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Alternaria leaf blight of carrots

Mar 3, 2017 6:39 AM

Fungal causal agent: Alternaria dauci

Symptoms:  Small leaf spots with water soaking is the first symptom, later stage symptoms may also have a yellow halo around the enlarged black/brown lesions. This may be followed by moderate to severe blighting of leaves. Period from February-April is ideal for disease development and spread of the pathogen in Florida based on the assessments from last 2 years in North Florida. 

Management:. When prolonged periods of leaf wetness and warm conditions prevail, Alternaria leaf blight is hard to control. Fungicides are a primary control strategy but as the crop matures, good coverage is difficult to obtain. In humid areas fungicides may be required before symptoms develop. The use of pathogen-free seeds is critical to prevent the introduction of the pathogen. Some carrot cultivars are fairly resistant to Alternaria leaf blight, and a wide range of disease tolerances exists among commercial cultivars. Review this link for more information http://ipm.ucanr.edu/PMG/r102100711.html. Check http://premier.cdms.net/webapls/formsloginRef.asp?/webapls for current labels.