Biological control
Buddleia weevil larvae
Most pest plants have arrived in New Zealand without their natural enemies that may have kept them in check in their own countries. Biological control or 'biocontrol' involves bringing some of those natural enemies to New Zealand to help control the plant. Biocontrol organisms are usually insects but can also be animals, rusts or viruses.
Biocontrol agents provide assistance in the control of pest plants that are widespread. It is a very long term approach to pest control.
Before any new organism is brought into New Zealand, strict testing procedures are followed, often over a period of years, to ensure that the new organism poses no risk to valued species. The biocontrol agent has to be proven to attack only the pest plant and no other plant species.
Landcare Research undertakes the research and trialling of such biocontrol organisms which are then released by either regional council or Department of Conservation (DOC) staff (after approval from the Environmental Protection Authority (EPA)). Release sites are studied further to ascertain the success of the release and to guide future releases.
Greater Wellington contributes towards the biological control collective which includes the majority of regional councils, DOC and several district councils. Greater Wellington biosecurity officers currently release biocontrol agents in the Wellington region. When agent populations are high enough, they may distribute them on to new sites.
Common pest plants and their agents
The following are some of the many agents available in the Wellington region (as of July 2009). For more information contact a Biosecurity Officer in your area.
Broom Broom seed beetle Bruchidius villosus
Broom twig minerLeucoptera spartifoliella
Broom psyllid Arytainilla spartiophila
Broom shoot moth Agonopterix assimilella
Broom leaf beetle Gonioctena olivacea
Gorse Gorse colonial hard shoot moth Pempelia genistella
Gorse pod moth Cydia succedana
Gorse seed weevil Exapion ulicis
Gorse soft shoot moth Agonopterix umbellana
Gorse spider mites Tetranychus lintearius
Gorse thrips Sericothrips staphylinus
Nodding thistle Nodding thistle crown weevil Trichosirocalus horridus
Nodding thistle gall fly Urophora solstitialis
Nodding thistle receptacle weevil Rhinocyllus conicus
Old man's beard Old man's beard leaf fungus Phoma clematidina
Old man's beard leaf minerPhytomyza vitalbae
Old man's beard sawfly Monophadnus spinolae
Ragwort Ragwort cinnabar moth Tyria jacobaeae
Ragwort flea beetle Longitarsus jacobaeae
Other agents
Blackberry Blackberry rust Phragmidium violaceum
Boneseed Boneseed leafroller Totrix s.l.sp chrysanthemoides
Buddleia Buddleia leaf weevil Cleopus japonicus
Californian thistle Californian thistle blight Phoma exigua var.exigua
Californian thistle rust Puccinia punctiformis
Hemlock Hemlock moth Agonopterix alstromeriana
Mistflower Mistflower fungus Entyloma ageratinae
Mistflower gall fly Procecidochares alani
Scotch thistle Scotch thistle gall fly Urophora stylata
Smilax Smilax rust Puccinia myrsiphylli
Thistles Green thistle beetle Cassisa rubiginosa
Tradescantia Tradescantia leaf beetle Neolema ogloblini
Biocontrol agents are currently being researched for a wide range of common pest plants including banana passionfruit, wild ginger, Japanese honeysuckle and Darwin's barberry
Success stories
There have been a few success stories for biological control.
Ragwort agent success article
For more information contact us on 0800 496 734, email pest.plants@gw.govt.nz or visit the Landcare Research website