How to Control Submerged Weeds

Submerged plants have stems and leaves that grow under water. Eurasian milfoil, hydrilla, and curly-leaf pondweed are common examples of invasive submerged weeds that should be managed. Some submerged weeds have flower spikes that emerge an inch or two above the water and/or leaves that float on top of the water, like a few varieties of pondweeds. To identify specific plants growing in the water, check out our Aquatic Plant Identifier.

Manual/Mechanical Control:

Submerged plants can be effectively removed manually by raking or pulling the entire plant and root system from the pond or lake bed. New growth of pondweeds and others can occur from root fragments or seeds. Milfoil, Hydrilla, and Coontail are examples of plants that re-grow from fragments, so a messy rake job can result in spreading of the plants. If done carefully, manual removal of nuisance submerged weeds is a responsible aquatic plant management technique.

Herbicide Control:

There are a wide variety of submerged weeds, and multiple herbicide control options, depending on the target species. #1-4 are broad-spectrum and #5 is selective.

1. Dibrox (for ponds and lakes) – Liquid that controls many submerged or floating weeds (for ponds or lakes). Dilute and spray.
2. Spritflo (for ponds with no outflow) – Liquid that controls many submerged and some floating weeds (for ponds). Pour it in and it spreads throughout water body.
3. Hydrothol (for lakes) – Granules control many submerged weeds. Broadcast granules evenly.
4. Flumigard (for ponds and lakes) – Liquid or granules control many submerged and most floating weeds. Dilute liquid or dissolve granules and spray over weeds.
5. 2,4-D (for ponds and lakes) – Selective liquid controls Water Shield, Milfoil, Coontail, and certain other plants. Dilute and spray.

To determine the best approach for specific plants, visit our Weed Control page.