Ciara O'Brien

Doctor of Philosophy (The University of Queensland)
Optimisation of a Stem-Implantation Technology for the Chemical and Biological Control of Chinee Apple (Ziziphus mauritiana)

Ciara O'Brien


Say “goodbye” to invasive woody weeds with a novel technology using stem-implanted capsules to deliver biological herbicides. Imagine killing unwanted invasive weeds using native fungi! My research will revolutionise the field of woody weed management by combining the ‘power’ of science with that of nature to tackle the thorny problem of chinee apple. My research builds upon a system initially developed to control parkinsonia – one of the worst woody weeds naturalised in the rangelands and wetlands of Australia. I am now standing on the shoulders of this research to do the same for a new problem weed by exploring twin approaches: to develop my own biological solution, as well as to investigate a more targeted application of synthetic herbicides for effective and environmentally-safe control. 


Chinee apple (Ziziphus mauritiana Lam.) is a deciduous thorny tree or shrub native to South Asia (India, Sri Lanka, Bangladesh) and Africa. In Australia, it was initially introduced to the early mining settlements of Northern Queensland (i.e., Charters Towers, Ravenswood, Hughenden) in the late-nineteenth century (~1863) for its ornamental and horticultural value in other countries. It has since become a significant weed in the grasslands and rangelands of Northern Australia (i.e., Queensland, Western Australia, and the Northern Territory). Its densely formed thickets influence the structure, function, and composition of rangeland ecosystems by outcompeting native pasture species. The subsequent loss of pasture cover affects the quality of services (e.g., agronomic productivity, livestock carrying capacity, mustering) obtainable from this diverse, natural resource. This has led to its identification as a priority threat to the pastoral industry by graziers and landholders. This invasive shrub also threatens the biodiversity of tropical woodlands by displacing native vegetation (e.g., Eucalyptus spp.) of cultural and environmental significance. The transformation of these natural landscapes is associated with the decline or extirpation of many granivorous bird species, such as the endangered black-throated finch (Poephila cincta).

The management of Z. mauritiana is limited to the application of synthetic herbicides and mechanical clearing operations.  The former has been the management paradigm for most woody weed species for decades. Whilst their efficacy is undisputed, there are concerns regarding the suitability of synthetic herbicides in ecologically sensitive or low-value habitats. This greater appreciation for environmental stewardship has promoted significant developments in the field of woody weed management by either (i) reducing the dosage levels of current synthetic compounds or (ii) improving their application methods. There is considerable interest in the exploration of host-specific, natural enemies (i.e., biological control agents: herbivorous insects, pathogenic fungi, bacteria or viruses) for limiting the vigour, competitiveness or reproductive capacity of Z. mauritiana in Northern Australia. The successful biological control of some “poster child” invasive plant species (e.g., Prickly Pear: Opuntia spp., Skeleton Weed: Chondrilla juncea, Parkinsonia: Parkinsonia aculeata) offers hope for a similar outcome with Z. mauritiana.  

My research project investigates the pathogenicity of native fungal endophytes associated with healthy and diseased populations of Z. mauritiana in Northern Queensland (i.e., Alligator Creek, Charters Towers, Bowen, Mulgrave, Collinsville) for the development of a bioherbicide to combat this problematic weed. The effectiveness of BioHerbicides Australia’s (BHA Pty Ltd) proprietary stem-implantation system and their Di-Bak® range of encapsulated synthetic herbicides is also being evaluated for the management of Z. mauritiana in rangeland environments. Innovative solutions, such as these, are highly anticipated by Queensland landholders as they feel increasingly defeated in the war against woody weeds. 

Role Model

Most STEM disciplines are male-dominated and there is a considerable lack of female representation in STEM-qualified occupations throughout Australia (~15% in 2021) (1). This leaves a generation of young women without identifiable pathways to pursuing careers in science, technology, engineering, and mathematics. Because of this, it is crucial to celebrate ‘real-life’ scientists to create a sense of belonging and identity in STEM-fields, particularly for underrepresented or marginalised groups. This is best summarised by the concept of “seeing is believing” whereby positive interactions with female role-models enhances others’ perceptions of their own potential. Whilst there is an improvement in gender equity, there are not many prominent female leaders or mentors in my discipline. Therefore, we must be a source of one another’s inspiration by modelling success, perseverance, and limitless ambition to our female peers within the agricultural industry. I believe I am a ‘role model’ to other women or young girls for the following reasons: 
1. Promotion of STEM: I am an active member of my student community at The University of Queensland through my role in the school’s engagement committee (SAFS: School of Agriculture & Food Sciences) and my involvement in the teaching of undergraduate university courses in various STEM-related disciplines, such as (i) introductory biology, (ii) agricultural biochemistry, and (iii) plant biosecurity. As a young female leader, I am continually redefining the future of STEM by modelling initiative, resilience, and confidence in my work environments. I create meaningful connections to ‘science’ for the undergraduate students by finding a STEM-issue of individual importance or relevance to them (e.g., climate change, food security, environmental conservation). This is the most impactful and genuine approach for creating a sense of belonging in STEM-fields for the younger generation.
2. Commitment to Development: I strongly value the importance of opportunity in personal and professional development – whether it be by sitting front-and-centre in every meeting or pushing my boundaries of ‘comfortability’ at a national conference.
3. Proven Academic Capability: I am a diligent, high-achieving student with a proven record of academic capability thereby encouraging self-efficacy and achievement among my female peers. 
4. Female Advocacy: I am a strong advocate for the empowerment of my female peers. In my experience, we can create a more inclusive and equitable STEM industry by championing the success of other women through collaboration, celebration, and promotion. I support my female peers by (i) attending their professional milestones, (ii) sharing or offering my individual expertise, and (iii) collaborating on projects where possible. 


As student representative of my school’s (SAFS: School of Agriculture & Food Sciences) engagement committee, I am offered engagement opportunities with key domestic and international stakeholders to reposition the agricultural industry as both innovative and technological. I am also incredibly passionate about the social, cultural, and intellectual development of my ‘higher degree by research’ (HDR) peers that are in STEM-related fields (i.e., agricultural, wildlife, veterinary, equine or food sciences). Since the commencement of my research career, I have avidly promoted STEM through several activities:
1) Professional Development Events: I am an active member of my student community, championing the coordination, promotion, and delivery of professional development opportunities on (i) building a digital presence, (ii) strategic networking, and (ii) publishing your research. These events offer young researchers’ (masters- and PhD-level) the opportunity to strengthen their transferable and professional skills for future employment in STEM-fields.
2) School Outreach Programs: As part of my role on the engagement committee, I developed the ‘Young Agricultural Scientist Challenge’ for the Future Experiences in Agriculture, Science and Technology (FEAST) program - a residential program for secondary school students aspiring to undertake rewarding science careers in the agriculture, animal, plant, and food industries. This fun-filled challenge showcased the ‘science’ driving the future of agriculture in a race-style format. The students experienced the excitement of being plant disease detectives, extracted DNA from strawberries and even got their hands dirty creating soil boluses. The resources developed from this event have been adopted for other school outreach programs, such as ‘Moo Baa Munch’ (AgForce’s School to Industry Partnership Program) and ‘UQ’s Young Achievers Program’, that support the career aspirations of school students from underrepresented and regional groups. I have also presented at the ‘FEAST Young Researchers Panel’ for two consecutive years to share my education journey and promote career opportunities in agriculture, food technology and environmental science. 
3) Teaching Opportunities: I have teaching roles in undergraduate courses at The University of Queensland in various disciplines, such as introductory biology, agricultural biochemistry, and plant biosecurity. As a STEM educator, I can inspire the next generation of prospective agricultural scientists, particularly young women, by exploring cutting-edge research in both the classroom and laboratory. 
4) Conferences, Seminars & Showcases: I recently presented at the 22nd Australasian Weeds Conference in Adelaide, South Australia – the largest national conference in my research discipline. These platforms create an awareness for the importance of STEM fields by showcasing the relevance and impact of other researchers’ work (e.g., university academics, postgraduate students, industry professionals). I have also promoted my research to a more targeted, smaller audience, such as at the ‘Hidden Vale Research Showcase’.
5) International Engagement: We occasionally have visits from international universities that lead to collaboration and the exchange of STEM research ideas.  I recently presented at a discussion panel with Jeonbuk National University (JBNU) in South Korea. This was an invaluable opportunity to share my research findings and solicit feedback from an international academic community. We also increased the visibility of STEM impact and prestige in Australia. 

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