Brown or leaf rust of wheat

Puccinia triticina (P. recondita)

DISEASE:  Leaf or Brown rust

PATHOGEN:  Puccinia triticina (Syn. Puccinia recondita f. sp. tritici)

HOSTS: Wheat, barley and  common

Barberry (Berberis, Mahoberberis and Mahonia spp.)

Symptoms

The most common site for symptoms is on leaf blades, however, sheaths, glumes and awns may occasionally become infected and exhibit  symptoms.

Uredia are seen as small, circular orange blisters or pustules on the upper surface of leaves.

Orange spores are easily dislodged and may cover clothing, hands or implements. When the infection is severe leaves dry out and die. Since inoculum is blown into a given area, symptoms are often seen on upper leaves first.

As plants mature, the orange urediospores are replaced by black teliospores. Pustules containing these spores are black and shiny since the epidermis does not rupture.

Yield loss often occurs as a result of infection by Puccinia recondita f. sp. tritici. Heavy infection which extends to the flag leaf results in a shorter period of grain fill and small kernels.

Scattered oval to circular small brown pustules (rusty-red uredospores) containing a powdery mass of orange to red-orange spores develop on the upper leaf surfaces, leaf sheaths, glumes and awns.

Black pustules form as the plant approaches maturity (Telia). Microscopically, teliospores are two celled and thick walled.

Pre disposing (environmental) factors

Warm-humid weather conditions with intermittent rains.

Hot days 25-30^ºC and mild nights (15-20^ºC)

Leaf wetness from rain or dew

Life and disease cycles for Puccinia tricina

Management

Use of resistant varieties is the best way to control wheat losses to leaf rust.

Check fields periodically during the season, especially when warmer temperatures start to develop.

It is recommended to implement practices that include the eradication of volunteer plants and crop debris, which can harbor inoculum over the winter. 

Generally there is no economic benefit from applying fungicides to control leaf rust when resistant varieties are grown but Possible disease race shifts may make it necessary to use fungicides.  Propiconazole  or Tilt and Tebuconazole or Folicur  @0.5 lt/ha  is recommended