Charcoal Rot
Inside of stalk
showing charcoal rot

This disease is caused by the fungus Macrophomina phaseolina which attacks 400 plants, such as soybeans, edible beans, corn and sorghum.  The disease is most often found in hot and dry regions.  The symptoms are generally not seen until after flowering and are silver gray lesions on the stalk near the soil line.  This disease has not been of economic concern except for isolated areas.
Diseased stalk due to charcoal rot

Life Cycle: The fungus overwinters in the soil but can also be seed borne.  The sunflower root comes into contact with small sclerotia like bodies which infect the plant. 

Damage: Losses are often associated with hot and droughty conditions.  Poor plant health related to other diseases, insect and hail damage can promote the disease.  Infected plants generally die before seed set is finished.

Economic Thresholds: Not available.

Scouting Method: Not available    

Management: The disease has not been of consequence with the exception of localized areas.  Crop rotation is one tool but susceptible crops should be avoided.  Soil moisture management via good weed control, reduced tillage, reduced populations, balanced fertility and avoiding traditional high temperature periods by early or delayed planting can help. 

Research: There is some hybrid tolerance and overall improved plant health will likely aid in further tolerance.    

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

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