Hundreds of mites sent from Auckland to Tonga to tackle invasive plants

Friday, 6 May 2022

Hundreds of mites mass-reared in an Auckland facility have been sent to Tonga to tackle an invasive plant that is out-competing native species.

Cuttings infested with the gall mites were shipped to the island nation this week, where they will grow in a colony, before being released around the island onto African tulip trees.

Gall mites were originally brought over to New Zealand in 2016 from Ghana to be sent on to Rarotonga. A back-up colony was kept in case any other countries needed them – but Covid-19 restrictions pushed plans out until now.

Hundreds of mites form a gall which feed on the African tulip tree and stunt its growth

Manaaki Whenua Landcare Research NENS coordinator Temo Talie said the mites formed galls of hundreds which stunted plant growth.

Gall mites were carefully transferred onto African tulip tree leaves before being sent over to Tonga.

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The trees are the only food source for the gall mites, making them the perfect biocontrol agents, as they won’t damage other plant species, he said.

They were kept across two facilities in New Zealand and fed on African tulip trees that were grown in containment.

Finding a way to get them over to Tonga with the travel restrictions was difficult, as they normally took them over themselves by hand, he said.

They were hand-transferred onto new plants to ensure the new population was free of any pests before undergoing extensive testing to make sure they would pose no risk to other plants.

Tonga’s national invasive species co-ordinator Viliami Hakaumotu said the mites would be reared by Ministry of Agriculture staff before being released in all parts of Tonga where they are needed.

It would take about 6-12 months before the mites were widely released and established in Tonga.

The African tulip tree is considered one of the 100 worst alien invasive species in the world and one of the top 30 terrestrial invasive plants.

They were originally introduced to many Pacific Islands as an ornamental plant.

Talie said because they reproduced asexually and their seeds were windborn they could spread like crazy, and it was hard to get rid of them.

Some mites have been kept in New Zealand to be sent out to more countries, with Vanuatu next on the list.

CORRECTION: An earlier version of this story said hundreds of thousands of mites were being sent to Tonga, which was based on inaccurate information supplied by Manaaki Whenua Landcare Research. Hundreds of mites are actually being sent. Updated at 11.11am, May 7, 2022.