Agri-horticultural pest control compositions having outstanding control effect on pests, in particular, agri-horticultural pests, which comprise as active ingredients one or more 4-(3-butynyl)aminopyrimidine derivatives represented by the general formula [I], namely,where R1 is typically selected from among:a) phenylc) -SiR5R6R7 (R5, R6, and R7 which may be the same or different represent a linear or branched alkyl having 1-6 carbon atoms, a linear or branched haloalkyl having 1-3 carbon atoms which is substituted by one halogen atom, a linear or branched cyanoalkyl having 1-3 carbon atoms which is substituted by one cyano group, and phenyl)d) hydropgen atomR2 typically represents a hydrogen atomR3 typically represents a hydrogen atomR4 represents a hydrogen atomand one or more agri-horticultural pest control compounds selected from among agri-horticultural antimicrobial compounds, say, multi-site contact active compouns, nucleic acids synthesis inhibitory active compounds, mitosis and cell divesion inhibitory active compounds, and/or agri-horticultural insecticidal, miticidal or nematicidal compounds, say, acetylcholinesterase inhibitors, GABA-gated chloride antagonists, and sodium channel modulators. Since the 4-(3-butynyl)aminopyrimidine derivatives and the existing antimicrobial active compounds and/or insecticidal active compounds are used in admixture, the 4-(3-butynyl)aminopyrimidine derivatives which are useful as pest control agents, particularly as agri-horticultural pest control agents, need be used in smaller amounts and yet their antimicrobial or insecticidal activity can be improved.
