A mower combination including an agricultural vehicle and a front mowing unit as well as two lateral mowing units located behind and to the sides of the front mowing unit. Each of the lateral mowing units has a conveyor unit to deposit cut crop as a swath. A control unit receiving a plurality of signals from the combination including signals representing a steering angle of the agricultural vehicle, a speed of operation of each conveyor unit and a lateral displacement of each conveyor unit and comparing them against a predetermined set of values. As required the control unit adjusts the speed of operation of at least one conveyor unit based on this comparison. Swaths produced by towed rear mowing units are controlled, in particular to enable aligned curved swaths to be produced when the mower combination is turned, or to enable a narrow swath to be produced when the mower combination is turned.