An IPM Program for Managing Fungal Leaf Blight
Diseases of Carrot in New York. B. K. Gugino, J. E. Carroll, T. L.
Widmer, P. Chen, and G. S. Abawi, Department of Plant Pathology, Cornell
University, New York State Agricultural Experiment Station, Geneva 14456.
Plant Dis. DOI: 10.1094/PD-91-0059. Accepted for publication 24 August
2006.
Fungal leaf blight diseases caused by Cercospora carotae and
Alternaria dauci occur each year on processing carrot in New York.
Growers spray fungicides up to eight times on a regular spray schedule to
manage these diseases. The goal of this study was to develop an effective
management program for carrot fungal leaf blight diseases and to implement
the program on an as-needed basis. A 25% disease incidence threshold was
found to be appropriate for deciding when to spray the first fungicide.
Regular field scouting and weather forecast monitoring effectively
identified conditions favorable to the pathogen, increases in disease
severity, and the appropriate timing for additional sprays, without
reducing yield. Growing carrot plants in fields with a minimum 2-year
rotation out of carrot delayed the date the first fungicide spray was
applied, as did planting less-susceptible cultivars. The less-susceptible
cultivars also required fewer fungicide sprays during the season and were
less severely diseased. Utilizing a 25% disease incidence threshold as
well as planting less-susceptible cultivars and rotating out of carrot for
a minimum of 2 years will reduce fungicide use, improve fungal leaf blight
disease management, and reduce production costs.
