If the grass has any significant size you should tank mix a propanil based product. In fact, Stam increases the flexibility and this is why Stam plus these residual herbicides are more popular than true delayed PRE programs. Compared to typical rice herbicides, Prowl is a bargain and is probably the most popular delayed PRE herbicide. The only limitations are that broadleaf weeds will be released and that Prowl can fail is there is too much rainfall or flushing or if the flood establishment is delayed. Bolero delayed PRE is a unique weed control program.
Bolero requires wet conditions for optimal activity.
But there are a few Missouri growers who use the Bolero delayed pre, flush regularly and achieve good weed control. Bolero is a very good sprangletop herbicide, controls most other grasses and also controls a number of aquatic weeds. The major limitation with a Facet delayed pre program is sprangletop. Facet has virtually no activity on this weed. Finally, to really confuse things- it's popular to mix delayed PRE herbicides together in any possible combination.