Alternaria on leaf
Alternaria on leaf

This disease is very common on senescing leaves but is of little consequence in the traditional production regions of the High Plains and Northern Plains.  However the disease can have significant yield losses in hot and humid areas.  The disease defoliates the leaves by creating dark spots.  The stem is infected as well resulting in stem breakage.

Life Cycle:
Alternaria stem
Alternaria on stem
There are several species of Alternaria which all overwinter on diseased stalks.  Disease development is promoted by extended warm and moist conditions.  Extended wet periods can hasten the disease significantly.   

Damage: Excessive leaf loss will lead to yield loss.  Reports of yield loss up to 90% have been reported in subtropical areas.  Yield loss has been reported in SE and eastern parts of the U.S.

Economic Thresholds: Not available.

Scouting Method: Not available    

Management: Headline® fungicide is labeled to control Alternaria.  There may be hybrid differences but no test results are available from the public sector.  Crop rotation is another tool.

Research: Little or no research is being done on this disease since it is of no consequence in the major production regions.  This might become a greater concern if the crop moves into environments that are more conducive to the disease development. 

Photos: Visit the Photo Gallery.

Source:  NDSU Extension Bulletin 25 Sunflower Production Handbook, NDSU Extension Service, September 2007 and High Plains Production Handbook June 2005

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

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

return to top of page

   More about Sunflower ►