Disclosed is an apparatus for spreading solid active agents and a method for controlling the apparatus. A boom is pivotably mounted on a vehicle. A sensor arrangement detects an angular velocity and/or an angular position of the boom about a pivot axis. A control unit processes output signals of the sensor arrangement to control signals for an actuator to adjust the boom. The actuator has an active pressure side for each of the two adjustment directions of the boom. Approximately equal pressure levels prevail in the active pressure sides of two actuators operating in opposition or of a double-acting actuator, when the boom is stationary or moves only slightly in relation to the carrier vehicle. A defined differential pressure is adjustable between the active pressure sides of the actuators when the boom is shifted in relation to the carrier vehicle.