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Causal organism - Fusarium spp.
Primarily: F. avenaceum, F. culmorum, F. graminearum,
Microdochium nivale, F. poae
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Wheat, barley, oats, rye, grasses and numerous other species.
These fungi form a complex of diseases on seeds, seedlings and adult plants. Seed-borne Microdochium nivale can cause a seedling blight resulting in seedling death and thinning of plant stand. This is particularly likely in late sown crops where seedlings emerge slowly.
Brown lesions on cereal stem bases , which are frequently found in the spring, may be a result of Fusarium infection. Fusarium is less aggressive than eyespot and consequently lesions are often restricted to the outer leaf sheath. Fusarium infection can often appear as a secondary invasion following damage from some other source. Fusarium lesions are are often found starting at a split in the leaf sheaths at the stem base where crown roots split the leaf sheath when emerging. This infection can then spread up the leaf sheath causing long dark brown streaks at the stem base. Plants affected by late frosts typically become colonised by Fusarium - which is often wrongly blamed for the death of the tiller.
Many of the Fusaria cause a range of symptoms - often termed 'ear blights'. Fusarium culmorum infection frequently results in the whole or part of the ear becoming bleached. This symptom is most commonly seen when ears become infected during the early flowering stages. Later infections may result in infection of the grain but without obvious bleaching of the ears.
The most commonly seen symptom in the UK is the dark brown staining of the lower nodes. On older plants Fusarium infection can produce a true foot rot, where the stem base becomes brown and rotten, resulting in lodging and whiteheads. This symptom is rare in the UK, although it can be found in very dry seasons. It is very common in the USA in areas where crops are exposed to very severe drought conditions.
