Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Cooks Islands Project Becomes a Reality

Grand balloon vine.

Grand balloon vine.

New Zealand’s Ministry of Foreign Affairs and Trade (MFAT) has agreed to fund a 5-year project to develop weed biocontol for the Cook Islands, and the project is now underway.

The Cook Islands comprise 15 islands, the largest being the well-known holiday destination Rarotonga. A large number of plants introduced for their ornamental value, edible fruit, or timber have become seriously invasive, and are now threatening native biodiversity, traditional cultural practices, and the sustainable development of the island group. The programme of work for the Cook Islands was agreed in consultation with regional experts involved in agriculture, biodiversity conservation and biosecurity. After careful consideration the eight most appropriate targets were selected.

“Biocontrol agents developed elsewhere will be released against five species: mile-a-minute (Mikania micrantha), Noogoora burr (Xanthium pungens), grand balloon vine (Cardiospermum grandiflorum), strawberry guava (Psidium cattleianum), and giant reed (Arundo donax),” confirmed Quentin Paynter, who is leading the project. One of the first projects out of the blocks will be to gain permission to release a rust fungus (Puccinia spegazzini), which has already been released against mile-a-minute in Papua New Guinea, Fiji and Vanuatu, and requires no additional testing. It is hoped releases of the rust can get underway in the Cooks Islands this calendar year. Some testing of another rust fungus (Xanthium pungens), used successfully in Australia against Noogoora burr, will be undertaken this year to check it is safe to release in the Cook Islands and populations there are susceptible. No additional testing is needed for a third rust fungus (Puccinia arechavaletae) and a weevil (Cissoanthonomus tuberculipennis), identified as good potential agents for grand balloon vine in South Africa, where this weed is also problematic. “We plan to import these species into containment and obtain clearance for their release in 2016/17,” said Quent. Most of the species to be worked on are not weeds in New Zealand. However, strawberry guava is naturalised here and may become a problem in the future. A scale insect (Tectococcus ovatus), recently released in Hawai‘i, appears to be sufficiently specific for the Cook Islands and we will import it into containment for final clearance for release there in 2016. Giant reed is definitely a weed in New Zealand. Next year we plan to import two insects developed as biocontrol agents for this target in the USA, a gall wasp (Tetramesa romana) and a scale insect (Rhizaspidiotus donacis) . “We could also seek permission to release them in New Zealand if there is sufficient interest in doing so,” commented Quent.

Novel research will be undertaken for the remaining three species: red passionfruit (Passiflora rubra), African tulip tree (Spathodea campanulata), and peltate morning glory (Merremia peltata). New agents will be developed for red passionfruit. We will import two attractive Heliconius butterflies into containment for host testing next year. Agents will also be developed for African tulip tree, a major invasive weed throughout the Pacific Region. Potential agents were identified in preliminary surveys for biocontrol agents conducted in Ghana in 2009, funded by the Secretariat of the Pacific Community. Our plant pathologist, Sarah Dodd, will assist collaborators from Rhodes University in South Africa to complete additional surveys in Ghana next month. “Once all the potential candidates are known the best ones will be selected for host-testing,” explained Sarah. A molecular study of peltate morning glory will begin shortly to determine, if possible, how and when this plant colonised the Pacific region. There are conflicting views about whether this invasive vine is native or introduced to various islands, which needs to be resolved before any further steps could be taken to develop biocontrol for this target.

Throughout the project we will be working closely with Maja Poeschko of the Ministry for Agriculture in Rarotonga, and Gerald McCormack, who directs the Cook Islands Natural Heritage Project. We hope that this project, through the development of new agents and capacity, will in time also benefit the wider Pacific.

Many thanks to MFAT for providing the funds for this project through its International Development Fund.