Determination of wetness duration for regional plant disease management using a geographic information system

Many fungal plant diseases tend to be associated with the length of wetness duration on foliar surfaces. A Geographic Information System-based model simulation which incorporates 4km resolution weather radar (NEXRAD)-derived precipitation estimates and a variety of other weather and climate data into a plant canopy energy balance-based scheme to estimate wetness duration periods on the 4 km spatial scale over regional areas has been developed and initially tested with promising results. Validation of the simulated leaf wetness duration was carried out at several wheat field sites in Lower Michigan during the 2002, 2003, and 2004 growing seasons. Overall, the system correctly identified wetness conditions from 80-85% of the time during the test periods. While the results suggest satisfactory performance with wetting events associated with precipitation, the simulation also tended to underestimate wetness duration associated with the formation of dew, especially at the onset of the event. This method of monitoring wetness duration over large areas should ultimately enhance the ability of growers to make decisions critical to plant disease management.