Rust Damage & Control
rust on leaf
Suflower Rust on back
of sunflower leaf
May 2011 Update - See Sunflower Rust - NDSU Extension Service Publication
This disease can have severe economic impacts throughout the entire sunflower production region. North Dakota field tests in 2008 in a highly diseased field resulted in a yield of 200 pounds per acre of unusable production where no fungicides were used.

Life Cycle: There is one main fungus, Puccinia helianthi, that impacts sunflower around the world.  There are several other North American rust species but are not considered of economic consequence.  The development of rust occurs in warm and moist conditions.  Rust does not require an alternate plant to reproduce.  Overwintering is on plant debris and the spores germinate in the spring and go through several stages before brown infectious pustules are formed.  Under favorable weather conditions the disease can multiply very fast.  It takes only light dew under favorable conditions to accelerate the development.
rust damage
Damage: In severely infected fields the plants senesce prematurely resulting in reduced test weight, oil content, seed size and yield. 

Economic Thresholds: Rust is most often found on the lower under-side of leaves.  The pustules are cinnamon-red and readily recognizable.  Control measures should be considered when rust is found on the upper four leaves and the plant is in the vegetative stages and up to R-6.  Recommendations from 2008 fungicide research trials indicate when rust has infected the upper four leaves at 1 percent or less than products like Headline and Quadris can be used.  If the infestation of the upper four leaves is 3 percent or greater than Folicur may be the best fungicide choice (See the Rust Diagrams below).  An infestation on the upper leaves at R-6 or later will not likely have a negative yield affect.  
Management: Hybrid resistance is the first consideration.  Races of rust change periodically so a hybrid may not be resistant to all races.  Controlling volunteer and wild sunflower in the spring near a commercial field will reduce sources of innoculum.  Rust can be controlled by fungicides.  There are three labeled products for the control of rust on sunflower:  Folicur, Headline and Quadris.  The labels of each are listed below. 

Research: The National Sunflower Association (NSA) has been very proactive.  In 2007 the NSA funded a national collection of rust isolates to determine if races have changed and which races are most predominate.  Collections were made in 2008 and 2009.  Data from 2007 collections can be found below (Gulya, Rust Races 2007) and a partial summary of 2008 results can be found below (Gulya, Rust Races 2008).  To date there are two races which are predominate in both the southern and northern plains.  In greenhouse inoculation, 88 % of the hybrids tested were susceptible to both races.  Two differential breeding lines are resistant to 90% of all races collected.  Private companies are transferring the gene(s) into their elite breeding material.
The NSA has also funded fungicide trials in 2008 and 2009.  The results of the 2008 trial are available below (Markell, fungicide trial 2008).  In 2009 the NSA funded a Ph.D. student in plant pathology to assist in fungicide trials and isolate collections and begin the process of a molecular ‘marking’ the resistant gene(s).  The NSA has applied for funding from USDA’s Agricultural Marketing Service to hire a post doctoral associate to transfer the resistant gene(s) into confection background material.  Word of that grant will be known in late 2009.

Photos: Visit the Photo Gallery.

Another resource about Diseases can be found in the Archive section of The Sunflower magazine.
Additional Resources
2008 Rust Survey Map file size: 698 kb
2008 Rust Survey Map

Effects of Fungicide in Controlling Rust file size: 753 kb
Effects of Fungicide in Controlling Rust

Gulya, Tom (2009) file size: 2377 kb
Sunflower Rust Status-2008: Race Frequency across the Midwest & Resistance Among Commercial Hybrids

Headline Fungicide Information Sheet file size: 76 kb
Headline Fungicide Information Sheet

High Plains Sunflower Production Handbook file size: 1554 kb
High Plains Sunflower Production Handbook

Markell, Sam (2009a)  file size: 2245 kb
Evaluation of Fungicides and Timing for Rust Control in Inoculated Trials in North Dakota (PowerPoint)

Markell, Sam (2009b)  file size: 99 kb
Evaluation of fungicides and fungicide timing on control of sunflower rust (Puccinia helianthi) at three locations in North Dakota in 2008. (Research paper)

More Rust Detail for 2009 file size: 21 kb
More Rust Detail for 2009

NDSU Extension Bulletin 25 - Revised 9/2007 file size: 5591 kb
NDSU Extension Bulletin 25 - Revised 9/2007

Quadris Label file size: 18 kb
Quadris Label

Rust Diagrams file size: 260 kb
Rust Diagrams

Sunflower Rust and Fungicides file size: 4651 kb
Sunflower Rust and Fungicides

Supplemental Label for Folicur  file size: 112 kb
Supplemental Label for Folicur

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