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Causal organism - Septoria nodorum (Stagonospora nodorum)
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Mainly wheat, but occasionally barley and rye.
Septoria nodorum can be seed borne and infect seedlings, resulting
in water-soaked
, dark green areas on the coleoptile,
later becoming necrotic. Twisted,
distorted and stunted seedlings may also occur. On mature leaf tissue the
first symptoms of infection are small necrotic lesions.
Later these develop into brown oval lesions surrounded by a chlorotic
halo.
These lesions frequently coalesce
to produce large areas of dead, dry and sometimes split tissue. Pycnidia
form within affected tissue, but these are a pale pinkish brown colour and
difficult to see in the field, even with a hand lens. They are best seen by
viewing the lesions in transmitted light with a hand lens. Septoria nodorum
can also infect the ears, particularly of wheat, causing glume
blotch.
Dark brown patches like burn-marks develop on the glumes,
which later become purple-brown. Glume blotch symptoms are easiest to see
on green ears.
