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There are several headrots other than Sclerotinia that affect sunflower. These are found primarily in the High Plains. Rhizopus is the most common. The infected head turns brown and mushy. Once the head dries up it becomes hard and brittle.
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Life Cycle: The fungus enters the head through wounds produced by hail, birds or insects. In wet and hot weather the infection spreads throughout the head.
Damage: Losses can be significant and some fields have been reported to be totally infected. In NSA field surveys, Kansas fields had a high incidence of 20% in 2007 compared to 5% in 2006 and 1.5% in 2005. Other states reporting damage of 5% or more in one or more of the survey years are Texas and Colorado. The 2007 damage in Kansas may likely be associated with extremely high sunflower moth incidence.
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Economic Thresholds: This is not well defined since there is not a fungicide treatment available.
Scouting Method: Not available
Management: There is no fungicide treatment available for this fungus. Good head insect control such as the sunflower moth is believed to be the primary management factor of the disease.
Research: Very limited work has been done on the other headrots.
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
For further information, click on the links below. Another resource about Diseases can be found in the Archive section of The Sunflower magazine.
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Additional Documents
High Plains Sunflower Production Handbook (document) File Size: 1518 kb
NDSU Extension Bulletin 25 - Revised 9/2007 (document) File Size: 5461 kb
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