These products should not be used in a pond or lake with an overflow of water. When used carefully according to the label instructions, aquatic herbicides can be safe and effective management tools.
There are a variety of aquatic herbicides approved for treatment of algae. Most contain various active ingredients that include forms of copper. Others may include dyes, endothall or other active ingredients. You can learn more about the various aquatic herbicides and their effectiveness in Management of Aquatic Plants.
Keep the following basic points in mind when considering the use one of these aquatic herbicides:. Many ponds suffer from filamentous algae problems. Where possible, you should strive to reduce nutrients entering the pond to prevent or reduce excessive algae growth.
Chemical treatments for algae are inexpensive and effective but usually must be repeated annually or even multiple times per year to keep algae under control. For further information and publications on pond management in Pennsylvania visit the Penn State Extension website or contact your local Penn State Extension office.
Let's Stay Connected. By entering your email, you consent to receive communications from Penn State Extension. View our privacy policy. Thank you for your submission! Home Filamentous Algae. Filamentous Algae. Different species of filamentous algae exist, but all have a similar growth habit. These algae begin growth in the winter and early spring on the pond bottom. Summary Algae growth is sometimes referred to as a "bloom" because the algae grow so quickly.
Value and Concerns to the Pond Ecosystem All types of algae are important to pond and lake ecology because they serve as food sources for protozoans, insects, and fish. Preventing Filamentous Algae Problems Any overabundant plant growth is a symptom of excessive nutrients phosphorus and nitrogen in the pond water.
Filamentous Algae Control Multiple methods of control are available for filamentous algae that generally fall into physical, biological, or chemical categories. Biological Controls The use of barely straw has been shown to reduce filamentous algae growth in some ponds. Chemical Controls When used carefully according to the label instructions, aquatic herbicides can be safe and effective management tools. Keep the following basic points in mind when considering the use one of these aquatic herbicides: Positively identify the target plant.
All aquatic herbicides have certain plants that they target. It is critical to properly identify the problem plant before you can determine which herbicide s will be effective in controlling it. Herbicide dosages are based on the pond area acres or water volume acre-feet. Improper calculation of pond area or volume may lead to incorrect dosing of the chemical. If the pond area or volume is underestimated, insufficient chemical may be applied resulting in little algae control.
If the pond size is overestimated more common , too much chemical may be applied, resulting in a fish kill and other environmental damage.
Consult the fact sheet titled Pond Facts 4: Measuring Pond Area and Volume for information on how to properly measure pond area and volume. Obtain the required state permit. This permit is required for any chemical application to any private pond or lake. You can also learn more about this permit from the publication entitled Permit Requirement for Use of An Aquatic Herbicide in Ponds Purchase the herbicide. Common herbicides can be purchased at home and farm supply stores, hardware stores, or from various online suppliers.
Follow the herbicide label carefully. This can also occur when large amounts of algae die off all at once, either naturally or after the application of an algaecide. Bacteria consume oxygen while decomposing the dead algae, which can result in dangerously low oxygen levels for fish. The cause of these algal accumulations is an overabundance of nutrients, particularly phosphorus and nitrogen, in the water.
In some cases, nutrients are purposely added to fish ponds to fertilize them. Fertilizers will stimulate the growth of planktonic algae, which are eaten by microscopic animals called zooplankton and insects. These serve as food for such fish as bluegill or golden shiner, which in turn are eaten by larger predatory fish like bass. However, in many cases, the overabundance of nutrients is unintentional, and is caused by runoff from fertilized fields and wastes from livestock, pets, and wildlife such as geese and ducks.
Another common source of nutrient enrichment in ponds is poorly functioning septic systems. Early and regular measures to control these nutrient inputs will help reduce the problems associated with these algae.
Preventing algal accumulations from occurring in the first place is preferable to and less costly than controlling them once they develop and become a problem. The key to effective, long-term control of algal blooms is limiting and reducing the input of nutrients into the pond from the previously mentioned sources. An effective way to increase bank stability and reduce soil erosion and runoff of nutrients is by establishing and maintaining a buffer strip of undisturbed vegetation around the pond.
Buffer strips are defined as vegetated transition zones between natural wetland areas, such as ponds, and adjacent areas that have been modified through human activities. The buffer strip should be at least 15 to 50 feet wide, and the width will depend on the condition of the buffer strip how densely vegetated it is , the value of the pond, and the degree of modification and impact of the adjacent areas. In general, the width of the buffer strip can be smaller when the buffer is in good condition, the pond is of comparatively low functional value, and the adjacent land has a low potential for disturbance.
Buffer sizes should be larger when buffers are in poor condition disturbed soils, poorly vegetated , the pond is of high value, and the adjacent land has the potential to be modified or disturbed. Another preventive measure that can be taken is to steepen the sides of the pond to help eliminate shallow water areas and prevent sunlight from reaching the bottom of the pond where filamentous algae first begin to grow.
A slope for each 3 feet of distance from the shore there is a 1-foot drop is recommended. This is usually not an option with existing ponds, and may not be possible if the pond is used for swimming or by young children. In general, ponds should be at least 3 feet deep to reduce the growth of bottom-growing algae and other potential aquatic plant weeds, and 6 to 7 feet deep if the pond contains fish that will overwinter there.
Proper aeration and good water flow are both helpful in maintaining a healthy aquatic ecosystem and reducing algal accumulations. Without proper circulation and exchange of water, ponds tend to become stagnant. Ponds with inlets and outlets will have fewer problems associated with algae or anoxic absence of oxygen conditions that can lead to fish kills.
It should be noted that nutrients are recycled in ponds, so even after excessive inputs of nutrients have been reduced, it can take a number of years for ponds to fully recover. However, unless long-term steps are taken to control and reduce the input of excessive nutrients, repeated mechanical control or multiple applications of chemicals will be necessary to control algal accumulations. Cultural control refers to strategies that can be used to alter the aquatic environment in such a way that filamentous algae lose their competitive advantage.
One such strategy is called shading, which involves applying non-toxic, water-soluble dye products such as Aquashade to the water early in the growing season to control algae by blocking sunlight needed for growth. These dyes are inexpensive, but multiple applications may be necessary to maintain the required concentration. It is important that these dyes be applied early in the season before the algal blooms appear; once the algae reach the surface, the dye will have no effect.
Dyes are not a form of chemical control because they have no herbicidal properties; they simply color the water. Mechanical control involves physically removing the large clumps of filamentous algae using a rake or net. This method can be effective, but provides only short-term control and will need to be repeated throughout the peak growing season due to the rapid growth rate of the algae.
The removed algae can be composted or used as garden mulch. Applying chemicals is another method to achieve short-term control of algae. However, there are several things to consider when using chemicals to control algal accumulations.
If you use chemicals, it is very important to read and follow the label completely to learn about toxicity, use restrictions, application recommendations, and safety information.
You should remember that pesticide labels are legally binding documents and must be followed. Pesticides are registered for specific uses and to control specific pest species.
It is also important to apply the correct amount of the chemical, and a good estimate of the amount of water in the pond is necessary to do so. The most effect time to apply chemicals is when the algae are beginning to grow spring and not when the algae have become firmly established.
Some chemicals work most effectively at temperatures above a certain threshold and may not provide good control at lower temperatures.
Under these conditions, the decomposition of dead algae may use up all the oxygen, and the risk of a fish kill is high. Because of the rapid growth rate of many algal species, algaecides often do not provide seasonal control of algae. Reapplications may be necessary, but it is better to apply frequent small-scale treatments rather than wait until the algae cover large areas of the pond again.
Finally, some herbicides are toxic to fish and other wildlife, and there is a risk of killing beneficial, non-target plant and animal species. Copper sulfate is a commonly used algaecide, but it can be lethal to fish at concentrations necessary to achieve algal control. Trout, ornamental goldfish, and grass carp are particularly sensitive to copper sulfate, and alternative algaecides should be used in ponds stocked with these species.
Copper is also toxic to invertebrates such as snails and zooplankton, which are important food sources for fish. Both the toxicity and effectiveness of copper sulfate are largely determined by water alkalinity. The greater the alkalinity of the water, the less toxic copper sulfate is to fish, and the greater the concentrations of the chemical that are needed for effective algal control.
Before using any copper treatment, you should measure the total alkalinity of your water. You can purchase your own test kit, or send your water samples to commercial laboratory for analysis. Copper sulfate also becomes more toxic to fish with increasing water temperatures.
For this reason, it is recommended that copper sulfate treatments be avoided during the warm summer months. Filamentous algae are not necessarily good or bad for wildlife or water quality.
Removing filamentous algae can be done by skimming the surface of the water. However, they best way to reduce algae growth is to limit the amount of phosphorous that enters the water.
Phosphorous is a nutrient that fuels algae growth, and it commonly enters waterbodies through storm drains. The best way to reduce phosphorous input is to sweep up the leaves, grass clippings, and fertilizer from your driveway and street and properly dispose of these pollutants.
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