Aquatic Weeds and Algae
Not all aquatic weeds are bad. If fact, vegetation in and around ponds is valuable for fish and wildlife habitat. It can also help reduce stream bank erosion. But when vegetation grows too abundant it becomes weeds and some control is necessary.
When considering aquatic weed control, keep these two points in mind:
- Prevention is always better than treatment
- You must identify the weeds before you consider control
Prevention
Keeping weeds from ever becoming a problem is much better than trying to treat and control them once they become established.
The two best strategies for prevention include:
- Reduce fertilizer runoff into your pond and
- Reduce the amount of silt running into your pond.
Grass Buffer Strips
A great option for controlling both issues is to maintain a grass buffer strip around your pond. This continuous barrier of permanent grass helps to intercept soil particles and nutrients as they wash off surrounding fields or lawns. It also helps to limit sediment washing into your pond, which causes shallow slopes/water depth and more weed issues.
Grass is also a great sponge for absorbing fertilizers like nitrogen and phosphorus. It helps prevent these chemical elements from running off from surrounding areas and into the pond. Less fertilizers in the water means less algae and other weed problems.
Take a serious look at what you can do to prevent problems. It will be significantly cheaper than dredging out a silted-in pond or applying some of the weed controls listed below.
Controlling Aquatic Weeds in Ponds
The first step in controlling algae and other aquatic weeds is to properly identify the weeds in the pond. If you miss this step, you'll likely waste money on products that don't work and delay getting control of the situation.
A great source for identifying and managing aquatic plants is the website Aquaplant: A Pond Manager Diagnostic Tool from Texas AgriLIFE Extension and Texas A&M University.
You are can also bring a sample to our local Extension office for identification.
Options for Pond Weed Control
• Mechanical and physical
Pulling, raking or physically removing weeds is a good way to control small quantities.
• Biological
Grass carp (also known as white amur), are a non-native, plant-eating fish that will reduce the abundance of some aquatic plants. However, grass carp are not the "silver bullet" in terms of aquatic plant management given their preferences for specific types of plants that can limit their usefulness. Grass carp may also increase the occurrence of algae blooms as a result of their redistributing nutrients in the water. Check out this publication Using Grass Carp to Control Aquatic Plants from Ohio State on the full range of facts on grass carp
Purchase grass carp through aquaculture producers associated with the Kansas Aquaculture Association.
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 follow any restrictions that apply.
Each of these options is discussed in a very good K-State Research and Extension publication called Aquatic Plants and Their Control. Select the options that work best for your situation.
Other resources
- Blue-Green Algae
- Identification and Management of Blue-green Algae in Farm Ponds
- Toxicologist urges people, pets to beware of blue-green algae
- Nuisance Aquatic Plants in Missouri Ponds and Lakes (A Photo Identification Guide)
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