199 IDŐJÁRÁS Quarterly Journal of the Hungarian Meteorological Service Vol. 111, No. 2–3, April–September 2007, pp. 199–208 Input data representativeness problem in plant disease forecasting models Lalić Branislava 1* , Dragutin T. Mihailović 1 , Slavica Radovanović 2 , Jelica Balaž 1 and Ana Ćirišan 1 1 Faculty of Agriculture, University of Novi Sad, Dositej Obradović Sq. 8, 21000 Novi Sad, Serbia 2 Hydrometeorological Service of Serbia, Kneza Viseslava 66, Belgrade, Serbia E-mails: branka@polj.ns.ac.yu; guto@polj.ns.ac.yu (Manuscript received in final form February 13, 2007) Abstract—In this paper, the LAPS surface scheme and the BAHUS biometeorological model are shortly described. LAPS has been applied for within-crown microclimate simulations in an apple orchard at experimental site Rimski Sancevi in the northern part of Serbia. The simulated values of leaf wetness duration, air temperature, and relative humidity within the tree crown are compared with the data measured in the orchard during the 2003 apple growing season. On the basis of biological and meteorological inputs coming from the outputs of either the automatic or the climatological weather station, or LAPS, BAHUS was applied in order to give the messages on occurrence of apple scab and fire blight diseases. BAHUS outputs obtained for the three meteorological input data sets are compared with time and intensity of infections observed in the apple orchard. Key-words: agrometeorological modeling, SVAT models, data representativeness, diseases forecasting 1. Introduction The first recorded agrometeorological forecast was made by Réaumur in year 1735 (Réaumur, 1735). This pioneer work was related to the forecast of phenological development for several crops based on thermal sum concept. Over almost three centuries, an “army” of scientist coming from different meteorological and agricultural communities has invested a great deal of effort * Corresponding author