Stem Rust & Crown Rust in Oats

An agronomist contacted me in regards to finding rust in an oat field in Southern Manitoba. I toured out there today to find both stem and crown rust present in the field.  I also toured a MCVET oat trial where I could find stem rust in each of the entries.  I have provided a review below of stem rest and crown rust in oats.

Stem rust
Stem rust is caused by the fungus Puccinia graminis f.sp. avenae.  The disease appears as elongated reddish-brown pustules mainly on stems but also on leaves and heads. The powdery spore masses in the pustules can dislodge readily.

Stem rust causes yield losses through absorbing of nutrients that would otherwise be used for grain development, interferes with plant vascular tissue which can lead to shriveled grain, and it can weaken the stem causing lodging.

Stem Rust

Stem Rust in Oats. Photo by: Pam de Rocquigny, 2014

Crown rust
Crown rust is caused by the fungus Puccinia coronate f.sp avenae. The characteristic symptom is the development of round to oblong, orange to yellow pustules, primarily on leaves but also on stems and heads. The powdery spore masses in the pustules are readily dislodged. The pustule areas turn black with age.

Losses result from damage to leaves (particularly the flag leaf), which leads to reduced photosynthesis and transport of carbohydrates to the developing grain. This causes shriveled grain and reduced grain quality.

Crown Rust

Crown Rust in Oats. Photo by: Pam de Rocquigny, 2014

There isn’t much to be done at this stage of the growing season if rust is found.  However, in future growing seasons control options would include planting resistant varieties, seeding early if possible, and application of fungicides.

Submitted by:  Pam de Rocquigny, MAFRD Cereal Crops Specialist

For additional information, visit MAFRD’s website:



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