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Causal organism - Omphalina pyxidata
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Little is known about the disease cycle although this is a soil-borne fungus which survives between susceptible hosts as sclerotia or as mycelium on root debris. It infects crops soon after emergence, colonises roots, produces sclerotia and then produces air-borne basidiospores. These spores may play a part in long distance spread of the disease. As patches of the disease in crops tend to be sharply defined it does suggest that it is the soil-borne phase of the disease that is the most damaging but that it spreads only slowly. The role of the basidiospores is unclear.
Importance
The disease is sporadic in nature, affecting a small number of crops each year, mainly winter barley. Winter wheat is much less frequently affected and losses each year will be very small in comparison with other diseases. Limited trials in winter barley suggests infection can reduce fertile tiller number by 40% and that yields by 25-50%. An experiment to determine the host range showed the mean percentage of plants with sclerotia on the roots as follows:
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Rye |
43 % roots infected |
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Spring wheat |
16 % roots infected |
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Winter barley |
14 % roots infected |
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Triticale |
12% roots infected |
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Winter wheat |
11 % roots infected |
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Spring barley |
4 % roots infected |
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Winter oats |
2 % roots infected |
