A customer recently contacted us regarding lake weed control. Below is his question and our response.
I live on a fresh water lake, our beach is sand covered with a little mud. It’s a gradual slope out about 200’ to a depth of 15’...I have used Aquacide Pellets before with some success but my question is if there is a product I can apply now while the lake is out that will kill the weed roots? The lake is all the way out and the bottom is exposed. Not frozen, just damp?
There are two main types of aquatic weed killer, systemic and contact.
Systemic aquatic herbicides (Aquacide Pellets, Fluridone Liquid & Shore Klear/Aqua Neat) are absorbed into the lake weed as it draws in sunlight and nutrients to grow larger.
Contact aquatic herbicides (Aquathol Super K Granular, Hydrothol Granular & Harvester Liquid) simply kill the lake weed foliage they make good contact with and do not directly affect the root system. Aggressive repeat treatment with a contact product may cause the weeds to die completely.
To answer your question, lake weeds need to be visible and actively growing for either herbicide to be effective. The best option for exposed shoreline weeds is a systemic herbicide for emergent weeds (Shore Klear/Aqua Neat) or physical removal with a Lake Rake. Yes, physical removal is labor intensive, however anything you do physically to remove lake muck and shore weeds will reduce nutrients in the pond. Once the water level rises, there will be less nutrients and less new growth in the pond.
Once water returns to the pond, apply a systemic herbicide (Aquacide Pellets or Fluridone Liquid) at the first sign of new growth. Normally one early spring treatment is all you need.
If some weeds are still present after treatment with a systemic herbicide, follow 30 days later with a contact herbicide (Aquathol Super K Granular, Hydrothol Granular or Harvester Liquid).
Please email or call me if you have questions or need additional information.
Please feel free to email me or post questions you may have and I will respond accordingly.