Author
Simon Victor Fowler
fowlers@landcareresearch.co.nz
Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group
Lincoln, New Zealand
Coauthors
Paul Peterson, Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group, Palmerston North, New Zealand
Paul Barrett, Massey University, Palmerston North, New Zealand
Abstract
Heather (Calluna vulgaris) was deliberately introduced into Tongariro National Park, New Zealand, in 1912. By the 1990’s it had severely infested over 50,000 ha of this world heritage site. Mechanical or chemical control was costly, with low efficacy and severe non-target effects. The heather beetle, Lochmaea suturalis, was used for biocontrol from 1990 because of its history of damaging outbreaks in valued native heather ecosystems in Europe. Unexpected challenges occurred with safety testing of other Ericaceae and with a microsporidian disease. Beetle populations were hard to establish in NZ and multiplied slowly compared to Europe. Experimental studies showed natural enemies were not interfering with the heather beetle in NZ, but that genetic bottlenecking, low host plant nitrogen (N) and the variable southern hemisphere climate, could be challenging beetle performance. By the 2020’s, heather beetle performance had dramatically improved, probably from increases in N levels in heather (perhaps from airborne pollution), rather than from genetic rescue/evolutionary adaptation, or climate change. Post-biocontrol, there has been recovery of native flora, zero direct non-target effects, but some, potentially temporary, secondary invasion by exotic grasses. Ongoing monitoring is assessing the long-term sustainability of this biocontrol success, and how to integrate it with other management interventions spatially and temporarily across NZ.
keywords
safety testing
poor establishment
foliar nitrogen
air pollution
secondary invasion
Highlights
Complex host range testing and a microsporidian disease were unexpected problems with heather beetle
Poor performance was due to low hostplant N, not natural enemies, genetic bottlenecking or climate
Increasing N in heather, perhaps due to increasing air pollution, led to eventual biocontrol success