Barricade and Dimension are actually in the same class of herbicides which means they work with the same mode of action for most of the same weeds and there would be no benefit to using each so close together. It is more recommended to rotate each season between different actives to prevent resistance buildup. Typically Dimension is more recommended in the spring as it is best for crabgrass and has early post emergent control of it as well (in a separate application). Using the max rate in one season would prevent you from using either in the fall which is also a recommended time for pre-emergent applications for winter/spring weeds.
We would not recommend applying herbicides such as Dimension 2EW Herbicide during active precipitation or after rainfall. The manufacturer recommends to water this product in within 24 hours after application, so it would be best if you apply it the day before rain is expected again if you do not manually water the product in for pre-emergent applications.
Yes, if you have used the maximum rate of prodiamine for the year you may use Dimension 2EW Herbicide since they are two different actives. You can either spot treat or blanket spray. We would recommend blanket spraying as it would give you better results for pre-emergent control.
