The present invention is: a plant disease control agent containing as an active ingredient a compound represented by formula (1) (in the formula, R1 and R2 represent a hydrogen atom or a methyl group, with the exclusion of cases where R1 and R2 would be identical) or a salt thereof; a plant disease control method for applying the plant disease control agent to a diseased plant; and a novel compound represented by formula (1) or a salt thereof.