PROBLEM TO BE SOLVED: To provide a composition that exhibits a superior controlling effect with respect to plant diseases.SOLUTION: This composition for controlling plant diseases contains a pyridazine compound represented by formula (I) (in the formula, R1 represents a chlorine atom, a bromine atom, a cyano group or a methyl group, and R2 represents a hydrogen atom or a fluorine atom), and exhibits a superior controlling effect with respect to plant diseases.COPYRIGHT: (C)2014,JPO&INPIT【課題】植物病害に対する優れた防除効果を示す組成物を提供すること。【解決手段】式(I)〔式中、R1は塩素原子、臭素原子、シアノ基又はメチル基を表し、R2は水素原子又はフッ素原子を表す。〕で示されるピリダジン化合物を含有する植物病害防除組成物は、植物病害に対する優れた防除効果を示す。【選択図】なし