Provided is a method which exerts an excellent effect in controlling a pest in a field of soybean, corn or cotton. A method of controlling a pest (weed, harmful arthropod) in a field of soybean, corn or cotton, including treating a field before, at or after seeding with a seed of soybean, corn or cotton treated with one or more diamide compounds, with one or more PPO-inhibiting compounds selected from the group consisting of flumioxazin, sulfentrazone, saflufenacil, oxyfluorfen, fomesafen, fomesafen sodium and a compound represented by the formula (I):
