Sharp Eyespot
Ceratobasidium cereal (Rhizoctonia ceralis)
Pathogen
Fungus
Hosts
Wheat, barley, oats rye, triticale, grasses.
Symptoms
Pale lesions with distinct dark borders appear on the stem up to 30cm above the soil surface. A purplish-brown fungal mass may develop in the lesion. If the stem is cut open, fruiting bodies, sclerotia, can sometimes be found inside.
Some strains of sharp eyespot can infect the roots leading to weak straggly plants usually appearing in discrete patches and often exhibit a purple discolouration. The plants tend to recover with secondary root growth appearing in the spring.
Early infections and high sharp eyespot disease pressure can lead to `white-heads` and lodging.
Development
The source of infection is mycelium in the soil. Infection and development is favoured by dry, cool autumns and springs.
Favourable Factors
Slow plant growth through the winter and spring, light soils.
Importance
Common in the UK and leads to loss of yield, shrivelled grain and increased lodging risk. Yield loss is lower than with true eyespot.
Control
Timely application of fungicide
Break crops in the rotation can reduce the level of inoculum although the wide range of volunteer hosts limits the effectiveness of this technique.
Notes
Sharp eyespot can be differentiated from true eyespot by:-
i) More sharply defined lesions
ii) Fungal mass can be scraped off
iii) Multiple lesions – up to 30cms up the stem
iv) Sclerotia in stem
