Decoys have their place throughout the season. In the early season, well before the onset of the rut, doe decoys are effective in encouraging otherwise reluctant deer to emerge from cover before legal light disappears. In the immediate pre-rut and during the rut, doe decoys continue to encourage deer—both does and bucks—to show themselves within legal shooting hours.
Buck decoys are most effective through the early rut and in the heart of the rut, when a buck’s naturally aggressive tendencies compel him to challenge any potential competitors for breeding rights. In my experience, this behaviour wanes in the late rut, when bucks are highly mobile in search of the last receptive does.