Common root rot

B. sorokiniana causes foliar spot blotch, root rot, and black point on grains, as well as head blight and seedling blight of wheat and barley. Infected seedlings develop dark brown necrotic lesions on roots, crowns, and lower leaf sheaths. Leaf blade and sheath infections develop as distinct oval to elongated light to dark brown blotches. Root and crown infections can be so severe that infected plants dry out without producing any seed. Under favourable conditions, spikelets may be affected, causing grain shrivelling. The susceptibility to the pathogen increases around Zadoks’ growth stage DC 56 (three-quarters of the inflorescence emerged). At this stage, if weather conditions are conducive, i.e. continuous rain for 5–6 days followed by warmer temperatures (day average of 20–30 C), spot blotch epidemic can develop very rapidly. Under low light intensity, the pathogen may colonize host tissue intercellularly without causing visible damage. Fungal infection accelerates leaf senescence at later growth stages.