Skeleton Weed

The Skeleton Weed Control Campaign

(Chondrilla juncea L.)


South Australian Department of Agriculture

A.F. Tideman


Astutely, Australia had been warned as early as 1912 by its quarantine service that skeleton weed could become a serious agricultural problem. It was gazetted as a prohibited plant under the Commonwealth Quarantine Act even though at the time it was not a serious weed anywhere in the world.

In 1935, Arthur Perkins, the then Director of Agriculture, wrote to his technical staff warning them that skeleton weed had become established in Victoria.

He predicted serious consequences to crop production and asked that a careful watch be kept. G N Clarke, the Botanist at the Waite Agricultural Research Institute, published Perkin's concern in an article in the Journal of the South Australian Department of Agriculture.

By that time, skeleton weed, which had originally been found in 1913 near Wagga Wagga in New South Wales, had proved to be so competitive in the Riverina that large areas of wheat had not been harvested because of the tangled mass of wire-like stems and the low yields. A £5 000 reward for a means to eradicate the weed was offered by the NSW Government. It has never been claimed.

Besides the physical problems at harvest time, skeleton weed, with its deep penetrating root system and its quick response to opening rains, was able to beat the crop for nitrogen and soil moisture.

Skeleton weed was not all bad. It did have some redeeming features which farmers tried to exploit. In the rosette stage sheep would eat the weed and fat lambs could be produced on it. Once this was realised farming practices were changed in the Riverina from continuous wheat cropping to phases of legume based pastures, including lucerne.

Section 12. Hundred of Parilla

Mr C R Gilbertson, who owned Section 12 in the Hundred of Parilla was the first to officially report skeleton weed in South Australia. He took a specimen into the local hotel where the publican wrapped it and posted it to the Department of Agriculture.

On the 19th March 1947, Miss Eardley, who was the Systematic Botanist at the Waite Agricultural Research Institute, reported to the Department,

'I find the identification of the plant from the property of Mr C R Gilbertson is urgent for a quite an unexpected reason.The plant is skeleton weed (Chondrilla juncea) which is such a pest in the wheat fields of New South Wales. I am not sure of the nearest occurrence in Victoria at the moment   but this is the first occurrence in South Australia.'

At the time, the Mallee farmers around Parilla and beyond, were successfully introducing sheep onto their farms. Most had realised the value of carrying sheep on their farms before but had been unable to do so because of the lack of finance, drought and the unavailability of extra superphosphate to establish medic pastures and the shortage of labour during the war years.

In 1947 there were large sheep movements into the state from New South Wales and Victoria for sale at Loxton and Pinnaroo when fanners were able to throw off the war time constraints. Dealers, living near these markets, acted as intermediaries and sold the sheep throughout the region. This movement of sheep, wind and a series of more than usual summer rains paved the way for the introduction and spread of skeleton weed.

The Eradication Campaign

Without hesitation an eradication campaign, engineered by Frank Pearson, the District Agricultural Adviser and Hector Orchard, the Department of Agriculture's Weeds Adviser, commenced on the day following Miss Eardley's warning.

Orchard pinpointed seven patches of the weed, totalling one-third of a hectare spread over 80 ha. The weed was obviously well established but there was no hesitation to eradicate it, action strongly supported by the Government and the farming community. The infestations were burnt and the soil sterilised with sodium chlorate.

The property was quarantined under the terms of the Noxious Weeds Act 1931 which prevented stock from moving on or off the property.

Orchard then commenced surveying surrounding farms and within a few days found what appeared to be the parent area of skeleton weed in South Australia. The infestation was five kilometres away on Section 2, Hundred of Parilla owned by a sheep dealer, A A C Hill. The skeleton weed half covered an area of about 80ha. He had known of the infestation for five or six years but had not been concerned because the sheep ate it.

By the end of March, 11 days later, Orchard reported four more infestations extending into the Hundreds of Wilson and Price raising the total known area to about 25ha.

On April 3rd1947 Orchard was sent to gain all the information he could from the Victorian Department of Agriculture. From that visit he based the campaign to eradicate skeleton weed on the use of salt and Atlacide at the rate of 375kg per hectare to sterilize the soil. The Atlacide treatment cost $35.00 per hectare. The burning of stubbles, hand pulling to stop seeding and leaving patches isolated and uncultivated were the other recommendations.

With these limited choices and the knowledge that skeleton weed had spread from Wagga Wagga in New South Wales, despite the efforts of landowners and the authorities, Orchard must have known that eradication of the weed from South Australia was unrealistic. However pressure from the Government appointed Weeds Advisory Committee and landowners to get rid of the weed was very great but nobody wanted to do the work or pay the bill. It was to be five years before the aim to eradicate skeleton weed was abandoned and even then the call was renewed each time a new area of the state was broached.

The campaign to eradicate did receive some criticism. The Advertiser published an article, 'Skeleton Weed -Bane or Blessing' which encouraged landowners to make the best use of it by grazing as it spread.

After applying 225kg of Atlacide per ha to 30ha of the weed through a 3.9m boom spray mounted on a Jeep, Orchard reported at the end of 1947, 'The first phase of the eradication program has been completed'.

Working alone, Orchard applied a second spray of Atlacide to the same areas in January 1948.

During 1948 the one-man campaign was given additional resources. Two field assistants, Brooks and Watts, were appointed but despite the team's efforts, Orchard had to report during June 1949 that 100ha of the weed had been found on 62 properties in the Murray Mallee and the picture was deteriorating daily.

At the beginning of 1950, acting on pressure from the Local Government Association and a submission to Government by the Pinnaroo District Council, the Department of Agriculture appointed a full time officer to treat infestations. In hindsight this proved not to be good tactics leaving many landowners free from owning their problem.

AR Evans was appointed fulltime at an annual salary of $15.90 per week. Records show that he was appointed 'because of his youth' as his duties involved 'tedious manual labour'. The estimated annual cost of his operations and the associated eradication program which involved field days, window displays and door to door awareness was $2010.

During the following 12 months Evans visited 495 properties at least twice before he gave up, claiming with good reason, that he was under-paid and frustrated. His very detailed, hour by hour logbook, showed that he had spent the equivalent of eighteen 44-hour weeks inspecting and treating skeleton weed. The rest of his time was taken up travelling, maintaining his equipment and assessing the extensive research plots and demonstration sites set up by Orchard and his field assistants, Brooks and Watts.

The landowners were satisfied. After all the Government was treating the skeleton weed and as Evans' records showed, over 90% were: content to sit on their hands and let him do all the work.

At the time of his resignation Evans claimed that only two hectares of skeleton weed had actually been eradicated despite all the effort and the $6000 spent on the problem since the campaign had started. In his final report he therefore recommended that the Government abandoned attempting eradication in the Murray Mallee and retreat to the west of the River Murray and there treat every patch as it appeared.

Orchard was not prepared to give up so easily. He suggested employing a skeleton weed supervisor with three field assistants operating across three zones in the Murray Mallee and adjoining areas at an estimated annual cost of $21 000. Fortunately common sense prevailed and at the beginning of 1952 the Government officially abandoned attempts to eradicate skeleton weed from South Australia and commenced a special program to advise farmers how to control it. Ray Taylor was engaged fulltime on this program, only treating the weed when it was found outside areas of general infestation. The program lapsed after three years when Taylor was promoted to be an Agriculture Adviser.

The whole skeleton weed campaign came to a virtual halt in July 1957 when Hector Orchard was tragically killed while on duty near Morchard. His Government supplied Austin utility, made for English conditions was not very suitable for gravel roads in northern South Australia. The vehicle rolled in a creek bed.

Reorganisation took two and a half years during which time Arthur Tideman was appointed Weeds Adviser. A new Weeds Act was proclaimed and a three person Weed Control Section was established in the Department. Max O'Neil was appointed Assistant Adviser and Max Ross the first graduate Research Officer.

These years of relative inactivity by the Department had done nothing to promote weed control across the State, despite the intentions of Dr Allan Callaghan, the Director of Agriculture. By the beginning of 1960 skeleton weed could be found on every farm in the Murray Mallee and outbreaks were being sighted west of the River Murray.

Yearly Leaps

During 1960, the Weed Control Section in the Department recorded 30 outbreaks along the Murray Plains west of the River. At the same time the weed was spreading south. In the Upper Southeast 50 outbreaks were recorded by the end of 1960.

Early in October 1961 the first outbreak in the northern wheat belt was found on Hill River Station by Max McKay, a sales representative from ICI. Not wishing to embarrass his client he used the 'pub network' to inform weed control officers in the Department who conducted a detailed search several days later. They found skeleton weed well established over two hectares. Over the next five years more than 120 outbreaks were found from Freeling in the south of the wheat belt to Wilmington in the north and treated by Local Government authorized weed control officers.

Early in December. 1962 an outbreak was found 20 kms west of Wirrula on the Eyre Highway. It was found by Mr Driver who owned the adjoining property. This was considered as serious blow to South Australian agriculture as it was realised that the whole of the Peninsula was very vulnerable to serious infestations of skeleton weed as the sandy soils were ideally suited to its establishment and growth and any treatments would be difficult over the very large properties typical of the area.

On the 18th of January 1963, the author, with a number of helpers from the Minnipa Research Centre, conducted an all-day field day in 40C heat to promote identification of skeleton weed and its treatment. Lectures were given on the hour every hour between 8.00 am and 4.00 pm. The landowners were greatly alarmed and grateful for the opportunity to learn what they were up against. Despite the short notice more than 400 attended during the day, coming from as far away as Tumby Bay, Bookabie and Kimba.

Following the field day local farmers took control into their own hands and carted more than 100 tonnes of salt to spread over the area. Their efforts virtually eradicated that outbreak but failed to stop further outbreaks quickly becoming established.

In 1963 the first outbreak on York Peninsula was found at Arthurton. Before the year was over local government inspectors had recorded another 20 outbreaks.

And so, by this time, skeleton weed had penetrated all agricultural areas of the state except Kangaroo Island. The battle has continued ever since with the tide thankfully turned by the discovery of picloram, an effective herbicide for spot treatments of newly found outbreaks and the introduction of biological control agents.

1960. A Milestone in Skeleton Weed Research and Control

For many years prior to 1948, the search for better ways of controlling the weeds of South Australia had largely been confined to field observations by landowners and botanical studies of their habits.

During September 1948, growth regulating herbicides became available. With their introduction weed control research was born, stimulated by chemical companies such as ICI, Shell and Velcicol. Their assessment for use within the South Australian environment required sophisticated spraying equipment and scientific measurement which had been lacking until that time.

With a little scientific background but with a great deal of enthusiasm, Hector Orchard, the weed control specialist in the Department of Agriculture and Frank Pearson, the District Agricultural Adviser for the Murray Malllee, sprayed areas of skeleton weed with various forms of 2,4D (2,4 dichlorophenoxy acetic acid) and later MCPA (2-methyl-4 cblorophenoxy acetic acid).

Their first report stated (1950), 'Trial areas sprayed showed 10 to.15 % of plants with above ground portions completely dried out, 60-70% with severe burn off of leaves and the remainder practically untouched' . (Note: The herbicide used was not stated but it was probably the ester form of 2,4D) . They realised that these herbicides could be used selectively in cereals and decided it was worthwhile to try further.

Orchard continued this work at many sites until 1955 when he felt confident enough to recommend using 1.5 kg per hectare of the amine form of 2,4D for skeleton weed control in cereals.

A year later the CSIRO published results of research work conducted in New South Wales which proved that better yields could be obtained from skeleton weed infested paddocks by fallow spraying with 2,4D thirty to fifty days before sowing the crop.

Orchard quickly tried these recommendations in the Murray Valley but found them ineffective because the complete lack of soil moisture kept the skeleton weed inactive until the opening rains, which were unpredictable, and then crops had to be sown immediately.

With the appointment of Max Ross as a full-time Research Officer, at the beginning of 1960 it allowed South Australia to take part in the National skeleton weed research program which, from 1961, was directed, co-ordinated and assessed by the Technical Subcommittee for Skeleton Weed Research under the direction, initially, of the Commonwealth Standing Committee on Agriculture and then after its formation in the 1966, the Australian Weeds Committee.

During the following decade of research the programs were well funded by the farmers through their wheat industry levy which was subsidised by the Federal Government. By 1970, $630,000 was distributed by the Technical Subcommittee enabling agronomic research and herbicide evaluation in each region across southern Australia where skeleton weed had become established. South Australia received approximately $60,000 enabling an additional Research Officer, Bob Luxmore, to work full-time on the problem.

As a result of this combined research, by the late 1960s, very satisfactory chemical control of small areas of skeleton weed could be achieved, mainly due to the discovery of a herbicide, picloram, by the Dow chemical Co (picloram, marketed as Tordon in various formulations is still used effectively today, 30 years after its discovery). It proved to be 100 times more biologically active than 2,4D. But unfortunately legumes were particularly susceptible. Only one gram of the active ingredient could kill 100 sq m of lucerne.

Armed with picloram landowners have subsequently prevented skeleton weed from becoming a serious economic problem on the Eyre Peninsula despite the first outbreak in that region occurring in December 1962. That discovery was most fortunate considering the very difficult problems caused by droughts and rising costs of production which farmers have had to face over the past 20 years.

The co-ordinated research program also provided methods for sowing and grazing lucerne and annual medics to control large areas of skeleton weed. Many other herbicides were also tested for skeleton weed control in cereals without finding a better treatment than the use of 2,4D

In desperation, rather than by any scientific prediction, the Technical Subcommittee allotted funds to a skeleton weed biological control program which was conducted by CSIRO at Montpellier in France and at Canberra. Doubt and reluctance turned to joy and relief in 1971 when a biological control agent, Pucinia chondrillina was released.

Biological Control

Agriculturalists in South Australia and in the other states had dreamed of biological control using natural predators to keep skeleton weed in check. A technique used with remarkable success in the 1930s in Queensland to control prickly pear.

At an Australian Agricultural Council meeting in 1956, attended by ministers for agriculture from each state and their senior executive officers, it was agreed that the possibilities of biological weed control should be researched. The South Australia representatives supported that decision.

The Council allocated resources to the Entomology Division of CSIRO in Canberra, which enabled preliminary feasibility studies over a wide range of weeds. The results of these studies were presented to weed scientists at the second National Weed Control Conference in 1960. The feasibility studies were far from encouraging in the case of skeleton weed. Firstly, few insect predators had been recorded in the literature. Furthermore, skeleton weed belonged to the Compostae Family and therefore had many useful plants as close relatives with a high probability of any predators attacking them if they were brought into Australia. Finally, to further dampen any enthusiasm, the centre of origin of skeleton weed, the place to look for the most likely useful predators, was southern Russia, an area of the world at that time inaccessible to Western researchers because it was behind the Iron Curtain. Consequently, the 1960 Weeds Conference recommended that other Australian weeds be given higher priority for biological control research.

Dr Doug Waterhouse, then Chief of the Division of Entomology, CSIRO, wasn't to be put off. He was an expert on insect biological control and was able to direct considerable funds from his Division to establish an Australian biological research station at Montpellier in France where work on a wide range of weed problems could be conducted without the need to bring possible predators through the rigid Australian quarantine procedures before they were assessed.

In 1968, Dr Tony Whapshere was appointed the first director of the centre at Montpellier and commenced field surveys to find predators of a number of Australian weeds. Waterhouse made sure that skeleton weed was on the list. Whapshere and his team made rapid progress, despite difficult social and political problems in France at the time. By the end of 1970 fifteen predators of skeleton weed had been identified and, surprisingly, the most promising seemed to be, not an insect, but a species of rust, Puccina chondrillia.

The author was invited to Montpellier in June 1970 to observe progress of the rust research and to learn first-hand methods of infecting the weed with the Puccinia spores should the day arrive when they could be released on skeleton weed in Australia.

By then specificity testing of the rust, using Australian native flora and commercial crops, was well advanced and there was no evidence that the rust could infect any other plants but skeleton weed.

After thorough examination of Whapshere's work by many Australian scientists the Australian Agricultural Council approved release of the rust in 1971, together with two other control agents, a gall mite (Aceria chondrillae) and a gall midge (Cystophora schmidt).

The Puccina rust was an instant success. The first case anywhere in the world of a rust species being used to control a weed. Malcolm Catt, a weed research scientist in the South Australian Department of Agriculture, was given the task of releasing the rust spores under the direction of the author and with close supervision from Richard Groves, CSIRO, Canberra. Six one-meter square areas at carefully selected sites in the Murray Mallee, were sprayed with the Puccina spores in early September 1971.

In the following March Catt set off to assess whether the rust had become established. He stopped out of Murray Bridge for other reasons and found the rust happily established on the leaves of skeleton weed growing on the roadside. He was still many kilometres from the first infected test site. An excited telephone call alerted those who were office bound and as Catt's day progressed, so his story expanded. Puccina had gone to work in the field all by itself. Subsequent surveys found that the spores had penetrated over the entire Murray Mallee region.

The initial results were dramatic. Carefully measured sites in the Murray Mallee carried out over the next five years, revealed that the average density of skeleton weed rosettes had been reduced from about 200 per sq m to 30. The area of wheat crops needed to be sprayed for skeleton weed control had been reduced by 75 percent

But the 'mother of all weeds' was not to be beaten. In 1973, Hull and Groves, after very careful field observations, published a paper in the Australian Journal of Botany in which they reported three forms, or biotypes, of skeleton weed in the eastern States which they labelled Form A, narrow leaved, Form C. broad leaved and an intermediate, Form B. It soon became apparent that two of the released agents, the Puccini a rust and the Aceria mite were careful to choose only the narrow leaved biotype as the host. The midge, the third agent, was capable of attacking all three forms.

Fortunately, in South Australia, the narrow leaved form was at first the most prevalent but gradually the other biotypes, less under attack, became more evident. By the early 1990s a third of the infestations of skeleton weed on Eyre Peninsula were the Form B biotype.

To stop that trend different forms of the rust were sought but were not found . The joy and great expectations of Malcolm Catt's day in the field turned to concern for the future. The warning was clear, the skeleton weed campaign could not ride to success on biological control alone. All forms of control, including competition from fertility building pastures, spot spraying and the use of selective herbicides in crops had to continue.

The 1970's and 1980's

With picloram to treat new outbreaks and the release of the biological control agents in the early 1970s containment programs in one form or another continued across the state during the 1970s and the 1980s. While the severity of the weed in many places gradually decreased the boundaries of the infestations continued to spread.

During this time some desperate attempts to upgrade control programs were attempted, largely by local government with technical assistance from Government agencies. Some local government authorities offered subsidies for the purchase of picloram and legally enforced control was stepped up. These measures consistently failed. Landowners could not see real cost-benefits. Authorities therefore gradually realized that researched, control packages that landowners could economically use was the best path to follow.

This strategy was well enunciated by Richard Carter, a Crop Protection Advisor, in 1987. He offered detailed control programs and associated costs for the farming systems across the state. That strategy was endorsed at an Australian Workshop on the Management of Skeleton Weed held in March 1991.

Estimates made by the CSIRO in 1980 claimed that the National benefit to the Wheat Industry from the biological control alone of skeleton weed during the period 1973-1974 to 1999-2000 would create a net saving to that Industry of $4 billion from the additional 80.7 million tonnes of wheat produced. However the future sums add up, one must acknowledge that the skeleton weed campaign had been largely successful due to the combined efforts of landowners, scientists and governments which have averted what could have been the complete failure of wheat production in South Australia and the other wheat growing regions of Australia.

Further Reading

Carter RJ (1987). Skeleton Weed Control Program. A South Australian Animal and Plant Control Commission publication.

Marden JS (1980) et al. Returns on Australian Agricultural Research. Industries Assistance Commission CSIRO

Tideman AF (1968) et al Skeleton Weed in South Australia.. The First Twenty Years. Skeleton Weed Survey in the Mid-northern Districts. Skeleton Weed Survey in two Districts of the Murray Mallee . Department of Agriculture Agronomy Report No 3.Available from the Waite Institute Library, Adelaide University.

Walsh MJ (1990) et al.  Edited Proceedings of the Australian Workshop on the Management of Skeleton Weed . Walpeup Mallee Research Station publication.

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