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Sunflower Rust (07/26/18)

Sunflower rust is favored by frequent dews and moderate to warm temperature, and growers are encouraged to scout for sunflower rust as sunflowers approach bloom.

Sunflower Rust

Sunflower rust is favored by frequent dews and moderate to warm temperature, and growers are encouraged to scout for sunflower rust as sunflowers approach bloom. Confection-type sunflowers are particularly sensitive to rust, but oilseeds can be susceptible to the disease as well. Yield and quality losses can be very high if an epidemic develops early in the season.

Signs and Symptoms.

Sunflower rust is commonly first observed near shelter belts, near last year’s sunflower residue or near wild/volunteer sunflowers. Pustules are cinnamon-brown and dusty, often first found on the leaves in the lower canopy (Figure 1). If an epidemic occurs, pustules may be found on stems, petioles and leaves.

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Management of Sunflower Rust.

Timing. If rust reaches approximately 1% severity on the upper four fully expanded leaves at or before bloom (R5) a fungicide should be considered (Figure 2-3). At R6 or later (after bloom) fungicide applications have not had impact on yield in out trials.

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Efficacy. DMI fungicides [FRAC 3: Triazole] (tebuconazole, etc..), QoI fungicides [strobilurins: FRAC 11: Strobilurins Headline, Quadris, Aproach) and fungicides containing those modes of actions are among the most effective on rust in our trails.

 

Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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