28 September 2006
The Chinese weevil Cleopus japonicus was released into Rotorua’s Whakarewarewa Forest on Friday, 22 September 2006, as the first step in biological control of Buddleja davidii (buddleia) in New Zealand.
The release ceremony marked an important milestone for Ensis Forest Biosecurity and Protection (FBP) researchers, government funding providers, the Forest Biosecurity Research Council, and members of the forest industry who have supported this initiative.
Buddleia is a woody species with attractive purple flowers that was introduced to the country as an ornamental shrub and has since become one of the biggest weed problems in New Zealand forestry.
Its capacity to out-compete young trees makes buddleia a serious problem for forest owners, particularly in the Central North Island.
Dave Little, Harvesting and Marketing manager of Crown Forestry, says that forest owners see the release of cleopus as a milestone in buddleia control, and they will be watching with great interest to what impact it may have.
“The industry is under constant pressure to reduce chemical use, and the cleopus initiative demonstrates how we are keen to support serious efforts to find alternatives.”
Ensis FBP scientists based in Rotorua identified the leaf-eating weevil ten years ago as a potential biological control agent against this aggressive weed.
Cleopus was approved for release by ERMA [Environmental Risk Management Authority] after a long and rigorous process to screen the insect’s diet to ensure it does not have an appetite for native or beneficial species.
Ensis scientist and project leader, Dr Brian Richardson says if cleopus is able to establish successfully in the New Zealand environment, it has the potential to stunt the growth of buddleia through defoliation and enable young trees to out-compete the weed.
This could mean cost-savings to the forest industry, and a decrease in the amount of chemical herbicides required to control buddleia.
“Buddleia now costs the New Zealand forest industry between $0.5 and $2.9 million annually in control costs and lost production.
“It also compromises biodiversity in native forest areas where weed control is seldom carried out, including slips and river beds,” he explains.
For local and regional authorities in affected areas, buddleia has become a common weed along roadsides.
Dr Richardson explains that buddleia has potential to become a serious weed in regions throughout New Zealand, as indicated by ecological modelling studies.
It is anticipated that the cleopus weevil will slowly spread into all areas where buddleia is abundant, a process that will be encouraged by further releases in affected forests.
“Over time, if cleopus establishes and thrives, people with buddleia in their garden may notice their shrubs being chewed but these plants can be protected using normal insect control techniques.”
Dr Richardson says the release of a new insect into New Zealand’s environment is a significant occasion, so the cleopus weevil was liberated In Whakarewarewa Forest with the blessing of local iwi.
“We wish cleopus all the best, and hope it enjoys a good feast on buddleia in New Zealand.”
The first release of cleopus marks the start of the next phase of research into buddleia biological control.
Cleopus will be released at five study sites in plantation forests around the Bay of Plenty and Hawke’s Bay.
“After the initial testing, cleopus will be made available to regional councils and others,” Dr Richardson explains.
The Foundation for Research, Science and Technology has been a key investor over the last decade in the development of the science underpinning cleopus and will continue to provide funding to support post-release monitoring and research.
The investment has been made through the Foundation’s Environmental Research Fund.
Hamish Campbell, a Senior Business Manager with the Foundation, says cleopus is an excellent example of the outcomes that can result from long term investment in science and a partnership approach.
“The benefits of the development of this biological control agent are both environmental and economic, evidenced by the fact that government and industry have collaborated to support an initiative that probably couldn’t have delivered such good results without a partnership approach.
“It requires long term investment in science to realise this kind of outcome, but the benefits to the economy and the environment will be significant,” Mr Campbell says.
The current focus of Ensis scientists is on determining how cleopus survives in the wild, how fast it can spread, and what impact it can have on buddleia in a working plantation.
Dr Richardson says they will be monitoring release sites regularly over a number of years and using the data from this project to develop a better understanding of biological control systems in general.
“The next stage is to build models that will help us predict the likely effectiveness of different biological control agents and increase the probability of choosing agents that will succeed in New Zealand.”
Despite the need for management tools to control buddleia and other weeds, Dr Richardson says biological control is never undertaken lightly and every effort is made to reduce risks to the environment.