The current MLA funded research project will build on previous research investments made into parkinsonia management by focusing rearing and release efforts on Eueupithecia vollonoides (nicknamed “UU2”) . We will continue collaboration with local government for identification of new release sites, mass rearing and further releases of UU2 are planned across QLD, NT and WA.
This project will also screen an additional agent for parkinsonia biological control. The stem-galling fly from Argentina (Neolasioptera aculeatae) was identified as a potential agent during initial native range surveys and warrants further investigation. The stem-galling fly has the capacity to reduce the growth and reproduction of parkinsonia, but host-specificity of this species is yet to be comprehensively evaluated and needs to undergo an appropriate risk assessment prior to being permitted for release into Australia.
Research by Queensland Government researchers on biological control of parkinsonia has resulted in the introduction of three insect species between 1989 and 1995; a sap‐sucking bug (Rhinacloa callicrates Herring) and two seed‐feeding beetles (Mimosetes ulkei (Horn), and Penthobruchus germaini Pic). The seed‐feeding bruchid, P. germaini, is widely established across northern Australia, while R. callicrates appears to be common in Queensland. These were inadequate on their own to control parkinsonia populations. CSIRO therefore recommenced native range surveys to identify potential control agents in 2002, with new surveys conducted across central and South America, including in Argentina, Brazil, Costa Rica, Guatemala, Mexico, Nicaragua, Paraguay, Peru, USA and Venezuela. Several species identified in Mexico and Argentina were imported into CSIRO’s quarantine facilities in Brisbane to conduct host‐specificity studies to determine the risk associated with releasing these insects into the Australian environment. Based on detailed tests to demonstrate their safety, CSIRO received approval from the Commonwealth of Australia in 2012 and 2014, to release two closely related leaf‐feeding moths, Eueupithecia cisplatensis and Eueupithecia vollonoides (nicknamed UU1 and UU2, respectively).
Established biological control agents on parkinsonia include seed‐feeding weevil Penthobruchus germaini (top three images) and leaf‐feeding moths in the genus Eueupithecia approved forrelease as part of this project. Photo sources: Queensland Government (QG) and CSIRO.
Understanding the physiology of the two leaf-feeding moth species, allowed for improved mass-rearing and release techniques for these biocontrol agents with the goal to establish populations across parkinsonia infestations in northern Australia. Mass rearing hubs were established at CSIRO’s facilities at the Ecosciences Precinct in Brisbane, the Queensland’s Department of Agriculture and Fisheries’ Tropical Weeds Research Centre, Charters Towers, and the Northern Territory’s Department of Natural Resources, Environment, the Arts and Sport in Darwin. From these mass-rearing hubs, agents are shipped across Australia for release onto weed populations through a vast network of collaborators including state and territory government agencies, regional biosecurity officers, Traditional Owners, NGOs and landholders. Since the commencement of mass-rearing in 2013, releases of UU1 and UU2 totalling over 900,000 and 220,000 individuals respectively, have been made. The coverage of these releases has been extensive (see Figure and Table below); UU1 and UU2 have been released at 162 and 34 sites respectively and populations of these species are being detected at >60% of the release sites at least one year after initial releases.
Releases (left) and establishment (right) of E. cisplatensis (UU1; red dots) and E. vollonoides (UU2; blue dots) on parkinsonia infestations across northern Australia, showing releases relative to parkinsonia occurrence (squares; data source: QDAF – WONS survey 2005).
Release and monitoring of UU1/UU2 in the field. a) Pupae are released within a delta trap for protection, b) larvae are released on a ‘nest’ of parkinsonia foliage, c) larvae feeding, d) female adult, e) using the beat sheet method for monitoring populations for establishment and abundance.
Releases of UU1 and UU2 across northern Australia between 2013-2018.
|Species||State||No. release sites||Total no. releases||Total pupae released||Total larvae released|
Plans for the future
Evaluation: Once UU1 and UU2 have reached sufficient densities across the landscape, it would be of value to undertake a comprehensive quantitative evaluation of the combined impacts of these agents and P. germaini on parkinsonia populations. In addition to their chronic effects on plant health, biological control agents, when established across the landscape, can also periodically build up to outbreak densities at certain sites and times and have additional impacts on weed populations. These outbreaks typically coincide with recovery of weed populations from other stressors (e.g. drought). The recovery of areas of northern Australia from drought may therefore present circumstances for opportunistic surveys of parkinsonia infestations to see how UU1 and UU2 perform in such circumstances. Such evaluation would enable characterisation of the impacts of the biocontrol agents and to meaningfully undertake cost‐benefit analyses of different types of parkinsonia management.
Integration: Biocontrol is one tool in the integrated weed management toolbox. Management of parkinsonia is best done as part of an integrated management approach, and biological control is rarely a “silver bullet” management tactic on its own. Therefore, the following may be a prudent approach to parkinsonia management.
- Manage small parkinsonia infestations (and large infestations that are easy to access) early by killing adult/reproductive plants using established and approved chemical or mechanical methods.
- Use biological control in large infestations to allow them to be a chronic stressor on plant health and reproduction, while resources/time can be garnered to manage parts of parkinsonia infestations where the agents fail to establish due to some reason.