Weed experts gathered in South Australia

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HMAA member, Kate Blood, reports on the weed conference, which was held in Adelaide in September. She was part of the Victorian delegation.

The roads were certainly lined with gold on the way to Adelaide. Roadsides between Victoria and South Australia (SA) were lined with flowering garden plant, Gazania species, reinforcing the very reason 320 delegates from across Australia and New Zealand travelled to South Australia in late September for the 22nd Australasian Weeds Conference.

Among them were a small number of Victorian invasive species experts, who took the opportunity to learn and share the work we have been doing since the last conference in 2018 in Sydney.

One of the highlights was the focus on the latest developments about invasive garden plants. There has been a lot of progress since the awareness-raising activities of over two decades ago. The Gardening Responsibly program (www.gardeningresponsibly.org.au) has just been launched and its striking conference display and workshop attracted the attention of delegates. Aimee Freimanis gave a dynamic presentation detailing the Gardening Responsibly initiative and its aim to provide access to and increase demand for, low invasive risk ornamental garden plants. It uses an eco-label to identify environmentally friendly products and is backed by a robust and transparent plant risk assessment framework that classifies plants according to invasive risk.

Research into nursery catalogues from 1866 to 1992 in New Zealand has shown that the most invasive environmental weeds of garden origin in NZ made an early entrance into the market and have been sold for an extended period of time. Jennifer Bufford and Philip Hulme (Lincoln University, New Zealand) state, “These results suggest that early introduction and sustained propagule pressure through continued marketing and sale increases the likelihood that a species will become an environmental weed”.

There has been a lot of work in recent years on the illegal trade of declared plants online and we heard from Victoria Byrne of Agriculture Victoria about the confusion over the identification of Salvinia species traded in Victoria. A national internet surveillance program has shown that the trading of weed species online is frequent and widespread with over 100 species of declared species detected including cacti, aquatic and invasive horticulturally popular plants. Misidentification and use of non-scientific names by traders is common, posing a significant threat to biosecurity across the country.

We were challenged to guess the source of the bulk of the 248 new weed records in SA over the past 13 years. Chris Brodie, of the State Herbarium of SA, showed us that over 86 per cent of these new weeds were of garden origin. Examples of these include garden cosmos (Cosmos bipinnatus) and sulphur or yellow Cosmos (Cosmos sulphureus).

The heart-wrenching session about weeds in Australia’s arid landscape showed graphic images of livestock and wildlife that died a grizzly death due to the painful spines of the invasive garden cactus, Hudson pear (Cylindropuntia pallida). While speaking of cacti, Paul Hodges from the South Australian Arid Lands Landscape Board, showed the importance of biological control agent, cochineal beetle, in the arid land regions of SA. The biocontrol agents are used for the control of invasive opuntioid cacti (various Opuntia and Cylindropuntia species) including those that have escaped from gardens.

The conference theme was about innovation for the future and several presenters focussed on technology. Robyn Cleland, Chief Environmental Biosecurity Officer in the Department of Agriculture, Fisheries and Forestry, looked at the future of environmental biosecurity including sophisticated technology being used to detect, for example, plant material in mail, luggage, and shipping containers. These include low energy and 3D x-ray, and robotics.

Andy Sheppard from CSIRO looked into the next decade at the technology that is coming to manage weeds. Drones and machine learning are shaping the response and are being used together to successfully survey areas for some weed species. There are multiple imaging platforms and different aerial technology now being used for this purpose. If you thought algorithms were complex for social media, you should see how they are being used with machine learning to speed up plant identification and it is getting faster all the time.

WeedScan and weed ID App is using similar technology. This tool under development for launch in 2023, coordinated by the Centre for Invasive Species Solutions, is so remarkable in its technology, it was even able to successfully identify a lantana cupcake in a recent bake-off. Common invasive garden plant, Lantana camara, featured a couple of times in the program. New insights from population genomics have shown that there are variants in the invasive populations across Australia that will help target future biological control agents and other treatment techniques to particular populations.

DNA detection in the field for different organisms is getting faster, smarter and more convenient. The detection of some aquatic weeds can be done by taking water samples and surveying for the plant’s DNA. Honeybee pollen can be used to detect some plant species. Then of course there are robotics! Autonomous robotics are being used to detect, map and treat weeds. Gene technology holds lots of potential to change the building blocks of weeds, through gene masking or disruption, to reduce their growth abilities.

It will be interesting to see when some of these technologies will be adapted to weeds of gardens and horticulture making them valuable for the home gardener.

Weed detection technology is advancing in other ways. A very nice synergy between art and science is the digital 3D weed models created by NSW artist Rachel Klyve (see https://sketchfab.com/dpicomms). These 3D models have been created for 25 weeds that are prohibited matter in NSW and provide a very useful tool for teaching weed identification without having to use live plant material or two-dimensional photographs. The models have been successfully used in training and have assisted in the identification of serious weed incursions (see more at https://weeds.dpi.nsw.gov.au/).

University of Wollongong’s Sonia Graham presented about the social science of weed management and reinforced the importance of understanding people to be successful in creating behaviour change when it comes to, for example, invasive garden plants.

There were examples of detection, treatment or eradication programs for invasive garden plants invading natural areas including: plume poppy (Bocconia frutescens) in MidCoast Council, NSW; hawkweed (Pilosella species) in the NSW high country being surveyed with drones and detector dogs; limnocharis (Limnocharis flava) in Darwin, NT; aquatic Amazon frogbit (Limnobium laevigatum) in Queensland; exotic vines and scramblers in threatened ecological communities in NSW; and wilding conifers in New Zealand.

The Australasian Weeds Conference is a valuable forum for weed researchers and practitioners to share knowledge and come together to collaborate. This conference was even more important to help people reconnect after a long break. The Weed Management Society of South Australia Inc did a great job hosting the conference. See more at 22nd Australasian Weeds Conference (eventsair.com).

Acknowledgement Kate Blood is with the Department of Environment, Land, Water and Planning, Victoria.

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