Aquatic Plant Control Methods
First, Identify the Plants You Want to Control
Successful water-plant control begins with correct plant identification.
The 12 plants or plant groups identified in "Aquatic Plant Identification" below are those most likely to become nuisances in Missouri ponds and lakes. Most are found statewide. "Aquatic Plant Identification" in "Related Information" below includes the important identifying features of the plant or plant group.
It is important to remember that these plants do not always cause problems in a body of water. Although they have the potential to grow our of control, they can also coexist peacefully in small numbers with other water plants.
If you cannot identify you nuisance plant from these descriptions, contact a Conservation Department fisheries management district office for help.
Choose the Right Method for the Problem
Once the problem plant has been identified, it can be removed by careful use of herbicides or by various non-chemical methods.
Herbicides are an effective method of control when the plant can be positively identified, the area to be treated is accurately measured and the correct amount of chemical is applied. Before choosing a herbicide, carefully read the label to find out which plants it should be used on and how and when to treat the plants. The label is the final authority. Any use of the herbicide not in compliance with the label is illegal.
Although they provide good control when applied correctly, herbicides have their drawbacks. If used improperly, herbicides can poison not only plants, but aquatic animals as well. The decay of large amounts of dead plants (whether caused by herbicides or other influences) can lower dissolved oxygen concentrations to lethal levels for fish. Chemical control isn't permanent; re-treatment may be necessary and can become quite expensive. And most importantly, we don't yet know the long-term effects of most herbicides on the environment.
For these reasons, we recommend that pond and lake owners also consider non-chemical methods for water plant control. Some of them may require no more effort than herbicide application and are less expensive. These methods include:
- Shading with black plastic
- Weeding and removing new growth
- Stocking grass carp
- Deepening the pond edges
- Drawdown
- Blanketing with sand or gravel
- Eliminating nutrient sources.
Detailed descriptions of these non-chemical control methods and their effectiveness for different plants are given in specific Aquaguides (see "Aquaguides" under "Related Information" below).
Because herbicide brands, regulations and application methods change so frequently, we don't cover them here. If you would like more information on aquatic herbicide use, contact your Conservation Department fisheries management district office for assistance.
