Septoria Blotch of Oats

Phaeosphaeria avenaria


Glume Blotch.

Septoria Avenae Blotch.


Dark brown to purple spots develop into tan to dark brown oval or irregularly shaped blotches, to 2 cm round, with yellow rims on leaves in late winter to spring and cover and kill the entire leaf. It may spread to leaf sheath then stems forming grey brown or shiny black blotches. Dark brown blotches may appear on the head and grain. Lodging may occur in severe attacks. Tiny black fruiting bodies may be seen in the centres of older blotches.

Species Affected:

Oats, Wild Oats.


More common in warm, moist conditions.

Survives on Oat residues and in very susceptible varieties it may be transmitted on seed.

Spores spread by raindrop splash and wind.

Spreads most rapidly in cool, rainy conditions.

Life Cycle:

Fruiting bodies in residues release spores in autumn and are spread by raindrop splash or wind to infect young Oat plants. In very susceptible varieties the initial infection may come from seed.

Origin and History:


More common in coastal areas.


Most damaging in early sown and short-straw crops.

Yield losses of up to 30% have been recorded.

Management and Control:

Sow resistant varieties. See Disease Susceptibility of Oat Varieties.

Avoid early sowing before May 15 in high rainfall areas.

Avoid areas where Oat stubble is present.

Burn, bury or graze infested Oat straw in cropping and adjacent paddocks.

Use longer rotations and avoid planting Oats adjacent to previous Oat crops. Rotate with any other crop or pasture not containing Avena species.

Related and Similar Species:

Septoria Nodorum Blotch of Wheat (Phaeosphaeria nodorum)




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