Stripe rust (Puccinia striiformis)

Stripe rust: biology

Stripe rust in wheat continues to be a concern in western Canada. The disease was can be found in winter wheat across the southern regions of all three Prairie provinces.

Stripe rust is spread through wind currents. Primarily, the disease originates from regions in the US Pacific Northwest. Once infection takes place, small, circular spots that are vivid orange-red in color, form on the lower leaves. Collectively, these spots (spores) look like long stripes, and can easily be wiped off the leaf onto hands, clothing and shoes.

The open pustules cause moisture and nutrient loss in the leaf. If left untreated, spores will move from the young plant to the flag leaf, where yield loss will occur.

In early stages of infection, orange pustules occur in blotches. Gradually the pustules take on a striped appearance, as they occur in line formations on leaves.

Conditions of high humidity and cooler temperatures (11-22°C) are favourable for the onset of stripe rust. However, once the disease has been established, drier conditions do not limit the progression of the disease.

The effect of a green bridge contributes to the incidence of stripe rust. In a year where crop development is late, the disease can be present on later maturing spring wheat plants. If these plants are still green when winter wheat plants emerge in the fall, the spores can infect and overwinter on the young winter wheat crop. Volunteer wheat plants also act as a host for the disease, and facilitate the spread of spores.

Stripe rust is not necessarily a disease that causes losses prior to the emergence of the flag leaf. But once it moves to the flag leaf, the effects are detrimental to a producer's yield. Early infection on a susceptible variety can cause yield losses of 40%. If left untreated, the disease can infect the glumes and the head of the plant, causing grain quality to be affected. Some varieties are more susceptible to the disease than others. Winter wheat, CPS and white wheat varieties are more susceptible, while durum and some HRS varieties have good resistance. However, many HRS wheat varieties, including Barrie, Superb and McKenzie are very susceptible. Check your provincial seed guide for a more comprehensive variety list, and their susceptibility to stripe rust.