Stripe Rusts of Wheat and Barley

The most distinctive sign of this pathogen is yellow-orange pustules, which contain infectious urediniospores oriented linearly between leaf veins. Glumes are often infected. Stripe rust symptoms usually appear earlier in the season than other rusts because the fungus develops at lower temperatures than the other rust fungi. As the plants mature, the pustules turn dark and shiny as teliospores are formed. Teliospores do not play a role in survival or disease development in wheat.

Different strains of the stripe rust pathogen are specific to wheat and barley. The stripe rust fungus has been responsible for some of the most devastating epidemics on wheat in California.

Barley stripe rust was first detected in the United States in Texas in 1991 and in California in 1993 and 1994. Major epidemics on barley in California occurred in 1996, 1997, and 1998.

The fungi grow only on living host plants and survive between seasons on volunteer wheat, barley, and some wild grasses. Rust spores are spread by wind to initiate infections. Disease development is most rapid at temperatures of 50° to 60°F (10° to 16°C) with intermittent rain and dew, although disease can continue to develop at higher temperatures and drier conditions. Secondary cycles of disease occur at 7- to 10-day intervals under optimal conditions. Strains infecting barley can survive in warmer, drier climates than those infecting wheat. Infections increase water loss and decrease the amount of photosynthate available for grain filling. This reduces kernel number and weight.

Cultural Control

Plant resistant cultivars (see wheat and barley cultivar information) to control this disease. Monitoring, detection, and sharing information within the grower community are critical to prevent major stripe rust epidemics. Contact your local farm advisor if you suspect a stripe rust infection in your field.

If cultivar resistance breaks down, foliar fungicides can be applied to control disease outbreaks. Application timing will depend on when initial infections occur and on the specific label restrictions for each fungicide. The objective is to protect the flag leaf from infection and to protect the plant during the grain-fill period.