Scotch heather was introduced between 1912 and 1922 to the central North Island with a view to establishing grouse hunting. While the grouse quickly succumbed to the area's harsh winters, the heather thrived, and is now a problem weed covering 50,000 hectares in Tongariro National Park and on nearby New Zealand army land. While the original vegetation in the area was a diverse mix of tussock and other plants, the heather out-competes other plants, creating a monoculture.
In the early 1990s Landcare Research began to investigate the possibility of biocontrol, and imported the heather beetle from Scotland. After captive breeding for several years to eliminate pathogens and parasites, heather beetles were released from 1996 onwards.
Paul Peterson from Landcare Research tells Alison Ballance the heather beetle has been slow to establish, but it finally seems to be gaining the upper hand at one site, and the researchers now have a few ideas as to why it has taken to so long for anything to happen and what they might do in future to speed things up.