Loose smut of barley caused by Ustilago nuda (Jens.) Rostr. is a disease that becomes evident mainly after heading of the host. The spikes of infected plants emerge from the boot slightly earlier than those of healthy Plants. Powdery masses of spores are formed in place of kernels. These masses of spores are covered at first with a membrane, which ruptures early to expose the dark brown chlamydospores. Under certain conditions, sori may form in the upper leaves mostly in the nag leaf. These sori appear five to ten days before heading. The chlamydospores are dislodged from the smutted heads by air currents at the time healthy plants are in flower, leaving bare rachises.