Barley is the only cereal which is required to meet standards set out in the grade table for smut. Barley seed cannot be graded in Canada unless it meets germination, purity and smut requirements for its designation. There is an exception for seed which has been treated with a product registered as a control product under the Pest Control Products Act for the control of true loose smut(Ustilago nuda).

Although all cereals can be affected by smut, the pathogen is unique to each crop kind. True loose smut in barley is caused by Ustilago nuda. It is a seed born fungal disease which over-winters in the embryo as dormant mycelium. When the seed germinates, the mycelium begin growing again, insinuating itself into the young barley plant and attacking while the head is forming, substituting masses of spores for the kernels. This can create further infection if wind blows spores into flowering barley plants. If conditions are wet, the spores will germinate and establish themselves in the embryo and start the cycle over again. Diseases of Field Crops in Canada, 1988.

In the seed lab we examine 400 embryos for each smut test. This test is very labour intensive and requires special equipment and expertise as well as accreditation by the Canadian Food Inspection Agency. The embryos must be extracted from the seeds and then stained overnight. Once staining has been achieved, examination under the microscope is necessary. The smut mycelium will be visible to a trained eye and will be reported as a percentage. Results on smut tests can be available within two days.