October 2014

The Nation Reviewed

She’ll be cactus

By John van Tiggelen
In central Victoria, locals are taking up arms against the invading wheel cactus

Pigeon Hill, a granite outcrop just west of Maldon, in central Victoria, overlooks plains that roll out all the way to the Murray. These can look lovely in early spring. The explorer Thomas Mitchell, casting his eyes over them in 1836, thought them lush: so lush, he called them “Australia Felix”. His report sparked a land rush, followed by a gold rush, but today, a good few droughts later with the promise of worse to come, the territory is close to clapped-out. Dairy, olives and apples have come and gone. Shearing sheds are fewer and farther between. Once-vigorous communities have slid into welfare dependency. The agriculture left to thrive is of the sort that just needs land as a buffer from homes: chicken broiler farms, cattle feedlots, piggeries.

It’s good country for cactus.

Up on Pigeon Hill, the wheel cactus, a particularly resilient species, bides its time. The hill is thick with it. Consisting of flat, grey-green lobes as big as dinner plates, each stacked upright and bristling with needle-length spines, the plant grows in clumps that could fill a kitchen. Younger plants stream down the hill’s flanks onto the plains below. Nearby ridges wear caps of the same Colorbond hue. There are metastases, too, on the distant peaks studding the northern plains, including Major Mitchell’s original vantage points of Pyramid Hill and Mount Hope.

“It’s teetering,” says Doug Beach, a local weed-control contractor. “The cactus is on the point of getting away and taking over. In another five years it could be a nightmare the way it’s going. Its only weakness is the time it takes to flower and fruit, but once it does [after three or four years], its spread is exponential: a ten-year-old plant can produce 100 fruit or more. It will just go whoosh.”

The plant has recently been turning up in Western Australia’s wheat belt. Just two years ago it was declared a “weed of national significance”, largely for its runaway impact on South Australia’s Flinders Ranges, where aerial drones have been trialled to monitor its spread.

But Pigeon Hill remains “Cactus HQ”, says Beach. In all likelihood the wheel cactus was introduced to the area as a hedge plant, or possibly for its purple fig-like fruit to make jam, by Mediterranean migrants who moved here after World War Two to help build the Cairn Curran Reservoir on the Loddon River. Beach, who is 48, recalls roaming and rabbiting among the hill’s granite boulders as a kid with his mates. “We used to smash up the cactus with sticks. Back then you only saw it on the hill. It just sort of sat here, but there’s been an explosion in the last ten years.”

Weeds are opportunists by definition, and the drought of 1998–2009 left the surrounding country vulnerable. Another factor was the decimation of rabbit populations by the calicivirus – rabbits, as well as sheep, kept the cactus in check by eating the succulent young shoots. But the key catalyst, says Beach, has been social change. Around Maldon, many farms have been sliced into large blocks sold to tree-changers. Unlike farmers, the new arrivals come in search of a lifestyle rather than a livelihood. They’re here for the views, or the space, and might use their blocks to run alpacas, horses or dirt bikes, as is the case on Pigeon Hill. Weed control is either not an issue or beyond them, with many visiting only on weekends. Things get rougher farther north, where moribund towns increasingly subsist on pensions rather than primary industry. Outside Wedderburn, 100 kilometres north of Maldon, Jeroen van Veen manages Nardoo Hills, a Bush Heritage property that preserves remnant open woodland. With the help of volunteers, he has cleared “between 10- and 20,000 cactuses the size of a twin-cab ute” from the property. Unfortunately, nearby Mount Buckrabanyule remains coated in cactus, and its landholders aren’t in a position to do much about it. As a result, not only does Nardoo Hills face constant reinfestation but also the cactus is marching west, into the mallee.

The wheel cactus is a relative of the prickly pear, Opuntia stricta, which overwhelmed farming land in western New South Wales and southern Queensland nearly a century ago. But the imported insects that ended the prickly pear’s run in the 1920s are not nearly as effective in killing Opuntia robusta. In the ’50s, when the wheel cactus went feral, some farmers tried mechanical raking or slashing, only to find that each broken lobe readily took root to form a new cactus. Later they kept the cactus at bay by spraying various concoctions of diesel, dieldrin and arsenic.

They had to: back then, farmers could be prosecuted for harbouring weeds that menaced neighbouring properties. Though notionally this remains the case (under the Catchment and Land Protection Act), compliance is no longer enforced in Victoria. “It’s not thought wise to get people’s backs up,” says Beach diplomatically, while van Veen points out that the state government’s 2012 cuts to the Department of Primary Industries, which included the closure of four regional offices in north-west Victoria, have left precious few compliance officers in the field. But there’s another reason not to prosecute: it takes a lot of chemical to kill a cactus at a time when the right to farm organically might well be presented as a legal defence.

So, instead, it’s largely left to volunteers to check the cactus’ advance. Twelve years ago, retiree Ian Grenda took up the cause. His 6-hectare block, on a rocky ridge about 5 kilometres from Pigeon Hill, was infested with cactus. The standard method at the time was to punch a hole into each outer wheel with a screwdriver and fill it with glyphosate herbicide (also known as Roundup). It was messy work, and highly prickly. Also, a “clean kill” remained elusive – the plant often recovered. Grenda tried alternatives: whacking the plant and brushing the pulp with herbicide, blowing a cavity inside the lobe with a battery-operated pump, and spraying the cactus at night. (Cacti are dormant by day.) He even trialled shooting shotgun pellets packed with dried herbicide into the plant.

Eventually, he settled for a “forestry spear”, an applicator gun with a long, sharp nozzle that probes deeply into the cactus lobes. In 2006, he and fellow tree-changers formed the “Cactus Warriors”, a loose band of Landcare volunteers who, with the permission of local landholders, have since devoted one Sunday a month to “stabbing” wheel cactus.

On one such Sunday this spring, some 30 people turned up on a block of lightly wooded farmland. Typically, the owner of the property was not among them. The cactus grew in all directions but, having seeded in bird droppings, was concentrated in circles under large, semi-solitary eucalypts. In its native Mexico, the cactus is spread by fruit bats. In Australia, crows are thought to be the main culprits, though other likely suspects include wattlebirds, cockatoos, emus, currawongs, silver-eye finches and foxes.

The volunteers traipsed off toting backpacks filled with blue herbicide, with a spear in one hand and a can of spray-paint in the other. Treated plants take months to wilt and die, so they are marked with paint. Over the course of the morning, the Warriors covered about 30 hectares, leaving behind families of “smiley faces” daubed on the highest wheels.

Yet volunteers can only achieve so much. Although the cactus has been beaten back from a number of gullies and hills, reinfestations and fresh satellite clusters are forever arising. Beach, who doubles as a Cactus Warrior, worries the plant is a bellwether of climate change. If the war is to be won, he says, it has to be won soon. An ancient stone fence runs across Pigeon Hill. On one side, Beach has reduced the cactus to patches of rotting lobes, albeit at the considerable expense of the absentee owner. On the other side of the fence, the impenetrable array of pale-green discs rolls on and on. If only the landholders could afford to hire him. “I love being on the hill,” Beach says. “It’s like an army advancing, and if you can halt it, you’re doing something meaningful. It’s hard to imagine the kind of job where you come home every day and think you’ve helped the world become a better place, but killing cactus is like that.” 

John van Tiggelen

John van Tiggelen is a freelance writer and the author of Mango Country.


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