Australia's wattles threatened by pests

Australia's iconic wattle plants are under growing threat from a foreign disease, a new report says.

Australia's wattle species are under threat from foreign diseases, a new report says. (Credit: Carolyn Barry)

WATTLE IS AUSTRALIA'S NATIONAL floral emblem and the inspiration for the our sporting colours, but scientists say these native plants are under threat from a variety of diseases incubating overseas.

These diseases are evolving in overseas plantations growing Australian wattles, the Invasive Species Council (ISC) says. They suggest native wattles, of which there are about 1000 species, (Acacia genus) could be "sitting ducks" for newly evolving plant pests that could make their way to Australia.

The warning follows the recent outbreak of myrtle rust, a deadly plant-killing fungus that has already invaded New South Wales, Queensland and parts of Victoria. Myrtle rust attacks the gum family of plants, or Myrtaceae, which include about 2500 species. It was detected in Victoria in January this year, having taken less than two years to colonise the rest of the east coast of Australia.

Myrtle rust, which produces masses of powdery yellow or orange spores, has evolved the ability to infect tea tree, bottlebrush and eucalypt species.

"It may prove to be one of the most calamitous environmental pests of the century," says John DeJose, CEO of the ISC.

Wattle at risk from disease invasion?

The concern is that Acacia diseases will find their way to Australia.  "We're worried that acacia pathogens evolving overseas may impact Australian ecosystems in the same way as has myrtle rust.," John says.  

The diseases could enter Australia via several possible common routes, including the flower trade, or travellers' clothing and footware.

"If the overseas disease threat eventuates, it could cause serious damage to Australia's wattles," John says.

The golden wattle appears on the Coat-of-Arms, the Order of Australia, the crest of the Governor-General.  It even has its own day of celebration: National Wattle Day, on September 1.

However, the plant's importance is not just relegated to ceremony; it has a vital role in its ecosystem.

"Australia's wattles are nitrogen-fixers, a primary source of scarce nitrogen in our ancient, depleted soils," John says. No-one knows how severely exotic pathogens might disrupt this essential ecosystem services provided by wattles."

He called on the federal government to develop a contingency plan for invasive plant pathogens of Acacia species reported in overseas plantations, such as Ceratocystis albifundus and Ceratocystis acaciavora.

"Our ecosystem health is already in decline, largely due to the impacts of invasive species, one of the top three threats to nature in Australia," John says. "Profound changes to the plant mix in an ecosystem can cause big problems for a range of animal species that depend on them for survival."

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