The apparatus includes an endless rope trained over two distally mounted sheaves which define paths spanning either side of said sheaves and means for the continuous application of herbicide to the endless rope. The means for applying herbicide to the rope includes an immersion basin in which portions of the rope are continually pulled through a bath of liquid herbicide. The endless rope is fabricated of synthetic polymeric material, such as nylon, and is made by applying heat to the two free ends until the polymeric material melts and the two free ends are then welded together. Since the endless rope is under some tension, as it traverses the path defined at each end by the sheaves, a second endless rope is tack-welded to the edge of the drive rope at spaced intervals of 1 to 3 inches, again by application of heat to the outer surfaces of the two ropes at the point of contact until the polymeric material is melted to the extent required for welding the two ropes together. In this manner, the second rope is under no tension and therefore can carry herbicide on its outer surface for application to weeds through wiping engagement. The distally mounted sheaves are journalled at the end of a boom which extends transversely of a frame work installed onto a tractor and which has height adjustment means allowing the boom and the endless rope trained thereon to be raised or lowered so that the wetted rope wipingly engages the weeds but does not engage the crop.