Weed 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. These agents include; Aceria lantanae onLantana camarae and Eueupithecia cisplatensis (UU2) on Parkinsonia aculeata, with Cecidochares connexa on Siam weed and potentially Stomphastis sp on bellyache bush.

The lantana budmite, Aceria lantanae, has been released throughout northern Queensland on various varieties of lantana and environmental conditions. Monitoring will to continue to assess for further establishment and spread of the agent. Field-collected galls from northern Queensland to be used for releases in new and unestablished locations within Queensland.

The new biological control agent gall-fly (Cecidochares connexa) for Siam weed (Chromolaena odorata) was approved for release in late 2018. Mass rearing and releasing expected to commence by June 2019 at TWRC. No biological control agents have previously been released within Australia on Siam weed, but the gall-fly is producing significant damage in PNG and neighbouring islands. Experimental plots at three sites within northern Queensland will assess pre and post-establishment damage of the agent.

CSIRO are contracting QDAF to mass-rear and release UU2. This project we be undertaken for two years, commencing mid-2019, to improve establishment rates of UU2 throughout northern Australia. No monitoring will be involved in the project.

Surveillance of previous released biological control agents is important to monitor establishment rates and spread and detect any new locations. Yearly and monthly surveys are conducted on a variety of agents and collections of associated insects are catalogued. Other biological control programs are also assisted through field assessments e.g. parthenium and lantana agents.

Bellyache bush biocontrol

Research officers: Kunjithapatham Dhileepan and Di Taylor

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 renewed biocontrol effort with funding from MLA and the Queensland Government’s War on Western Weeds program resulted in the in the importation and establishment of colonies of a leaf-miner (Stomphastis sp.) from Peru. Host specificity tests for leaf-miner has been completed and an application seeking approval for its field release has been submitted. Based on feedback from the regulatory authorities, additional host specificity tests are being continued. A gall midge on a Bolivian native Jatropha host (Jatropha clavuligera), and leaf-feeding midge native to bellyache bush in Paraguay, are being considered as a 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 ongoing host specificity tests suggest that the two midges are host specific, one of the midges will be imported into quarantine in Australia for detailed host specificity tests.

Prickly acacia biocontrol

Research officers: Kunjithapatham Dhileepan, Di Taylor and Boyang Shi

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, focusing 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, a gall mite (Aceria sp.) deforming leaflets, rachides and shoot-tips in Ethiopia and Senegal; a gall midge (Lopesia niloticae) inducing leaf rachis galls 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 in quarantine in Brisbane, Australia.

Invasive lianas biocontrol

Research officers: Kunjithapatham Dhileepan and Di Taylor

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 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). Cat’s claw creeper, being 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 (Cercospor ella 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 will are being conducted in collaboration with CABI (UK).

Parthenium biocontrol

Research officers: Kunjithapatham Dhileepan, Jason Callander and Kelli Pukallus

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 the 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 be continued over the next three years.

Biological control of Navua sedge: feasibility studies

Research officer: Kunjithapatham Dhileepan

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 attack 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. This is usually the most expensive and time-consuming component of biocontrol research. Additional funding has now been obtained (5/2019). If proven host specific approval will be sought for its release in Australia. In view of previous records of rusts on Navua sedge in Gabon and Nigeria, future surveys efforts will also focus on West Africa.

Biological control of Clidemia

Research officer: Michael Day

Clidemia hirta (Koster’s curse) is a major 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. 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.

Clidemia hirta is a fast growing rainforest shrub that grows to about 3 m. It is mainly a species of the understory, where it can suppress the growth of other plant species, but it can also grow in open, sunny areas. Shrubs mature in one year and each fruit produces over 300 (range 360-832) seeds which are dispersed by birds and mammals. A single shrub can produce over 3 million seeds annually. Seedling emergence can still occur 10 years after the removal of mature plants.

Prospects for biological control of C. hirta are very good. Seven agents have been released in Hawaii and six of these have established. Liothrips urichi Karny (Thysanoptera: Phlaeothripidae) has been released in numerous countries and appears to be effective in open, sunny areas. However, it is not so effective in shaded areas. The fungal pathogen Colletotrichum gloeosporioides (Penz) Sacc. f. sp. clidemiae Trujillo (Melanconiales) was released in Hawaii in 1986 and is causing leaf fall and dieback, especially in shady, high humidity areas. The other four species appear to only cause minor damage in Hawaii.

This project will initially target the thrips and cultures will be imported from either Hawaii or Palau. 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.

Cactus biocontrol

Research officer: Michael Day

Eight Cylindropuntia spp. have naturalised in Australia, of which six species are present in Queensland and are classed as prohibitive or restricted weeds. All species are approved targets for biocontrol. A biotype of Dactylopius tomentosus was introduced into Australia as a biocontrol agent of C. imbricata in 1925 but it does not control other Cylindropuntia species. Research shows that different D. tomentosus biotypes have different host ranges and impacts within the Cylindropuntia. A biotype of the same species, which is effective against only C. fulgida var. mamillata , was released in 2016. Three different biotypes that attackC. pallida (Hudson pear), C. imbricata (rope pear), C. spinosior (snake cactus) and C. prolifera (jumping cholla) have also been released in Queensland. All four new biotypes have established at one site at least, where their host plant occurs. However, some biotypes still need to be mass-reared to facilitate field releases throughout Queensland and other states. The biotype ear-marked for C. spinosior does not appear to be performing well in the field and other biotypes of the cochineal are being investigated to find a more effective biotype.

In addition to the mass-rearing programme, genetic studies on the different Cylindropuntia spp. were conducted to separate the species and therefore match populations of Cylindropuntia spp. with the correct D. tomentosus biotype without the need for long time-consuming glasshouse trials.

As there will be numerous Dactylopius tomentosus biotypes present in the field in due course, it is desirable to develop a diagnostic test to distinguish these biotypes once they have established in the field. This will make re-distribution much more efficient and ensure the right biotype is released on the most suitable Cylindropuntia species. With the resignation of the experimentalist who was going to perform this work, these studies will need to be conducted in South Africa.

Chromolaena biocontrol

Research officer: Michael Day

Chromolaena odorata was first reported in Queensland in 1994 and is also present on the Australian territories, Christmas and Cocos Islands. Chromolaena was the target of a national cost-share eradication program until 2012. However, it was approved as a target for biocontrol in 2011, following several reviews of the eradication program. The gall fly Cecidochares connexa is deemed host specific, having been tested in seven countries against a total of 122 species, representing 31 families, including 38 species in the Asteraceae. The gall fly was subsequently released in 12 countries, including PNG, Indonesia, Guam and Timor Leste, where it is controlling or aiding the control of chromolaena. It was imported into quarantine at the ESP in February 2012 and tested against species in the Eupatorieae. Eighteen plant species were tested in choice-minus-chromolaena and no-choice trials, with some galls forming, and some larvae completing development to adult on Praxelis clematidea. Further trials showed that populations of C. connexa could not be sustained on P. clematidea and only minimal damage occurred. An application seeking approval to field release C. connexa was submitted to Department of Agriculture and Water Resources (DAWR) and the Department of Environment and Energy (DoE&E) in March 2015. DAWR and DoE&E have recently approved release the gall fly and permits have been obtained. Collaborators in PNG have been approached to collect and send the insect. The gall fly will be re-imported into quarantine and reared through one generation, prior to establishing rearing colonies at ESP and TWRC. The gall fly will then be released on all known infestations of chromolaena in Queensland.

Mother-of-millions biocontrol

Research officers: Michael Day and Natasha Riding

Mother-of-millions (Kalanchoe spp. = Bryophyllum) are native to Madagascar and have become major weeds in Queensland and northern NSW. In an earlier project, field surveys were conducted in Madagascar and four potential biological control agents prioritised. Host specificity testing was conducted on two species and these attacked closely related plants in several genera, which are ornamentals. A decision was made to apply for the field release of one species, Osphilia tenuipes through the Biological Control Act. Populations of two insects (including O. tenuipes) held in quarantine for 10 years were culled while the application was progressed. A new biological control project on mother-of-millions, along with several other weed species is being funded by Department of Agriculture and Water Resources (DAWR) through Agrifutures, as part of the Rural Research and Development for Profit Round 2 call. Under this proposal, this project aims to improve available control options for farmers by exploring options for biological control in Madagascar. This project will build on the earlier biological control program, which identified several species worth investigating. Under this proposal, potential agents from Madagascar will be collected and imported into the quarantine facility at ESP for host specificity testing. Applications seeking approval for release will be submitted to the regulators if applicable. In November 2017, a root-feeding flea beetle Bikasha sp. was imported into quarantine and its biology and specificity will be determined. To date, most biology studies have been completed and host specificity testing has commenced. The beetle has fed as adults on all test species to which it has been exposed. The beetle has also been tested as larvae against some species. Larvae have completed development on a few test species so far. Testing will continue for the next year. Osphilia tenuipes is currently in quarantine in NSW where further host specificity testing is being conducted. As a consequence, an application seeking field release of this insect through the Biological Control Act has been suspended.

Giant rat’s tail grass biocontrol

Research officer: Michael Day

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. More recently, biological control focused on an indigenous fungus Nigrospora oryzae, but it does not appear to be as damaging against giant rat’s tail grasses as it is to giant Parramatta grass. A new biological control project on giant rat’s tail grass, along with several other weed species, is being funded by Department of Agriculture and Water Resources (DAWR) through Agrifutures, as part of the Rural Research and Development for Profit Round 2 call. Under this proposal, this project aims to improve available control options for farmers by exploring options for biocontrol in South Africa. This project will build on the earlier biological control program, which identified several species worth investigating. Populations of wasps from the genera Tetramesa and Eurytoma have been found on different species of Sporobolus. An endophagous beetle has also been found but it has subsequently been found to attack other grass species so will not be considered. The three wasp species have been sent for identification. Field host-range testing has commenced and all three wasp species appear to be suitable for introduction into Australia. Laboratory testing in South Africa is continuing on Tetramesa sp. A., as it appears to be the most damaging. These trials will continue under this current round of funding.

Biocontrol of pasture weeds in Vanuatu

Research officers: Michael Day and Tamara Taylor

Landcare Research NZ Ltd has entered into a contract with DAF to be a collaborator in a new 5-year weed biocontrol project based in Vanuatu funded by the NZ Ministry of Foreign Affairs. The work will build upon previous work in Vanuatu funded by the Australian Government and managed by DAF. The three main pasture weeds targeted under this project areSenna 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, i.e. they have not previously been studied in terms of biological control. Overseas exploration in the respective native ranges of each species will be conducted to locate potential candidates. Potential candidates for S. tora will be brought into the quarantine at ESP, 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. Five other weeds will also be targeted under this project and will involve importing effective agents from Queensland or elsewhere into Vanuatu. The weeds are Spathodea campanulatum, Parthenium hysterophorus, Lantana camara, Mimosa diplotricha and Dolichandra unguis-cati, all restricted weeds in Queensland. Agents for S. campanulata will be considered for introduction into Queensland to help manage this weed here if warranted.