Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2006
Publication Date: 1/13/2007
Citation: Gugino, B.K., Carroll, J.E., Widmer, T.L., Chen, P., Abawi, G.S. 2007. An ipm program for the management of fungal leaf blight diseases of carrot in new york. Plant Disease 91:59-65
Interpretive Summary: Fungal leaf blight disease of carrots caused by two fungi is an annual problem in New York, however the amount of disease is variable between fields and growing seasons. Therefore, it is important to manage these diseases on an as-needed basis. The objective of this study was to establish an integrated management program to reduce fungicide applications by scouting a field and only applying fungicides when the disease reached a certain level. Fungicides applied only when the disease incidence reached 25% for an individual field were two to six times fewer without a reduction in marketable yields. The different carrot cultivars planted influenced the time when this 25% level was reached. In addition, crop rotations out of carrot also impacted the level of disease. The results presented are important in that they provide a recommended fungal leaf blight management program for carrots in New York that can reduce the number of fungicide applications without reducing yields.
Technical Abstract: Fungal leaf blight diseases caused by Cercospora carotae and Alternaria dauci occur annually on processing carrots in New York and growers were applying up to eight fungicide sprays to manage them. The use of a 25% disease incidence threshold to prompt the first fungicide application and timing subsequent sprays by increases in disease severity and weather forecasts was evaluated in grower fields in 1997 and 1998. The IPM plots, compared to the grower standard plots, required two to six fewer fungicide applications without reducing yield. The validation of the IPM program was conducted over six subsequent years from 1999 – 2004 and the effect of crop rotation and carrot cultivar susceptibility were also assessed. Carrots growing in fields with longer crop rotation intervals reached the 25% disease incidence threshold later in the season and required fewer fungicide applications. The more resistant carrot cultivars also reached the 25% disease incidence threshold later, required fewer fungicide applications and had less severe disease. Validation of the IPM program in New York showed that both fungal leaf blights can be effectively managed using a 25% incidence threshold to prompt the first fungicide spray and applying subsequent fungicides based on increases in disease severity, weather forecasts, or spray interval.