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Fungicide Resistance Management Guidelines for the Control of Tomato Diseases in the Mid-Atlantic and Northeast Regions of the United States
Christian A. Wyenandt, Extension Specialist in Vegetable Pathology, New Jersey Agricultural Experiment Station, Department of Plant Biology and Pathology, Rutgers University, Bridgeton, NJ 08302; Steven L. Rideout, Assistant Professor of Plant Pathology, Department of Plant Pathology, Physiology and Weed Science, Eastern Shore Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Painter, VA 23420; Beth K. Gugino, Assistant Professor of Plant Pathology, Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802; Margaret T. McGrath, Associate Professor, Department of Plant Pathology and Plant-Microbe Biology, Long Island Horticulture Research and Extension Center (LIHREC), Cornell University, Riverhead, NY 11901; Kathryne L. Everts, Professor of Plant Pathology, Department of Plant Sciences and Landscape Architecture, University of Maryland, Salisbury, MD 21801, and Plant and Soil Sciences Department, University of Delaware, Newark, DE 19716; and Robert P. Mulrooney, Extension Plant Pathologist, Plant and Soil Sciences Department, University of Delaware, Newark, DE 19716
Wyenandt, C. A., Rideout, S. L., Gugino, B. K., McGrath, M. T., Everts, K. L., and Mulrooney, R. P. 2010. Fungicide resistance management guidelines for the control of tomato diseases in the mid-Atlantic and northeast regions of the United States. Online. Plant Health Progress doi:10.1094/PHP-2010-0827-01-MG.
Foliar diseases and fruit rots occur routinely on tomato, an important crop grown throughout the Mid-Atlantic and Northeast regions of the United States where it is produced for both fresh-market and processing. To enable these tomato growers to more effectively manage economically important diseases, a fungicide resistance management table has been developed which promotes the importance of understanding FRAC (Fungicide Resistance Action Committee) codes and provides an integrated pest management tool for tomato growers which will allow them to develop season-long disease control programs with an emphasis on fungicide resistance management.
Tomato is an important crop grown throughout the mid-Atlantic and Northeast regions of the United States. Most diverse fresh-market vegetable growers produce tomatoes which are regularly affected by foliar and fruit rot pathogens. The four largest tomato-producing states (New Jersey, Virginia, Pennsylvania, and New York) in the mid-Atlantic and Northeast regions produce more than 10,000 acres of fresh-market and 2,000 acres of processing tomatoes with a value of more than 140 million dollars annually (6). In recent years, several new fungicide chemistries labeled for use in vegetable production have been registered in the United States. Many of these fungicides have a specific mode of action (MOA) that targets pathogen development at a single site. Fungicides with a single-site MOA are often considered high-risk for development of fungal resistance and possess a much greater risk for resistance development than fungicides with multiple MOAs (e.g., protectant fungicides such as chlorothalonil or mancozeb). In the mid-Atlantic and Northeast in recent years, fungicide resistance has developed in pathogens which incite diseases of important vegetable crops, including gummy stem blight [Didymella bryoniae (Auersw.) Rehm] in watermelon and other cucurbits, powdery mildew [Podosphaera xanthii, formerly Sphaerotheca fuliginea (Schlecht ex Fr.) Poll.] in all cucurbit crops and Phytophthora blight (Phytophthora capsici Leonian) in bell pepper (1,2,5,9). Resistance to strobilurin fungicides has been well documented in potato early blight (Alternaria solani), and insensitivity in tomato early blight (Alternaria tomatophila) in New York State is suspected (8).
Unfortunately, some growers become concerned about managing resistance only after fungicide failures have occurred (5). Many vegetable growers do not recognize that the primary goal of resistance management is to delay development of resistant pathogen populations rather than to manage resistant strains (5). Vegetable growers face many challenges in trying to properly manage resistance development on their farms due to a limited understanding of FRAC codes (Fungicide Resistance Action Committee) and the large number of diverse fungicide chemistries available to control important vegetable diseases.
To help vegetable growers appreciate the importance of understanding and managing fungicide resistance development, a fungicide resistance management guide has been available in the mid-Atlantic region since 2007 (10). This guide has become an important IPM tool for many vegetable growers, crop consultants, and extension agents in the region, and due to its success and acceptance, a new fungicide resistance management table has been developed specifically for fresh-market and processing tomato growers in the Mid-Atlantic (New Jersey, Pennsylvania, Virginia, Delaware, and West Virginia) and Northeast regions (New York, Connecticut, Maryland, Rhode Island, New Hampshire, Vermont, and Maine) of the United States. The purpose of this fungicide resistance management table is to: (i) promote the importance of understanding of FRAC codes in managing fungicide resistance; (ii) maximize appropriate use of specific fungicides that have a high-risk for resistance development; and (iii) provide an integrated pest management (IPM) tool that encourages tomato growers to develop season-long control programs that integrate fungicide resistance management in the mid-Atlantic and Northeast regions of the United States.
Fungicide Resistance Management Guidelines for Tomato Disease Control in the Mid-Atlantic and Northeast Regions
The fungicide resistance management table consists of fungicides listed for control of economically-important tomato diseases from commercial recommendations guides developed for the mid-Atlantic region (Pennsylvania, New Jersey, Delaware, Maryland, Virginia, and West Virginia), New York State, and Northeast region (Maine, New Hampshire, Vermont, Connecticut, Maryland, and Rhode Island) (4,7,8). Included in the table are fungicide brand names, corresponding active ingredients, FRAC and risk management codes, and fungicide resistance management guidelines (Table 1). Thirty-one fungicides and one biological control agent labeled for use on tomato, representing 18 different FRAC codes, are listed for these diseases. Codes indicating the risk for resistance development (L = low risk, M = medium risk, and H = high risk) established by the FRAC committee are also presented in Table 1 (3). For some fungicides, there is a range for the risk of resistance development (Table 1). For example, the active ingredient cymoxanil (FRAC code 27) has a risk rating of low to medium according to FRAC standards (Table 1). For fungicides with two different active ingredients the resistance risk for each may be different (Table 1). For such fungicides, the resistance risks are shown for both active ingredients in Table 1. Additionally, fungicides are color-coordinated by FRAC code to help distinguish FRAC groups (i.e., different MOAs). A superscript R pathogen risk indicates that resistance is known to develop in that particular pathogen (Table 1). Likewise, a superscript R fungicide risk indicates that resistance to that particular fungicide is known to develop depending on the pathogen (Table 1). Most importantly, if resistance has been detected in a pathogen for a particular fungicide/pathogen combination in the mid-Atlantic or Northeast regions the designated X is colored red emphasizing that a particular fungicide/pathogen combination has a very high risk for resistance development (Table 1). For example, resistance in early blight to azoxystrobin, a FRAC code 11 fungicide, has been detected in our region and therefore the X is colored red (Table 1). However, resistance in early blight to other FRAC code 11 fungicides have not been detected in the region and the Xs are colored black (Table 1). Additionally, resistance is known to develop in pathogens such as in powdery mildew, botrytis, or late blight where each is listed with a superscripted R, but resistance has not been detected to those fungicides listed for their control in the mid-Atlantic or Northeast regions and the Xs are colored black (Table 1).
Table 1 (click for larger view). Fungicide resistance management table for the control and management of tomato diseases in the mid-Atlantic and Northeast regions of the United States.
The far right-hand column of Table 1 includes fungicide resistance management guidelines for low- and high-risk fungicides with general instructions on resistance management. The fungicide resistance management table is printed on heavy paper and laminated so it can be placed in a pesticide shed or weighing area for easy reference and durability. Included with each table is a form on which notes on applications, specific FRAC group use, and dates can be recorded for specific crops (Table 2). Although growers are required by law to keep a record of pesticide applications, there is no requirement to keep track of specific fungicide chemistry use in terms of resistance management. If growers do not keep track of resistance management, they may unknowingly apply high-risk fungicides without a protectant fungicide or use inappropriate fungicide rotations (i.e., rotating among fungicides in the same FRAC group), thereby enhancing the opportunity for the development of resistant pathogen populations (5).
Table 2. Fungicide application form for developing and scheduling season-long fungicide programs for tomato disease control.
The 2010 table for the control of important tomato diseases in the mid-Atlantic and Northeast regions are available to print free of charge at the New Jersey Agricultural Experiment Station’s (NJAES) Vegetable Crop Resource Center website at www.njveg.rutgers.edu. Free laminated copies of the table can be obtained by state and local agricultural agents for distribution in mid-Atlantic and Northeast regions by contacting Dr. Andy Wyenandt at email@example.com.
1. Davey, J. F., Gregory, N. F., Mulrooney, R. P., Evans, T. A., and Carroll, R. B. 2008. First report of mefenoxam resistant isolates of Phytophthora capsici from lima bean pods in the mid-Atlantic region. Plant Dis. 92:656.
2. Everts, K. L. 1999. First report of benomyl resistance in Didymella bryoniae in Delaware and Maryland. Plant Dis. 83:304.
5. McGrath, M. T. 2001. Fungicide resistance in cucurbit powdery mildew: experiences and challenges. Plant Dis. 85:236-245.
7. Orton, T. J., Garrison, S. A., Ghidiu, G. M., Hamilton, G. C., Majek, B. A., Wyenandt, C. A., Dugan, D., eds. 2010. Commercial vegetable production recommendations. Online. Agr. Exp. Station Publ. E001. Rutgers Univ., New Brunswick, NJ.
8. Reiners, S., and Petzoldt, C. H., eds. 2010. Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production for New York State. Online. Pesticide Management Ed. Prog., Cornell Univ., Ithaca, NY.
9. Wyenandt, C. A., Maxwell, N. L., and Ward, D. L. 2008. Fungicide programs affect ‘practical’ resistance development in cucurbit powdery mildew of pumpkin. HortScience 43:1838-1845.
10. Wyenandt, C. A., Rideout, S. L., Everts, K. L., Mulrooney, R. P., and Maxwell, N. L. 2009. Development of a fungicide resistance management guide for vegetable growers in the Mid-Atlantic states. Online. Crop Management doi:10.1094/CM-2009-0316-01-MG.