Contact II is perfect for this application. It can be used both in ponds and on land and when mixed at 16 ounces per gallon of water (for land use), it will give a non-selective kill of all vegetation it contacts. Because it is inactivated upon contact with soil, it will not spread out and kill more vegetation than you wanted to – it will only kill where you put it. Products like Contact II are sometimes called “liquid trimmers” due to their ability to provide precision results. NOTE: areas treated with Contact II should not be watered (or rained on) for 24-36 hours after application, so be careful about the weather when planning to apply Contact II.
The difference is that a non-selective weed killer will eliminate ALL the vegetation you apply it to, while a selective weed killer will be selective about what it kills. Selective weed killers are good for killing broadleaf weeds (like dandelions) without killing the grass areas that the weeds are growing in. To know what a broadleaf is compared with other vegetation, look at a leaf. You will see a branched out vein structure in the leaves, but in grasses the vein structure runs parallel.