Wasps fly in face of pest goals

An army of wasps has been released in a Birkenhead reserve to help take down a pest plant that has made the area its home.

Auckland Council’s biosecurity team said the gall wasps, released February 19, will help treat 6000 square metres of the giant reed.

Luckily for park-goers, the gall wasps are the ‘‘non-stinging’’ type.

While it appeared to fly in the face of national moves to eradicate wasps, senior regional biosecurity advisor Holly Cox said there were all types of different wasps, including beneficial ones.

‘‘They [gall wasps] don’t pose a risk to human safety and don’t compete with honey bees,’’ Cox said.

Manaaki Whenua, Landcare Research, had brought in the gall wasp as a biocontrol agent against the giant reed. The wasps attack the stems of the reeds, causing them to swell and stop growing.

Biocontrol agents, using insects to kill weeds, have been used in New Zealand for a long time, she said.

The giant reed is a notoriously difficult pest to control, invading large areas of wetlands and it was known to force out all other plants.

‘‘Attacking the giant reed via gall wasps will change the area’s ecosystem gradually, rather than abruptly like a herbicide or manual controls, benefiting and supporting our native species,’’ Cox said.

The science behind biocontrol requires years of checks and scrutiny before releasing an insect into the bush.

‘‘Sometimes it can take up to eight years, from finding a biocontrol agent and its suitability to New Zealand.’’

Landcare needs to determine factors such as whether it will harm New Zealand or the people and animals that live here.

This is the first gall wasp release in the Auckland region, taking place on the same site as the lacebug release last year to control the Chinese privet.

The lacebugs haven’t killed the privet yet, but these things take time, Cox said.

Kaipa¯ tiki Local board chairwoman Danielle Grant said the Birkenhead War Memorial Park was a priority area.

‘‘The weeds in the middle of the park have been an issue for years. This project is another step towards our shared goal,’’ Grant said.

SUPPLIED Kaipa¯tiki Local Board members assist Auckland Council’s biocontrol agent release in Birkenhead.