Mechanical/Physical Control Options
Water lettuce can be removed by raking or seining it from the pond’s surface.
Biological Control Options
Click here if you would like to read about possible insect control measures.
Chemical Control Options
The active ingredients that have been successful in treating water lettuce include endothall (G), diquat (E), glyphosate (G), imazapyr (G), penoxsulam (E), bispyribac (E), and flumioxazin (E). E = excellent, G = good
Aquathol K, and Aquathol Super K are dipotassium salts of endothall and comes in both liquid and granular formulations. The Aquathol K liquid formulation has been effective on water lettuce. Contact herbicides act quickly and kill all plants cells that they contact.
Reward is a liquid diquat formulation that has been effective on water lettuce. It is a contact algaecide and 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.
Rodeo, Aquamaster, Eraser AQ, Touchdown Pro, and AquaNeat are liquid glyphosate formulations and have been effective on water lettuce. 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.
Galleon is a liquid penoxsulam formulation. It is a broad spectrum, 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. Galleon may be sprayed directly onto emergent plants or applied directly into the water. Galleon should not be applied in areas where it will be diluted rapidly. Galleon will take 60-120 or longer to completely kill the target plants. Galleon will need a surfactant for foliar and exposed sediment applications.
Tradewind is a bispyribac-sodium product and comes in a water soluble power formulated in packets. Each packet should be mixed in water first then sprayed or injected. It is a selective, 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. A surfactant will be needed if the herbicide is applied foliage of floating or emergent plants.
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 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 (See General Water Use Restrictions).
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.
It is against Texas law to possess water lettuce. It should not be transported or allowed to spread.