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Keep an Eye Out for Sunflower Rust (07/30/15)

As sunflowers begin to bloom it is important to scout for sunflower rust.

Keep an Eye Out for Sunflower Rust

As sunflowers begin to bloom it is important to scout for sunflower rust. Environmental conditions have been very favorable for the development of sunflower rust; heavy dews, moderate to warm temperatures and frequent rains that keep the canopy humid. Sunflower rust was observed in multiple locations early in the season and is likely working its way up the canopy in some sunflower fields. In general, confectionary sunflowers are more susceptible and at greater risk for yield and quality losses.

The disease is often first observed near shelter belts (where dews last longer because of shade and protection from the wind), a field bordering last year’s sunflower crop (particularly if rust was present) or a stand of wild sunflowers (which harbor the pathogen). When scouting, look for pustules with dusty cinnamon-brown spores that can easily rub off; very similar to dry bean rust.

Research data from both NDSU and the University of Nebraska (funded by the National Sunflower Association) has shown that a fungicide application is important to protect yield when the rust severity on the upper four fully-expanded leaves reaches 1% at or before R5 (Figure 1). Labeled products containing a FRAC 3 (tebuconazole generics) or FRAC 11 fungicides (Headline, Quadris, Priaxor [mixture of FRAC 11+7]) have generally performed better than FRAC 7 fungicides for rust management. 

General information, and disease assessment diagrams, can be found in the NDSU Sunflower Rust publication PP1557. The National Sunflower Association website (www.sunflowernsa.com) houses some excellent information on sunflower rust management.  Some direct links to detailed fungicide trial reports are below (the first is perhaps the most useful)

http://www.sunflowernsa.com/uploads/research/446/Friskop_EvalFungicides_10.pdf

http://www.sunflowernsa.com/uploads/research/582/friskop_rust_11.pdf

http://www.sunflowernsa.com/uploads/research/1184/friskop_fungicide.trials_paper_12.pdf

ppth.markell.1.sunflower rust 1

ppth.markell.2.sunflower rust 2

Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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