Referring to the storage unit that stores occurrence time frame for pest for each identification information of the pests, to identify a first pest which includes at least a portion of the generated predicted period until harvest predicted day of the crop pesticide spraying subject, and refers to the storage unit for storing identification information before harvesting dates and the corresponding pests each pesticide name, a pesticide name corresponding to the identification information of the first pest, the occurrence predicted period of the first pest identify the first of pesticide names according to the long pre-harvest dates from the period from the start date until the end date of the harvest forecast date or the occurrence forecast period, from the harvest forecast date, and before harvest on the first of the pesticide name dates the the day of going back, is calculated as a scatter Date relating to the pesticide name, computer processing to output and said spraying date and the first of the pesticide name is run.病害虫の識別情報ごとに病害虫の発生予想期間を記憶する記憶部を参照して、農薬散布対象の作物の収穫予測日までに発生予想期間の少なくとも一部が含まれる第一の病害虫を特定し、農薬名ごとに収穫前日数及び対応する病害虫の識別情報を記憶する記憶部を参照し、前記第一の病害虫の識別情報に対応する農薬名であって、前記第一の病害虫の発生予想期間の開始日から前記収穫予測日又は前記発生予想期間の終了日までの期間より長い収穫前日数に係る第一の農薬名を特定し、前記収穫予測日から、前記第一の農薬名に関する収穫前日数を遡った日を、当該農薬名に関する散布日として算出し、前記第一の農薬名と前記散布日とを出力する処理をコンピュータが実行する。
