More recently research has provided an understanding of the important roles of sulphur, zinc and selenium in animal nutrition and areas of marginal deficiencies of these elements have been identified.

Australian research on the importance of trace elements in plant and animal nutrition has resulted in enormous benefits to the Australian community in terms of increased and cheaper productivity, and large areas of inherent low fertility have been converted to prosperous farmland (e.g. the change in South Australia of the 'ninety mile desert' to 'Coonalpyn Downs'). At the same time this research has had important world-wide significance and has established Australia as an international leader in this field.[70]

Pest and disease control

Some experimental studies, often conducted by a single scientist or team of scientists, have led to major discoveries, such as the identification and control of a particular predator, pest, weed, or plant or animal disease. For example, in 1935 the work of Dr. H. R. Angell[71] was notable in drawing attention to the fungistatic properties of the vapours of certain hydrocarbons in controlling downy mildew of tobacco in covered seed beds. This finding was not only a boon to Australian tobacco growers, but also Angell's method, with modifications, was adopted world wide.

Techniques have been developed, or are now being developed for controlling a wide range of insects, including cattle ticks, Australian Plague locusts, the Sirex wasp, the potato moth and cock chafer grubs, all of which cause losses of importance. Similarly, such studies as those of I. W. Beveridge on the aetiology and control of footrot, L. B. Bull on mycotic dermatitis, H. E. Albiston and A. W. Turner on black disease, and W. Mules on the control of blow fly strike have all yielded great benefits to the sheep industry.

In many instances measures for the control of pests, parasites, predators, weeds and diseases have been based on the use of chemicals (insecticides and weedicides), poisons or vaccines which, for the most part, have been developed overseas. The possibilities of using methods of biological control, however, have long been of interest to Australian scientists and they have reported some outstanding successes.

The first of these successes resulted from the combined efforts of the Commonwealth Government and the Governments of Queensland and New South Wales which, in 1919, together constituted a Commonwealth Prickly Pear Board. At that time some six species of the prickly pear cactus (Opuntia sp.), which had originally been introduced from South Africa, had infested some 10.5 million hectares in the grazing and farming areas of South-Eastern Queensland and northern New South Wales. The cactus was estimated to be spreading at a rate of about 0.5 million hectares a year. Various mechanical methods of destroying the plant had been tried without success and, although poisoning with arsenical compounds certainly killed the plant, this was too hazardous and expensive a method to use on a large scale.

Australian Academy of Technological Sciences and Engineering