Sales and trades of the popular arum lily (Zantedeschia aethiopica) are to be banned throughout Western Australia from September this year under changes to the State’s Declared Plants list.

The ban, from September 1, extends an existing ban on the invasive and poisonous plant already in place in parts of the South West including Albany, Bunbury, Busselton and Jarrahdale.

Director of Invasive Species with the Department of Agriculture and Food, Damian Collopy, said the nursery industry supported the ban, and had been given until the end of August to clear existing stocks.

“The ban includes the trading or selling of arum lilies at weekend markets and other casual outlets such as fetes,” Mr Collopy said. “It also means that movement of the plants or their seeds are prohibited throughout Western Australia,” he said.

Mr Collopy said the plant’s new Declared Weed status throughout Western Australia would apply to all its named cultivars and varieties including ‘Childsiana’, ‘Green Goddess’, ‘Pink Marshmallow’ and ‘Pink Mist’.

Mr Collopy said there had been a clear double standard that had allowed nurseries in Perth to sell arum lily, while it was illegal to sell the plant in some other WA regions. “Community groups and individuals have long lobbied for arum lily to be made illegal to sell anywhere in WA, and for control to be required on private and public lands where it has established,” Mr Collopy said.

In the South West arum lily has invaded thousands of hectares of pasture paddocks, forest and wetlands, requiring massive efforts by property owners and communities to clear it. “We have had a number of cases of child poisonings in Australia, and it is harmful to pets and livestock,” Mr Collopy said. “Every part of this plant is toxic.”

The President of the Nursery and Garden Industry (WA) (NGIWA) Colin Groom said his industry appreciated the consultation prior to the decision on the new State wide ban. “NGIWA supports the changes to the declaration of arum lily that incorporate a suitable grace period for businesses to clear any stocks they currently hold,” Mr Groom said. “NGIWA is committed to assisting its members manage environmental issues such as invasive plants in a positive way.” Mr Groom said members had been advised of the declaration changes through their industry newsletter.

Department of Agriculture and Food
Government of Western Australia
22 May 2006

A toxic weed that was first introduced into Western Australia as a garden plant is flourishing following recent summer rains.

“It is the worst year that biosecurity officers have ever seen for the germination of the declared plant narrow-leaf cotton bush,” said Department of Agriculture Biosecurity Officer Simon Merewether. “It is appearing in areas from Serpentine to Harvey.”

Narrow leaf cotton bush (Gomphocarpus fruticosus) is native to South Africa and was introduced to Australia as a garden plant. It has toxic sap but is rarely eaten by livestock as it is unpalatable, though it can cause serious problems as a contaminant of hay. If left uncontrolled, it can form dense thickets many hectares in size. Narrow leaf cotton bush gets its common name from the white thread-like attachments on the seeds and is also known as swan plant because of its swan-shaped seed pods. The weed mainly germinates in spring and autumn, but can germinate at any time under warm, moist conditions. The current outbreak does offer landholders an opportunity.

“Controlling this pest now will deplete the seed bank,” Mr Merewether said. “But be aware that control operations may need to be carried out several times due to multiple germinations which are a result of the wet summer conditions. Small infestations can be controlled by pulling out plants, however wear rubber gloves and take other precautions to avoid contact with the toxic sap, and make sure you get all the roots or it will sprout back.”

Narrow-leaf cotton bush can be sprayed with two herbicides, glyphosate and triclopyr. Spraying information can be found in Farmnote 43/2003 or on the DAWA website www.agric.wa.gov.au, search for “cotton bush”.

Department of Agriculture
Government of Western Australia
20 February 2006

Mail order bulb catalogues which include several plants that are well known weeds have prompted complaints to The Department of Agriculture. Department weeds research officer Sandy Lloyd said one species of particular concern was chincherinchee (Ornithogalum thyrsoides) which can poison livestock.

“It can spread into pastures and, if sheep eat it, they get a condition called foetid haemorrhagic diarrhea,” she said. Ms Lloyd said farmers should practice good biosecurity and avoid buying any garden plants that could be weeds or toxic to livestock.

“Mail order catalogues are convenient but it’s better to spend some time choosing plants that are safe. Chincherinchee is already spreading between Kojonup and Albany - we don’t need any more of it.”

Other species of bulbs and corms available by mail order and the internet are already a problem in native bushland. Ms Lloyd said that many community groups around Perth and in the south-west were working to eradicate infestations of several common garden bulbs that had escaped into bushland. This included the baboon-flowers (Babiana species), black flag (Ferraria crispa), freesias, sparaxis watsonias and soldiers (Lachenalia species).

The Environmental Weeds Action Network had published a book Bushland Weeds - a practical guide to their management, which gives information about controlling bulbs and other weeds in bush. It is available from The Wildflower Society (Tel. 9383 7979). Ms Lloyd said gardeners who wanted to do the right thing in preventing weed problems with bulbs could learn to recognise the species of most serious threat and choose not to buy, grow or exchange them, and never dump these plants in the bush where they would readily spread.

Some information on weed problems from bulbs is available from the Department of Agriculture’s Gardennote No. 16, ‘Bulb and corm-producing plants that become bushland weeds’, which is also online at www.agric.wa.gov.au The Weeds CRC website www.weeds.crc.org.au also has information about weedy garden plants.

Department of Agriculture
Government of Western Australia
15 February 2006

The State Government today announced that it had started a campaign against rubber vine (Cryptostegia grandiflora) in the Kimberley, after an infestation of the potentially devastating weed was found near Derby in Western Australia’s north. The Department of Agriculture and the Department of Conservation and Land Management (CALM) have begun an intense search and spraying campaign after the plant, which is recognised as a weed of national significance, was found near a camping area adjacent to the Willare Bridge on the Fitzroy River.

Environment Minister Judy Edwards said the woody perennial vine was an introduced species which originated in Madagascar and was first reported in Australia in Queensland in the late 19th century.

“The vine aggressively colonises areas, forming impenetrable thickets that smother vegetation,” Dr Edwards said. “It has the potential to impact on native ecosystems, primary industry and tourism. The heaviest infestation is within a kilometre downstream of the bridge and searches are under way to determine its full extent. So far, we know the infestation covers an area of at least 270 ha, at various densities, adjacent to the Fitzroy River.”

The Minister said investigations were continuing to identify all owners of infested land. Under the Agriculture and Related Resources Protection Act, it was the responsibility of the landholder to control infestations.

“CALM is providing significant resources to search surrounding areas and destroy isolated plants, while the Department of Agriculture is providing advice on control and spraying of the core infestation,” Dr Edwards said. “Through this co-operative and co-ordinated approach, attempts will be made to eradicate the infestation within two years and keep the affected area under surveillance for another three.”

Rubber vine effects can include: choking native vegetation, damaging native ecosystems and decreasing biodiversity; preventing access by both stock and native animals to water; harbouring feral animals such as wild pigs; increasing the difficulty in mustering of livestock; loss of pasture and grazing land; and increasing the risk of erosion due to decreased ground cover.

“We would ask people to keep an eye out for unusual plants when camping in WA and also to ensure they clean their trailers, caravans, tents and other equipment before moving on,” Dr Edwards said. “This will help prevent the spread and introduction of exotic pests to WA.”

Department of Agriculture and Department of Conservation and Land Management
Government of Western Australia
21 December 2005

Australia’s once fire-tolerant landscapes are being burned alive by a spreading invasion of African grasses. In a development with profound ecological implications for Australia’s native plants and animals, vast areas of woodland in the north and centre of the continent are now at risk, scientists warn. The enemy is a host of African grasses such as gamba grass, para grass, mission grass and buffel grass. These build up huge fuel loads, causing fires of an intensity and timing that native trees, shrubs and grasses cannot withstand, says Professor David Bowman of Charles Darwin University.

“The irony is that this continent has been shaped by fire, and its vegetation has developed a remarkable tolerance to it. Humans came and re-shaped the ecosystems using fire. But Australia has never had to cope with blazes like this before,” he says. “These ‘fireweeds’ are becoming widespread, invading areas of high conservation value in the arid zone and monsoonal tropics of the Top End, and displacing the native grasses and shrubs.”

Dr Tony Grice from the CRC for Australian Weed Management points to Guinea grass as another African grass species that can have dramatic effects on fire regimes.

“Guinea grass was introduced as a pasture plant but in ungrazed areas it can become very bulky and provide more fuel for high intensity fires. It’s especially common in riverine environments”, Dr Grice says. Producing up to four times the fuel load of native grasses, the African weeds cause conflagrations which destroy eucalypts, acacias and other shrubs that make up the unique Australian landscape and which normally thrive in the natural fires of lower intensity and frequency.

“In no time a woodland can be replaced with a grassland - and an African grassland at that,” Prof. Bowman warns. “Because these grasses occupy the richest areas, one of their impacts is to destroy the refugia - the last refuges of Australian native plants and animals in intense drought. If these go, then there is nothing to replenish the landscape.”

According to Dr Grice, the negative effects of African grasses on the local environment should have been taken into account before they were planted.

“We have created this invasive grasses problem in the north without due regard to the ecological impact”, Dr Grice says. “Scientists and the pastoral industry now urgently need to work together to find ways to stop their spread.”

Charles Darwin University, NT and
Cooperative Research Centre for Australian Weed Management
2005

Australia’s beautiful Blue Mountains are one of the invasion beach-heads for a devastating assault by alien plants which, in places, are starting to take over the native landscape. The qualities that make the Blue Mts one of Sydney’s iconic beauty spots both for locals and overseas visitors also place them at particular risk of plant invasions, a senior plant scientist warned today.

Dr John Hosking of the Co-operative Research Centre for Australian Weed Management and the NSW Department of Primary Industries said that the more researchers looked the more plant invasions they were discovering.

“In NSW alone in the past four years we have identified more than 120 alien plants that have either naturalised into the native environment or are in the process of doing so,” he says.

The invaders include garden favourites like agapanthus, various pittosporums, Juniperus, Cistus, Erica, Ajuga, Arbutus and Clematis, certain pines, cypresses and elms - and even native Australian plants from interstate, like WA kangaroo paws.

“The Blue Mountains resembles the tip of a very large iceberg. It is one of the most likely areas for new weeds taking off, because it is accessible, populated, and has many visitors and a range of climates and soil types. These together create many opportunities for invasive plants to establish. The sandstone country is a harsh place for plants to live, but nevertheless alien plants from places like South Africa are now getting a firm foothold.”

The agapanthus, beloved of Australian gardeners, is emerging as a potential weed threat in parts of NSW and Victoria because of its hardiness and drought resistance.

“In the Blue Mts, the ledges below the Three Sisters lookout are full of agapanthus, which has taken over from whatever natives were there before,” Dr Hosking says. “It may look pretty, but it is no longer a truly Australian landscape.”

Researchers are currently recording around 30 ‘new’ naturalised plant species in NSW alone every year. Some may be totally new records, and others have merely been identified for the first time. The risk, he says, is that an invasive plant can lurk in the background, unnoticed, for years - and then increase rapidly when conditions are just right: when the landscape is disturbed, the climate changes or its seed is carried by humans, birds, wind or water to a suitable spot. Particularly vulnerable, he says, are the river valleys in places such as the Blue Mts, where seeds and plant fragments can be easily spread by water and find fertile ground to grow in. High levels of nutrients from sewage and land runoff are exacerbating the problem.

Cooperative Research Centre for Australian Weed Management
30 March 2005

It could be Australia’s botanical ‘cane toad’ - a rampant plant that breaks concrete, blocks drains, invades houses, smashes up roads and totally smothers large tracts of land. Authorities in three states are on high alert for Japanese Knotweed, an invasive plant that once adorned southern Australian gardens - but jumped the fence and, according to scientists, now poses one of the biggest threats to our native landscape since blackberries.

“Potentially it could be even worse than blackberries,” says John Weiss, a researcher with the Australian Weeds CRC and Keith Turnbull Institute in Victoria. “It’s tougher to eradicate because of its deep roots and massive rhizomes that can lift roads and grow right through the trunks of other trees.”

Japanese Knotweed made its first garden escape back in the early 20th century and has been stealthily taking up residence in the wild in Tasmania, Victoria and NSW where weed control authorities have it at the top of their hit-list for eradication. Since blackberries now occupy an estimated 8 million hectares of southern Australia - arguably the nation’s largest plant threat - the concern over knotweed isn’t exaggerated, says John Weiss. The plant has the potential to colonise the wetter areas of the southern third of the continent.

“The largest infestations are in Tasmania, but we have now identified four in Victoria and several have also been found along rail lines in NSW. In one case a Tasmanian family tried for 30 years to eradicate it and failed. In cool, wet parts of the continent it can go rampant, completely taking over the understorey. Two of the infestations in Victoria were right alongside National Parks. We found them just in time and are targeting them for eradication.”

Evolved for harsh conditions in Japan’s volcanic landscape, Knotweed rates as one of the world’s worst weeds, a vigorous invader of riparian zones in temperate Europe, the USA, Canada and New Zealand

“In the UK knotweed is so serious it is rated as a hazardous material. If you find it on your property you have to dig at least a couple of metres deep in order to get out all the roots,” Mr Weiss adds. “The rhizomes are very big and powerful and can spread at a rate of two metres a year - like bamboo, only worse.” Knotweed can be controlled with herbicides, but it takes at least five years of persistent spraying to get on top of it, he says. “Even then you can’t be sure you’ve got it all.”

So far, scientists believe, the knotweed in Australia has only reproduced asexually. If it ever began setting seed, hybridising and producing new strains, there would be real trouble. Biological control is a possibility, but the science has yet to be done to investigate possible agents to control it, John Weiss says.

Cooperative Research Centre for Australian Weed Management
27 April 2005

Serrated tussock is one of Australia’s worst plant pests occupying more than a million hectares. However, it’s facing a resounding defeat in Victoria with the State’s serrated tussock infestation down by nearly 40%. There’s no magic bullet for the tussock (Nassella trichotoma), says David McLaren, the unpalatable grasses project leader of the Cooperative Research Centre for Australian Weed Management from the Victorian Department of Primary Industries (DPI).

“The campaign is working in Victoria because it has united scientists, government and farmers, and because it is community-led. Over a period of 10 years we’ve brought together all the people and groups who have an interest in eradicating this pest grass,” he says. “The success of the group is based on shared experience and shared effort.”

The Victorian Serrated Tussock Working Party was founded in 1996 and includes representatives from 27 Landcare groups, 11 local councils, five Catchment Management Authorities and two Victorian Government departments.

“Serrated tussock is useless to stock, prolific, and extremely invasive. In 1954 there were just four hectares of tussock in Victoria. By 1980 it occupied 30,000 ha and by 1990s the weed covered 130,000 hectares in Victoria alone,” says Dr McLaren. “Due largely to the Working Party, we’ve turned that around, and now we’re down to 85,000 hectares.”

Dr McLaren says the Victorian success is due to government, community and scientific cooperation combining to create a concentrated effort to get on top of the weed.

“Researchers are providing the tools: chemical, biological and mechanical. Government agencies are spreading the word though their extension services, while Landcare groups and individual landholders are providing on-the-spot practical control.” Dr McLaren says that preventing serrated tussock from seeding is the key to the program. This prevents spread and through time the seedbank diminishes reducing the problem.

“It’s been estimated that more than thirty million hectares of southern Australia are potentially at threat from serrated tussock invasion,” says Dr McLaren. “The strength of the Victorian Working Party has been that it has used a suite of weapons to deal with the grass, but also encouraged compliance among landholders. Carrots and sticks are part of the process - rate rebates for compliance, the threat of prosecution for non-compliance,” he says. The Serrated Tussock Working Party process has been widely admired for its success, and is being adopted as a model to combat Australia’s other Weeds of National Significance (WoNS).

Cooperative Research Centre for Australian Weed Management
25 May 2005

Blackberries are Australia’s worst weed. They are tough, aggressive and they appear to be out-pacing national efforts to control them. Three years of collecting and examining DNA ‘fingerprints’ of the biological control agent, blackberry leaf rust (Phragmidium violaceum), has given researchers a picture of why biological control of blackberry has been a limited success, says PhD student Don Gomez of the Cooperative Research Centre for Australian Weed Management based at the University of Adelaide. Weedy blackberries occupy nine million hectares of land. Almost half of this area is inaccessible to conventional weed control.

“Biological control remains the only feasible means to control the weed in remote and environmentally sensitive areas” says Mr Gomez, “but there are at least fifteen weedy species of blackberry in Australia and not all of them are equally susceptible to the rust. The problem for land managers is to ensure that the most effective and virulent rust strains get to where they are needed.”

Blackberry leaf rust was first identified in Victoria in 1984, which was the result of an unauthorised introduction. The first authorised introduction of the rust occurred with a release of a single strain of the rust as a biological control agent in 1991. More recently, CSIRO have released eight additional strains of the rust in NSW, Victoria and Western Australia in 2004. The intention is that these strains cause disease on a broader range of blackberry species.

“The rust likes a warm - not hot - January and an annual rainfall of more than 800mm,” says Mr Gomez.

Blackberries infected with the rust are easily recognised during spring and summer, with purple-brown blotches on the upper side of the leaf and powdery yellow pustules on the lower surface of the leaf.

“Rust can look spectacular on blackberries, but the weed is extremely tough and it may take several years of infection before a significant reduction in weed density is observed” he says. While biological control is the best long-term option for controlling blackberry in inaccessible areas, integrated weed management should be applied where possible,” says Mr Gomez.

“Slashing and burning are effective in the short term and allow access for other methods. Herbicides work best when they are applied during a time of active growth, but even these have different effects on the different species of blackberry,” he says.

Cooperative Research Centre for Australian Weed Management
8 June 2005

A national effort is underway to find and destroy a devastating plant invader before it can engulf large swathes of Australia’s coastal tropics. Spotter helicopters are working their way up tiny valleys, searching the rainforest and woodlands for signs that Siam weed (Chromolaena odorata) may have planted a stealthy foothold in the prized heritage region.

Siam weed is rated as one of the world’s worst tropical plant pests. Originally from South America it has gobbled up huge tracts of farmland and forest in Africa, Asia and the Indian subcontinent. Ten years ago it was detected in Australia, with infestations around the North Queensland towns of Tully and Townsville. Scientists say it could potentially invade anywhere on the coastal strip from Lismore (NSW) to Geraldton (WA) where rainfall is high (more than 1000mm).

A huge co-ordinated effort involving the Commonwealth and governments of Queensland, Western Australia, New South Wales and the Northern Territory in conjunction with local government, farmers and landholders is under way to try to identify fresh outbreaks. Normally hard to spot amid dense tropical vegetation, what gives the invader away are its eye-catching clusters of white-mauve flowers, which can even be seen from the air at this time of year.

“Siam weed is potentially as bad, or worse, than lantana,” says Brett Davis, a senior project officer with Queensland’s Department of Natural Resources and Mines. “It’s poisonous to cattle, it can smother crops of sugarcane or banana plantations, and it can climb right into the rainforest canopy and swamp the native vegetation.”

Siam weed forms dense, impenetrable thickets several metres high which engulf native vegetation, especially along river banks and on forest fringes. When these dry off they add greatly to the bushfire hazard, posing a direct menace to the fire-sensitive rainforest. It grows faster than native grasses and vegetation and, like lantana, can completely replace the pasture grasses under eucalypts, leaving cattle and native wildlife with nothing to eat.

“We’re asking everyone in northern Australia to be on the lookout right now for potential infestations of Siam weed,” Mr Davis says. “If we catch them early, there’s a good chance of eradicating the plant before it does any damage.”

Siam weed’s tiny fluffy seeds make it a particular menace, because they spread easily on vehicles, machinery, livestock and even the clothing of people who walk or work in the bush, Mr Davis says.

Queensland Department of Natural Resources and Mines
11 July 2005

A breakthrough discovery by a volunteer land management group is offering new hope in the battle against a devastating plant invader, bridal creeper. Bridal creeper is a major invader of bushland in Victoria, New South Wales, South Australia and Western Australia. But members of the land management community on Kangaroo Island (SA) have come up with an innovative way to spread a biological control agent, which attacks and weakens the creeper.

According to Dennis Gannaway, National Bridal Creeper Management Coordinator, the Kangaroo Island landholders were facing a heavy infestation of bridal creeper, one of Australia’s top twenty plant enemies, the Weeds of National Significance.

“Dean and Bev Overton, as active community volunteers, manage bushland on the north west of the island where the plant is rampant,” says Mr Gannaway. “They were confident that the rust fungus was attacking the weed, but they were not satisfied at the natural rate of spread. It was taking too long.”

Bridal creeper (Asparagus asparagoides) was introduced as an ornamental plant to Australia from South Africa in the late nineteenth century and was once popular in wedding bouquets. In South Africa it is an uncommon plant that is kept in check by its natural enemies, including the rust fungus Puccinia myrsiphyllii. The rust is one of three biological control agents that have been released in Australia by CSIRO to combat the weed. Rust fungus is normally spread by wind, but the Overtons discovered that it can also be distributed in a rainwater solution which has become known as ‘spore water’.

“At first, they simply mixed the spores of the rust in rainwater in biodegradable plastic bags, and threw these bags into thick infestations on roadsides,” says Mr Gannaway. “Now they have developed a method which can be used in anything from hand held spraypacks to agricultural sized spray equipment to spread the ‘spore-water’ mixture.”

“The effect on the weed has been immediate and dramatic,” he says. “The water-based spray has received the green light from state and federal regulatory authorities for unrestricted use, provided it is not sold as a commercial product.”

The Victorian Department of Primary Industries has a new research project to scientifically test the spore water technique across a range of environments.

“Whilst the technique has worked well in wetter areas such as Kangaroo Island, we are not sure how useful this will be in drier regions such as South Australia’s Riverland,” says Mr Gannaway.

Mr Gannaway has prepared an information package on the use of spore-water, how to prepare the mixture, and the best methods of distributing the spores. This is available from the Weeds Australia website at http://www.weeds.org.au/WoNS/bridalcreeper/

“Local innovation and ingenuity are enhancing the rust’s natural spread to have a serious impact on the weed,” says Mr Gannaway. “For example, land managers in the Eyre Peninsula are using the Kangaroo Island spore-water to treat large infestations which have recovered rapidly in bushland burnt out in the recent fires. Bridal creeper can recover quickly from fire, but the land managers are spreading spore-water along infested ridges to take advantage of prevailing winds which will spread the spores even further.”

Bridal creeper predominantly invades natural habitats but also impacts on citrus groves. Its climbing stems and thick foliage smother native plants, while underground it forms a dense mat of rhizomes and tubers which choke out root growth of other plants and prevent seedlings becoming established.

Three biological control agents have been released in Australia by CSIRO: the leafhopper (Zygina) in 1999, the rust fungus in 2000 and the leaf beetle (Crioceris) in 2002. Mr Gannaway says that biocontrol of any weed does not mean total eradication of the weed.

“Biocontrol aims to reduce the dominance of bridal creeper to a point where it does not dominate bushland and is economically insignificant in orchards,” says Mr Gannaway.

One of the reasons that biocontrol is a long-term process is the need for extreme caution when importing any living organisms from another country.

“All the natural enemies for bridal creeper, which were collected from South Africa, were scrupulously tested by the CSIRO before they even entered Australia,” he says. They were then kept under strict quarantine once they entered Australia and were subject to a further series of tests to ensure that they attacked only bridal creeper.

Mr Gannaway says that the recent discovery of a new form of bridal creeper is grounds for concern. This was recently confirmed to be growing in isolated patches in the border area between Victoria and South Australia. The Western Cape form of bridal creeper is showing resistance to the rust fungus.

A mapping project will be conducted later in the season to determine the extent of this form’s growth range. Mapping and further research into this plant will prevent the re-infestation of areas that have been cleared of common bridal creeper.

Department of Water, Land and Biodiversity Conservation
Government of South Australia 27 July 2005

Scientists are reporting early success in the battle against one of the world’s largest outbreaks of the devastating waterweed salvinia in the iconic Hawkesbury-Nepean river system in NSW. The weed, which engulfed an 88-km stretch of the rivers in 2004 has been beaten back to a few isolated patches, and is now being bombarded with special weevils which, it is hoped, will keep it permanently in check.

The salvinia infestation - rated the largest in temperate Australia - has been checked with mechanical harvesters, mop-up spraying and now, biological control in a major campaign staged by members of the Cooperative Research Centre for Australian Weed Management. The control program has so far cost $1.6 million but researchers expect that weed controllers will have to remain vigilant for a long time to ensure the outbreak does not recur. Following successful methods used on other major waterways in Australia and overseas, Cyrtobagous weevils were released at carefully selected sites on the Hawkesbury last spring and summer.

“The weevils have been extremely successful in warmer parts of Australia but it remains to be seen if they can survive the winter that far south and so keep the lid on the salvinia outbreak permanently,” says Mic Julien of the Weeds CRC and CSIRO.

The salvinia battle in the Hawkesbury-Nepean is one engagement in a huge war being waged across the continent, as thinly resourced State and Federal agencies, local government and landholders struggle to control Australia’s worst environmental threat - invasions by exotic plants. The Hawkesbury story, like the recent success against serrated tussock in Victoria, is heartening evidence that these battles can be won, and are worth fighting, says Weeds CRC chief executive officer Dr Rachel McFadyen. The Hawkesbury also illustrates the kind of challenges the nation’s ‘weed warriors’ are up against. In 1994 it was heavily infested with another Latin American plant, water hyacinth, which was successfully controlled before salvinia took over. Water weed expert Geoff Sainty cautions that the Hawkesbury typifies the problems facing many of the nation’s urban river catchments - slow flowing, warmish waters, rich in nutrients from sewage, farm runoff and erosion form ideal ‘farms’ for exotic water weeds brought in from overseas or interstate.

Lurking submerged in its nutrient-rich, slow flowing waters is another major problem plant called Egeria, whose bulk now amounts to tens of thousands of tonnes (around 400 tonnes per hectare) and whose stems reach 5-6 metres deep. On the surface it forms a dense mat that chokes the propellers of boats, preventing use of the river. Egeria has been present in the Hawkesbury since the 1960s, and is slowly getting worse as, unlike surface plants, there is no easy way to control it.

Cooperative Research Centre for Australian Weed Management
10 August 2005

Patriotic Australians who like to plant a wattle on National Wattle Day - September 1 - are this year being asked to take special care to plant a local variety. As well as being beautiful, wattles can be weeds. When taken out of their native environment to other parts of the continent, some wattle varieties can take over or even wipe out the local native bush as effectively as any introduced plant pest, warns Sandy Lloyd of the Weeds CRC.

“Wattles are prolific seed producers, so when you take them out of their native range where they are naturally controlled by insects, the seedlings survive very successfully - and they start taking over.”

Cootamundra wattle (Acacia baileyana) is unkindly referred to as the “Coota-bloody-mongrel wattle” after it infested large areas of native bushland in its own state of NSW, in Victoria, Western Australia, South Australia and Queensland where it is a declared weed and widely regarded as a foe by bush restoration groups and farmers. Cootamundra Wattle is a hardy tree which tolerates salt and frost, grows in partial shade to full sun on a range of soil types, and is drought tolerant when established. It invades heathland, woodland, grassland, dry sclerophyll forest and the banks of watercourses. It is moving into intact bushland in several states, displacing local wattles and forming dense stands that shade out other native plants. It also fixes nitrogen in the soil, making it unsuitable for the germination of many native plants.

The Sydney Golden Wattle (A. longifolia) is another homegrown menace outside its east coast range, and a weed in Victoria, South Australia and Western Australia.

“There are community groups raising money to buy chainsaws to get rid of the Sydney Golden wattles that have infested many areas of WA,” says Sandy Lloyd. “That’s how bad it has become. The problem with wattles is that they tend to colonise areas of native bush, where conservation often relies on the efforts of volunteers - and so are undermining all the effort, care and time that goes into trying to keep the bush in its original state.”

Several native wattle varieties are listed as pests in Environmental Weeds: A Field Guide for SE Australia by the Weeds CRC’s Kate Blood. They include: The Golden Wreath Wattle (A. saligna), a weed in NSW, SA and Victoria and The Mountain Cedar Wattle (A. elata), a particularly invasive tree of higher rainfall regions, able to take over undisturbed forest. Even Australia’s national emblem, the Golden Wattle (A. pycnantha) is now reported by scientists to be an environmental weed in some parts of the country. Many of these weedy wattles are available in nurseries and garden centres, and there is growing concern that conscientious gardeners looking to plant native gardens are unwittingly helping to spread them across the landscape.

Cooperative Research Centre for Australian Weed Management
31 August 2005

An invasive South American grass which arrived in Australia in the 1930s and became a serious weed by the 1980s, is about to meet its match. Chilean needle grass (Nassella neesiana) fits perfectly into Australia’s dry landscape, where it replaces both native grasses and valuable pastures. However, it is low in nutrition, and the sharp needle-like seeds can ruin sheep fleeces and penetrate their hides.

A relative of the highly invasive serrated tussock, Chilean needle grass is on Australia’s ‘most unwanted’ list of Weeds of National Significance (WoNS). Scientists say it is the worst environmental weed threatening native grasslands and has the potential to spread throughout south-eastern Australia, southern Queensland and even into Western Australia.

Agricultural scientist Charles Grech from the Victorian Department of Primary Industries has spent the last three years trying to find a way to defeat the invader.

‘We are hopeful that testing underway now in South America will come up with a solution. There’s a naturally occurring rust fungus there which attacks Chilean needle grass leaves, but we’re still a long way from a fully approved biocontrol for Australian conditions”, Mr Grech said.

Fortunately, well planned grazing management can also keep the weed under control in most areas, says Mr Grech.

“It isn’t the most palatable grass,” says Mr Grech, “but in trials we’ve found that under high stocking rates, sheep and cattle will eat it. Grazing has the spin-off benefit that it reduces the production of seed, so seedlings of other species get a chance to compete with the invader.”

Chilean needle grass produces modest feed during winter, but is less palatable when it flowers in late spring, says Mr Grech.

“Short duration, high intensity grazing knocks the plant back and a long rest period allows other faster growing competing grasses to recover.”

In a past trial on the NSW northern tablelands, the dry weight of Chilean needle grass fell from more than 50%t to about 30% after a season of rotational grazing, while other perennial pasture grasses increased. Intense grazing also changes Chilean needle grass from rank unpalatable tussocks to a shorter, green and more acceptable grass.

Mr Grech says that Chilean needle grass was first brought to Australia in 1934, when it appeared near Northcote, Victoria. It is not known if it came in fodder, or as seeds attached to equipment or animals. For most of the year the grass is hard to identify, growing in pastures and grasslands with other grasses such as fescue and native species. However in spring it produces distinctive tall stems with large purple coloured seeds (1 cm long with a 6 cm tail) that hang off the stem to one side like a flag.

An unusual feature of the grass is that in addition to normal flower seeds, it produces hidden seeds that are formed in the nodes and bases of the flowering stems. These ‘stem seeds’ are self-fertilised and account for about a quarter of total seed production. They assist the plant to reproduce despite grazing, slashing and fire.

Mr Grech says that there are herbicides registered in each State for Chilean needle grass, but that spraying with herbicides is only a short-term solution which has disadvantages.

“In the long term, integrated weed management is the only viable solution to the problem,” says Mr Grech. “Herbicide resistance is just one reason why chemical sprays are only a short-term answer - just one tool in the toolbox, along with burning, slashing, and physical removal in areas of light infestation.”

A survey of landowners in south-eastern Australia has shown that the cost of controlling Chilean needle grass can be between $60 and $120/ha, depending on the density of the infestation.

“The key to controlling Chilean needle grass is not to let it get a grip in the first place,” says Mr Grech. “It’s very competitive, and it has a large and persistent seedbank. But reducing its seed production helps maintain other competitive pasture species.”

Mr Grech says that anyone suspecting that they have an infestation of Chilean needle grass should immediately contact their local weed authorities. If there are only a few plants, they should be quickly removed by hand and destroyed, rather than creating bare areas by spot spraying. Stock or machinery being moved from an infested area should be thoroughly inspected and cleaned.

Victorian Department of Primary Industries
28 September 2005

Tropical plants from round the world are securing an invasion foothold in one of Australia’s most precious ecosystems - the northern rainforest. In a disturbing development, researchers in the CRC for Australian Weed Management say they are finding invasive alien plants in areas of rainforest previously undisturbed.

“Until now it was thought that weeds only established round the edges and in disturbed areas of rainforest,” explain Dr Helen Murphy and CSIRO’s Dr Dave Westcott, who are trying to establish the nature, extent and processes involved in the invasion. “However, certain plants - such as pond apple, guava, coffee and mango trees - can establish in relatively undisturbed areas of forest. And some, like pond apple, are quite capable of dominating surrounding vegetation.”

Other invaders include the Central American tree Miconia - responsible for ecological disasters overseas - and the African tree Harungana, which has reinvaded areas of native forest round Mt Bartle Frere where it was once thought to have been eradicated. The finding adds to concerns over existing pressures on the rainforest caused by fragmentation and human impacts. The invasive shrub lantana has already penetrated many areas of rainforest throughout the wet tropics, and can persist by making its way into the canopy as a climber up other trees.

“The serious aspect of this is that an invading plant can cause changes to the structure of the rainforest - some of these changes may in turn make it easier for other invaders to penetrate,” says Dr Murphy. “At present we have no idea how big the threat is, but in 200 research plots scattered across the wet tropics we have logged around 50 invasive plant species. Individual plots may have as many as 12 or 15 of these environmental weeds.”

A further dilemma lies in how invasions of the rainforest can be controlled, Dr Westcott says. Use of fire and bulldozers are clearly out of the question in rugged terrain and conservation areas. As yet there is little in the way of biological controls for the invaders, while manual control is costly.

Adding to the problem are Australian native animals and birds, like the cassowary and fruit bat, which are inadvertently helping spread the invaders by eating their fruits and distributing seed in their droppings. Australia has around 64 birds and animals which disperse rainforest seeds - and around three quarters of the world’s tropical forest plants have fleshy fruits capable of being spread in this way.

“Such diversity of species and interactions means that understanding and managing invasion in rainforest systems will not be easy. Indeed we are at a very early stage,” says Dr Murphy.

Cooperative Research Centre for Australian Weed Management
2 November 2005

Branched broomrape, one of the world’s most serious crop pests, has made a shock appearance in southern Australia due to perfect seasonal conditions. Previously with only a toehold in Australia, the parasitic plant that sucks the goodness out of growing crops and can lead to export restrictions has emerged at new sites in the Murray region of South Australia.

But despite the sudden outbreak, scientists consider they may have an answer in the form of a world-first system for killing seeds while they lie dormant in soil. The huge boomspray nicknamed the “Broominator” and a natural herbicide based on pine oil represent a major advance in weed control, offering the best means of killing off the future seed bank while still in the soil, says Dr John Matthews of the Weed CRC and Adelaide University.

“The new outbreaks mean that at least we know where the pest is,” says Dr Matthews. “You could say it has shown its hand - but we have a very promising means for controlling it.”

Branched broomrape (Orobanche ramosa) is regarded one of the world’s worst pests of crops such as carrots, cabbages, canola, beans and lentils as well as weeds of crops and pastures. A single plant can shed up to 500,000 seeds in a season and these may lie dormant in the soil for up to 15 years. It has invaded many countries but so far has only secured a toehold in Australia.

“Any farm where branched broomrape is found is immediately quarantined,” says Dr Matthews. “None of our overseas trading partners will accept agricultural products from Australia if they are contaminated with broomrape.”

Branched broomrape has a totally parasitic life cycle, he says. It produces very large numbers of small seeds, which lie dormant in the soil until they sense the chemical signals given off by the approaching roots of another plant.

“When a broomrape seed senses an approaching root, it grows a tube which attaches to the root and sucks the nutrients out of it,” says Dr Matthews. “This very successful parasitism allows the broomrape to spend most of its life hidden underground. It emerges from the ground as a small plant in the spring, flowers, and produces half a million seeds per plant, all within a few weeks. Then it disappears.”

Dr Matthews says that a small patch of broomrape was found in Australia in 1911, but this died out and the pest was not seen again until the 1990s. Now the present infestation has been found over an area of nearly 200,000 ha in the Murray region of SA.

The quarantine protocols, although tedious for affected farmers, mean that machinery is washed down with a seed sterilant, and stock are quarantined for a period after grazing on potentially infested land.”

Dr Matthews says that control of broomrape still poses a number of technical challenges and is difficult but not impossible.

“In the long term, biocontrol using specific fungi to attack the seeds may be successful,” he says. “There are herbicides which are effective at preventing the plant from setting seeds, but because the parasite emerges for such a short time, and is hard to detect, this opportunity is often missed.”

Methyl bromide has been successfully used to fumigate isolated outbreaks of broomrape, but this chemical is being phased out of agricultural use following the Montreal Protocol of 1987, as a threat to the ozone layer. A herbicide derivative marketed as InterceptorAE, made from extracts of natural pine oil, is being used as a soil drench to kill the seeds of broomrape in the soil. Dr Matthews believes that this will be a very effective weapon against the parasite.

“Interceptor kills the seeds and has none of the problems of methyl bromide,” he says. “It is even registered as organic. The disadvantage is that it has to be carried into the soil deep enough to actually reach the buried seeds. This requires very large amounts of water in non-irrigated paddocks. We’re experimenting with a 10,000 L boomspray - known as the Broominator - with the Broomrape Eradication Program of the SA Government. But although it has potential, there’s still a very high financial cost and cost in water per hectare.”

Dr Matthews says that a combination of education, vigilance, and prompt attention to any identified outbreaks are the essential elements of a program to control this very serious invasive plant.

“If the broomrape eradication program is to succeed - and failure to control broomrape would have serious financial consequences - there’s an urgent need for continuing funding and government support both at State and Federal level,” he says, “and continuing support from farmers all over Australia for those affected. So far, we’ve held this threat at bay. But there are untold millions of branched broomrape seeds waiting their opportunity in the Australian soil. We shouldn’t give them any chance of success.”

Cooperative Research Centre for Australian Weed Management
23 November 2005

A beautiful invader is threatening one of Australia’s most precious and beloved natural wonders - the World Heritage-listed Lord Howe Island, off the coast of NSW. A Taiwanese native bulb, Formosa lily or tiger lily (Lilium formosanum), has spread across the island from the coastal dunes to the high mountain slopes, raising the spectre of previous invaders like the rat which had catastrophic impacts on the unique Lord Howe ecology.

Lying 700 km north-east of Sydney, Lord Howe has a global reputation for its spectacular native flora - including its famous cloud forest - and the fact that over 40% of its 241 native plants are found nowhere else on earth. However, this unique assemblage of plants and animals that has arisen from both Australasian and Pacific island ancestry over millions of years is under threat from invasive plants. Over 300 introduced plant species have been recorded on the island - exceeding the number of native species.

The Formosa lily is an emerging problem, says Weeds CRC doctoral researcher Susie Warner. The bulb is native to Taiwan but has been widely cultivated as an ornamental around the world. The first herbarium record for the plant on Lord Howe was in the early 1970s and is another of Australia’s now-notorious “garden escapes”.

“Since establishment it has spread across the island, colonizing virtually every ecosystem and habitat from the beach, to the forest, to the upper slopes of Mt Gower and Mt Lidgbird,” she says. “It has become well established over large areas both in the open and in the forest, displacing native plants.”

The lily has also naturalised along the east coast of mainland Australia and could emerge as a major problem there too.

“Although Formosa lily is perennial, during the winter it dies back to an underground bulb whose size varies with the age of the individual. On Lord Howe, aboveground growth begins in July and plants produce a single shoot between then and mid summer. “Around January, this shoot produces multiple large white flowers tinged with purple, and each of these gives rise to a large capsule containing many hundreds of tiny seeds which are easily scattered by the wind.”

Lord Howe faces a number of threats from invasive plants including Crofton weed, bitou bush and cherry guava, and in 2004, the Lord Howe Island Board secured a NSW Environmental Trust Grant to tackle some of the island’s environmental weeds.

Cooperative Research Centre for Australian Weed Management
7 December 2005

The Department of Conservation and Land Management says a freshwater lake on the Nullarbor is under threat from an invasive species of weed. The department says athel pine has been discovered growing near the Boonderoo Lake, about 300 kilometres east of Kalgoorlie.

The lake is one of only two freshwater lakes on the Goldfields and the department says it is essential to prevent the weed from establishing itself in the area.

Sylvia Clark from the federally-funded Natural Resource Management project says the weed is capable of destroying whole ecosystems by increasing soil salinity. She says a team of experts will travel to the lake to try to eradicate the weed.

“Athel pine is a very invasive weed, occasionally it disperses and produces hundreds and thousands of seedlings, so it’s very important to get these seedlings out from this lake before they take over the entire system,” she said.

Department of Conservation and Land Management
Government of Western Australia
21 April 2006

SHALLOTTE, North Carolina, USA - Officials in North and South Carolina have fired the opening salvos in what surely will be a years-long battle to eradicate beach vitex from the coasts of both states.

Clemson University has begun tests on four sites on Pawleys Island to determine the best method of getting rid of the non-native, invasive plant, and Bald Head Island, N.C., is three months into an eradication program that will continue at least through the summer.

The deciduous, ground-cover plant is native to Korea and was first introduced to area beaches as a way to repair dunes after the devastation of Hurricane Hugo in 1989. It produces attractive purple flowers along with pleasant-smelling, gray green foliage during warm months and has been sold in commercial nurseries as a landscaping plant. It can grow from any part of runners that may be up to 60 feet long or from an estimated 10,000 to 20,000 seeds produced /m². But it has been found to inhibit the nesting of sea turtles, crowd out native dune plants and be less effective at holding and building dunes than things such as sea oats and bitter panicum.

“It’s a vicious contender,” said Betsy Brabson, coordinator of the S.C. Beach Vitex Task Force.

The plant has been banned by governments in Pawleys Island and Georgetown County in South Carolina and in Ocean Isle Beach, Holden Beach, Caswell Beach and Bald Head Island in North Carolina. The town of Oak Island, one of two places it is known to exist in Brunswick County, has not banned it, said town manager Jerry Walters.

It has also been spotted along beaches in Florida, Alabama and Mississippi, Brabson said. It is known to exist along much of the S.C. coast and as far north as Ocracoke Island in North Carolina. Brabson said the mass of roots on the plant stops sea turtles from digging nests through it and dead hatchlings have been found in the growth, unable to reach the sea before they dehydrated.

David Nash, coordinator of the N.C. Beach Vitex Task Force, who lives on Oak Island, said N.C. officials are concerned it could take hold on uninhabited barrier islands that are important wild bird nesting sites.

No one is sure how long it might take to eradicate the plant from any one site, although John Middleton, Bald Head Island village manager, said officials there are estimating from the experience of other invasive species that it could take up to five years. Bald Head appropriated $30,000 for plant removal, which started in January.

The village has received a $15,000 grant from the U.S. Fish and Wildlife Service to continue the program through the summer. Clemson officials have applied for a $133,000 grant from the federal Fish and Wildlife Foundation to battle the plant in South Carolina.

Middleton said he isn’t sure what the next step will be on Bald Head, but it likely will involve more hand removal or coating the plant with a chemical that will kill it. Middleton said the village will burn beach vitex plants that have been removed from 75 sites on the island.

Because it is so prolific and can grow from almost any part of the plant, individuals are encouraged not to try to remove beach vitex themselves. Rather, they should notify Brabson at 546-9431 or Nash at (910) 452-6393 if they think they spot it.

Officials in both states are hoping that beach vitex will be declared a federal noxious plant, which would ban its sale throughout the United States.

Steve Jones
The Sun News
Shallotte, North Carolina, USA
7 April 2006

HAWKES BAY, NEW ZEALAND - The death toll is rising at Pekapeka Swamp, and Garth Eyles is pleased. Willows are the enemy here, invaders that have clogged and choked the waters of the historic 97 hectare wetland during years of neglect. Now it is being rescued. The Hawke’s Bay Regional Council has a long-term plan of counter-attack, aiming to clear Pekapeka completely of pest willows and debris, and restore it as closely as possible to its original state. To that end, the death of each and every willow at Pekapeka has been a hard-won victory. It’s taken four years of helicopter spraying and countless hours of groundwork to deal with thousands of stubbornly-regenerating willows. The persistence has paid off. The landscape is now startlingly stark, littered with tree trunks standing as lifeless sentinels in a deserted battlefield, but in a year or two they will fall over and disappear under the water, as new plantings of flax, cabbage trees, kahikateas, kauri, kowhai, and many other native varieties grow into prominence.

“The willows are going now and a new landscape is emerging as the willows are dying. The trick will be to create a new landscape, other than what’s there. You can’t just leave it to regenerate. It’s not the same as it was before European settlement,” Mr Eyles says.

Two students have worked through the summer, pulling out willow seedlings, and the Pekapeka Shooting Association, which has shooting rights in the wetland for 10 years, is doing its bit by keeping willows and weeds out of pond areas.

Mr Eyles’ sights are now focusing on the next stage of the restoration, clearing rubbish and weeds. The debris in the swamp includes concrete dumped there from a hotel that burned down in Hastings. The worst of the weeds are Japanese honeysuckle, old man’s beard, blackberry and convolvulus. A weir will be built near the old piggery, so Pekapeka can maintain its winter water levels for longer in the spring and summer. It will have a fish pass to allow eels and fish to get into the wetland as the quality of its water improves. Managing the water levels is important, because a wetland needs 50 percent open area to keep the water healthy. Keeping the water levels up will also help to control raupo, which doesn’t like water more than a metre deep.

Pekapeka will need more areas of open water, and these might even have to be created with explosives, Mr Eyles says. “But first, we’ll need to make sure it would work, and get the necessary consents.”

The planting of a new landscape at Pekapeka will attract typical wetland birds such as pukeko - a bittern was heard there recently, for the first time in many years - and add to its natural diversity.

“We have a plan to develop the best wetland values we can achieve in bio-diversity, flood control and public recreation.”

Mr Eyles’ personal vision is for Pekapeka to form the southern end of the Hawke’s Bay pathway network.

“You could hop on your bike and cycle to Bay View, but that will be for the next generation. We’re lucky councillors are supporting this project, knowing it’s such a long-term project.”

Pekapeka has not always been treated so kindly. Europeans arrived in the 1800s and set to work to work to drain it. In the 1950s, more drains were built all around the wetland. Then, in the 1960s, most of the area was taken under the Public Works Act to be part of a flood control system for the Heretaunga Plains.

“Engineers saw it in that light,” Mr Eyles says. Their plan was to keep it as a swamp, full of reeds and debris to hold water back.

The building of drains was stopped and Pekapeka became largely ignored. That was when the willows moved in. In 1998, the regional council decided it was time to set things right at Pekapeka. By that time, willows covered 90%of it. Pekapeka used to have a distinctive swamp smell, which came from rotting raupo. But as willows edged out the raupo, the smell disappeared. Now Mr Eyles aims to bring it back.

“I tell people I’m trying to return the stink to Pekapeka. I’m trying to return the wetland to its more natural state.”

There are some things that are unlikely to change at Pekapeka, such as the main highway that was built straight through it. But that could in the end prove to be an asset to the second-most important wetland in Hawke’s Bay. The council plans to enhance the wetland by bringing the public into it, teaching them about its ecological value and history, and making it part of their recreational lives. There are drawings showing a walking track right around the circumference, and an area set aside for picnics and educational displays. People will be able to walk around and through Pekapeka, watch birds and wildlife, and enjoy it as part of their natural heritage.

Such an ambitious project does not come cheaply. The council has allocated $130,000 toward it, and hopes a sponsor will come forward with another $120,000. Overall, the restoration of Pekapeka has cost $518,000 since 1998. Killing willows has absorbed $209,000 of that. By the end of the current five-year plan in 2010, the cost is expected to reach $631,000.

Kathy Webb
Hawkes Bay, New Zealand.
15 April 2006