Yellow spot, caused by the fungus Pyrenophora tritici-repentis, is an important stubble-borne disease of wheat. While the primary infection originates from wheat stubble, the secondary infection occurs in the crop canopy and can be spread by wind.
This fungal infection reduces the photosynthetic area and can result in reduced grain yield. Trials in Western Australia have reported up to a 20 per cent yield reduction in infected very susceptible varieties.
- A one-year break from wheat and practices that reduce surface stubble, decrease inoculum levels and provide control.
- If wheat-on-wheat must be grown, avoid sowing susceptible varieties into last year's wheat or barley stubble.
- Temperatures of 15°C to 28°C, with up to 12 hours of leaf wetness, are optimal conditions for infection.
- Typical tan-coloured lesions surrounded with yellow halos on leaves and distinctive blackfruiting bodies on stubbles are good diagnostic indicators of yellow spot infection.
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