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Will Brockelsby – Department of Conservation

(Te Apārangi Sponsored Speaker)

Will Brockelsby is keen entomologist, invertebrate ecologist and iNaturalist addict. While not specialised in any particular taxa, he does have a soft spot for charismatic large weevils, moths, micro snails and harvestmen. Particularly interested in the conservation of invertebrate species and their habitats.

Lecture information:

A restoration ecology conundrum: unintended consequences of a successful flax weevil (Anagotus fairburni) translocation to Mana Island and the importance of its pathogen Beauveria pseudobassiana.


The flightless endemic flax weevil (Anagotus fairburni) was deliberately translocated to Mana Island, New Zealand in 2004 and 2006. The weevil population grew exponentially and by 2018 the weevils had destroyed large areas of their host plant (Phormium spp.) on the island, to the point there was concern they were limiting the flax resources essential to native birds and lizards.

Investigations into possible natural enemies of the flax weevil led to the discovery of a strain of entomopathogenic fungus (Beauveria pseudobassiana) at the release site on the island that was highly lethal to weevil larvae. This native pathogen was abundant at the flax weevil release site, but uncommon elsewhere on the island, leading to the hypothesis that flax weevils were able to disperse ahead of its natural enemy. We investigated the feasibility of spreading the fungus ahead of the weevil dispersal, to protect flax plants from collapse and death. A trial site was established in the centre of the island well ahead of known weevil distribution. In March 2020, 43 marked flax plants were treated with either the virulent fungal strain or a control solution. The flax plants were then stressed by deliberately introducing flax weevils.

The application of the fungus failed to protect flax plants at the experimental site, with 35 out of 43 marked plants (2022) in a state of heavy collapse or death. However, Beauveria appears to be spread by the adult weevils as they move across the island.