, Volume 30, Issue 2, pp 119-126

Management of wheat and barley root diseases in modern farming systems

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Abstract

Root diseases, namely take-all and Rhizoctonia, Pythium and Fusarium root rots, are so widespread and occur so uniformly within fields of wheat and barley in the U.S. Pacific Northwest (PNW) that we have come to accept these crops with these diseases as normal ‘healthy’ crops. The main reasons for the expanding range and increasing prevalence of root diseases on wheat and barley in this and many other cereal-growing areas of the world are two-fold: increased frequency of cereals in the rotation and the use of less, or no, tillage. Both trends are here to stay because of their economic advantages and environmental benefits. Managing these diseases in these modern farming systems is no small challenge since, unlike most leaf diseases of these crops, all cultivars of wheat and barley are more or less equally susceptible to all four root diseases. Through a combination of cultural practices, the severity of these diseases can at least be limited to ‘chronic’, while ‘acute’ outbreaks or what growers call ‘wrecks’, are relatively rare. These practices are timely and effective management of volunteer and grass weed hosts before planting; placement of fertiliser, especially phosphorus, beneath the seed within easy access of diseased roots; soil disturbance below the seed; trash removal from within the seed row; pairing the row for a more open canopy to favour warming and drying of soil beneath the crop residue; and the use of fresh seed and treatment of the seed with a combination of fungicides for improved seedling vigour. No equivalent effort has been made in any other crop to manage a disease complex without the benefit of host plant resistance. In spite of this, these practices, together with take-all decline, only elevate yields to about 80% of the potential as revealed by fumigated (methyl bromide) check plots. Future research must concentrate on the development of host plant resistance, including host plant resistance with transgenes.

A Keynote paper presented at the Second Australasian Soilborne Diseases Symposium, Lorne, 5–8 March 2001