Target pest: Ulex europaeus (Fabales: Fabaceae), gorse
Agent introduced: Exapion ulicis (Coleoptera: Curculionidae) = Apion ulicis, gorse seed weevil
Cameron et al. (1989) - first releases made in 1931 at Nelson and Alexandra. Approximately 235,000 adult weevils were released throughout New Zealand from 1931-1946.
Gourlay (2007a), Hill et al. (2007) - established readily within 10 years and has become common and abundant in most areas except the West Coast in the South Island.
Impacts on target:
Cameron et al. (1989), Gourlay (2007a) - in some areas they can destroy as much as 99% of seed in spring.
Gourlay et al. (2004) - an insecticide exclusion trial in Canterbury, South Island showed that while gorse pod moth [released as Cydia succedana but subsequently considered likely to be C. ulicetana] 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 75â€“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).
Hill et al. (2007) - along with gorse pod moth can destroy 85-95% of seeds formed in spring, but as gorse produces seed at times of the year when the weevil is not reproductively active, the reduction in the annual seed crop is not sufficient to control gorse.
Impacts on non-targets:
Cameron et al. (1989) - host range tests carried out in both England and New Zealand showed E.ulicis could not attack any other plant.
Paynter et al. (2004) - surveys record no non-target feeding, as predicted by lab tests.
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.
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. 520â€“522
Gourlay H (2007a). Gorse Seed Weevil. 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/
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/
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
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