A supplemental label for Callisto has been posted on CDMS that allows preemergence or postemergence applications for broadleaf weed control in oats. This label is for oats grown for seed, not for oats underseeded with alfalfa. The preemergence rate is 6 fl oz/a and the postemergence rate is 3 fl oz/a. Postemergence applications need crop oil or surfactant to control emerged broadleaf weeds. The addition of ammonium sulfate or 28% UAN will improve weed control, but may also increase the risk of injuring the oats. The preemergence application should provide greater crop safety than postemergence applications. The spectrum of weed control will be the same as when Callisto is used in corn.