Abstract: Disclosed are pyrimidine derivatives represented by general formula (I) ##STR1## wherein X represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a haloalkyl group or a cyano group; Y.sup.1 represents an alkyl group, a cyanoalkyl group, an alkoxy group, an alkenyl group substituted with a hydroxy group and a halogen atom, an alkynyl group which may be substituted with a hydroxy group, a methylamino group, an alkoxyalkyloxy group, an alkylthioalkyl group or a group of the formula --CH.sub.2 OR.sup.1 where R.sup.1 represents a hydrogen atom, an alkyl group, an alkenyl group or an alkynyl group; Y.sup.2 represents a halogen atom, an alkyl group or a haloalkyl group; R represents a hydrogen atom, an alkyl group, a nitroso group, an alkoxyalkyl group, an alkoxyalkyloxyalkyl group, an alkenyl group, an alkynyl group, a formyl group or an alkylthioalkyl group, with the proviso that (a) when Y.sup.1 represents an alkynyl grop or when Y.sup.1 represents an alkoxy group and Y.sup.