ISHS Acta Horticulturae 823: XI International Symposium on the Processing Tomato
DISEASE-WARNING SYSTEMS FOR TOMATOES: WHERE ARE WE IN NORTH AMERICA? |
| Author: | M.L. Gleason |
| Abstract:
Disease-warning systems are decision tools for growers and crop advisers that help assess the risk of a disease outbreak based on one or more factors in the Disease Triangle: the environment (usually weather conditions); the crop; and the pathogen(s). Tomatoes were among the first crops for which disease-warning systems were developed; the FAST model was published in the 1970s, and the TOMcast model became widely used by growers in northern North America over the past two decades. The objective of this paper is to review progress in implementing disease-warning systems, with primary focus on the changes and challenges associated with obtaining weather data for input to these systems. TOMcast is a useful starting point, given its exceptional success in implementation by growers of processing tomatoes in Ontario and the northern U.S. TOMcast was developed by Dr. Ron Pitblado at the University of Guelph’s Ridgetown Campus, Ridgetown, Ontario now the research director with Weather INnovations Incorporated in Chatham, Ontario www.weatherinnovations.com. It targets three diseases: early blight (caused by the fungus Alternaria solani), Septoria leaf spot (Septoria lycopersici), and anthracnose fruit rot (Colletotrichum coccodes). TOMcast’s basic algorithm uses two weather inputs – leaf wetness duration, and the average air temperature during these wet periods - to generate a disease risk rating, called a Disease Severity Value (DSV), each day. Values of DSV range from 0 (no risk) to 4 (high risk). The DSVs are summed; when the sum reaches a threshold (35 in the early part of the growing season after transplanting, and 20 later in the season), a fungicide spray is applied to the crop. Once the fungicide is applied, the DSV total is re-zeroed and begins to accumulate again. Growers typically revert to a weekly fungicide-spray program once the fruit begin to show red color. TOMcast has saved tomato growers an average of 2 to 3 fungicide sprays per season compared to traditional weekly spray programs, with no loss of disease control or crop yield or quality. | |
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