A modular element for the manufacturing of an arm or of an arm segment of a spray bar provided with spray nozzles, including a first profile determining a longitudinal housing open downwards and at each of its longitudinal ends. A reinforcement is disposed above the first profile in such a way that the respective longitudinal axes of the reinforcement and of the first profile belong to the vertical plane P of longitudinal symmetry of said modular element. A plurality of stiffeners longitudinally connect at least the first profile and the reinforcement to each other, and two plates are disposed at one of the longitudinal ends of said first profile and laterally connect at least the longitudinal ends of the first profile and of the reinforcement to each other.
