‘Panic’ takes over the Riverina, but it's not hairy

WEED INFESTATION: Graham Centre researcher Yuchi Chen among a pile of panic grass tumble weeds at Charles Sturt University. Picture: Les Smith
WEED INFESTATION: Graham Centre researcher Yuchi Chen among a pile of panic grass tumble weeds at Charles Sturt University. Picture: Les Smith

The tumble weeds currently rolling around Wagga and surrounds are a lot more sinister than they look. 

Despite what you may have heard, they’re not hairy panic, or witchgrass. 

“What we’re seeing here is panicum hillmanii, or Hillman’s panic, which was introduced from North America,” Charles Sturt University phD student Yuchi Chen said. 

“We now have evidence to prove they’re spreading across NSW, most likely from Victoria or South Australia.” 

The noxious weed was introduced around the 1900s. Herbarium records indicate 15 years ago there were very few samples in NSW, but now it’s taken over in the Riverina. 

Graham Centre researchers collected specimens from 82 locations in a 200km radius around Wagga in February to March last year. 

Around the region Hillman’s panic represented more than 90 per cent of samples.

Although tests are ongoing, researchers hypothesize it is now the dominant species in southern NSW. 

Apart from being unsightly and a serious fire danger, the plant is potentially harmful for grazing livestock.

Most panic grasses contain one or more chemical compounds (saponins) which can cause liver damage and secondary photosensitisation in animals. 

This causes severe skin irritation, scabbing and swelling and can be lethal. 

“Yuchi’s research has helped us identify which species are here in the Riverina, everyone calls it hairy panic, which is native, but that’s not actually that prevalent… we’re now taking a molecular approach to study the DNA to be able to explain which species is which,” his supervisor Professor Leslie Weston said. 

“We know hairy panic and witchgrass cause photosensitisation, what we’re doing now is looking to determine which saponins cause it and which species profile as more toxic.” 

The results should help manage livestock in future outbreaks but in the meantime, Mr Chen said farmers should take measures to control it including spraying or burning. 

“If they've found the grass they should keep in mind to check livestock regularly because from far away it’s hard to observe mild to medium photosensitisation symptoms,” he said. 

Prof Weston said changes to agricultural production practices have contributed to the mass-infestation. 

“This particular species has blown in by wind from Victoria in this direction, but in general the panicums are more common because of an increase in no-tillage crop production,” she said.

There are 38 species of panic grass found across South Australia, Victoria and NSW, also causing crop and pasture losses. 

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