Previous research (2003-2023)

Summary of previous research

CSIRO initiated a biocontrol project for cabomba in 2003 and undertook native range surveys in collaboration with FuEDEI in northern and central Argentina, southern Paraguay, Uruguay and Brazil between 2003 and 2009. These surveys focused on arthropods and resulted in identification of three potential biological control agents, one weevil (Hydrotimetes natans) and two moths (Paracles sp. and Paraponyx sp.). Preliminary studies at the time suggested that the cabomba weevil may be the most promising agent for further consideration for the biological control of cabomba in Australia.

Cabomba was endorsed as a target for biological control in November 2006 by the national Natural Resource Management Standing Committee (such endorsement is now the responsibility of the Environment and Invasives Committee and is required in Australia before permission to release a biological control agent is sought).

Research continued in 2016, with new projects focusing on:

1. Confirming, with surveys in the native range, that there are no other candidate biological control agents than the cabomba weevil Hydrotimetes natans, which was identified as the most promising in past research,
2. Undertaking comprehensive testing to demonstrate that the weevil does not pose a threat to non-target plants and,
3. If approved by the authorities, releasing the weevil across the range of the weed in Australia.

This research was undertaken as part of two projects led by AgriFutures Australia and primarily supported by funding from the Australian Government Department of Agriculture, Water and the Environment as part of its Rural R&D for Profit programme rounds 2 and 4:

• Round 2: Biocontrol solutions for sustainable management of weed impacts to agricultural profitability (2016-2020)
• Round 4: Underpinning agricultural productivity and biosecurity by weed biological control (2019-2023)

The overlapping projects had been designed to complement each other and include the following main activities:

• Define management goals
  • What water asset managers would like biological control to achieve.
• Develop bioclimatic models to identify optimal location(s) to source the promising biological control agent
  • The climate of the native and invaded ranges of the target weed are characterised and compared using a distribution modelling tool. By comparing meteorological data from the different regions, specific area(s) of the native range can be identified where potentially best climatically suited candidate agents will be found.
• Source the candidate agent and test its host-specificity
  • Host-specificity testing is necessary to determine the potential range of plants (hosts) which will be attacked by the candidate agent in Australia. Testing methods are always tailored to the particular agent and seek to understand the potential range of plants that would be accepted by the agent after its release in the field. Testing follows a centrifugal phylogenetic approach that concentrates on closely related plant species to the target weed.
• Prepare and submit an application for release of the candidate agent to the relevant authorities, provided testing results demonstrate that non-target plants in Australia would not be at risk.
• Monitor vegetation at future release sites to gather baseline data prior to the release of the agent.
• Once permission to release the agent is obtained, mass-rear and release the agent into the field across key water bodies to identify the most effective release method that leads to establishment of the agent.

• Partner with relevant stakeholder networks (water assets) to facilitate large-scale releases of the agent across the range of the weed in Australia. Wherever possible, measure the impact of the agent on the weed populations and flow-on effects on vegetation and water quality to quantify benefits of the project.
• Develop an Integrated Weed Management (IWM) program for cabomba, in collaboration with those developing other control tactics for this weed.

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Achievements of Rural R&D for Profit round 2 project: Biocontrol solutions for sustainable management of weed impacts to agricultural profitability (2016-2020)

Defined goals for management of cabomba

Through interactions with water asset managers (Seqwater) who are responsible for managing 90% of the Australian infestation Cabomba caroliniana, the following framework for integrated weed management of the weed was developed, with each broad category comprising a series of specific objectives:

1. Containment is the principal goal given the current nature of infestations (i.e. four lake/dam systems principally impacted at present)
2. Eradication is the goal for new outbreaks in high priority locations (e.g. any incursions that could result in spread into larger lake/dam systems, i.e. transfer risk).
3. Anticipation of water quality implications of removing large amounts of weed biomass through management
4. Understanding impacts of local catchment land-use context on C. caroliniana invasions

Containment objectives in freshwater systems may need to be met almost entirely by biocontrol given the impermissibility of use of chemical control methods. Eradication objectives in non-potable water systems may be possible using the one chemical (Shark™; Active ingredient: 240 g/L Carfentrazone-Ethyl) registered for control.

Undertook bioclimatic models to identify optimal locations and conducted native range surveys and host-specificity tests for potential biocontrol agent(s) and imported at least one potential agent in quarantine

Bioclimatic modelling

Bioclimatic models were developed in the CLIMEX package to better understand current and prospective distributions of C. caroliniana in Australia, to identify optimal areas to survey for candidate biocontrol agents and to identify suitability of release sites in Australia for candidate agents.

In Australia, most C. caroliniana infestations occur in southern Queensland and the northern New South Wales hinterland. In Queensland it occurs in shallow, permanently flowing creeks and deep, slow-flowing pools of coastal river systems. There are smaller infestations found in Victoria and the Northern Territory. Cabomba caroliniana infestations have not yet been found in WA, SA, TAS or the ACT. Bioclimatic modelling, based on the known climatic tolerances of C. caroliniana and availability of suitable water bodies, indicated it could potentially spread beyond its current distribution, especially across southern and eastern Australia.

Matching the climate of Australian infestations of C. caroliniana, to its native range revealed that the known populations of the species in north-eastern Argentina, southern Paraguay and north-eastern Brazil were optimal places to survey to source candidate agents that would be the best bioclimatic fit for Australia. Surveys were thus undertaken in these locations over the course of this project. The focal candidate agent for this project, the cabomba weevil, Hydrotimetes natans (see ‘Native range surveys’, below), has only been recorded to date in the region (north-eastern Argentina, southern Paraguay) that is best matched with the climate where C. caroliniana infestations exist in Australia. Projecting the climatic envelope of the native range distribution of H. natans onto Australia revealed that the major C. caroliniana infestations in eastern Australia were likely to be suitable for establishment of weevil populations.

Native range surveys

Over the course of the project, surveys of natural enemies of C. caroliniana were undertaken in the native range (guided by the bioclimatic modelling): Argentina (Nov-2017; Apr-2018; Jan-2019), Paraguay (Nov-2017; Apr-2018; Jan-2019) and Brazil (Sep-2019). These surveys validated earlier surveys that there was only a small number of insect herbivores present on this submerged aquatic weed: four Coleoptera, three Lepidoptera, three Diptera and one Hemiptera species (Schooler et al. 2009, 2012). Based on the published literature, most of these were likely to be too general in their host range for consideration as potential biocontrol agents for C. caroliniana in Australia (Cabrera-Walsh et al. 2011, Schooler et al. 2012). The exception was the cabomba weevil (H. natans), which was prioritised for host-specificity testing and imported into quarantine in Australia.

Host-specificity testing

The cabomba weevil, H. natans was imported from Paraguay and Argentina into a quarantine facility in Australia for comprehensive host-specificity testing. Testing was concentrated on a broad range of plant species, including native Australian species, selected based on their phylogenetic relationships to the target weed. A total of 16 plant species from the families Cabombaceae, Nymphaeaceae and Hydatellaceae were tested − 13 in the laboratory in Australia and 3 in the laboratory in Argentina. In addition, field host-specificity assessments were performed at four sites in Argentina and Paraguay where the weevil was recorded on C. caroliniana. Co-occurring non-target aquatic species with C. caroliniana (e.g. Egeria najas, Nymphoides indica, Nymphaea prolifera, Salvinia minima and Ludwigia grandiflora) were examined for the presence of H. natans and any sign of feeding by larvae and adults.

Field host-specificity: In the field in Argentina and Paraguay, observations revealed the presence of H. natans almost exclusively on C. caroliniana except for a single H. natans adult observed on N. prolifera adjacent to C. caroliniana. However, no feeding on N. prolifera was noticed which suggested that it was likely a casual occurrence.

Adult and larval feeding on leaf discs/sprigs: Feeding lesions caused by adult H. natans were observed on C. caroliniana, Brasenia schreberi, Nymphaea caerulea, N. gigantea, N. nouchali, N. prolifera and Victoria cruziana but not on N. mexicana and C. caroliniana var flavida. The feeding lesions on non-target plants were superficial and exploratory. Larval feeding trials on C. caroliniana var. flavida, N. prolifera, N. caerulea and V. cruziana demonstrated larvae are highly specific and unable to feed on non-target species. All larvae on non-target species died within four to five days of exposure to these species.

No-choice trials: Larval feeding, oviposition and larval development to adult occurred consistently on C. caroliniana. No oviposition occurred on any of the Nymphaea or Trithuria test plant species and hence no progeny development was observed. In B. schreberi, oviposition occurred on four of the six replicates tested. Among the four replicates that showed evidence of oviposition, larval feeding was noticed on three replicates, and pupation and adult emergence was observed in only one replicate.

Choice and continuation trials: Choice trials with C. caroliniana and B. schreberi suggested partial lifecycle development of H. natans on B. schreberi. Oviposition and larval development were observed on two of the five replicates tested. However, larval development to pupation was observed on only one replicate of B. schreberi with two pupae recorded. Only one of the two pupae metamorphosed into an adult, which however died soon after emergence, and the other pupa did not emerge as adult. In continuation trials, offspring from parental H. natans did not complete lifecycle on any of the replicates of B. schreberi. No pupation was observed on B. schreberi despite egg laying in three replicates and larval development in one replicate. In contrast, a healthy and reproducing colony of H. natans was maintained on C. caroliniana, which has yielded five generations in the eight-month period between April 2019 to December 2019 in the same period over which the laboratory testing was undertaken.

In summary, as evident from the decision tree below, results from a suite of laboratory/glasshouse-based host-specificity testing in the native range and in a quarantine facility in Australia, as well as field observations in the native range demonstrated that H. natans has a high degree of specificity towards the target weed C. caroliniana. Based on these results, we concluded that the level of risk H. natans poses to non-target native and introduced species in Australia is negligible and that H. natans will potentially be an effective biocontrol agent for C. caroliniana (Schooler et al. 2006).

Submit application to the Commonwealth regulators seeking approval to release at least one potential agent. Upon receiving approval, release biocontrol agent(s)

A release application for the cabomba weevil, H. natans was submitted to DAWE on 10 March 2020 (Kumaran et al. 2020).

Identify optimal rearing methods and nursery sites for field release of potential biocontrol agent(s)

Mass-rearing methods

We undertook multiple importations of the cabomba weevil because of difficulties with establishing colonies in the quarantine facility due to its unknown biology. Detailed investigations of the biology of the weevil have enabled us to fully characterise the life cycle of this species (Kumaran et al. 2020).

This detailed study of the weevil’s lifecycle was crucial to the completion of the host-specificity studies (see ‘Host-specificity testing’, above), and formed the basis for developing a mass-rearing protocol with the following steps.

• Source C. caroliniana from lakes/creeks and clean to get rid of pests, algae, fine sediment and bacteria; this hygiene step will boost the quality of the plant stock which will aid successful rearing of the weevil.
• Maintain a stock of C. caroliniana in 1-ton tanks, and replenish with additional, frequent (4 to 6 weeks) field collections.
• Set-up C. caroliniana in smaller ‘Nally’ bins (Nally; Viscount Plastics, Sumner Park, Queensland, Australia); this system requires:
  • Reverse osmosis water with nutrients,
  • Water pump, shade / shade cloth mesh cover to limit sunlight ( C. caroliniana and the weevil prefer share with limited light).
• Introduce ~30 weevils into Nally bins with C. caroliniana (5 clusters, each with 6 sprigs), leave 2 to 14 days for egg laying depending on the need. Retrieve / take weevils out; keep them to setup a new array of rearing Nally bins.
• For the exposed C. caroliniana (‘Breeding Tank’) that is now free of adult weevils: Add new, clean C. caroliniana into the Nally bin every 2–3 weeks depending on larval feeding and availability of plant material for developing larvae.
• Maintain the ‘Breeding Tanks’ for the period of larval and pupae development through to adult (40–50 days).
• Set up new tanks with weevils already retrieved and newly emerged weevils. Frequent exposure of C. caroliniana to weevils is required to increase the colony number.

If approved for release by DAWE, further refinements of this mass-rearing protocol outside the confines of the quarantine facility to enable water asset managers to set-up their own colonies in larger tanks, in place of Nally bins.

After approval for release by DAWE, there were further refinements of this mass-rearing protocol outside the confines of the quarantine facility to enable water asset managers to set-up their own colonies in larger tanks, in place of Nally bins.

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Achievements of Rural R&D for Profit round 4 project: Underpinning agricultural productivity and biosecurity by weed biological control (2019-2023)

Identified potential agent release sites and conduct pre-release monitoring for biocontrol of Cabomba

A pre-release monitoring program was established to understand the vegetation dynamics of cabomba-infested waterbodies prior to the deployment of management techniques (incl. biocontrol and novel herbicides). Monitoring sites were selected to span a North-South bioclimatic gradient and included Ross River Lagoon, QLD (tropical); Lake Kurwongbah, QLD (subtropical); Mooball Lagoon, NSW (subtemperate) and Myall Lakes, NSW (temperate). These sites were selected because they are earmarked as targets for weevil release and integrated weed management, through discussions with local stakeholders and water asset managers.

As part of pre-release monitoring, baseline macrophyte abundance data and site-specific environmental parameters were collected to estimate the relative abundance of C. caroliniana and co-occurring aquatic plant species. Baseline data was collected at two spatial scales viz., manual sub-meter scale measurement and a whole site scale monitoring. For manual sub-meter scale measurement of macrophyte species composition and biomass, a mechanical sampler (harvester) fitted with a cutting bar and a plant collection rake was used.

Sampling for pre-release monitoring was initiated at Lakeside Road site at Lake Kurwongbah in November 2020. Pre-release monitoring was next setup at Ski Road and Mick Hanfling sites in Lake Kurwongbah, and in a farm dam near Eumundi (QLD) and in Mooball Lagoon (NSW). Sampling method followed was similar to the Lakeside Road site, except that only manual sampling was undertaken in Mick Hanfling Park site and Seibs dam because of small site areas. In addition to subtropical Southeast Qld, monitoring was conducted in Central Qld. Three sites in Townsville in the Ross River catchment (Kingfisher lagoon, Blacks Weir and Aplins weir) that are suitable for integrated cabomba management research was monitored for macrophyte abundance.

The submersed macrophyte biomass differed largely between sites and collection times. In general, the small billabongs had the highest aquatic plant biomass. The macrophyte biomass also differed on a spatial and temporal scale in the Lake Kurwongbah sites.

Cabomba dominated the macrophyte community for most sampling occasions. One of the Lake Kurwongbah sites had a comparatively small amount of cabomba in the first sampling occasion, but this increased towards the second sampling event, where the proportion of cabomba was around 70-100% of the macrophyte biomass. Species richness (number of species including cabomba) differed between sites. Overall, the smaller lagoons had a lower species richness than the lake or river sites.

Several macrophyte species were present at various sites, including Hydrilla verticillata, Salvinia molesta, Nymphoides indica, Potamogeton octandrus and Cabomba caroliniana. Cabomba caroliniana was present at all sites, but the native species P. octandrus and H. verticillata were also common in some of the sites. In general, the macrophyte density decreased with water depth as can be seen when comparing the bathymetric and macrophyte density map below.

Regulatory review of release application and releases of the agent approved by regulators

The regulatory review and final risk assessment of cabomba weevil was completed by DAFF in February 2021 and it was determined that the overall risk associated with the release of weevil to be negligible. The final DAFF risk assessment report approved the release of Hydrotimetes natans. A small batch of cabomba weevil (H. natans) was released from the quarantine facility in July 2021 and was set up in a glasshouse outside the quarantine.

Releases of the cabomba weevil were undertaken in QLD commencing March 2022. A total of six releases were made thus far in three sites spanning tropical and subtropical regions. Four releases were made at Seibs dam near Eumundi, QLD, and one release each was made in Lake Kurwongbah and in Ross River in Townsville; a total of 748 weevils released at these sites thus far. Post-release monitoring in May 2022 showed apparent adult feeding damage on cabomba and presence of 1 pupa, an early sign of persistence of the weevils at release sites. These sites are being monitored regularly (~ every two months) to confirm persistence of weevils, and additional releases are planned until the end of the project.

Expanded the number and/or size of nursery trial sites involved in the mass-rearing of candidate biocontrol agent/s

Partnering with Seqwater, a weevil mass rearing facility at Lake Kurwongbah was setup in November 2022. Tanks were set up and water pumped directly from the lake and reticulated to allow water flowing from one tank to another. Cabomba plants were collected from Lake Kurwongbah and maintained in these tanks to optimize the weevil rearing conditions. The setup was continuously monitored by Seqwater staff to monitor the conditions of cabomba growth in the mass rearing tanks, and water parameters such as temperature, pH and dissolved oxygen were also monitored.

Preliminary observations showed presence of pupae in one of the six tanks in which cabomba weevils were first introduced in December 2022. Continuous monitoring of weevil breeding in the tanks and release of additional weevils from the Dutton Park facility until the end of the project period was undertaken to ensure rearing of the weevils at the nursery site.

Weevil rearing using Nally setup is ongoing at Dutton Park, and large tank setups are also being trialled to inform mass rearing at Lake Kurwongbah.

Developed mass-rearing protocols for biocontrol agents and transferred technology for the adoption by third party facilities

Mass-rearing protocols were developed based on our knowledge and experience drawn from the life history and biology studies conducted and colony rearing of weevils in Nally setups under controlled environmental conditions.

Prior to setting up the mass rearing facility, the technology transfer workshop was held at the Dutton Park facility during Sep 2021. CSIRO personnel demonstrated steps involved in rearing of cabomba weevil including maintenance of cabomba plants, safe handling of weevils, quality of plant materials and signs of successful weevil breeding. In addition, CSIRO personnel participated in discussions on risk assessment, optimal rearing setup and pumping water from the lakes that has assisted in setting up the nursery sites.

Small breeding tanks along with 1 ton tanks for maturation in rotation was also proposed. This proposed method works on the principle of a continuous and staggered ‘rotation’ of production cycle for rearing new weevils. It is a slightly scaled-down version and hybrid approach of the CSIRO lab breeding work and tank setup but may require more investment of staff and time. The hybrid approach has two components for the mass rearing process: (1) the Cabomba-weevil exposure occurs in smaller-scale 68L ‘Nally’ tank setups, and (2) the exposed plant material (weevils removed) is transferred to 1 ton tanks for maturation of the weevil larvae and pupae. Each 1 ton tank can hold three Nally’s worth of exposed plant material, with capacity for additional top-up of fresh Cabomba to aid larval and pupae development. The CSIRO lab work confirmed that the principles of this method are sound; and the components suggested in this hybrid approach have to-date been the most reliable under laboratory conditions.

Media for Cabomba weevil

• https://www.csiro.au/en/news/News-releases/2023/New-biological-control-released-against-invasive-cabomba-weed
• weevil story from 10 News
• https://www.australianresources.com.au/new-biological-control-released-against-invasive-cabomba-weed/
• https://www.moretondaily.com.au/news/world-first-at-lake-kurwongbah
• https://www.brisbanetimes.com.au/national/queensland/weevil-scheme-why-scientists-have-put-bugs-in-seq-s-water-supply-20230302-p5cov1.html
• https://thewest.com.au/news/environment/scientists-hatch-weevil-plan-to-conquer-invasive-plant-c-9914013
• https://www.theleader.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/
• https://www.canberratimes.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/
• http://www.greencareer.net.au/news/weevil-aimed-at-weeds
• https://www.pacificlongboarder.com/news/Weevil-genius-the-South-American-bug-set-to-be-a-new-best-friend-to-Australian-waterways/&key=65cb7690ad5361e62fd75fe39b4c75c2&ver=1&mid=923228634
• https://7news.com.au/news/qld/the-south-american-bug-set-to-be-a-new-best-friend-for-australian-plants-and-animals-c-9925024&key=67bb949795bf4fd1ff6ce08fe1ae1511&ver=1&mid=922586938
• https://app.mediaportal.com/isentia/#/playnow/v2?id=R00097934648&channel=ABC%20Radio%20Brisbane&location=Australia&date=2023-03-06T09:31:14&program=Mornings&item_id=920704667&prospect_id=2399835334&is_video=false&keywords=CSIRO&expiry=1709717474&signature=hF56FjN7MM43dBe-DpJ7-CYcUYQ8RpUVjEra5jdCPg9V3aBsh885nsZ7ZXjlBJsPcIzxLCxKXvr2bZCZSCbVD~Dak1vYmjqB~m1qZKCQS-FUdGSfsLPM4n4yjp3Sb7Dh-Aw4H0HlrVg3~MkO3~nsFjRsgT040LSoCY7vjBhU0xk~7EOelnMs9cBGgqvCQ4hGoYVzoML~eq2x16GbofdC2rBz~v2iiO~za8Z-4NO7xCnvdQ~cpygepUvoxP5ypobnD7tQrdjVR5UAtgtDsmhS-5FDeBhZNjRtK9qznGbwHRSJijM3i2MxGAB-GiLbsN1erbD3PbVHDKKAqWu6u44yww__
• https://www.bradenton.com/living/article272698825.html&key=daa7b8bec33c744911b490f3e94e09eb&ver=1&mid=920246289
• https://www.kentucky.com/living/article272698825.html&key=7eaf0cd6377772227ef7f959fac8d88d&ver=1&mid=920233152
• https://www.msn.com/en-au/news/australia/weevil-scheme-why-scientists-have-put-bugs-in-seq-s-water-supply/ar-AA188cZ7&key=abded5018bc3c58ba7baf1300f48bfaf&ver=1&mid=920207518
• https://www.moretondaily.com.au/news/world-first-at-lake-kurwongbah&key=1469ed4e8a5507755073069cb6ccc9f6&ver=1&mid=919901667
• https://asianewstoday.com/biocontrol-weevil-released-to-fight-invasive-weed-in-australian-waterways/&key=2d130fe129b6c418bd47d94b8ca31c0b&ver=1&mid=919861496
• https://www.watoday.com.au/national/queensland/weevil-scheme-why-scientists-have-put-bugs-in-seq-s-water-supply-20230302-p5cov1.html&key=ac3f37ff34001a99dc29a33e42078138&ver=1&mid=919845065
• http://www.namnewsnetwork.org/?p=212927&key=50167d5c9ecc47d8c49f12d386749ea6&ver=1&mid=919658880
• https://www.newcastleherald.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/&key=b386fa7c4d935c99c96ee308eea8d739&ver=1&mid=919620871
• https://www.muswellbrookchronicle.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/&key=ecac5f18abc2c8fb89b61ae8a3ea29a9&ver=1&mid=919621186
• https://www.thesenior.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/&key=32cd79503e5c363db5d91c7db55bbe9a&ver=1&mid=919620582
• https://www.hawkesburygazette.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/&key=80d250d840883b67829938000792c493&ver=1&mid=919618340
• https://westsidecommunitynews.com.au/the-south-american-bug-set-to-be-a-new-best-friend-for-australian-plants-and-animals/&key=251bf406c4bf98778e33a63362a8e05d&ver=1&mid=922597693
• https://24ssports.com/the-south-american-beetle-becomes-a-new-best-friend-for-australian-plants-and-animals/&key=c9ed81ba5068414bce8dd453fea9e0f2&ver=1&mid=922595855
• https://www.sbs.com.au/news/podcast-episode/tiny-weevil-to-combat-south-american-pest-in-australian-waters/vshwrrmf4&key=43e8abdd4927a3e9c57b4b48dd8b1185&ver=1&mid=920263212
• https://www.theage.com.au/national/queensland/weevil-scheme-why-scientists-have-put-bugs-in-seq-s-water-supply-20230302-p5cov1.html&key=69d936fe0e1cbc2334f2509bbff07e12&ver=1&mid=919796982
• http://www.sydneysun.com/news/273583248/biocontrol-weevil-released-to-fight-invasive-weed-in-australian-waterways&key=6996adf8056491378b3102c161dbd43d&ver=1&mid=919683656
• https://au.news.yahoo.com/scientists-hatch-weevil-plan-conquer-233728278.html&key=3d9d112c3a78a1fdc16edd2c1c288aac&ver=1&mid=919586363
• https://www.lismorecitynews.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/?cs=12&key=36629d8f206599ba2491846f814896fb&ver=1&mid=919581303
• https://theqldr.com.au/environmental-issue/2023/03/02/weevil/&key=2ed93e58ab73ed0301f92515824c4679&ver=1&mid=919579826
• https://www.innereastreview.com.au/story/8105765/scientists-hatch-weevil-plan-to-conquer-invasive-plant/&key=d6ee132c37c52d249fe702438727b35b&ver=1&mid=919580792

References

Cabrera Walsh G, Schooler S, Julien M (2011) Biology and preliminary host range of Hydrotimetes natans Kolbe (Coleoptera: curculionidae), a natural enemy candidate for biological control of Cabomba caroliniana Gray (Cabombaceae) in Australia. Australian Journal of Entomology 50: 200–206.

Kumaran N, Vance T, Raghu S (2020) Application to release the cabomba weevil Hydrotimetes natans for the biological control of the weed Cabomba caroliniana in Australia. CSIRO Report.

Schooler S, Julien M, Cabrera Walsh G (2006) Predicting the response of Cabomba caroliniana populations to biological control agent damage Australian Journal of Entomology 45: 327–330

Schooler S, Cabrera Walsh G, Julien M (2009) Cabomba caroliniana Gray (Cabombaceae). In: R. Muniappan, G.V.P. Reddy, A. Raman (Eds.), Biological control of tropical weeds using arthropods, Cambridge University Press, Cambridge, pp. 88–107.

Schooler S, Cabrera Walsh G, Julien M (2012) Cabomba caroliniana Gray–cabomba. Biological control of weeds in Australia. CSIRO Publishing, Collingwood, Victoria, Australia, pp. 108–117.