Managing Aquatic Plants

While aquatic plants are a natural part of the aquatic ecosystem, it is common for them to become too prevalent and control efforts may need to be implemented. Although aquatic plants can be a problem if they are too abundant, not all aquatic plants are bad. In fact, vegetation in and around ponds is valuable for fish and wildlife habitat and can also help reduce stream bank erosion. When aquatic plants become too prevalent and start to overtake a pond they are referred to as aquatic weeds and some control is necessary. When considering aquatic weed control, remember these two points; prevention is always better than treatment and you must identify the weeds to determine the best option for control.

PREVENTION

Keeping weeds from ever becoming a problem is much better than trying to treat and control them once they become established. Reducing fertilizer runoff into your pond and reducing the amount of silt running into your pond are two of the best prevention strategies. Grass is a great sponge for absorbing fertilizers like nitrogen and phosphorus, helping to prevent these chemical elements from running off from surrounding areas and into the pond. Less fertilizer in the water means fewer weed problems. Maintaining a grass buffer strip around your pond is a great way to manage both of these strategies. The continuous barrier of permanent grass that the buffer strip creates will help intercept soil particles and nutrients as they wash off surrounding fields or lawns. It will also help limit sediment washing into your pond, which causes decreased water depth and increased weed issues. Taking a serious look at what you can do to prevent problems will be significantly cheaper than dredging out a silted-in pond or applying some of the weed controls listed below.

CONTROL

The first step in controlling aquatic weeds is to properly identify the type of weed that is in the pond or at least correctly classify it. Aquatic weeds are classified into four categories; floating plants, submerged plants, emersed plants, and marginal plants. Not knowing the type of aquatic weed you are trying to control can lead to wasted money on products that do not work and delay getting control of the situation. If you are unsure what type of aquatic weeds are in your pond, you are can bring a sample to your local Extension office for identification.

When it comes to aquatic weeds, there are many options for control. These options are briefly described below.

• Mechanical and physical control - Pulling, raking or physically removing weeds. This can be a good way to control small quantities.

• Biological - Grass carp are a non-native, plant-eating fish that will reduce the abundance of some aquatic plants. However, grass carp are not the "fix all" in terms of aquatic plant management because they prefer certain types of plants over others which can limit their usefulness. Grass carp may also increase the occurrence of algae blooms as a result of their redistributing nutrients in the water.

• Herbicides - There are a number of herbicides that control aquatic weeds, but you must match the correct product with the correct weed. Always read the label for specific rates and application instructions, and follow any restrictions that apply.

When managing a pond it is important to remember that prevention and quick action will be the best lines of defense when it comes to aquatic weeds. Nutrient runoff and shallow water systems are major contributors to the growth of aquatic plant life. It is also important to remember that aquatic plants are part of the natural ecosystem and provide many benefits to surrounding aquatic life. For more specific information, refer to K-State Research and Extension’s publication titled, “Aquatic Plants and Their Control.”

[For more information, please contact Adaven Scronce, Diversified Agriculture and Natural Resource agent, adaven@ksu.edu or 620-331- 2690.]