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David Rosenberger

David Rosenberger


Cornell University's Hudson Valley Laboratory
(845) 691-7231

My program is focused on discovering and evaluating strategies for managing tree fruit diseases and on delivering information about fruit disease management to fruit growers, extension educators, private consultants, and agrichemical companies. Because of my location at a field station in the Hudson Valley, a portion of my research is dedicated to fruit diseases that are more common in southeastern New York than in other parts of the state. In addition to working on diseases that occur in the field, I also study the biology and management of fungal pathogens that cause apple decays after harvest.

Research Focus

The objective of my research is to determine the best ways of integrating pesticides, biological information on pathogens, genetic resistance to diseases, and IPM techniques into cost-effective and environmentally sound pest control strategies for apples and other tree fruits. My annual field evaluations of fungicides provide apple growers with information they need to control apple diseases at the lowest possible cost. Apple pathogens included in my studies are Botryosphaeria species that cause cankers and summer fruit decays, Colletotrichum species that cause bitter rot, Zygophiala jamaicensis, the cause of flyspeck, and Penicillium species that cause postharvest decays of apples. I am also studying Fabraea leaf spot on pears and fire blight of apples and pears. As part of my extension assignment, I am frequently called upon to identify unusual diseases and contributing factors in development of epidemics in commercial orchards and apple storages. Results of my research and seasonal observations on disease development are available to cooperative extension clientele via publication in Scaffolds Fruit Journal, a Cornell Extension publication that is available on-line at <>.
For the past 15 years, I have conducted extensive research with Penicillium expansum, a fungal pathogen that causes apple decays during storage. Our research has shown that inoculum for P. expansum in apples recycles from year to year on the bulk bins that are used to store fruit after harvest. We are evaluating postharvest handling methods that will minimize both inoculum loads on bins and the transfer of spores to freshly harvested fruit. Improved sanitation is essential both for controlling Penicillium species and because of food safety concerns and regulations.
In a new project, we are assessing impacts of glyphosate herbicide on apple tree health and one the storage life of apples from trees exposed to sublethal doses of glyphosate. Initial results suggest that glyphosate exposure contributes to internal browning, a physiological disorder of apples that develops during storage. We are also attempting to determine if glyphosate's known ability to suppress host plant defense mechanisms may be contributing to outbreaks of various canker diseases.

Outreach and Extension Focus

The objective of my extension programming is to provide useful information about diseases on tree fruits to clientele groups that include fruit farmers, extension professionals, private and corporate consultants working with tree fruit growers, and agrichemical company representatives working on development and sales of fungicides. I collect and compile information from a broad range of sources that include journal articles, oral communications from colleagues and consultants, information from the world-wide web, and results of my own applied research. Information from these sources is integrated into my extension publications and oral presentations at fruit grower meetings and at in-service education events where I present information relevant to understanding the preceding season and preparing for the next season.
Extension articles and presentations during the past year focused on the following subject matter areas:
1. Approaches for controlling apple scab and other diseases in orchards where the most commonly used fungicide group (SI fungicides) are no longer effective due to development of fungicide resistance.
2. Selecting and timing fungicides for controlling flyspeck and summer fruit decays on apples.
3. Using sanitation and fungicides to control postharvest decays of apples during storage and to reduce risks of contaminating fruit with human pathogens.

Teaching Focus

Adult education through cooperative extension fruit schools, in-service training events, field tours, web pages, newsletter articles, and telephone and e-mail inquiries

Awards and Honors

  • 2013 IFTA Researcher Award (2013) International Fruit Tree Association
  • Award of Merit (2005) Northeastern Division of the American Phytopathological Service: The highest service award provided by the Northeastern Division for “Meritorious contributions to the progress of Plant Pathology.”
  • 2001 USDA Group Honor Award for Excellence (as member of the NE-183 Regional Research Project) (2001) The NE-103 Project, “Multidisciplinary Evaluation of New Apple Cultivars, was given the award "For providing timely information to apple growers nationally about the likely success of establishing new apple cultivars in different regions while meeting consumers' desire for diverse and tasty apples." NE-183 was organized in 1994 through the cooperative efforts of Dave Rosenberger at Cornell and Duane Greene at the University of Massachusetts
  • NERA 2000 Award for Research Excellence (2000) Presented to participants in the NE-183 Regional Research Technical Committee

Selected Publications

Journal Publications