Siam weed taking over Queensland farms

Graziers Geoff and Vicki Toomby have been battling Siam weed for several years at Wonderland Station at Alice River near Townsville.

Mr Toomby said the weed, which grows 5m a year and can climb 20m high, was "out of control", taking over some of their quality grass country and poisoning their cattle.

"It does your pasture in straight away. You've got nothing," Mr Toomby said.

"We lose cattle and we don't know. We were going to do post-mortems on them, but every time we find them, they're too far gone."

The Toombys have used every available control method on the weed, from mechanical to herbicide controls.

"There's one block here we cleared twice with the dozer and raked it," Mr Toomby said.

"We've done that two years in a row and sprayed it, and it's back thicker than ever now. It's out of control."

In 2019, stem-galling fly was introduced in northern Queensland and the NT as another way to tackle the weed.

Mass-reared at DAF's Tropical Weed Research Centre in Charters Towers, the fly causes galls along the stems and growing points which acts as a nutrient sink to weaken the plant, resulting in a reduction in flowering and seeding.

Mr Toomby introduced the flies at two sites on his farm in 2019, hoping they would help fight the incursions.

"Initially, we saw a lot of galls, but in the last 12 months, there's been nothing at all," he said.

Now, he must continue with the other methods, but with the price of fuel and inputs jumping to record levels, he's afraid Siam will consume his farm.

"We've got two dozers, but those are sitting here because we can't afford to run them at $2.13 a litre for diesel, plus we can't afford to pay anyone to drive them, plus the cheapest chemical we can get is $900 for 20 litres," he said.

"This Siam weed is going to take over all these urban areas. It's everywhere. It's not just a problem - it's a major problem. It's taken over. It's beaten us."

First identified in Australia in 1994 along the Tully River and at Bingil Bay in FNQ, Siam weed has since been found in the Townsville, Mossman, Innot Hot Springs and Mount Garnet areas.

It spreads via wind, water, animals and vehicles, and has the potential to spread across northern Australia and down the eastern and western coastlines in areas where annual rainfall exceeds 600mm.

Further north, Cassowary Coast Regional Council has released more than 300 stem-galling flies in the Munro Plains area to combat Siam.

Environment portfolio holder and councillor Jeff Baines said while the stem-galling fly does not eradicate the weed fully, "it has proven to successfully reduce and minimise the spread of the weed".

Until 2012, there was a nationally cost-shared eradication program, but it was declared not technically feasible to eradicate Siam weed.

In Queensland, Siam weed is now managed by local governments.

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