Water Pennywort

Control Options

Cultivation Options

Description of This Plant

Control Options

Mechanical/Physical

Water pennywort can be cut and the roots can be dug up but physical control is difficult because it can reestablish from seeds or remaining roots.

Biological

There is no known biological control for water pennywort, although goats are known to forage on many types of emergent vegetation.

Chemical

The active ingredients that have been successful in treating water pennywort include 2,4-D (G), diquat (G), triclopyr (G), glyphosate (G), and imazapyr (E). E = excellent, G = good

Navigate and Aqua-Kleenare 2,4-D compounds that have been effective on water pennywort. 2,4-D compounds are systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides.

Reward is a liquid diquat formulation that has been effective on water pennywort. It is a contact herbicide. Contact herbicides act quickly and kill all plants cells that they contact. A non-ionic aquatically registered surfactant (see the label) will have to be added to the Reward solution for good results.

Renovate is a liquid triclopyr formulation that is effective on water pennywort. It is a selective broadleaf, systemic herbicide. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides. An aquatically registered surfactant (see the label) will improve the effectiveness of triclopyr.

Rodeo, Aquamaster, Eraser AQ, Touchdown Pro, and AquaNeatare liquid glyphosate formulations and have been effective on water pennywort. These are broad spectrum, systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides. An aquatically registered surfactant (see the label) will have to be added to the glyphosate solution for good results.

Habitat contains the active ingredient, imazapyr, which inhibits the plant enzyme AHAS (acetohydroxyaced synthase). Habitat is a systemic herbicide that is effective on post-emergent floating and emergent aquatic vegetation. Imazapyr is effective at low-volume rates and does not contain heavy metals, organochlorides or phosphates, making it safe to humans and livestock. Habitat requires the use of a spray adjuvant when applying on post-emergent vegetation.

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 control the 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.