Project overview
Nodding thistle is native to Eurasia. It is mainly found in Waikato, Bay of Plenty, Hawkes Bay, Canterbury and Otago where it invades pasture, roadsides and wasteland.
Three agents have been released to attack nodding thistle and are established throughout New Zealand. The nodding thistle receptacle weevil (Rhinocyllus conicus) is effective at destroying most seeds produced by primary flowers in spring and early summer. The nodding thistle gall fly (Urophora solstitialis) complements the receptacle weevil by attacking seed produced by secondary and tertiary flowers later in the season. The nodding thistle crown weevil (Trichosirocalus horridus) damages rosettes, especially during the cooler months of the year. Nodding thistle populations have noticeably declined in recent years in many parts of New Zealand due to these agents.
Two new agents recently released against Californian thistle, the Californian thistle stem miner (Ceratapion onopordi) and the green thistle beetle (Cassida rubiginosa), are likely to add further pressure to nodding thistle.
