Abstract
This paper describes the development of the forecasting service since 1977 by highlighting the results of various attempts that have been directed at elucidating the origins of primary populations of Spodoptera exempta over eastern Africa. The dates between the last outbreak of each season and the first outbreak of the next season (offseason period) provided a mean number of days for estimating dates of potential onset of primary outbreaks. The development of computer-based data processing routines (database management) and of an expert system for forecasting the occurrence of outbreaks in East Africa are described, as examples of decision-support tools in pest management.