Field evaluation of carrot cultivars for susceptibility to fungal leaf blight diseases in New York

Carrot cultivars grown in New York were evaluated for susceptibility to the fungal leaf blight pathogens Alternaria dauci (1999) and Cercospora carotae (2000-03) in an experimental field under continuous carrot cultivation since 1996. Replicated plots were established in a randomized complete block design. Plants were rated for disease incidence and severity at regular intervals. Cultivar susceptibility was ranked based on the area under the disease progress curve. An IPM program for carrot leaf blights conducted in growers' fields provided the opportunity to determine the impact susceptibility had on the date the 25% disease incidence threshold was reached to prompt the first fungicide application. Of the cultivars evaluated, Bolero, Carson, Calgary, Ithaca, and Fullback were less susceptible to A. dauci whereas, Bolero, Carson, and Bergen were less susceptible to C. carotae. Fontana was most susceptible to both fungal leaf blight pathogens. In grower fields less susceptible cultivars reached the 25% threshold later than their more susceptible counterparts. Carrot cultivar susceptibility was incorporated into an IPM program for these diseases.