Transferring a Successful Program from Hawai’i to New Zealand

Mist flower (Ageratina riparia (Regel) R. King and H. Robinson: Asteraceae) is an invasive weed that is widespread in tropical and warm temperate regions. It was intro-duced to New Zealand in the early 1930s and today is widespread in the North Island. Mist flower invades a range of habitats including native forests, where it can displace rare species and limit regeneration. New Zealand is undertaking a biological control program for mist flower based on 3 agents that were used successfully against the weed in Hawaii: a white smut fungus (Entyloma ageratinae Barreto and Evans), a gall fly (Procecidochares alani Steyskal), and a plume moth (Oidaematophorus beneficus Yano and Heppner). The white smut fungus and the gall fly were the most effective agents in Hawai’i, and so are the initial focus of the New Zealand program. The host specificity of these biological control agents was tested prior to their use in Hawai’i, Australia and South Africa, but additional tests, of plants significant in New Zealand, were conducted as part of this program. Results were consistent with previous findings: both agents are highly specific to mist flower, and are unlikely to damage any other plant species. The white smut fungus was released in New Zealand in November 1998 and has successfully produced secondary infections at all release sites. Permission to import and release the gall fly has been requested. A monitoring program has been established so that the impact of the biological control agents in the field can be determined