Invasive plant biocontrol research

Weed biocontrol agent rear and release

Research officers: Kelli Pukallus and Ainsley Kronk

This project aims to mass-rear, release and monitor biocontrol agents in northern Queensland including Cecidochares connexa (stem-galling fly) on Siam weed (Chromolaena odorata).

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 within northern Queensland in November 2019 are targeting Siam weed populations throughout northern Queensland, with assistance from Local Government, landholders, NRM groups, Qld Government Departments and the Department of Defence. Adult C. connexa flies are being sent to the Northern Territory to assist with establishing a field and rearing colony.

The impact of C. connexa on Siam weed populations, pre and post release monitoring of Siam weed populations is being done at sites across the Siam weed distribution in north Queensland.

Surveillance of previously released biological control agents is continuing to monitor establishment and spread including maintaining a catalogue of associated insects and agents occurring on target weed species.

Parkinsonia biocontrol

Research officers: Kelli Pukallus and Clare Warren

Parkinsonia aculeata is a woody invasive weed species found throughout northern Australia. Previous biological control projects have seen UU (Eueupithecia cisplatensis) mass-reared in large numbers at the Tropical Weeds Research Centre at Charters Towers and released within Queensland, Northern Territory and Western Australia.

This project will see the expansion of mass-rearing and release of the biological control agent UU2 (Eueupithecia vollonoides) throughout northern Australia. This project is conducted with funding from Meat and Livestock Australia and CSIRO through the Australian Government’s Rural Research and Development for Profit program.

Bellyache bush biocontrol

Research officers: Kunjithapatham Dhileepan, Di Taylor and Kai Hart

Bellyache bush (Jatropha gossypiifolia) is a serious weed of dry tropical regions of northern Australia, particularly riparian and sub-riparian habitats. Biocontrol efforts between 1997 and 2003 resulted in the release of a seed feeding jewel bug. So far there is no evidence of is field establishment. Host specificity testing of the Jatropha rust strain from Trinidad by CABI (UK) has been completed. In quarantine, the Jatropha rust induced limited sporulation on two of the Australian native non-target test plant species. In the field susceptibility studies for the two non-target species in Trinidad there was no evidence of rust infection or there was no sporulation suggesting that the two non-target test plants are not natural hosts for the rust species. Currently studies on the life cycle of the Jatropha rust are in progress at CABI (UK) to look for the sexual stages teliospores) of the rust. A leaf-miner (Stomphastis sp.) was imported from Peru and a colony of the agent has been maintained in quarantine. Host specificity tests for the leaf-miner have been completed and an application seeking approval for its field release has been submitted. Based on feedback from the regulatory authorities, additional host specificity testing is being conducted. A gall midge collected on a Bolivian native Jatropha clavuligera, and leaf-feeding midge native to bellyache bush in Paraguay, are being considered as prospective biological control agents. Preliminary host specificity tests for the two midges are in progress in Argentina. A morphological and molecular taxonomic study on the species status of the two midges is also in progress. If proven as distinct species from the polyphagous crop pest Prodiplosis longifila, and the preliminary host specificity tests suggest that the two midges are host specific, the midge from Paraguay will be imported into quarantine in Australia for detailed host specificity tests.

Prickly acacia biocontrol

Research officers: Kunjithapatham Dhileepan, Di Taylor, Boyang Shi, Mahbubur Rahman and Kai Hart

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. Biological control efforts so far have focused on agents from Pakistan, Kenya, South Africa and India, with limited success to date. Hence, the search for new agents, focussing on gall-inducers, was redirected to Ethiopia and Senegal, based on plant genotype and climate matching. Surveys were conducted on V. nilotica subspecies with moniliform fruits including the invasive subspecies indica. Prospective biological control agents have been identified based on damage potential, field host range and climate match. A gall thrips (Acaciothrips ebneri) inducing shoot-tip rosette galls and a gall mite (Aceria sp.) deforming leaflets, rachides and shoot-tips in Ethiopia; and a tephritid fly (Notomma mutilum) inducing stem-galls in Senegal have been prioritised for further studies. The gall thrips from Ethiopia has been imported into quarantine in Brisbane, Australia and host specificity tests are in progress. The eriophyid gall mite from Ethiopia has been imported into quarantine in Pretoria, South Africa and host specificity tests are also in progress there. Results to date suggest that both agents are highly host specific, at the subspecies level of the target weed. Future research will focus on the host specificity testing of the tephritid gall fly from Senegal which has been imported into quarantine in Brisbane, Australia.

Cat’s claw creeper biocontrol

Research officers: Kunjithapatham Dhileepan and Boyang Shi

Cat’s claw creeper (Dolichandra unguis-cati) is a Weed of National Significance in Australia. Biocontrol 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 visible damage in the field. Field establishment of the leaf-tying moth has been noticed only in a few of the release sites. The leaf-mining beetle has established well in all release sites and is spreading widely. Future focus will be on monitoring the establishment status of all the three agents (tingid, leaf-tying moth and the leaf-mining beetle). 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 identified two rust fungi, a rust-gall (Uropyxis rickiana) and a leaf-rust (Prospodium macfadyenae) as prospective biological control agents. More recently, a leaf-spot pathogen (Cercosporella dolichandrae), causing widespread defoliation in South Africa, has been identified as a prospective biocontrol agent as well. Currently, host specificity testing of two plant pathogens, the leaf-spot pathogen and the rust-gall are being conducted in collaboration with CABI (UK).

Parthenium biocontrol

Research officers: Kunjithapatham Dhileepan and Boyang Shi

Parthenium weed (Parthenium hysterophorus L.), a noxious weed of grazing and cropping areas in Queensland, reducing pasture and crop production. It 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. These agents have become established and have proven effective against the weed in central Queensland (CQ). Parthenium is spreading into south Queensland (SQ) and southeast 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. Redistribution of field collected biological control agents from CQ and monitoring their establishment status in the field will continue over the next three years.

Navua sedge biocontrol

Research officers: Kunjithapatham Dhileepan, Boyang Shi, Melissa Setter and Stephen Setter

Navua sedge (Cyperus aromaticus), a perennial grass-like sedge, is an extremely aggressive weed affecting beef, dairy and sugarcane industries in the Queensland wet tropics. The sedge is unpalatable, and can form dense stands, by replacing palatable tropical pasture species. Over 500 beef producers, dairy farmers, crop and hay producers in the Atherton Tableland region are affected by the weed.

Current management options are mechanical and chemical, which are expensive and offer short-term relief. Biological control is the most cost effective and long-term management option. Though there are report of rusts on Navua sedge from West Africa, biological control options for the management of Navua sedge have not been explored to date.

In response to stakeholder demand, Biosecurity Queensland has funded a study to look for specialist natural enemies as biological control agents for Navua sedge in its native range. The native range of Navua sedge includes countries in equatorial Africa and islands in the Indian Ocean, off the coast of southeast Africa. Native range surveys were conducted in Eastern Africa, in view of their ease of access and local scientific support.

A smut pathogen that attacks Navua sedge’s flower head and seeds has been identified as a prospective biocontrol agent. The smut pathogen on Navua sedge was shown to represent a new species of Cintractia that differed in a molecular phylogenetical analysis from smut pathogens found on other sedges in East Africa. The newly discovered smut on Navua sedge is being described as a new species. Field host range and molecular studies suggests that the smut pathogen is likely to be host specific.

Further studies will be undertaken to conduct host specificity tests for the smut pathogen in a quarantine facility in CABI-UK, and seek approval for its release in Australia, if proven host specific. Additional funding will be needed to undertake detailed host-specificity testing in an overseas quarantine facility, which is usually the most expensive and time-consuming component of biocontrol research. In view of previous records of rusts on Navua sedge in Gabon and Nigeria, future surveys efforts will also focus on West Africa to specifically look for rusts affecting Navua sedge as biological control agents.

Risk assessment model for weed biocontrol

Research officer: Di Taylor

Host testing of weed biocontrol agents is an effective tool for predicting the likelihood of damage by a proposed biocontrol agent on non-target species. However, sometimes “false positives” occur when an agent attacks non-target plants which it would not under natural conditions and this can lead to a host specific agent being rejected for release by regulatory bodies. New Zealand regulatory authorities have adopted a quantitative risk analysis approach for interpreting such results. Victorian researchers (with our assistance), propose to validate this method for Australian weed biocontrol targets. The implementation of this approach will assist with the testing and release of suitable biocontrol agents in Queensland to control target weeds.

Clidemia biocontrol

Research officers: Michael Day, Jason Callander, Liz Snow and David Comben

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 the Ecosciences Precinct. If appropriate, an application seeking its release will be submitted to the Australian regulators.

Giant rat’s tail grass biocontrol

Research officers: Michael Day, Tamara Taylor, Natasha Riding, Lauren Kelk and Jason Callander

Giant rat’s tail grass is the common name of two species, namely 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, success has not been achieved and weedy Sporobolus grasses continue to rapidly spread into new areas. A biological control project was implemented in the 1990s but did not result in the release of any biological control agents. Under a new project, three wasps from the genera Tetramesa and Bruchophagous were found on the weedy Sporobolus species in South Africa. Field host-range testing has suggested that all three wasp species are suitable for introduction into Australia. Laboratory testing in South Africa has commenced on Tetramesa sp. A., as it appears to be the most damaging. Under a more recent project, research on these species will continue. The three wasp species will be sent for identification. Tetramesa sp. A will be imported in quarantine in Brisbane for detailed host specificity testing. Host specificity testing of Tetramesa sp. B will occur in South Africa.

Biocontrol of pasture weeds in Vanuatu and Queensland

Research officers: Michael Day, Tamara Taylor and Lauren Kelk

Manaaki Whenua Landcare Research NZ Ltd are collaborating with Biosecurity Queensland on a 5-year weed biocontrol project based in Vanuatu funded by the NZ Ministry of Foreign Affairs and Trade. The work builds on previous projects in Vanuatu funded by the Australian Government and managed by Biosecurity Queensland. 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 candidates. Potential candidates 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 Australian Government regulatory authorities. Five other weeds, Spathodea campanulatumParthenium hysterophorusLantana camaraMimosa diplotricha and Dolichandra unguis-cati, all restricted weeds in Queensland, will also be targeted under this project and will involve importing effective agents from Queensland or elsewhere into Vanuatu. Agents for S. campanulata will be considered for introduction into Queensland to help manage this weed here if warranted.

Efficacy of biocontrol on harrisia cactus in southern Queensland

Research officer: 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. Harrisia cactus was introduced to Queensland in the 1890s and is now found at numerous sites across the state, including the Whitsunday, Central Highlands, Isaac and Goondiwindi areas. Minor infestations also occur in Toowoomba region, Lockyer Valley, Ipswich, Central Queensland and Maranoa areas. Harrisia is a prolific seeder. It spreads quickly, and has the ability to take over large grazing areas. It grows particularly well on brigalow soils. In Queensland, the Brigalow ecological community has been listed under the EPBC Act as 'endangered' under the Queensland Vegetation Management Act 1999. The spraying of herbicides to control harrisia cactus may pose a risk to the listed community. The biological control agent, the mealy bug Hypogeococcus festerianus, was released in the 1970s and is providing effective control in central Queensland. However, the cactus is not considered under adequate control in south Queensland, with the core Goondiwindi infestation spreading out to Moonie, Milmerran, Toobeah and Yelarbon, as well as into New South Wales.

A University of Queensland PhD student is being co-supervised by Biosecurity Queensland researchers to better understand the differences in efficacy of the biological control agent in central and southern Queensland. The project will determine 1. Identity of the Hypogeococcus species introduced into Australia through molecular studies, 2. Effect of temperature on the life history of the Hypogeococcus species, 3. Effectiveness of the mealy bug on different harrisia cactus populations, 4. Effect of other biotic and abiotic factors on effectiveness of the mealy bug.

Cactus biocontrol

Research officers: Jason Callander, Tamara Taylor and Lauren Kelk

Six Cylindropuntia species are present in Queensland. All are classed as either prohibited or restricted weeds, and all are declared targets for biological control. To date, four Dactylopius tomentosus lineages, demonstrated to be specific and damaging to particular Cylindropuntia species, have been released in the field in Queensland: ‘Cholla’ on C. fulgida var. mamillata, ‘Californica’ lineage on C. pallida and C. prolifera, ‘Cylindropuntia’ lineage on C. imbricata and ‘Bigelovii’ lineage on C. spinosior. While there are very effective lineages for some Cylindropuntia species, e.g. ‘Cholla’ on C. fulgida var. mamillata, more effective lineages are still required for C. imbricata and C. spinosior. Current laboratory trials suggest that one lineage not previously tested shows particular promise as a biological control agent for C. spinosior. In addition to finding effective lineages for the two Cylindropuntia species, hybridization trials are currently being undertaken to determine whether efficacy of lineages will be compromised if lineages hybridise in the field. Field studies are currently underway to assess integrated control measures using a combination of chemical treatments and biological control on C. imbricata.

Mikania biocontrol

Research officer: Tamara Taylor

Mikania micrantha was first reported in Queensland in 1998 and is also present on the Australian territories, Christmas and Cocos Islands. Mikania is the target of a national cost-share eradication program. Cyclones hampered early eradication progress and a review of the program suggested that biocontrol options should be investigated. Mikania micrantha was nominated as a target for biological control in 2014, and host testing of rust pathogen Puccinia spegazzinii was conducted in 2015. Fifteen species in the Eupatorieae and six species in the tribe Heliantheae were host tested at Ecosciences Precinct. Pustules did not form on any other species other than M. micrantha. The rust Puccinia spegazzinii is deemed host specific, having been tested in four countries against a total of 274 species, representing 73 families, including 87 species in the Asteraceae and 21 species in the tribe Eupatorieae. Release of P. spegazzinii on Mikania micrantha has been approved by the Australian Government regulator following public and expert comment. A culture of P. spegazzinii has been maintained in the quarantine facility at Ecosciences Precinct in anticipation of release approval. A culture of the pathogen has now been established outside of quarantine, to be distributed for field release as required.

Weed management in the Pacific

Research officer: Michael Day and Jason Callander

Biological control options for several weeds that have not previously been targeted for biological control either globally, or in Australia will be explored. While the exact composition of all new target species will depend on individual country priorities, two of the weeds, African tulip tree (Spathodea campanulata) and Singapore daisy (Sphagneticola trilobata) are viewed as important in many Pacific island countries. Both weeds are restricted weeds in Queensland and so are priority species. Other components of the project, will entail providing effective biological control agents for each individual country’s priority weeds. These weeds include Mikania micrantha and Parthenium hysterophorus, both of which are restricted weeds in Queensland. There is already a biological control agent for S. campanulata, which could be introduced into Queensland, while overseas exploration in the native range to seek potential candidate agents would be required for S. trilobata.