The continuing battle with Ox-eye Daisy in Kosciuszko National Park – UPDATE of EMR feature

[Update of EMR feature article – McDougall, Keith, Genevieve Wright, Elouise Peach (2018)  Coming to terms with Ox-eye Daisy (Leucanthemum vulgare) in Kosciuszko National Park, New South Wales.  Ecological Management & Restoration, 19:1, 4-13.  doi: 10.1111/emr.12296]

Key words: Biocontrol, adaptive and integrated management

Introduction. In less than a decade, Ox-eye Daisy (Leucanthemum vulgare) went from being an obscure garden escape in Kosciuszko National Park (KNP), New South Wales (NSW) to one of its most pernicious invasive plant threats. By early 2019 it was abundant and, in places, dominant in over 3000 ha of subalpine communities and recorded at elevations up to 1700 m asl. The rate of spread took managers by surprise, rapidly increasing after the wildfire that burnt through the core area of infestation. Keeping up with it has necessitated learning on the run, the essence of adaptive management – expectations and goals are continually changing as we learn more about the species and as it responds to changing conditions. The program has some urgency because the main infestation occurs in a hotspot of threatened plant species.

Between 2011 and 2013, the NSW Office of Environment and Heritage set up a range of experiments to 1) evaluate available herbicides, 2) determine the impact of Ox-eye Daisy on natural vegetation and 3) develop rehabilitation techniques to repair a bulldozer line heavily invaded by Ox-eye Daisy. The third of these was soon abandoned after the surrounding vegetation was over-run by Ox-eye daisy. Metsulfuron methyl proved to be the most effective of the herbicide treatments. Using glyphosate was worse than doing nothing because it killed native plants, creating new opportunities for Ox-eye Daisy colonisation. The impact of Ox-eye Daisy was assessed by comparing paired plots and continues to be assessed in manipulative experiments. The diversity of native plants was found to be lower in heavily invaded areas than in adjoining areas, with Ox-eye Daisy having a tendency to grow in monoculture. The attainment of dominance is slower where there is little disturbance and a thorough cover of native species, but natural disturbances such as fire and grass death caused by native moth larvae can favour Ox-eye Daisy. In order to keep up with the spread of the species, managers are resorting to a combination of broadscale herbicide application by helicopter and regular monitoring of human dispersal pathways. Sadly, dispersal of seed by animals (both native and introduced) is far harder to track.

The experimental program coupled with adaptive management continues but staff have become aware that it may not be enough to prevent spread and further damage. Biological control, community engagement and new monitoring technology are becoming important tools in the fight. Here we describe current efforts to broaden the battle against Ox-eye Daisy.

Fig. 1. Candidate insects for biological control of Ox-eye Daisy. (Photos: CABI Switzerland.)

Further works undertaken. It is easy when tackling a major environmental issue to focus on the geographic core of the problem and forget that it is connected to the rest of the world. Ox-eye Daisy is mainly a risk to conservation values in KNP but there is no reason it won’t become a risk elsewhere. Accordingly, we have been liaising with the parks’ neighbours, other management bodies within the park, and land managers elsewhere. We have run three field workshops where we have shared our experience with these stakeholders, some of whom have Ox-eye Daisy amongst their invasive plant issues; the exchange of ideas has been valuable and we now have extra eyes in the park for outlying populations of Ox-eye Daisy.

Herbicides are very effective against Ox-eye Daisy but it is a resilient species with a large seed bank and long-lived seed; other weapons are required to effectively control it in the long-term. Since 2008, CABI Switzerland have been exploring the native range of the species for potential biocontrol solutions, work funded by agencies in Canada and the USA where Ox-eye Daisy is a serious invader of pastures, rangelands and wildlands. In 2016, the NSW Department of Primary Industries secured funding to launch a biocontrol project against Ox-eye Daisy in Australia, piggy-backing off the established body of work already happening in Switzerland

Several insect species have been identified by CABI as having potential as biocontrol agents (Fig. 1). These include two root feeders (a moth and a weevil) and a flowerhead-feeding fly. The root-feeding moth, Dichrorampha aeratana (Lepidoptera: Tortricidae), was short-listed as a favourable first candidate due to it having been tested extensively for host specificity (what it feeds on) and impact (on Ox-eye Daisy). It was imported into Australian quarantine in 2016 and has since undergone host-specificity testing on closely related Australian native daisies in both Australia and Switzerland. While this work is being completed, field monitoring plots have been established in NSW and Victoria to investigate plant population dynamics and soil seed banks prior to biocontrol being introduced. In addition to the root-feeding moth, CABI have also been sub-contracted to conduct host-specificity testing on the root-feeding weevil, Cyphocleonus trisulcatus (Coleoptera: Curculionidae), which will be considered as an alternative biocontrol option should the moth be unsuitable. The weevil is very damaging and long-lived, and appears to have a suitably narrow host range.

Testing of the potential biocontrol agents (listed above) will continue for the foreseeable future until enough data are gathered to assess whether they are safe for release in Australia. This process involves a risk assessment conducted by the Department of Agriculture and the Department of Energy and Environment.

Fig. 2. Launching a drone for monitoring the success of aerial herbicide application. An Ox-eye Daisy flower is in the foreground. (Photo: Elouise Peach, NPWS).

Lessons learned and future directions. Our greatest regret is not commencing control until Ox-eye Daisy was a problem. If the species had been treated when it was known only from small patches close to Nungar Creek in the 1990s, it would not have expanded to its current extent. The clear message from this is: remove non-native plant species when they are rare because, although most might never amount to much, some will and the consequences and cost of management are then huge.

Adaptive management is often recommended as the best way to tackle environmental problems and it has definitely been pivotal to the successes we have seen. Programs were abandoned when they weren’t working and we have been willing to trial new approaches before they are fully tested. The close relationship between managers and researchers has enabled the rapid progression from enquiry to practice to further enquiry, with monitoring being integral to decision making. Drones are now being employed to assist in monitoring (Fig. 2).

The Ox-eye Daisy fight in KNP has demonstrated the importance of integrated pest management, which includes research, herbicide application, biocontrol, management partnerships and community engagement. To date we have resisted a broad communication campaign that invites people to report sightings of Ox-eye Daisy because the species is so easily confused with native daisies. Targeted education (e.g. for walking and naturalist groups), however, will be explored in coming years. The battle against Ox-eye Daisy will be fought with many tools and its spread monitored by many eyes.

Stakeholders and Funding bodies. The on-ground project in KNP has been supported by the Saving Our Species program, the National Parks and Wildlife Service Find It and Fix It and Centenary Funding, the NSW Drought Relief Funding, and Essential Energy. The biocontrol programme has been funded through the Australian Government Department of Agriculture and Water Resources as part of its Rural Research and Development (R&D) for Profit programme.

Contact information. Keith McDougall, Department of Planning, Industry and Environment, PO Box 733, Queanbeyan NSW 2620; phone: +61 2 6229 7111; email: keith.mcdougall@environment.nsw.gov.au [for on-ground research and management]. Dr Andrew McConnachie, Senior Research Scientist (Weed Biocontrol), Department of Planning, Industry and Environment, Orange Agricultural Research Institute, 1447 Forest Road, Orange NSW 2800; phone: +61 2 6391 3917; email: andrew.mcconnachie@dpi.nsw.gov.au [for biocontrol]

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