By Tupou Vaipulu Jr.
African leaf-mining beetles (Paradibolia coerulea) have been brought into Tonga to control the growing invasive weed called the African tulip tree (Spathodea campanulata). The tree is invading indigenous forests and arable land causing reductions in natural biodiversity and agricultural productivity.
A total of 210 beetles were delivered recently to Tonga’s Ministry of Agriculture, Food, and Forests (MAFF). The beetles will be mass reared at the Vaini Research Station in Tongatapu before being released at several sites around Vava’u in January 2025.
The beetles are being reared by MAFF experts Emeline Ahoafi, Sekilini Havili and entomologist Mr. Saimone Manu.
“We did a survey and the result was that Vava’u had the most of these African tulips overall ... that’s why we’re releasing them there,” Mr Manu said. "They’re a weed and overtime they will cover other plants causing them to die, which we are already seeing in plantations."
The beetles feed on the leaves of the African tulips and will help control the spread of the invasive tree.
Tonga’s National invasive species co-ordinator Viliami Hakaumotu, said that the beetles will be released in Vava’u where a gall-forming mite (Colomerus spathodeae) was released in December 2023.
Both the beetle and mite were found in Ghana and developed with the assistance of Rhodes University in South Africa.
“The mites and beetles will work together in areas where the weed is too widespread for management through conventional methods,” he said.
While humans can also get the job done, Mr. Manu said that it won’t be as effective as the beetles. “People can try and cut them down but it’ll just regrow, it’s a very adaptable weed and using these beetles may be slow but it’s more effective”.
Manaaki Whenua – Landcare Research
The week control work is being done in other Pacific Islands countries.
The first batch of beetles were brought to Tonga by a team from Manaaki Whenua – Landcare Research, under the Pacific Regional Invasive Species Management Support Service’s (PRISMSS) Natural Enemies - Natural Solutions (NENS) Programme.
Spearheading the natural enemy weed control work across the Pacific, Lynley Hayes, the prgram lead, said the beetles have been tested to ensure no other plants are at risk from it and that they have already been released in the Cook Islands.
“These are leaf-mining beetles. Adult beetles eat holes in the African tulip leaves and their larva mine through them,” she said said "the beetles have been approved for release in Tonga and will ramp up efforts to help reduce the spread and density of the African tulip tree.”
Originally from West Africa, African tulip tree was introduced into the Pacific as an ornamental plant but has now naturalised and become problematic.
The Secretariat of the Pacific Regional Environment Programme (SPREP) Invasive Species Adviser, Mr. David Moverley said, “African tulip is a common problem across the Pacific."
This project is part of the Restoring Island Resilience Programme administered by SPREP, and funded by New Zealand’s Ministry of Foreign Affairs (MFAT) and the Global Environment Facility, to better manage invasive species in the Pacific and enhance the resilience of Pacific communities to climate change.
