The present invention provides an agricultural and horticultural agent and a method for controlling the same, which exhibits a high effect on plant bacterial diseases caused by bacterial wilt bacteria and the like which are difficult to prevent diseases and which are serious problems at the production site. The present invention is applied to a phenylacetonitrile derivative defined by the following formula [1]. (wherein R 1 represents a hydrogen atom, an alkyl group of C1 to C3 or COCF 3 , R 2 represents a hydrogen atom, an alkyl group of C1 to C3 or a halogen atom, and R 3 and R 5 independently represent a hydrogen atom or a halogen atom. R 4 represents a hydrogen atom, a halogen atom, a phenoxy group or an alkyl group of C1 to C3, and R 6 represents a hydrogen atom)本發明提供一種農園藝用藥劑及使用其之防除方法，該農園藝用藥劑對於難防除病害且於生產現場成為嚴重問題之由青枯病菌等引起之植物細菌性病害顯示較高之效果。本發明施用下述式[1]所規定之苯乙腈衍生物。(式中，R1表示氫原子、C1～C3之烷基或COCF3，R2表示氫原子、C1～C3之烷基或鹵素原子，R3及R5相互獨立地表示氫原子或鹵素原子，R4表示氫原子、鹵素原子、苯氧基或C1～C3之烷基，R6表示氫原子)
