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New work on biological control for Eucalyptus tortoise beetle

Investigating the potential of Eadya paropsidis (Braconidae) from Tasmania as a biocontrol agent for Paropsis charybdis in New Zealand : May 2012.

Wasp parasitising chrysomelid larva. Photo Anthony Rice
Eadya grooming
Eadya approaching Paropsis charybdis larva
Eadya attacks Paropsis charybdis larva

Despite considerable efforts to date, the eucalyptus tortoise beetle Paropsis charybdis continues to defoliate Eucalyptus nitens plantations throughout New Zealand, requiring constant management through aerial insecticide application, thus preventing expansion of this forest resource.

A parasitoid wasp of the spring-time larval stage of the eucalyptus leaf beetle Paropsisterna agricola (Chapuis) (Chrysomelidae) in Tasmania is being investigated as a potential biological control agent for New Zealand. The potential agent Eadya paropsidis was caught as adults on the wing from E. nitens plantations in northern Tasmania and brought into the laboratory in Hobart for preliminary host specificity testing. Using a sequential no-choice test method to examine the response of individual females, 9 of the 10 female parasitoids attacked P. agricola, while 7 of those 9 attacked P. charybdis larvae. Those P. charybdis larvae that were attacked proved to be a highly suitable physiological host for E. paropsidis development, emerging as a larger sized parasitoid larva from P. charybdis than from P. agricola.

This potential agent will be further evaluated by Scion and eucalypt growers with support from the Sustainable Farming Fund.

The Application

The successful application to the MPI Sustainable Farming Fund follows the initial work by Toni Withers of Scion.

We are in the process of developing milestones and these will be published here. This is a two year scoping study to locate, identify and conduct laboratory and field trials on a new bio-control agent to control the larval of the Eucalyptus Tortoise beetle in New Zealand. This scoping study has two core stages within it. If this project proves successful a 3 year proposal will be submitted to Sustainable Farming Fund in 2014.

From the Grant application:

Project Executive Summary

Eucalyptus trees are a promising plantation species for New Zealand. Unfortunately attack from the Eucalyptus Tortoise Beetle, Paropsis charybdis, is a significant barrier to ongoing commercialisation. Eucalyptus Tortoise Beetle was successfully controlled for two decades using a bio-control agent introduced in 1989. Unfortunately a tiny hyperparasite arrived in 2000 (Baeoanusia albifunicle) that kills the bio-control. Resurgence of the Tortoise Beetle pest has resulted. This project aims to conduct two seasons of field and laboratory research in Tasmania to determine whether a newly identified bio-control agent (Eadya paropsidis) that targets to larval stage of the pest is a suitable bio-control agent for introduction, or if others exist.

Contribution to sustainability or climate change objectives

New Zealand has traditionally focused on radiata pine plantation estates to supply domestic and international wood demand; however there is increasing focus on creating a more diversified forest estate. Increasing market prices for eucalypt hardwood timber and chips over softwoods (radiata pine) gives the industry good cause to invest in hardwood plantations. 

Eucalypts trees are widely used internationally and are renowned for their fast growth. They are already being grown for timber, ground-durable posts, amenity, urban and farm forestry purposes throughout New Zealand. With a range of species available adapted to our climate and with well known and studied wood qualities, eucalypts present a promising resource for regionally adapted forestry (e.g. NZ Dryland forests initiative). 

Unfortunately Eucalyptus nitens forests are the most severely impacted by the recent resurgence of the Eucalyptus Tortoise beetle. This pest threatens the viability of the entire short fibre pulp E. nitens estate. 

Particularly threatened is the FSC certified E. nitens chip export market; South Wood Exports Ltd export 250,000 GM Tonnes of chip annually at a value of $24 million PA. In the central North Island during the last decade Kinleith Mill used 100,000 tonnes of E. nitens chips annually to make quality pulp grades not possible from pine alone. This was estimated to add around $18 million to the bottom line for CHH (pers. comm. B Poole). Currently CHH are replanting this resource at a rate of approx 700 hectares per annum. This runs into millions of dollars of value currently being inadequately protected from this pest. 

Insecticide application is the control option presently available to plantation managers (FFR report by Watson Withers, 2010). Unfortunately, aerial spraying with synthetic pyrethroids (alpha-cypermethrin) over such large areas significantly disrupts the beneficial biological control agents of all pests (Loch, A. D., 2005. Mortality and recovery of eucalypt beetle pest and beneficial arthropod populations after commercial application of the insecticide alpha-cypermethrin. Forest Ecology and Management. 217, 255-265). Insecticide use within forestry was previously very low (reported as 0 mT in 2002 MfE report derived from 1998 figures). The current practice of aerial spraying of E. nitens is detrimental to the environment, and human health, and potentially threatens Forest Stewardship Council environmental certification. 

The sector is committed to finding alternatives to this aerial spraying, and support the identification of bio-control agents to target this major pest. This will reduce the need for insecticide use (particularly in spring) when many other species of biological control agents for minor eucalyptus pests are most active, thus providing an enormous environmental benefit.  

Eucalyptus trees are grown for timber, ground-durable posts, amenity, urban and farm forestry purposes throughout New Zealand. There is continued and growing interest in Eucalypts due to the timbers durability, strength and attractive appearance. Fast growth cycles offer potential for diversification from radiata pine as a key plantation forestry species, while also producing high value short fibre pulp suitable for quality paper production and as a bioenergy feedstock. Eucalypt plantations exist in both the Permanent Forest Sink Initiative (PFSI) and the Emissions Trading Scheme (ETS). 

The Eucalyptus Tortoise beetle, Paropsis charybdis, has been present in New Zealand since 1916, and remains one of the most significant barriers to sustainable economic production of commercial Eucalyptus in the sub-genus Symphyomyrtus. Species that are particularly badly impacted include the short-fibre pulp species Eucalyptus nitens, Eucalyptus globulus and E. grandis, the three primary eucalypt pulp species grown worldwide. Eucalyptus tortoise beetle also favours the popular amenity and farm forestry species Eucalyptus saligna, E. botryoides and E. viminalis, and has also begun to damage the promising Drylands Forests Initiative species E. bosistoana and E. quadrangulata.

In previous decades the Eucalyptus Tortoise beetle was successfully controlled with the egg parasitoid Enoggera nassaui, introduced in 1989. However, a resurgence of Eucalyptus Tortoise beetle has taken place since a hyperparasite (Baeoanusia albifunicle) arrived accidentally from Australia in 2000, specifically wiping out the egg parasitoid.

The Eucalyptus Tortoise beetle pest is now threatening the viability of the entire FSC certified E. nitens pulp export plantations in Southland of 20,000 ha (South Wood Exports Ltd) as well as other plantations and woodlots of the above mentioned species. To combat the renewed threat posed by the Eucalyptus Tortoise beetle and protect current forest estates, forest owners have begun aerially spraying insecticide.

The associated financial and environmental costs make aerial spraying of Tortoise beetle unsustainable for many growers. This proposal’s largest stakeholder Southwood Exports has a limited use derogation permit from the FSC for managing Tortoise beetle outbreaks by aerial spraying. Should this permit be revoked, the FSC- certified pulp export market of this company (valued at $24 mill p.a.) is in jeopardy as it relies upon maintaining its FSC status. By attempting to locate a spring-active biological control agent that targets the Tortoise beetle larvae before they can damage the tree in the key annual spring growth phase, we hope to be able to provide the projects stakeholders with sustainable management of Tortoise beetle.

Expected outcomes

The short-term outcome for this two year project is the successful importation of a promising biological control agent into Insect Quarantine facility in Rotorua. This will be supported by a documented rearing methodology for successful culturing of the biological control agent in the laboratory. In addition methods will have been proposed for the host specificity testing that will need to be undertaken, along with a list of the non-target organisms that will need to be screened within the next stage of the project, to ascertain the environmental safety of the new organism in the New Zealand environment. The EPA decision on this biological control agent will be publically available.

Once the promising biological control agent is imported it will be another three years of Quarantine host specificity testing before the results are reviewed and a decision made on whether it can be released in New Zealand. If permission to release it is granted, we estimate that from the start of this project, until the new biological control agent is released, will be at least 6 years. Usually new biological control agents take another two or three seasons to build up to sufficient numbers in the environment before they significantly impact upon the population dynamics of the pest. The establishment of the agent will be monitored by the industry partners, and insecticide volumes applied to plantations will be tracked. We can expect to see a reduction in reliance of the forest industry on aerial insecticide sprays to manage Tortoise beetle in E. nitens plantations within 8 years, and this will be easily evaluated by obtaining plantation management statistics from the companies involved.

Although the time-scale from conception to be being able to observe or measure the specific benefits of this project is long, the potential long term benefits to the New Zealand forest industry and the environment are large.



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