Flax planting trial to assess weevil damage


June 2017

Read the report (updated in July 2017)

Here is the news item:

In 2004 the flax weevil was introduced to Mana Island from Maud Island in the Marlborough Sounds as part of the restoration plan for Mana.

It rapidly established itself on Mana with large patches of mature flax now dying as a result. The weevils feed only on native flaxes with the adults eating the foliage and the larvae feeding on the roots.

This is of concern as the flax on Mana Island provides the almost exclusive habitat for the goldstripe geckos (for which Mana Island is the world stronghold). The flax provides an important nectar source for bellbirds, tui and at least two species of gecko.

At the June FOMI volunteer working bee, 200 flaxes were planted on Mana Island as part of a trial around the effects of the flax weevil. The flax plants had been grown from seed collected from Maud Island where the flax weevil originated.

Scientist Colin Miskelly is leading the flax weevil study, with the planting trial designed to assess whether flaxes sourced from Maud Island are more resistant to weevil damage than Mana Island flax. 

Colin has two hypotheses for the super-abundance of flax weevils on Mana. One relates to the type of flax and whether the Maud Island flax is more resistant to flax weevil damage. The other is about the potential lack of a natural bio-control agent that affects the weevil larvae –  which was left behind when the adult weevils were translocated.

He has produced a very valuable report about the trial which includes recommendations for monitoring the plantings, and a data sheet for recording plant presence and health. This will be included in FOMI working bee tasks for the next few years. The plants have been labelled and marked using GPS mapping.

Our thanks to Colin for this important piece of research, to Allflex who supplied the tags for labelling the sites, and to the volunteers who planted and labelled the flaxes. 

Read the July 2017 report by Colin Miskelly