A boom segment is provided for a spray boom assembly configured to carry a spray system of a work vehicle. The boom segment includes a truss panel formed as a unitary structure composed of fiber composite material and configured to support components of the spray system. The truss panel includes a panel wall extending along a length of the truss panel and defining an upper beam, a lower beam, and an array of braces spaced apart and extending diagonally and seamlessly between the upper beam and the lower beam to define a series of truss openings therebetween and a plurality of rigidifying ribs formed integrally with and projecting at an angle from the panel wall.