Smut is a disease affecting wheat and other cereals, caused by fungi of the order Ustilaginales. Affected ears turn into a powdery, blackish-brown mass. The smut powder is at first encased in a very thin, silvery membrane, which breaks easily leaving the smut-powder free. Under the influence of various factors (wind, rain), it is spread, leaving only the rachis on which traces of black powder can be seen. Stems bearing such rachis are stiff and shorter than healthy ones. At this stage, they are less visible in the field.