Soil residual herbicides have again become a necessary part of a weed control program and they can do some great things — when they work, but without soil moisture for incorporated herbicides or activating rainfall or overhead irrigation for pre-emergence herbicides, they do not work.
My main concerns right now are barnyardgrass control in rice and pigweed control in soybeans. Most other weed problems we can catch back up with even if they have gotten out of hand. On those two, however, if they are not under control early, there is often a run-away situation.
After the delayed pre-emergence herbicides, the next step will be early postemergence herbicides. With those, the objective is to kill any weeds that have emerged, and also to get some additional residual into the program.