Post-emergent herbicides are another form of aquatic herbicide that work to control weeds after they have already germinated. These products travel down the plant stalk and into the root system to kill the weed. So to achieve control with post-emergent herbicides, weeds must be actively growing when applied. Post-emergent herbicides should be used on a case-by-case basis, and it is important to read label instructions carefully before application, as different post-emergent herbicides may require specific rates or treatments in order for them to be effective. Additionally, post-emergents should not be used near bodies of water unless otherwise stated on the label, as some post-emergents can leach into lakes or other bodies of water.