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Reconsidering Leaf Wetness Duration Determination for Plant Disease Management

March 2015 , Volume 99 , Number  3
Pages  310 - 319

Tracy Rowlandson, Department of Geography, University of Guelph, Canada; Mark Gleason, Department of Plant Pathology and Microbiology, Iowa State University, Ames; Paulo Sentelhas, Department of Biosystems Engineering – ESALQ, University of Sao Paulo, Brazil; Terry Gillespie, School of Environmental Sciences, University of Guelph, Canada; Carla Thomas, Department of Plant Pathology and National Plant Diagnostic Network, University of California, Davis; and Brian Hornbuckle, Department of Agronomy, Iowa State University, Ames

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Relationships between leaf wetness and plant diseases have been studied for centuries. The progress and risk of many bacterial, fungal, and oomycete diseases on a variety of crops have been linked to the presence of free water on foliage and fruit under temperatures favorable to infection. Whereas the rate parameters for infection or epidemic models have frequently been linked with temperature during the wet periods, leaf wetness periods of specific time duration are necessary for the propagule germination of most phytopathogenic fungi and for their penetration of plant tissues. Using these types of relationships, disease-warning systems were developed and are now being used by grower communities for a variety of crops. As a component of Integrated Pest Management, disease-warning systems provide growers with information regarding the optimum timing for chemical or biological management practices based on weather variables most suitable for pathogen dispersal or host infection. Although these systems are robust enough to permit some errors in the estimates or measurements of leaf wetness duration, the need for highly accurate leaf wetness duration data remains a priority to achieve the most efficient disease management.

Copyright © 2015 The American Phytopathological Society