Bunt and smut fungi are potentially devastating diseases of cereals. The zero or very low tolerance levels at receival centres makes infected grain unsaleable or only saleable as low value stock feed. Fortunately, the regular use of seed applied fungicides (pickles) can cheaply and effectively control these diseases.
All cereals are susceptible to several smut and bunt fungi. In most cases, each of the cereal smuts are caused by a distinct species specific to each crop; that is loose smut of wheat is different to loose smut of barley.
Grain receival standards
There are strict receival standards for grain in relation to bunts and smuts. For loose smut the tolerance is a maximum of 3 pieces per half litre of grain for wheat and 0.1 g per half litre of grain for barley. For all other types of bunts and smuts there is a nil tolerance.
|Bunt and smut grain receival standards in Australia for 2018/19 (www.graintrade.org.au/commodity_standards)|
|Wheat Tolerance||Smut (Tilletia laevis)||Nil|
|Loose Smut||Max 3 pieces per half litre|
|Barley Tolerance||Loose smut||0.1 g of all pieces per half litre|
|Cereal smut (Ball and gall smut, other smut species)||Nil|
Fungicide seed treatments provide effective control of bunts and smuts by preventing seed-borne infection. In order to achieve effective control, seed treatments need to be applied to seed every year and good coverage must be achieved. If a seed lot is already infected, new clean seed should be sourced. Some seed treatments, particularly on poor seed, can cause issues with coleoptile length resulting in poor emergence. Always read the label.
Basic seed treatments provide a cheap means of controlling bunts and smuts. There are also a range of seed treatments that are dearer but provide control of some foliar and/or root diseases. These treatments may be useful in an integrated disease control program. SARDI produces an annual cereal seed treatment guide which provides comparison tables for actives and what diseases they effectively control.