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Pests and diseases

Over the years the seriousness of various wheat diseases has ebbed and flowed depending upon the weather conditions, the rotations (break crops) and the resistance or tolerance of the cultivars. Since the first crops were grown in the colony with varieties from England local selections were made and disease control practices followed traditional homeland practices. Bunt and rust soon became serious problems and treatments developed and selections from local plants made.

Vermin such as mice locusts and white snails have also created challenges for farmers.

Stem rust

A paper entitled “The role of minimal disease resistance standards for the control of cereal diseases” by Hugh Wallwork provided the following quote:

A severe epidemic of stem rust in 1889 led to an attempt to coordinate the control of the disease throughout Australia. A series of Inter-Colonial Rust-in-Wheat Conferences took place from 1890 to try and combat the problem. The importance of rust resistance was identified at the meeting, in a paper by William Farrer, Australia’s first wheat breeder. At the time there were no good sources of resistance available to wheat breeders in Australia. Farrer only made moderate progress by avoiding the most susceptible lines and by developing wheats better adapted to the less rust prone inland areas. Sources of partial resistance were identified among varieties available at that time and from the 1930s, better resistance from related species, from Kenya and later from a wider range of sources, began to be used in crossing.

After the Second World War, with improved mechanisation, wheat cultivation expanded in the summer-rainfall regions of northern Australia. This led to increased risks of stem rust in the region and the raised importance of having good rust resistance in all varieties was recognised by the industry. From the 1960s onwards, only resistant varieties would be accepted for release in the northern region of New South Wales and Queensland. Following severe outbreaks of stem rust across southern Australia in 1973–74, Irvine Watson, a plant pathologist of the University of Sydney, became a strong proponent of the need for all wheat in the country to be rust resistant, preferably with multiple genes. This led to a requirement for new varieties in southern NSW to have stem rust resistance from the 1970s onwards. It also led to the establishment of the National Cereal Rust Control Program to fast track the development of rust resistant varieties throughout Australia. In Victoria and South Australia, resistance to stem rust became an important objective, but because stem rust was not as frequent or severe, resistance did not become a condition for release of a variety. In Western Australia, stem rust was seen as less of a priority and it is only with recent outbreaks of stem  rust in the region and moves towards national standards that resistance has become a serious priority.

As a consequence of the policies in New South Wales and Queensland, stem rust has been effectively controlled in those states and, by reducing the level of inoculum emanating from the region, this has in turn provided valuable flow-on benefits to growers in Victoria and South Australia where no serious stem rust outbreak has occurred since 1974 despite some susceptible varieties being grown.

Cereal cyst nematode (CCN, eel worm)

Cereal cyst nematode (Heterodera avenae) was identified about the turn of the century but it was not until the 1950/60s it was realised that it was potentially a significant disease of cereals. One of the early investigators was Murray Matheson. Later papers by Fisher, Banyer and work by Chris O’Brien quantified and defined the problem by establishing its life cycle and general biology.

The breeding of Galleon barley (selected from varieties grown in Egypt) which was both tolerant, and resistant, resulted in a high yielding variety but also the resistance meant that following wheat crops yielded well. This work is spelled out in the attached Powerpoint lecture prepared by Tony Rathjen. In this presentation the research work of Albert Rovira, Dr Alan Dube and the field work of Trevor Dillon is highlighted as the resultant changes to varieties and rotations added hundreds of millions of dollars to cereal farming in South Australia. Dillon and others observed that where Festiguay was sown around the edge of paddocks, to reduce the impact of rust, that a crop in the following year after a pasture year yielded substantially better. Following this Rovira fumigated some soil on the Mudge property at Mudamuckla on Eyre Peninsula. While commercially impractical it demonstrated the impact of pathogens and showed the yield potential if their impact could be eradicated, It took some 20 years before a resistant wheat was released (Molineux bred by Rathjen) and then followed by Frame. Andie Barr was eventually successful in breeding Swan the first resistant oat variety.

Today CCN is one of the diseases farmers must address in their management decisions but thanks to the success of research and development they have all the tools they need ensure it has no impact on the yields of the South Australian cereal crop.

Reference

Take all/Haydie

Barley grass control with herbicides has greatly aided control.

Bunts and smuts

Bunts and smut have been a challenge for South Australian cereal farmers since the first crops were grown in the Colony. Initially bunt was treated by using horse urine spray/dip?? Bunt is typical of an early disease which was a major problem but science and the farmers found a solution and now rarely occurs. However vigilance must be maintained because pathogens can change and cropping practices result in a change which allows a disease to reoccur.

Alf Hannaford’s role has been critical in disease control in South Australian cereal crops and a history is available on the company website and the following quote from the story is applicable:

Mr Hannaford was farming at Riverton, South Australia, when caught in the infamous drought of 1914 and its effect on crops vital to the war effort.

This disappointing harvest and his own realisation that there was room for much improvement in the methods of pickling wheat awakened within him a fervent purpose that changed the course of his life and eventually altered the traditional cereal farming methods of those around him and beyond.

His first invention —The Hannaford Wet Wheat Pickler—was a great success and spurred him on to consider inventing a seed grading machine and a dry pickling method. He gave up farming and became an inventor and manufacturer.

In the early twenties 'The Hannaford Ideal Dry Pickler' appeared on the market and was an instant success. This was quickly followed by the 'Ideal Combined Grader and Dry Pickler', the first of its type on the market.

Farmers saw the common sense in grading for plump, virile seed and in pickling to prevent disease and infestation. This growing demand for Alf Hannaford machines warranted capital and expansion.

Stripe rust

Stripe rust was introduced to Australia in Victoria from France in 1979. However it was not until 1983 following the 1982 drought that it became apparent as a problem. The problem was exacerbated by lack of supply of fungicide at the time.

Reference

Wheat Rust Control in Australia Bulletin 110 SA Dept of Ag., Watson & Butler

Crown rot

Crown rot has been present in soils for many years but due to only durum varieties being particularly susceptible. It built up in successive durum crops and by year three became a serious problem. Currently there are no resistant varieties or suitable chemical treatments so the best solution to control is lengthened rotations between durum crops.

Minimum disease standards

A paper in AJAR by Hugh Wallwork states a set of Minimum Disease resistance Standards (MDS) has been developed for rust resistance in new wheat varieties in Australia. These standards aim to provide protection to growers from varieties that produce large amounts of inoculum and, more specifically, protect the usefulness of resistance genes by reducing the probability of new pathotypes evolving with virulences that can overcome them. This paper provides a historical background to the establishment of MDS in Australia, the rationale for its introduction and the appropriateness of different resistance scales, problems that have been encountered, and the way forward to fully implement MDS. A brief consideration is also given as to which other wheat and barley diseases MDS may usefully be applied to.

Role of research and extension bodies

Considerable detail on plant breeding is covered in that area of this document and, as has been shown above, breeding has been critical in beating many of the diseases. Plant selection for disease resistance was in some ways by chance by early colonists when they picked stronger or higher yielding plants. Early work at Roseworthy was funded by the Colony but in later years a range of industry levies matched by State and Federal governments have ensured ongoing plant breeding and research into diseases. In South Australia the SA Grains Industry Trust has been particularly important in funding research into local problems because it in some ways had different priorities to national research bodies.

An example of work that has provided a highly valued practical service for farmers is the advisory/diagnostic service developed by Alan McKay. It is unique in the world and is now using DNA methods to detect and track soil borne diseases for farmers. This approach is explained in the paper “Development of a routine DNA-based testing service for soil borne diseases in Australia” by Kathy Ophel-Keller et al.

The Right Rotations Program which commenced in the late 1980’s and in many cases worked through the Agricultural Bureau branches was critical in transferring the science to the farmers. It assisted farmers to identify CCN on the cereal plant roots and then provide advice on how to manage their paddocks to ensure control. It was rolled out across the State and went on to provide an ongoing conduit between farmer and scientist.

Vermin

Mice, rabbits white snails, locusts and he like periodically cause destruction in individual paddock or across regions of the State.

Mice often follow a run of good cereal seasons when plenty of grain is available between seasons and numbers build up. Control is attempted using baits but normally subside when feed is exhausted and winter cold causes their death.

Rabbits and locust information can be found elsewhere on the site by searching.

White snails have been an increasing problem, particularly on YP and EP where they climb the plants and cause problems when crushed during harvest.

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