Halo Spot
Selenophoma donacis
Pathogen
Fungus
Hosts
Barley, grasses particularly timothy and cock’s foot
Symptoms
Lesions are small, often square or rectangular with refined dark brown margins. Small black spore cases occur in lines in the centre of the lesion. Lesions are much smaller than Rhynchosporium and differentiation can easily be made. They occur on the leaf, stem and ear.
Development
Inoculum for the disease come from the stubble, volunteers or infected seed. Spread is mainly from watersplash.
Favourable Factors
Wet weather. Most common in South West England.
Importance
Can cause economic loss in severe cases but In most parts of the UK halo spot is not considered to cause significant yield loss.
Control
Some fungicides have been shown to give some degree of reduction or control of this disease.
