Gardeners fear butterf ly threat
A bug introduced to control the spread of buddleia plants could be affecting monarch butterfly numbers, gardeners fear.
The leaf weevil Cleopus japonicus was introduced in 2005 to target buddleia, which are considered a pest in New Zealand.
But keen gardeners – and columnists of The Press – Rosemary McLeod and Jane Clifton say they are concerned the impact on their plants could affect butterflies too.
McLeod said this year her buddleia plants have been ‘‘decimated’’ by the parasite. A friend’s plants had also been ‘‘absolutely savaged’’.
‘‘Not only does it make people like me pissed off, but monarch butterfly numbers have been dwindling. We think we’re doing God’s work.’’
But the Environment Protection Authority (EPA) says the benefits associated with the release of the weevil outweigh any adverse effects.
A decision by the Environmental Risk Management Authority – the EPA’s predecessor – from 2005, which approved the import for release of the weevil, says buddleia, which can be a shrub or small tree, is considered a serious weed in young pine plantations.
The report considered the weevil’s impact on the environment, public health, Ma¯ ori culture and values, and the market economy.
Greater Wellington Regional Council spokesman Stephen Heath said the council released the weevils into the Wellington region as part of its biosecurity role.
The first two releases were in 2007 at two sites in Porirua and Lower Hutt.
It later harvested leaf weevils and released them throughout the region, but in particular in Wairarapa, Wellington and the Hutt Valley, he said.
‘‘The EPA’s processes are thorough, and the impact of buddleia leaf weevil on the butterfly population was taken into account in the application for release,’’ he said.
Clifton said she had been growing hybrid buddleia for about five years.
‘‘In the last two years, they’ve just been skeletonised, and then I heard about this buddleia pest.’’
With the pest introduced so long ago, she was surprised to have noticed it affecting her plants only very recently.
She was not sure how the bug would affect monarch butterflies, but was concerned by its impact on other butterflies too.
Monarch Butterfly New Zealand Trust founder Jacqui Knight said did not believe that the weevil would affect butterfly population, despite noticing fewer monarchs this year.
There were a number of parasites affecting the plants that attracted butterflies, and population numbers were always up and down, she said.
She advised gardeners that, instead of planting buddleia, they should turn to other plants that also attracted monarch butterflies. ‘‘We’re encouraging people to plant more nectar flowers.’’