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Be on the lookout for blue-green algae

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While the days have gotten a little cooler recently the hot, sunny weather that we had previously was the perfect combination for pond weeds and algae to grow. While all pond weeds and algae can become a nuisance and start to overtake a pond, requiring control, one type of algae is of particular concern and that is blue-green algae. Blue-green algae can occur in a pond as a result of runoff that carries nitrogen or phosphorus into the pond. When the temperature reaches 75 degrees or higher the algae will grow and bloom. A period of hot, sunny days with little wind following an increase in runoff from rain also increases the likelihood of blue-green algae blooms.  

While filamentous algae (green algae) is very common on farm ponds and is not harmful to animals, blue-green algae include many species of photosynthetic cyanobacteria that live in the water and produce toxins that are poisonous to animals. The toxins that result from harmful blooms of blue-green algae are stored in the cyanobacteria until they die, and as the cyanobacteria decompose, the toxins are released into the water. Toxins from blue-green algae can affect the liver or the nervous system of animals that drink affected water. Animals that have consumed water from affected ponds may recover from toxins that affect the liver. However, if the toxins affect the nervous system of the animal it often results in death. While there is currently no antidote or treatment for the toxin, supportive care can be given to animals that show signs of being sick, and animals that have consumed toxins that have affected the liver can be treated to help them recover from the initial damage to the liver resulting from the toxins.  

When a pond has a harmful bloom of blue-green algae the water will have a scum that is most commonly bright green or blue/green as the name suggests, but can vary in color from blue-green to gray and even red, orange, or brown. The scum will often look like spilled paint, and the water of a pond that has blue-green algae will often smell bad. Blue-green algae blooms are typically the worst in areas of the pond where water is stagnant, such as a cove or inlet. Ponds that have little movement of surface water and are relatively clear are more likely to produce harmful blooms of blue-green algae due to the amount of sunlight that is able to pass through the surface water. If signs of a harmful bloom of algae are noticed in a pond, animals should not be allowed access to the pond, and water samples should be taken from the pond and sent to the Kansas State Veterinary Diagnostic Laboratory to be tested. Until the water has been tested and is confirmed safe, animals should be kept away from the pond. Two weeks from when the algae bloom starts is the average length of time it takes to get rid of the toxin. However, if the pond has a blue-green algae bloom, it can last from days to months depending on the weather conditions. The water should be retested before allowing animals to access the pond again to ensure that there are no longer toxins in the water. There are different options when it comes to treating a pond for blue-green algae, including copper sulfate and copper-based algaecides.  

For more information contact Adaven Scronce, Wildcat District diversified agriculture and natural resource agent, at 620-331-2690 or adaven@ksu.edu. 

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