Testing and management options for blue-green algae in farm ponds
Many areas of Kansas have been extremely hot for extended periods this summer. Couple the heat with abundant sunlight and conditions are ripe for the development of blue-green algae in farm ponds. Blue-green algae produce toxins that pose a health risk to livestock that use these ponds for drinking water.
This article explains how to send a water sample to be tested and management options for ponds with blue-green algae blooms. A companion article in this eUpdate discusses the development of blue-green algae, the risks to livestock, and tips for visual identification.
Management options for infected ponds
If a pond contains a harmful algal bloom, there are few choices for the livestock owner. Several options are discussed below:
- Provide an alternative water source for livestock. Using well water may necessitate drilling a well, which is not always an option. It takes time to have the well drilled, have the water tested, and set up a pumping unit and stock tank. Hauling water is expensive and time consuming but may be the only feasible way to supply clean water to livestock. Animals can be moved to another pasture with clean pond water or access to another water source. The duration of harmful algal blooms is difficult to predict and is influenced by weather conditions. The condition may last from days to months.
- Use copper sulfate to kill the blue-green algae. This chemical, however, will also kill competing organisms such as green algae, which help keep blue-green algae in check. Copper does not break down, but remains in pond sediment, where it can affect pond ecology for many years. Sheep are sensitive to copper. Hazardous levels of copper may remain in water and plants growing near treated ponds for several years after treatment. As blue-green algae die after the chemical application, toxins are released from the organisms and are dispersed more widely making the possibility of toxicity even higher. Keep livestock and other animals away from the treated water source. It is recommended to test the water 1-2 weeks after treatment to ensure the toxins have broken down before reintroducing livestock to the area.
- Reduce the amount of sunshine available to the blue-green algae. Increasing turbidity (cloudiness of the water) through stirring up bottom sediment is not recommended. Instead, spreading a buoyant straw such as wheat or barley straw in a thin layer across the surface will shade the algae and may result in a decrease in the blue-green algae bloom size. As the straw sinks, it needs replaced. This method of control will have little lasting effect on the pond. Addition of a pond dye is another option. Dyes inhibit the growth of algae by reducing the amount of available sunlight and are safe for fish, humans, and livestock. Adding dye is more of a preventative measure to keep the algae from growing and reproducing rather than a “fix” after a bloom occurs.
- Solar-powered pond aerators. This aerator can be mounted on the shore and are suitable for small or large ponds. They work well in locations that do not have electricity nearby. This option has a less negative impact on the environment compared to chemical control measures but is not a complete fix of the problem.
How long will the harmful algal bloom last?
Cooler, cloudy weather with high wind speeds generally shortens the duration. Before allowing livestock to drink water from a pond that was previously determined to have a harmful algal bloom, another water test should be taken to make certain that hazardous concentrations are no longer present. Harmful algal blooms are serious threats to livestock health and may be fatal. Testing suspect water sources is important to minimize livestock loss and poor animal performance. Upon confirmation of a harmful algal bloom, the best management practice is to find a different water source.
Testing for blue-green algae
If a producer suspects the presence of blue-green algae, a water sample can be sent to the Kansas State Veterinary Diagnostic Laboratory for testing. Because toxin concentrations can fluctuate widely within the same pond, animals drinking from the pond may or may not consume significant levels of the toxin. Because toxin consumption cannot be forecasted with any degree of accuracy, water from a pond that tests positive for blue-green algae is considered unsafe for livestock consumption. The level of toxin in the water is generally not analyzed due to the cost of testing and because toxin concentrations vary so much by location and time within the same pond.
How to Collect a Water Sample to Submit for Blue-green Algae Detection
- Find a location in the pond where algae is most concentrated. This may be a scummy area along the pond shoreline, or a patch of discolored water. If in doubt as to the best location, sample on the downwind side of the pond. Inlets and coves, where wind disturbance is minimal, are also good sites for collecting a sample.
- Use a clean plastic bottle with a screw lid to collect the sample. The bottle does not have to be sterile. A 20-ounce or 1-quart soft-drink bottle will work well. Rinse the bottle with pond water before collecting the sample. If present, be sure to include some of the pond scum in the sample. Avoid touching the water or wear gloves while collecting samples.
- Fill the bottle with pond water, screw on the lid, and immediately place it into a cooler with ice or transport it to a refrigerator.
- Keep the sample cool, but not frozen, until it is shipped to the lab. Although the sample can be kept cool for a few days before submitting it to the lab, it is recommended that it be shipped the same day it is collected. It is preferable to avoid collecting and shipping samples on days when they will arrive at the lab on the weekend and sit 1 to 2 days before being processed.
- Fill out a sample submission form that includes your name, preferred contact method, and contact information (phone, fax, email, or address). A submission form can be found at: http://www.ksvdl.org/docs/submission-forms/Bovine_Submission_Form.pdf. Fill out the owner/producer section of the form. Specify the test you are requesting as “blue-green algae” in the “Other tests not listed” line at the bottom of the form. Add any information you may need to identify where the sample was taken. Place the form in a re-sealable zipper bag so moisture from the ice packs does not cause it to disintegrate or the ink to run.
- Wrap the joint between the lid and the bottle with tape to seal it. Put the bottle in a re-sealable zipper bag and seal it. Place the bottle in a box or small polystyrene foam container and surround it with ice packs. Place enough packing insulation and ice packs around the bottle to keep it cool until it arrives at the lab. Multiple bottles can be included in one shipping container, but each should be clearly marked with the site where it was collected so results can be matched with water source.
To view a two-minute video illustrating how to collect a water sample for blue-green algae, go to https://www.youtube.com/watch?v=ZRNWzFwKKjE
Once the sample is properly collected, ship the water sample to:
Kansas State Veterinary Diagnostic Laboratory
1800 Denison Avenue
Manhattan, KS 66506-5601
Results should be available within 24 to 48 hours after the sample arrives.
For more information, please contact the Kansas State Veterinary Diagnostic Laboratory at 866-512-5650 or email firstname.lastname@example.org
This eUpdate article and the companion article contain excerpts from the KSRE publication MF-3065, “Identification and Management of Blue-green algae in farm ponds”. You can view the entire publication at: https://www.bookstore.ksre.k-state.edu/pubs/MF3065.pdf
Carolyn Baldwin, Range Management Specialist
Jeff Davidson, Watershed Specialist
Will Boyer, Extension Watershed Specialist