I’ve had several questions this past week on managing ponds, and it is getting to the time in the year where all of the weeds, land or aquatic, are coming to the surface (literally) and land owners/renters begin to panic. Everyone wants to have a good looking pond for whichever recreational activity you choose to use your pond for.
Aquatic plants are generally divided into four groups for management purposes. These groups are the algae, floating plants, submerged plants, and emergent plants. Algae are very primitive plants. Some algae are microscopic, others are thin and stringy or hair-like, while still others are large and resemble higher plants but without true roots.
True floating plants are not attached to the bottom. Floating plants come in sizes from very small (duckweed) to over a foot in diameter (water hyacinth). Most have roots that hang in the water from the floating green portions.
Submerged plants are rooted plants with most of their vegetative mass below the water surface, although some portions may stick above the water. One discerning characteristic of submerged plants is their soft stems, which is why they do not usually rise above the water’s surface.
Emergent plants are rooted plants often along the shoreline that stand above the surface of the water (cattails). The stems of emergent plants are somewhat stiff or firm. Many ponds have more than one type of aquatic plant, and care must be taken to identify all the aquatic plants inhabiting the pond. Some pond plants may be beneficial to local or migratory wildlife, and therefore, may want to be encouraged or at least not eliminated.
It is very important to correctly identify the weed you have before you try to take the next step of eliminating the plant. This is sometimes a little more difficult than one would think because some weeds tend to vary depending on environment. Any time there is a question the extension office is always more than happy to help identify a plant for you.
Once you have identified that weed, the next step is herbicide. I often get questions on if herbicides will kill fish in a pond. Aquatic herbicides should not kill fish if used at labeled rates. It is very important to read and understand the herbicide labels. The label is the LAW. When used at label rates, the registered aquatic herbicides are not toxic to fish and would not have been registered by U.S. EPA (Environmental Protection Agency) if they were.
A main reason fish often die 2 to 5 days after an herbicide treatment is because of oxygen depletion. The decomposing/rotting plants (actually the billions of bacteria and fungi consuming them) simply take up most of the available dissolved oxygen, and the fish suffocate. This problem is the reason that most treatments recommend only applying the herbicide to 1/4 or less of the pond at a time and allowing 10 to 14 days between applications. The limited application area and extended time period allow the vegetation to rot without reducing dissolved oxygen concentrations below critical levels to the fish and other aquatic organisms.
A pesticide applicator’s license may or may not be needed to purchase and apply aquatic herbicides. Most of the registered aquatic herbicides can be purchased without a pesticide applicator’s license. Aquatically registered herbicides may be purchased at local businesses that sell farm supplies and chemical.
It is best to apply these herbicides in the morning on sunny, low wind days (to reduce possible chemical drift). Sunny mornings increase uptake of the herbicide because the plant is actively metabolizing and therefore increases its effectiveness. It is best to apply herbicides early while the plants are actively growing (they uptake the herbicide better) and before the biomass of vegetation has built up. Once summer temperatures set in and vegetation biomass has peaked out (we are getting very close!), it is extremely risky to treat the vegetation because of the likelihood of oxygen depletion.
If the label states that surfactants are needed, then one (or more) should be added. Make sure to use only an aquatic registered surfactant – many are available. Short for ‘surface active agent’ – a surfactant is a compound that reduces the surface tension of water, thereby permitting it to penetrate a material more easily or to spread over the surface. Always check the label.
Educational programs of the Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.
- Farm to table – July 16 7-9 p.m. at Fair Grounds
- Palmer amaranth field day – July 12 at 858 Hazelwood Road, Barlow KY 42024
- Corn, soybean and tobacco field day – July 24 UK research farm Princeton, Ky.