Gerald J. Holmes

Associate Professor of Plant Pathology

Extension Specialist

• B.S. (Agronomy), California State Polytechnic University, Pomona
• Ph.D. (Plant Pathology), University of California, Riverside

My program revolves around extension and applied research of vegetable crops, especially sweetpotatoes, cucurbits (cucumber, melon, pumpkin, squash and watermelon) and postharvest diseases. My appointment is 100% extension, but includes research and teaching responsibilities.

Extension Actitivies

Extension activities include the diagnosis of vegetable diseases at the NCSU Disease and Insect Clinic, training of County Agents in disease diagnosis and control, publication of disease control recommendations, disease information notes and timely statewide advisories regarding important disease outbreaks and their management. Information is disseminated in a variety of formats including the world wide web, formal and informal oral presentations, publications in trade journals as well as peer-reviewed scientific journals, newsletters, interactive television, etc. There is great diversity in my extension program, but in essence it strives to be informed of industry problems and, in turn, provide appropriate education to the industry, mainly through Field Faculty/County Agents. This simple mission employs numerous methods and tools to fit the specific needs of the targeted audience.

A recently completed computer-based key to postharvest diseases of cantaloupe guides users through the diagnostic process.  A beta version of the key is here.

Research Activities

Applied research is an integral part of my overall program and forms an essential part of my extension activities. My research takes the form of short- and long-term projects aimed at the understanding and solution of existing and foreseeable problems in vegetable disease control. Each year several industry-sponsored and non-sponsored disease control methods are evaluated under field conditions in order to provide research-based information on disease control to the industry. Other research, often sponsored by commodity research boards, involves collaborative efforts (involving entomology, horticultural science, weed science, food science, etc.) targeting specific problems of current interest to the research board. Research is typically on fungal diseases because they are the most numerous and typically cause the greatest losses on a consistent basis. However, research on diseases caused by nematodes, viruses and bacteria are also addressed as needs arise. Current areas of research include forecasting cucurbit downy mildew, management of Phytophthora blight in cucurbits, Rhizopus soft rot of sweetpotatoes, Penicillium molds of sweetpotato and sweetpotato souring.

Teaching Activities

PP500 Plant Disease: Principles, Diagnosis and Management.

An applied course in plant pathology designed to enhance understanding and skills in the principles, diagnosis, management, and evaluation of plant diseases. This is an intensive, graduate-level course designed for field professionals such as county agents, agrichemical industry, crop consultants, and graduate students not majoring in plant pathology. Taught in the spring semester of even-numbered years.

Click here for my CV

Recent Publications

• Stanghellini, M. S., Schultheis, J. R. and Holmes, G. J. 2003. Adaptation and market potential of pumpkin cultivars in eastern North Carolina. HortTechnol. 13:532-539.
• Holmes, G. J., and Schultheis, J. R. 2003. Sensitivity of watermelon cultigens to ambient ozone in North Carolina. Plant Dis. 87:428-434.
  Links to watermelon ozone information
• Holmes, G. J. and Clark, C. A. 2002. First report of Geotrichum candidum as a pathogen of sweetpotato storage roots from flooded fields in North Carolina and Louisiana. Plant Dis. 86:695
• Holmes, G. J. and Stange, R. R. 2002. Influence of wound type and storage duration on susceptibility of sweetpotatoes to Rhizopus soft rot. Plant Dis. 86:345-348.
• Stange, R. R., Midland, S. L., Holmes, G. J., Sims, J. J. and Mayer, R. T. 2001. Constituents from the periderm and outer cortex of Ipomoea batatas with antifungal activity against Rhizopus stolonifer. Postharvest Biology and Technology 23(2):85-92.
• Holmes, G. J., Brown, E. A. and Ruhl, G. 2000. What's a picture worth? The use of modern communications in diagnosing plant diseases. Plant Disease 84:1256-1265.
• Holmes, G. J. 2000. Pumpkin fruit rot in North Carolina caused by Phytophthora nicotianae. Plant Disease 84:923.
• Azad, H. R., Holmes, G. J., and Cooksey, D. A. 2000. A new leaf blotch disease of sudangrass caused by Pantoea ananas and Pantoea stewartii. Plant Dis. 84:973-979.
• Holmes, G. J. and Eckert, J. W. 1999. Sensitivity of Penicillium digitatum and P. italicum to postharvest citrus fungicides in California. Phytopathology 89:716-721.
• Mclain, J., Castle, S., Holmes, G. and Creamer, R. 1998. Physiochemical charac-terization and field assessment of lettuce chlorosis virus. Plant Disease 82:1248-1252.
• Holmes, G. J., Jackson, L. F. and Perring, T. M. 1997. Imperial Valley conditions limit Karnal bunt in wheat. California Agriculture 51(3):29-33.
• Holmes, G. J., and Eckert, J. W. 1995. Relative fitness of imazalil-resistant and -sensitive biotypes of Penicillium digitatum. Plant Disease 79:1068-1073.
• Holmes, G. J., Eckert, J.W., and Pitt, J.I. 1994. Revised description of Penicillium ulaiense and its role as a pathogen of citrus fruit. Phytopathology 84:719-727.
• Holmes, G. J., Eckert, J.W. and Pitt, J.I. 1993. A new postharvest disease of citrus in California caused by Penicillium ulaiense. Plant Disease 77:537.

Contact Information

Dr. Gerald J. Holmes
North Carolina State University
Department of Plant Pathology
Box 7616
1413 Gardner Hall
Raleigh, NC 27695-7616

Lab: 2503 Gardner Hall

Tel: (919) 515-9779
Fax: (919) 515-7716
Email: gerald_holmes@ncsu.edu