Insects to control Californian thistle approved

ERMA New Zealand has approved an application to import two insects to control the weed Californian thistle.

The Californian Thistle Action Group's application to import and release Ceratapion onopordi (Brentidae) and Cassida rubiginosa (Chrysomelidae) to biologically control Californian thistle (Cirsium arvense) has been approved without any controls being placed on the release of the insects.

Ceratapion onopordi is a minute weevil from Europe whose larvae feed on and can debilitate the stems of a number of thistle species. Larvae of the beetle Cassida rubiginosa also reduce the growth and survival rates of many thistle species by feeding on their leaves.

Californian thistle occurs throughout New Zealand and is one of the most serious and persistent weed problems on pastoral and cropping farms.

The Authority members hearing the application considered all of the potential effects of the organisms on the environment, human health and safety, the economy, society and community, and Maori culture and traditions.

ERMA New Zealand General Manager New Organisms Libby Harrison says overall analysis indicates that the benefits of the release of the two insects outweigh any adverse effects.

The insects are to be released initially in Otago, Southland, Manawatu and Wanganui, with the expectation that they will eventually establish themselves throughout the country.

The final decision document is available on the ERMA New Zealand website, www.ermanz.govt.nz, on the new organism register of applications and decisions.

ENDS

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