A pesticidal composition comprises a synergistically effective amount of an inhibitor of chitin biosynthesis, type 1 compound and a pesticide selected from N-(3-chloro-1-(pyridin-3-yl)-1H-pyrazol-4-yl)-N-ethyl-3-((3,3,3-trifluoropropyl)thio) propanamide (I), N-(3-chloro-1-(pyridine-3-yl)-1H-pyrazol-4-yl)-N-ethyl-3-((3,3,3-trifluoropropyl)sulfinyl) propanamide (II), or any agriculturally acceptable salt thereof. A method of controlling pests comprises applying the pesticidal composition near a population of pests. A method of protecting a plant from infestation and attack by pests comprises contacting the plant with the synergistic pesticidal composition.