Symptoms and management of crown rust: the major disease of UK oats

Crown rust is the major disease of UK oats. Learn about the pathogen, including its life cycle, the key symptoms in infected crops and varietal resistance.

Beyond oats (winter and spring), the pathogen – Puccinia coronata ­– does not infect other cereal crops.

Although some forms infect several grass species, particularly ryegrass, these forms do not cross-infect oats.

Severe attacks have been more common in recent years. Such epidemics can reduce yield by 10–20%.

It is favoured by warm/humid weather and mild winters.

In infected crops, orange/brown pustules appear scattered over the leaf surface.

These initial symptoms are similar to those of wheat and barley brown rust (also caused by Puccinia spp.).

Leaf sheaths and, eventually, the oat panicle can also become infected.

As high temperatures (20–25°C) favour disease development, epidemics usually occur in June–July.

Late in the season, black pustules appear within crown rust lesions.

There are several key spore types associated with infection and spread in oat crops.

Uredospores

Produced on oat leaves, orange/brown pustules release orange airborne spores, which spread the disease, often across long distances.

Teliospores

Black pustules, produced later in the season, contain teliospores, which remain dormant on crop debris until the spring.

Basidiospores

In spring, teliospores germinate to produce basidiospores which infect the alternate hosts buckthorn (Rhamnus catharticus) and alder buckthorn (Frangula alnus).

Aeciospore

Aeciospores are produced on the alternate hosts, which can then reinfect oats.

AHDB Recommended Lists (RL) trials assess crown rust symptom expression in UK winter and spring oat varieties.

In the RL, varietal disease resistance ratings for crown rust are published on a 1–9 scale, where 1 indicates low resistance and 9 indicates high resistance.