1. A synergistic herbicidal composition comprising (A) at least one component selected from the group consisting of flazasulfuron, nicosulfuron and their salts, and (B) pyroxasulfone or a salt thereof. The composition according to claim 1, in which when mixing the ratio of the amount of (A) to the amount of (B), i.e. mass ratio (A) :( B) is from 27: 1 to 1: 50.3. The composition of claim 1, wherein (A) is flazasulfuron or a salt thereof； (B) represents pyroxasulfone or a salt thereof； and when mixing, the ratio of the amount of (A) to the amount of (B), i.e. mass ratio (A) :( B) is from 8: 1 to 1: 30.4. The composition of claim 1, wherein (A) is nicosulfuron or a salt thereof； (B) represents pyroxasulfone or a salt thereof； and when mixing, the ratio of the amount of (A) to the amount of (B), i.e. mass ratio (A) :( B) is from 2: 1 to 1: 15.5. A method of controlling or inhibiting an undesired plant, comprising applying to the undesired plant or to the location of the undesired plant synergistically herbicidally effective amounts (A) of at least one component selected from the group consisting of flazasulfuron, nicosulfuron and their salts, and (B) pyroxasulfone or its salt. 6. The method according to claim 5, in which (A) is applied in an amount equal to from 10 to 300 g / ha, and (B) is applied in an amount equal to from 7.5 to 500 g / ha. The method according to claim 5, in which (A) is flazasulfuron or its salt； (B) represents pyroxasulfone or a salt thereof； (A) apply in an amount equal to from 10 to 100 g / ha； and (B) is applied in an amount equal to from 12.5 to 300 g / ha. The method of claim 5, wherein (A) is nicosulfuron or a salt thereof； (B) represents pyroxasulfone or a salt thereof； (A) applied to1. Синергетическая гербицидная композиция, содержащая (A) по меньшей мере один компонент, выбранный из группы, включающей флазасульфурон, никосульфурон и их соли, и (B) пироксасульфон или его соль.2. Композиция по п.1, в которой при смешивании отношение количе
