Pyridazine compound and use thereof

A compound represented by formula (3):

• wherein,
• R2 represents a C1-C4 alkyl group;
• R3 represents a halogen atom, a nitro group, a cyano group, a C1-C4 alkyl group optionally substituted by at least one halogen atom, a C1-C4 alkoxy group optionally substituted by at least one halogen atom or a C1-C4 alkylthio group optionally substituted by at least one halogen atom;
• m represents an integer of 0 to 5;
• provided that, when m represents an integer of 2 or more, each of R3s is same or different;
• R4 represents a halogen atom, a nitro group, a cyano group, a C1-C4 alkyl group optionally substituted by at least one halogen atom or a C1-C4 alkoxy group optionally substituted by at least one halogen atom;
• R5 represents a halogen atom, a nitro group, a cyano group, a C1-C4 alkyl group optionally substituted by at least one halogen atom or a C1-C4 alkoxy group optionally substituted by at least one halogen atom;
• n represents an integer of 0 to 4;
• provided that, when n represents an integer of 2 or more, each of R5s is same or different.