David F. Ritchie

Professor of Plant Pathology

Extension Specialist

Plant Pathology Director of Graduate Programs

Appointment: 50% Research, 30% Instructional, 20% Extension

• B.A. (Biology), Goshen College
• M.S. (Plant Pathology), Michigan State University
• Ph.D. (Plant Pathology), Michigan State University

Research Activities

My program focuses on both discovery and problem-solving research dealing with bacterial and fungal plant pathogens that cause diseases of fruit and vegetable crops. Emphasis is on the population biology and evolutionary mechanisms and dynamics that lead to the defeat of host resistance and the characterization of pathogens that have gained virulence. The goal of this research is to develop knowledge that leads to more durable disease resistance and disease management strategies. The crop and pathogen system used is pepper and Xanthomonas axonopodis [campestris] pv. vesicatoria causal agent of the disease, bacterial spot. Problem-solving and integrated disease management research also is conducted on two fungal diseases of peaches, brown rot and peach scab. A major focus on peaches and other Prunus spp. is in the area of epidemiology and management of bacterial spot of stone fruits caused by Xanthomonas arboricola [campestris] pv. pruni.

Selected Publications

• Romero, A.M., Kousik, C.S., and Ritchie, D.F. 2002. Temperature sensitivity of the hypersensitive response of bell pepper to Xanthomonas axonopodis pv. vesicatoria. Phytopathology 92:197-203.
• Romero, A.M., Kousik, C.S., and Ritchie, D.F. 2001. Resistance to bacterial spot in bell pepper induced by acibenzolar-S-methyl. Plant Dis. 85:189-194.
• Pagani, C.M., Leoni, C., Silvera, E., and Ritchie, D.F. 2001. Characterization of fruit infection periods for bacterial spot on peach. Phytopathology 91:(Suppl.) S68.
• Wangsomboondee, T., and Ritchie, D.F. 2001. Competitiveness and aggressiveness of Xanthomonas axonopodis pv. vesicatoria strains with mutations in the avrBs2 locus. Phytopathology 91:(Suppl.) S93.
• Ritchie, D.F., and Pollard, D.W. 2001. Evaluation of fungicides for control of scab and brown rot of peaches, 2000. Fungicide and Nematicide Tests 2001:STF7. Am. Phytopathol. Soc. APSnet.
• Ritchie, D.F., and Pollard, D.W. 2001. Evaluation of sprays containing copper hydoxide or calcium hydroxide/copper sulfate for control of bacterial spot of bell pepper, 2000. Fungicide and Nematicide Tests 2001:STV35. Am. Phytopathol. Soc. APSnet.
• Ritchie, D.F. and Romero, A.M. 2000. Response of pepper genotypes having horizontal and/or vertical (major gene) resistance to bacterial spot, 1999. Biological and Cultural Tests 15:171.
• Ritchie, D.F. 2000. Brown rot of stone fruits. The Plant Health Instructor. APSnet Education Center. DOI:10.1094/PHI-I-2000-1025-01. Ritchie, D.F. 2000. Bacterial spot of pepper and tomato. The Plant Health Instructor. APSnet Education Center. DOI:10.1094/PHI-I-2000-1027-01.
• Kousik, C.S., and Ritchie, D.F. 1999. Development of bacterial spot on near-isogenic lines of bell pepper carrying gene pyramids composed of defeated major resistance genes. Phytopathology 89:1066-1072.
• Kousik, C.S., and Ritchie, D.F. 1998. Response of bell pepper cultivars to bacterial spot pathogen races which individually overcome major resistance genes. Plant Dis. 82:181-186.
• Kousik, C.S. and D.F. Ritchie. 1996. Disease potential of pepper bacterial spot pathogen races that overcome the Bs2 gene for resistance. Phytopathology 86:1336-1343.
• Kousik, C.S. and D.F. Ritchie. 1996. Race shift in Xanthomonas campestris pv. vesicatoria within a season in field-grown pepper. Phytopathology 86:952-958.
• Kousik, C.S., D.C. Sanders, and D.F. Ritchie. 1996. Mixed genotypes combined with copper sprays to manage bacterial spot of bell peppers. Phytopathology 86:502-508.
• Kousik, C.S. and D.F. Ritchie. 1996. Evaluation of bell pepper varieties against races 1-4 of the bacterial spot pathogen, 1995. Biological and Cultural Tests. 11:97.
• Ritchie, D.F. and W. Pollard. 1996. Fluazinam 500F for control of bacterial spot of peach, 1995. Fungicide and Nematicide Tests 51:54.
• Ritchie, D.F. and W. Pollard. 1996. Fungicides for control of brown rot and scab on peach, 1995. Fungicide and Nematicide Tests 51:55.
• Kent, S.J., M.E. Daub, and D.F. Ritchie. 1996. Gallic acid production protects Xanthomonas campestris pv. pruni from cytotoxic effects of hydrogen peroxide. Phytopathology 86:S16 (Abst.).
• Pagani, M.C., D.F. Ritchie, P.B. Lindgren, D.J. Werner, and C.S. Kousik. 1995. Identification of a DNA fragment that differentiates strains of Xanthomonas campestris pv. pruni. Phytopathology 85:1194. (Abst.).
• Ritchie, D.F. 1995. Effect of fluazinam, kocide, mycoshield, and ziram, and application time on bacterial spot of peach, 1994. Fungicide and Nematicide Tests. 50:61-62.
• Ritchie, D.F., Werner, D.J., and Hammerschlag, F.A. 1993. Field evaluation of tissue culture-derived peach trees for susceptibility to bacterial spot (Xanthomonas campestris pv. pruni). Acta Horticulturae 336:155-169. 2nd Intl. Soc. Hort. Sci. Symp. on "In vitro culture and horticultural breeding", 28 June- 2 July. Baltimore, MD.
• Dittapongpitch, V., and D.F. Ritchie. 1993. Indigenous miniplasmids in strains of Xanthomonas campestris pv. vesicatoria. Phytopathology 83:959-964.
• Ritchie, D.F., and V. Dittapongpitch. 1991. Copper- and streptomycin-resistant strains and host differentiated races of Xanthomonas campestris pv. vesicatoria in North Carolina. Plant Dis. 75:733-736.
• Ritchie, D.F. 1989. Improved peach tree longevity with use of fenamiphos in peach tree short-life locations. Plant Dis. 73:160-163.
• Werner, D.J., D.F. Ritchie, D.W. Cain, and E.I. Zehr. 1986. Susceptibility of peaches and nectarines, plant introductions, and other Prunus species to bacterial spot. HortScience 21:127-130.

Contact Information

Dr. David F. Ritchie
North Carolina State University
Department of Plant Pathology
2406 Gardner Hall
Campus Box 7616
Raleigh, NC 27695-7616

Tel: (919) 515-6809
FAX: (919) 515-7716
Email: david_ritchie@ncsu.edu