ESTIMATING WETNESS DURATION ON MAIZE EARS FROM METEOROLOGICAL OBSERVATIONS

The onset and cessation of surface wetness on maize ears were simulate d with six models, using hourly meteorological data, to examine the li nkage between wetness duration and possible forecasting of fungal infe ctions that produce mycotoxins. Two threshold models (using relative h umidity and dew point temperature), one regression model (using humidi ty and wind speed), and three physical models based on the energy bala nce approach, were compared. Also, spatial and temporal variability in wetness duration was measured and simulated at three sites located at distances up to 29 km from a central weather station. The estimated w etness values were compared with observations from cylindrical wetness sensors placed near ear level in maize canopies. The results relate t o potential mycotoxin warning systems and indicate that threshold mode ls can provide reasonable estimates of ear wetness duration in this re gion, that a comprehensive physical model can give superior estimates, and that wetness estimates made from a central weather station data c an be extended to nearby crop fields with a moderate degree of confide nce.