Brown rust can affect wheat, barley, rye and triticale. However, these plants are unable to cross-infect, as the disease is caused by different pathotypes.
Traditionally the disease is most commonly found in the UK during mid-late summer months, as the disease requires temperatures between 15-22 degrees Celsius, along with 100% relative humidity. However, with milder winters brown rust can often appear in high levels in the spring.
In early autumn infection, the disease can often be mistaken for yellow rust, as the pustules appear orange-brown, and 0.5-1.0 mm in diameter. Later in the season the pustules appear to be scattered randomly on the leave, which separates the disease from yellow rust, in which the pustules appear in straight lines vertically down the leaf. Brown rust infection of the glumes can reduce the specific weight of the crop.