Orange Hawkweed

Image credit: David Whelan

Orange Hawkweed (Pilosella aurantiaca subsp. aurantiaca) is a declared weed under the Tasmanian Weed Management Act 1999. It is an aggressive invader and forms dense mats. Without control measures in place, it poses a significant smothering threat to native and agricultural landscapes. Orange hawkweed infestations are found in Kosciuszko National Park in NSW and alpine areas in Victoria. In Tasmania, infestations exist in Fern Tree, with patches throughout the Central Highlands, Southern Midlands and other grassland, pasture, and roadside sites.

Orange hawkweed flowers. Matthew Baker, Tasmanian Herbarium
Orange hawkweed hairy leaves. Matthew Baker, Tasmanian Herbarium.

Orange hawkweed has bright orange flowers, but outside the flowering season (usually January to March) it is difficult to detect. The extremely hairy leaves of this plant are a unique feature to initially look for when trying to identify this weed.  Even as very young plants, the leaves have very characteristic long hairs that seem disproportionate to the rest of the plant. It spreads by seed dispersion and by extensive networks of stolons (above ground) and rhizomes (underground).  Interestingly, these root-like structures appear to emit a strong scent, attracting detector dogs to the infestation site – but more on dogs later.  Pollination occurs via insects and the wind, and their pollen is allelopathic. This means that it can affect the natural functions of surrounding plants, and in this case, it can inhibit the pollination, germination of seeds, and seedling growth of surrounding plants.

This weed has the potential to grow in most Tasmanian areas at altitudes over 1,000 metres, although is currently found at lower levels. It can easily spread to disturbed areas, such as fire-affected sites.  It is of the upmost importance that we address the existing infestations and prevent further spread, as the impacts of this weed could be both environmentally and economically disastrous. Some of our pristine natural areas, such as the Tasmanian Wilderness World Heritage Area, are at risk.

An Orange Hawkweed Management Plan has been in place since 2003, and Biosecurity Tasmania has funded NRM South to:

  • Identify key organisations with orange hawkweed on their land
  • Re-establish the orange hawkweed Network
  • Map the current known distribution and historical spread
  • Examine the utility of modelling to identify potential new infestations
  • Examine the efficacy of using trained dogs to detect orange hawkweed
  • Produce a status report, including recommendations for future eradication actions.

Introducing “The Fonz”

Black German Shepherd ‘Fonzie’ is Tasmania’s first detector dog specially trained in sniffing out orange hawkweed.

The use of detector dogs isn’t new, but it’s only in recent years that the full potential of a trained dogs’ sniffing power has been recognised.

NRM South provided funding for training Fonzie to sniff out this troublesome weed and he’ll be making repeated visits to Tasmania for follow-up surveys.

Image: Fonzie the detector dog in action in the Central Highlands, Tasmania.

Detector dogs on the mainland have been trained to find orange hawkweed, identifying plants that people have missed or the underground rhizomes (which remain when the plant has died back above ground). Using scent is highly efficient to detect rhizomes and small plants that may be growing in dense scrub/grasslands. NRM South supported detector dog training trials on orange hawkweed for “The Fonz”, a black German shepherd.  Fonzie appeared to be a quick learner, having already mastered the scent of serrated tussock.

RESOURCES

Orange Hawkweed Status Report (FULL)

Modelling Orange Hawkweed (CSIRO)

Orange Hawkweed in Tasmania – SUMMARY REPORT

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