There are two types of bacterial disease which infect oat foliage; halo blight (Pseudomonas syringae pv. coronafaciens) and stripe blight (Pseudomonas syringae pv. striafaciens).
What to look for
Paddock
Diseased plants may occur in patches, and is worse in wetter areas and wet seasons.
Vehicles may spread the disease by driving through wet infected plants.
Plant
Initially small light green oval water soaked spots on leaves and leaf sheaths up to 10mm in diameter.
Centres of spots change to a straw or brown colour surrounded by a yellow water soaked halo.
The lesions turn brown and join together to form irregular blotches.
Heavy infection leads to withering and death of leaves often from the tip.
Where did it come from?
Contaminated stubble
Insect vector
Blight bacteria survive on seed and crop debris.
They are spread by rain-splash or leaf contact.
Insects, particularly aphids, also spread them.
Management strategies
Stubble management
Clean seed
Unless infection is very severe, grain losses are insignificant, but hay quality is reduced.
Fungicides are not registered or effective against bacterial diseases.
Avoid sowing into infected stubbles and burn or incorporate stubble if the problem is widespread.
The disease can be seed borne, do not re-sow seed from infected crops.
Avoid paddock operations when leaves are wet to prevent disease spread.
