Hygrophila can be removed by raking or seining it from the pond but will reestablish from any remaining fragments and roots.
Aquashade and other non-toxic dyes or colorants. Dyes prevent or reduce aquatic plant growth by limiting sunlight penetration, similar to fertilization. However, dyes does not enhance the natural food chain and may suppress the natural food chain of the pond.
Grass carp will seldom control aquatic vegetation the first year they are stocked. They will consume hygrophila but it is not preferred and will be consumed only after more preferred plants are eaten. Grass carp stocking rates to control Hygrophila are usually in the range of 7 to 15 per surface acre or more. In Texas, only triploid grass carp are legal and a permit from the Texas Parks and Wildlife Department is required before they can be purchased from a certified dealer.
The only active ingredient that has been successful in treating Hygrophila is: flumioxazin (G). E = excellent, G = good
Clipper is a flumioxazin product and comes in a water dispersible granule which must be mixed in water first and then either sprayed or injected. It is a broad spectrum, contact herbicide. Contact herbicides act quickly. Flumioxazin should be applied to actively growing plants and a surfactant will be needed if the herbicide is applied foliage of floating or emergent plants. Water pH needs to be below 8.5 or flumioxazin will rapidly degrade and lose effectiveness.
One danger with any chemical control method is the chance of an oxygen depletion after the treatment caused by the decomposition of the dead plant material. Oxygen depletions can kill fish in the pond. If the pond is heavily infested with weeds it may be possible (depending on the herbicide chosen) to treat the pond in sections and let each section decompose for about two weeks before treating another section. Aeration, particularly at night, for several days after treatment may help avoid an oxygen depletion.
One common problem in using aquatic herbicides is determining area and/or volume of the pond or area to be treated. To assist you with these determinations see SRAC #103 Calculating Area and Volume of Ponds and Tanks.
Many aquatically registered herbicides have water use restrictions. For General Water Use Restrictions click here.
To see the labels for these products click on the name. Always read and follow all label directions. Check label for specific water use restrictions.
Hygrophila is a non-native, very invasive plant and should not be propagated. It is on the federal noxious species list.