Contact herbicides kill or injure only that part of the plant with which they come in contact. Annual weeds may be killed, but regrowth of perennial weeds from below-ground parts usually occurs following the application of a contact herbicide. Translocated herbicides are absorbed by the leaves or roots of plants and move within the plant. They are needed to kill underground parts of perennial weeds. Selective vs Nonselective.
Nonselective herbicides kill or injure almost all plants.
Fumigants kill most living things in the soil including weeds, weed seeds, insects, and disease organisms. The formulation of an herbicide refers to the material it is carried in or on, and its concentration in that carrier. The same herbicide can be available in more than one formulation. Herbicides in the liquid form can be water soluble, suspensions, or emulsifiable concentrates. All are mixed with water and applied as spray solutions.