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Alternaria
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.
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Life Cycle: 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.
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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.
Source: NDSU Extension Bulletin 25 Sunflower Production Handbook, NDSU Extension Service, September 2007 and High Plains Production Handbook June 2005
Photos: Visit the Photo Gallery.
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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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