Managing Lake Weeds With Aquatic Herbicides

Managing Lake Weeds With Aquatic Herbicides

      Aquatic herbicides are compounds approved for use in lakes and ponds. In 1976 there were 20 compounds deemed “safe” for use in water. Better testing thinned the group to just six.


The First BIG Problem: They don’t seem to work very well

          Professional aquatic herbicide applicators say you can expect about a 75% kill rate at best. The remaining 25% are “more herbicide resistant.” So guess which seeds survive for next years weed crop? The seeds from more resistant weeds! So with each succeeding year, more herbicide is needed to control 75% of the targeted weeds.

          It’s like drug-resistant bacteria is created by repeated exposure to antibiotics. Each generation the surviving bacteria is more resistant until most antibiotics are no longer effective.

          If you live on a lake that’s professionally treated, you’ve probably noticed your herbicide treatment becomes less effective over time.


The Second BIG Problem: How “safe” is safe?

          One of these “safe” compounds, (2,4-D) was part of the notorious “agent orange” used extensively in the Viet Nam War.

          These compounds are alleged to biodegrade quickly and pose no threat to humans or animals, typically after 24 to 48 hours. I’ve watched people swim in our lake within an hour after the “weed killer boat” sprayed their beach.


The only six herbicides approved for lake weeds

2,4-D: acts in 5 to 14 days

Used for watermilfoil and broadleafs, but not narrow-leaf plants like hydrilla.


Diquat: acts in 7 days

Diquat is a contact herbicide that kills the portions of plants it contacts, but is not effective on roots.


Endothall: acts in 7-14 days

Endothall, also a contact herbicide, kills parts of plants it contacts but isn’t effective on roots and rhizomes. Hydrothal 191 has been linked to fish kills.


Fluridone: acts in 30-90 days

Fluridone is a systemic aquatic herbicide requiring long exposure times, used for both hydrilla and Eurasian watermilfoil. It works best when entire water bodies are treated, but not so much in spot treating.


Glyphosate: acts in 7-28 days

Glyphosate is not effective on submersed plants, which begs the question, why is it approved for aquatic use? It’s used primarily for shoreline (emergent) plants.


Triclopyr: acts in 5-14 days

Triclopyr is used for broadleafs like milfoil but not narrow leaf plants like hydrilla.


LakeMat Pro vs Herbicides

LakeMat Pro is chemical-free, safe for people, animals and all aquatic life. LakeMat Pro works immediately, herbicides don’t.

Herbicide applications average $250 every year, or $2,500 over ten years (the length of LakeMat Pro’s warranty) A Large LakeMat Pro is $399 - once.

Herbicides drift, LakeMat Pro targets the exact area you want.

Herbicides deplete oxygen in water, (bad for game fish). LakeMat Pro doesn’t.

LakeMat Pro controls 100% of all weeds in a targeted area, herbicides don’t.

Herbicides do nothing for muck. MuckMat Pro creates a firm lake bottom.


To be fair, LakeMat Pros and MuckMat Pros are meant for individual lakefronts like yours. It’s impractical to use them to treat entire lakes. For large areas, chemical treatment is the most realistic method of controlling lake weeds. 

Large scale herbicide treatment for entire lakes needs to be done by licensed, experienced professionals.



LakeMat Pros are for lake weeds only.

MuckMat Pros are for both lake weeds and a firmer lake bottom.


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