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Bunt, or stinking
smut |
Causal organism - Tilletia tritici
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The disease is specific to wheat.
Symptoms are very difficult to see in the standing crop. Affected plants
are often slightly stunted and have 'squat', dark grey-green ears with slightly
gaping glumes. The flag
leaves of affected plants sometimes show yellow streaks. 
If infected ears are broken open they are found to contain, in place of true
seeds, seed-like 'bunt balls' each containing millions of greasy, black, foul-smelling
spores.
In severe cases, the whole field may smell of rotting fish. In wet weather
conditions the ears may appear to be covered in a black ink-like substance
as the spores are released and run out of the protective glumes onto the ear
and stem.
Many of the bunt balls within the ear are broken open during combining, the
spores are released and contaminate grain in both the combine and during subsequent
movement and storage handling. In severe cases, the grain can be so heavily
contaminated that it is rendered unusable.
The spores remain on the seed surface, being usually concentrated in the brush
hairs at the end of the grain. In severe cases the grain assumes a dark appearance
- often with an obvious foul smell. Older grains which have been stored for
some time may lose the obvious smell but are still dark in appearance.
