Invasive plant biocontrol research

Weed management in the Pacific

Project Leader: Jason Callander

Biological control options for several weeds that have not previously been targeted for biological control in Australia, or globally, will be explored. While the exact composition of all new target species will depend on individual Pacific island country priorities, African tulip tree (Spathodea campanulata) and Singapore daisy (Sphagneticola trilobata) are viewed as important in many Pacific island countries. These weeds are restricted weeds in Queensland and so are priority species for Biosecurity Queensland. Spathodea campanulata has been sucessfully nominated as a candidate for biological control in Australia. Biological control agents already exist for S. campanulata and these could be introduced into Queensland for host testing. Native range exploration to seek potential candidate agents for S. trilobata is currently underway. Other components of the project will entail providing effective biological control agents for individual country’s priority weeds.

Weed biological control – Clidemia hirta

Project Leader: Jason Callander

Clidemia hirta (Koster’s curse) is a fast growing weed of grazing, plantations, cropping and natural ecosystems in many countries. It was the target of a national cost-share eradication program, based in north Queensland. However, as more infestations were found, eradication of the species was no longer possible and it is now in ‘transition to management’. If left uncontrolled, it is possible that it can spread south along the Queensland coast to Hervey Bay. Prospects for biological control of C. hirta are very good. This project will initially target Liothrips urichi Karny (Thysanoptera: Phlaeothripidae), which has been released in numerous countries and appears to be very effective. Host specificity testing will be conducted in the quarantine facility at ESP. If appropriate, an application seeking its release will be submitted to the Australian regulators. If not appropriate, a another prospective biocontrol agent will be investigated.

Biological control of cactus species

Project Leader: Jason Callander

Invasive Opuntioid cacti are found within most Australian states and territories, with a great potential for increased distribution from the regions where they are currently established. Chemical control can be effective for some species, but in some regions the costs of chemical control exceeds the value of the land, highlighting the importance of finding alterative cost effective approaches to control invasive cacti in Australia. Biological control of some invasive cacti in Australia has been highly successful in many areas. However, for other species, no biological control agents have been deliberately released and, in most cases, differences in biotic and abiotic conditions influencing their efficacy have not been identified.

Biological control of lantana

Project Leader: Jason Callander

Complexities in lantana varieties have hampered biological control efforts to date, demonstrating a need for targeted matching biological control agents to specific lantana varieties. As such, Biosecurity Queensland has pledged in-kind support to a project led by NSW Royal Botanic Gardens. This project will undertake surveys to collect and supply lantana leaf samples from around Queensland for use in cutting-edge phylogenomic analyses to unravel the evolutionary history of Lantana camara. This project also seeks to evaluate the effectiveness of biological control on lantana in Queensland through a comprehensive insect-exclusion trial. The project will also seek to introduce and release two agents, the pathogen Puccinia lantanae, which was tested by CABI under contract, and the gall fly Eutreta xanthochaeta, which is aiding control in Hawai’i.

Weed biological control - Navua sedge

Project Leader: Kunjithapatham Dhileepan

Navua sedge is an extremely aggressive perennial sedge affecting the beef, dairy and sugarcane industries in the Queensland wet tropics. Biological control is the most cost effective and long-term management option for the weed. Navua sedge has been approved as a target for biocontrol in Australia, and a list of test plants for host specificity testing has been compiled. Surveys in equatorial Africa have identified a new smut fungus attacking flower heads and seeds, and a rust fungus attacking leaves and stems, as promising biological control agents. Both pathogens have been exported to CABI-UK. Research on the biology and host specificity of the two pathogens is in progress in quarantine in CABI-UK. Research on identifying native pathogens in Australia as prospective mycoherbicides and understanding the genetic diversity of Navua sedge populations in Queensland and in its native range (equatorial Africa) is also in progress.

Biological and chemical approaches to ‘on-farm’ management of the invasive weed, Navua sedge

Project Leader: Kunjithapatham Dhileepan

Navua sedge (Cyperus aromaticus) is an extremely aggressive perennial sedge affecting the beef and dairy industries in the Queensland wet tropics. The sedge is unpalatable and can form dense stands replacing palatable tropical pasture species. Current management options are mechanical and chemical, which are expensive and offer only short-term relief.  Biological control is the most cost effective management option for the weed in the long term. The project will develop biological and chemical approaches for effective management of Navua sedge.

Weed biological control - prickly acacia

Project Leader: Kunjithapatham Dhileepan

Biological control is the most economically-viable management option for prickly acacia (Vachellia nilotica subsp. indica), a serious weed of grazing areas in western Queensland, and also a Weed of National Significance. A gall thrips (Acaciothrips ebneri) from Ethiopia inducing shoot-tip rosette galls, a gall mite (Aceria sp.) also from Ethiopia deforming leaflets, rachides, and shoot-tips, and a gall fly (Notomma mutilum) from Senegal inducing stem-galls have been prioritised for further studies. Host specificity tests for gall thrips have been completed and an application seeking approval to release the gall thrips in Australia has been submitted (approval for release subsequently granted late 2022). Lifecycle studies and host specificity tests for the gall fly are in progress. Host specificity testing of the gall mite from Ethiopia in quarantine in South Africa has been delayed due to difficulties importing the agent. Host specificity testing of the gall mite will commence when it is safer to visit to Ethiopia to collect and export the gall mites.

Biological control of bellyache bush

Project Leader: Kunjithapatham Dhileepan

Bellyache bush is a serious weed of dry tropical regions of northern Australia, particularly riparian and sub-riparian habitats. Biocontrol research between 1997 and 2003 resulted in the release of a seed feeding jewel bug. So far there is no evidence of its field establishment. Host specificity testing of the Jatropha rust strain from Trinidad by CABI (UK) has been completed. An application seeking approval to release the rust in Australia is being prepared for submission. Host specificity testing for a leaf-miner (Stomphastis thraustica) from Peru has been completed and a release application submitted (approval for release subsequently granted late 2022).

A gall midge on Jatropha clavuligera in Bolivia and on bellyache bush in Paraguay is being considered as a prospective biocontrol agent for bellyache bush. Based on morphological, molecular, and preliminary host specificity studies, the midge has been described as a new species – Prodiplosis hirsuta. The midge will be imported into quarantine in Australia for host specificity tests.

Biological control of parthenium

Project Leader: Kunjithapatham Dhileepan

Parthenium weed (Parthenium hysterophorus L.), a noxious weed of grazing areas in Queensland, is a Weed of National Significance in Australia. Parthenium also causes severe human and animal health problems. Eleven biological control agents (nine insect species and two rust pathogens) have been released against parthenium in Australia. The majority of these agents have become established and have proven effective against the weed in the central Queensland (CQ). Parthenium is spreading into south Queensland (SQ) and south-east Queensland (SEQ), where many of the widespread and effective biological control agents in CQ are not present. Hence, the seed-feeding weevil (Smicronyx lutulentus), the stem-boring weevil (Listronotus setosipennis), the root-boring moth (Carmenta ithacae), the summer rust (Puccinia xanthii var. parthenii-hysterophorae) and the winter rust (Puccinia abrupta var. partheniicola) have been redistributed from CQ into SQ and SEQ.

Biological control of cat’s claw creeper

Project Leader: Kunjithapatham Dhileepan

Cat’s claw creeper is a Weed of National Significance in Australia. Biological control is considered the most desirable option to manage the weed. So far, a leaf-sucking tingid, a leaf-tying moth and a leaf-mining beetle have been approved for field release. The tingid has become established widely and is causing damage in the field. The leaf-tying moth is established at only a few release sites and is spreading slowly. The leaf-mining beetle has established well in all release sites and is spreading widely. Since cat’s claw creeper is a perennial vine with abundant subterranean tuber reserves, additional agents are needed to complement the existing agents. Surveys in Brazil, Argentina and Paraguay have identified a rust-gall and a leaf-rust as prospective biological control agents. A leaf-spot pathogen, causing widespread defoliation in South Africa, has been identified as a prospective biocontrol agent. Host specificity testing for the leaf-spot pathogen is in progress at CABI, UK.

Biological control agent compendium

Project Leader: Kelli Pukallus

Create a detailed biological control agent compendium for all agents released for the management of invasive weeds in Queensland. This would be include release procedure, agent information, agent locations (for field collections), general distribution and impact.

Parkinsonia biological control: UU2 colony maintenance

Project Leader: Kelli Pukallus

Maintain a small colony of UU2 (Eueupithecia vollonoides) at Tropical Weeds Research Centre for research.

Weed biological control agent rear and release

Project Leader: Kelli Pukallus

The stem-galling fly (Cecidochares connexa) is the first biological control agent to be released within Australia for Siam weed. Siam weed is a high priority, high risk invasive weed in Queensland. Approval for C. connexa release was granted in late 2018 and mass-rearing commenced in August 2019 at Tropical Weeds Research Centre in Charters Towers. Releases commenced in November 2019 targeting Siam weed populations throughout northern Queensland, with assistance from local government, landholders, NRM groups, Queensland Government Departments and the Department of Defence. Adult C. connexa flies are being sent to the Northern Territory to assist with establishing a colony for field release.

Giant rat's tail grass classical biological control

Project Leader: Tamara Taylor

Giant rat’s tail grass (GRT) is the common name for Sporobolus pyramidalis and S. natalensis. Current control efforts for weedy Sporobolus grasses rely on the use of chemical, mechanical, plant competition and pasture management. However, weedy Sporobolus grasses continue to rapidly spread into new areas. With funding from the Australian Government and AgriFutures, two wasp species (Tetramesa spp.) were found on GRT in their native range of South Africa. Rhodes University have conducted extensive field and laboratory host-range testing and have found both wasps to be host specific to the target species and potentially suitable agents for biological control of GRT in Australia. The wasps will be imported into quarantine in Brisbane to conduct further biological studies and begin host testing on Australian grass species.

Biocontrol of pasture weeds in Vanuatu

Project Leader: Tamara Taylor

This is a 5-year weed biocontrol project based in Vanuatu funded by the NZ Ministry of Foreign Affairs and Trade. The work will build upon previous work in Vanuatu funded by the Australia Government. The three main pasture weeds targeted under this project are Senna tora (a restricted weed in Queensland), Solanum torvum (a weed declared by some local governments) and Urena lobata, a widespread weed throughout the state. These weeds are new biological control targets, requiring overseas exploration in the respective native ranges of each species to locate potential biological control agents. Candidate agents for S. tora will be brought into the quarantine at the Ecosciences Precinct, while those for S. torvum and U. lobata will be studied in NZ. If appropriate, applications seeking approval to release the agents in Australia and Vanuatu will be prepared and submitted to the relevant regulatory authorities.

Harrisia martinii biological control and integrated management

Project Leader: Tamara Taylor

Native to South America, Harrisia cactus is a spiny perennial plant that can form dense infestations, choking out other pasture species and causing injuries to stock. A mealy bug biological control agent released in the 1970s appears to be providing effective control in some but not all areas of Queensland. During 2021 and 2022, investigations were conducted by a University of Queensland PhD student to identify the thermal limitations to the development of the mealy bug. Climate models will be produced. A potential new biocontrol agent in Argentina was also identified. A research organisation in South America will be contracted to collect the stem-feeding fly (Dasiops bourquini) and develop successful rearing methods, prior to importation into Australia for comprehensive host testing. Soil seed bank studies will examine the viability of seed in the soil after different long-term management regimes. Additionally, controlled aged testing of Harrisia seeds will be conducted to approximate seed longevity.

Endemic pathogens of giant rat's tail grass

Project Leader: Joe Vitelli

Sporobolus is a genus of ~200 grass species in tropical & subtropical parts of the world, including Africa, temperate and tropical Asia, Australasia and North and South America. In Australia, 19 species are endemic, and a further eight species are naturalised weeds. Giant rat’s tail grass (GRT) and the other introduced weedy Sporobolus grasses are unpalatable, perennial, tussock-forming grasses of serious concern to the grazing industry across eastern Australia. GRT reduces carrying capacity and productivity of more than 450,000 ha of pastoral land in eastern Queensland, NSW and areas of Victoria and is a high-risk fodder contaminant. Research will prioritise the endemic pathogens and determine their pathogenicity on 15 native Sporobolus species and ten closely related species and introduced pasture species. Given there are native species in the same genus, studies will be required to select the most promising pathogen to lower the risk to biodiversity and increase productivity in Queensland and NSW.

Biological control and ecology of chinee apple (Ziziphus mauritiana)

Project Leader: Olusegun Osunkoya

Ziziphus mauritiana (Rhamnaceae), commonly known as Indian ber or chinee apple, has become a major pasture and environmental weed in northern Australia. Its impenetrable thickets hinder stock and affect pasture production. Current management options (mechanical and chemical) are expensive. Despite its long-term presence (since 1880), only limited data are available on its distribution, economic loss and prospects for biological control. This project will involve preliminary research to pursue future weed biological control on the weed. Research will initially focus on the assessment of its spread, economic loss, genetic diversity and introduction history in Australia, develop a Climex model for the weed, and identify native pathogens in Australia as prospective mycoherbicides. We will nominate and declare Z. mauritiana as an approved target for weed biological control in Australia. Attempts will also be made to establish overseas collaborative partners in its native ranges.