A. Mother Nature has four principal methods of plant control: insects, disease, freezing temperatures, and drought. Unfortunately, weeds are be definition resistant to insects and disease, temperatures along the Gulf Coast are not likely ever to freeze over the surface of your pond, and drought is not an issue unless you are willing to manually drain the pond and hope that El Nino will not fill it again. Therefore, you will have to take matters into your own hands, and if your pond is small enough, you can do this literally. Just wade on in, scoop out the floating weeds, and hand pull the rest. They make a nice addition to your compost pile. Mowing also works well on shoreline weeds. |
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For larger, earth-bottom ponds, you might consider a form of biological control, the sterile triploid grass carp. These fish have a voracious appetite for pond weeds, consuming 30 to 40 percent of their body weight in weeds every day during warm weather. However, grass carp that have escaped into local creeks and Galveston Bay have played havoc with sensitive wetland areas and their use is strictly regulated by the Texas Parks and Wildlife Department. The Department, or your county Extension office, can send you additional information and the application for a permit to stock the carp, but be aware that if your pond drains into a creek, you will most likely be denied.
Chemical control is possible with herbicides listed for aquatic use if you can accurately identify the weeds you need to control. The four main groups of weeds are algae, submersed plants, floating plants, and immersed (leaves above the water surface) plants. Contact the county Extension office for detailed information to help identify your plant problem more precisely, and up-to-date recommendations on which herbicide to use and how to use it.
Usually, it is advisable to wait until the weeds are actively growing, to use the least toxic product available, and to make repeat applications as necessary. If your pond really is "full" of weeds you will want to treat them in sections, 1/4 to 1/3 of the pond at a time. As the weeds die back, they take oxygen out of the water which can result in a fish kill if you treat too many at one time. If you have a fountain, turn it on once the foliage begins to brown to help keep the water aerated.
Remember, the goal is to control the weeds, not to "nuke" the pond. Algae, especially the phytoplankton species, is an important part of your pond's food chain. Floating plants reduce the amount of sunlight entering the water, reducing algal blooms and even cooling a small pond in the summer. Submerged plants add oxygen to the water, and together with immersed plants, provide habitat for small aquatic animals. So treat for the excess, and then sit back to enjoy all the fish, frogs, and waterfowl that want to share your pond with you.