - larvae found attacking other introduced legumes, such as Scotch broom (Cytisus scoparius) and tree lupin (Lupinus arboreus), though lab tests in England predicted no non-target feeding and field records indicated the moth was narrowly oligophagous in Europe. This may be a “spill-over” effect at high moth population density, or due to asynchrony between target plant and agent. Also there may be issues with the provenance of insects since moths released in New Zealand were sourced from both England and Portugal and C. succedana (the name under which gorse pod moth was introduced to New Zealand) was recently split into 2 species (the other being C. ulicetana), and moths resembling both species were collected in New Zealand during non-target surveys. Furthermore, there are forms of difficult assignation present in the Iberian Peninsula that would require some research to determine their taxonomic status. Extensive surveys in New Zealand indicate no native legume species are attacked.
Landcare Research (2005) - although the level of non-target attack varies between sites, overall it appears to be quite low and probably of no major consequence to these exotic species. The reasons for the non-target attacks are unclear; one possibility is the taxonomies of the moth and the gorse. Moths used for host range testing and initial releases in New Zealand were from Yately Common in the UK; subsequently moths from Portugal were also released. Some taxonomists have recently split the pod moth into two species (C. succedana and C. ulicetana), with English moths considered to be C. ulicetana and the identity of moths in Portugal not yet known. In addition, gorse in the UK and Portugal are different subspecies. All moths looked at in New Zealand appear to be C. ulicetana; however, there does not appear to be any difference between moths collected from gorse and non-target species, so obvious taxonomic differences do not appear to explain the non-target attack.
Withers et al. (2008) - post-release host range trials and field surveys did not detect any attack on native New Zealand plant species, but contrary to predictions based on pre-release host range testing, several species of exotic plants, including Scotch broom Cytisus scoparius, Montpellier broom Teline (Genista) monspessulana, and tree lupin Lupinus arboreus (all tribe Genisteae), as well as lotus Lotus pedunculatus (tribe Loteae) growing in the vicinity of infested gorse plants, were shown to be hosts of gorse pod moth in both the North and South Islands. Three possible reasons for the failure to predict non-target attacks are a) poor synchrony between host flowering and biocontrol agent activity resulting in less preferred host being used when gorse pods were not available; b) that, as well as C. succedana [subsequently considered likely to be C. ulicetana], a cryptic species was accidentally introduced (closely related Cydia species have now been identified, raising this possibility); and c) that the population from Portugal has a different host-range to the tested (English) population.
Paynter et al. (2008) - gorse pod moth in the field has been found attacking non-targets Cytisus scoparius (Scotch broom), Genista monspessulana, Lupinus arboreus, Lotus pedunculata, and also occasionally Spartium junceum, Genista lydia, Lupinus polyphyllus, Cytisus proliferus (tagasaste, a minor fodder crop) and Lotus corniculatus. These are all non-natives and most are invasive weeds and no adverse environmental or economic impacts have been reported; however the host-range is broader than was predicted by host-range testing. Experiments and field surveys were carried out to test three hypotheses to explain why original host range testing did not predict the host range in New Zealand: (1) that, as well as gorse pod moth, a cryptic species was accidentally introduced; (2) asynchrony between oviposition of the biocontrol agent and flowering of the target plant, and (3) the population collected in Portugal has different host preferences from the tested English population. Morphology and DNA sequencing indicated that only one Cydia species was present in the New Zealand samples. Host range testing of moths collected at Yately Common, UK (where moths were collected for the original host range tests) did not contradict the original tests that indicated non-target attack was unlikely. In contrast, moths sourced from Portugal were capable of exploiting a broader range of plants, though in choice tests, gorse was preferred. It is concluded that the non-target hosts were not predicted because of the release of untested moths from Portugal and asynchrony between gorse pod moth flight period and gorse flowering causing deprivation and the use of less preferred hosts.
General comments: Landcare Research (2005) - some taxonomists have recently split the gorse pod moth into two species: C. succedana and C. ulicetana. Best advice at the moment is that the English pod moths are now considered to be C. ulicetana, but we do not yet know the identity of the moths in Portugal. [Moths from both countries have been released in New Zealand.]
Paynter et al. (2008) - Danilevsky and Kuznetzov (1968) recognized C. succedana (Denis and SchiffermĂĽller) and C. ulicetana (Haworth) as separate species. However, many authorities considered C. ulicetana to be an inferior synonym of C. succedana at the time that gorse pod moth was cleared for release in New Zealand. It was, therefore, introduced into New Zealand under the name C. succedana. Since then, however, Razowski (2003) reinstated the separation between C. succedana and C. ulicetana. There is, consequently, uncertainty regarding the distributions and host-ranges of both species because many literature records do not distinguish between the two. According to this separation, only C. ulicetana occurs in the United Kingdom. It is conceivable that both may occur in Portugal, although only C. ulicetana is currently confirmed to be present there, but several similar closely related Cydia species are present, raising the possibility that a cryptic species may have been accidentally introduced along with gorse pod moth as a culture contaminant [though trials reported in this publication - see 'Impacts on non-targets' section - suggest this did not occur].
References
Fowler, S.V., Gourlay, A.H., Rill, R.H. and Withers, T. (2004). Safety in New Zealand weed biocontrol: a retrospective analysis of host specificity testing and the predictability of impacts on non-target plants. proceedings of the XI International Symposium on Biological Control of Weeds. Cullen, J.M., Briese, D.T., Kriticos, D.J., Lonsdale, W.M., Morin, L. and Scott, J.K. (Eds). Canberra, Australia, CSIRO Entomology, 27 April - 2 May 2003.
Gourlay AH, Partridge TR, Hill RL. (2004). Interactions between the gorse seed weevil (Exapion ulicis) and the gorse pod moth (Cydia succedana) explored by insecticide exclusion in Canterbury, New Zealand. In: Cullen, J.M., Briese, D.T., Kriticos, D.J., Lonsdale, W.M., Morin L. and Scott, J.K. (eds) Proceedings of the XI International Symposium on Biological Control of Weeds. CSIRO Entomology, Canberra, Australia, pp. 520–522
Gourlay H (2007b). Gorse Pod Moth. In The Biological Control of Weeds Book (Landcare Research) https://www.landcareresearch.co.nz/discover-our-research/biosecurity/weed-management/using-biocontrol/the-biological-control-of-weeds-book/
Harman HM, Syrett P, Hill RL, Jessep CT. (1996). Arthropod introductions for biological control of weeds in New Zealand, 1929 - 1995. New Zealand Entomologist, 19(1): 71-80
Hill RL, Ireson J, Sheppard AW, Gourlay AH, Norambuena H, Markin GP, Kwong R, and Coombs E. (2007). A global view of the future for biological control of gorse, Ulex europaeus L. In Proceedings of the XII International Symposium on the Biological control of Weeds (eds Julien MH, Sforza R, Bon MC, Evans HC, Hatcher PE, Hinz HL, Rector BG), pp. 680-686. CAB International , Wallingford, UK. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.475.3210&rep=rep1&type=pdf
Landcare Research (2005). Making sense of field findings. What's New In Biological Control of Weeds?. Annual Review. 33: 4-5 https://www.landcareresearch.co.nz/publications/weed-biocontrol/
Landcare Research (2007a). New Zealand Arthropod Collection (NZAC) Biological Control Voucher Collection. http://www.landcareresearch.co.nz/resources/collections/nzac/holdings/biological-control-voucher-collection
Landcare Research (2014c). Who's who in biocontrol of weeds? What's new in biological control of weeds? 69: 10-11 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-69
Paynter QE, Gourlay AH, Oboyski PT, Fowler SV, Hill RV, Withers TM, Parish H and Hona SR (2008). Why did specificity testing fail to predict the field host-range of the gorse pod moth in New Zealand? Biological Control 46: 453-462
Paynter, Q.E., Fowler, A.H., Gourlay, M.L., Haines, M.L., Harman, H.M., Hona, S.R., Peterson, P.G., Smith, L.A., Wilson-Davey, J.R.A., Winks, C.J. and Withers, T.M. (2004). Safety in New Zealand weed biocontrol: A nationwide survey for impacts on non-target plants. New Zealand Plant Protection 57: 102-107
Sixtus CR, Hampton JG, Glare TR and Hill GD (2013). Is the gorse pod moth an effective biocontrol agent of gorse in New Zealand? The role of weed science in supporting food security by 2020. Proceedings of the 24th Asian-Pacific Weed Science Society Conference, Bandung, Indonesia, October 22-25, 201: 294-298
Withers TM , Hill RL, Paynter Q, Fowler SV, Gourlay AH. (2008). Post-release investigations into the field host range of the gorse pod moth Cydia succedana Denis & SchiffermĂĽller (Lepidoptera: Tortricidae) in New Zealand. New Zealand Entomologist 31(1): 67-76
