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Monitoring for Sunflower Rust (08/13/15)

I have had received fewer reports on sunflower rust than on dry edible bean rust, however, conditions for rust development have been very favorable in much of the state.

Monitoring for Sunflower Rust

I have had received fewer reports on sunflower rust than on dry edible bean rust, however, conditions for rust development have been very favorable in much of the state.  It is particularly important to keep an eye on confection sunflowers; they tend to be more susceptible to rust than oilseeds.  However, there are distinct resistant differences among hybrids; some are resistant and some are susceptible.

If rust is found on the top of the canopy (the top four fully-expanded sunflower leaves) at 1% severity or higher in R5 (bloom) a fungicide application may be warranted.  By R6 (flowering is complete) research trials have shown no benefit to a fungicide application.  Similar to dry edible bean rust; strobilurin and triazole fungicides are efficacious on rust. 

For more details, photographs and links to additional information, please refer to the crop and pest report article ‘Keep an eye out for sunflower rust’ in the July 30th issue of the crop and pest report.

Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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