If you use Casoron pre emergent herbicide in your beds can you tell me where you use it and how well it has worked for you. Do you have to dig under the mulch or does it provide a barrior broadcast on top of it? I have my licnece and have read the label. Just signed a commercial with lots and lots of mulch beds. Pre-m, round-up, or hand tiller. ( i mean the hand tool with three prongs) This is Canada so suggesting a lot of others may not help me.