Disease Models for Open Field and Covered Production
For the prediction of diseases in strawberry cultivation the measurement of free moisture is essentially. Therefore, the determination of leaf wetness showed to be a very good indicator for free moisture, which is caused by rain or dew. It is assumed, that rain or dew have a equal distribution to all plant parts which are air exposed.
Production in green houses or in plastic tunnels is different, because rain or dew does not occur on plants. Here, free moisture is mainly caused by sprinkler irrigation and/or by condensation. Irrigation under dry conditions will not lead to a long leaf wetness period. Whereas irrigation in a water saturated air will lead to a longer leaf wetness period. By this reason the models indicated for covered production will determine both, water saturation determined by leaf wetness and by the dew point. If the values of the actual temperature and relative humidity reach the dew point the occurrence of free moisture is assumed.