Casoron 4G Herbicide is a pre-emergent only and will not kill anything actively growing. We would recommend using Fertilome Brush Killer and Stump Killer. For the roots, apply the undiluted product with a paintbrush to completely cover the fresh-cut surface. Here is the link for the product:
http://www.domyownpestcontrol.com/fertilome-brush-killer-and-stump-killer-p-1545.html
Please let us know if you have any additional questions.
Casoron 4G Herbicide is not labeled for evergreens. We recommend using Resolute 65 WG Prodiamine Herbicide (Generic Barricade) for pre-emergent control. We also recommend you contact your local Master Gardener for a specific recommendation that won't harm the trees. They can be reached by clicking on the link below and selecting your state and county. Please let us know if you need help locating the product that they recommend or if you would like to place an order.
http://www.csrees.usda.gov/Extension/
Casoron 4G Herbicide is a dry granule applied with a granular spreader, then watered in as directed on the product label. It would not be mixed with water first, as it is not a water-dispersible granule suitable for spraying.
We would advise waiting till Casoron 4G Herbicide has completely dried before letting pets back in the area typically after 4-6 hours. The product is also not labeled to be used around lake, ponds, or rivers. We would recommend staying 25 ft away from any bodies of water and do not water in to the point of runoff.
Unfortunately we do not have a product that will control for up to 2 years, but we do carry Eraser Max Super Concentrate Herbicide that will prevent regrowth for up to a year. It will kill any weeds that are actively there since it is a non-selective post, but also prevent regrowth of weeds just like Casoron 4G Herbicide
There is not a liquid Casoron option available only the Casoron 4G Herbicide in the granular formulation. We do offer other liquid pre-emergent herbicides here on our site. Please check the label of the item to be sure they fit your needs.