Ag News – Blue-Green Algae Warning

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Warnings Issued for Blue-Green Algae

BY: Ellen Crawford, NDSU Extension Service, Revised by Miranda A. Meehan, Extension Livestock Environmental Stewardship Specialist, Michelle Mostrom, Veterinary Toxicologist


As temperatures begin to increase, health officials in several states are warning livestock and pet owners to be aware of dangerous blue-green algae blooms.
Cyanobacteria, also known as blue-green algae, can produce toxins that are harmful to livestock, pets, wildlife and people.
The growth of this bacteria is facilitated by high temperatures. Blue-green algae often occurs in stagnant ponds or dugouts with elevated nutrient levels, forming large colonies that appear as scum on or just below the water surface. Live cyanobacterial blooms can be green, but also red or yellow, and often turn blue after the bloom dies and dries on the surface or shoreline.

Some species of cyanobacteria can be toxic when livestock and wildlife ingest them. Toxicity is dependent on the species consuming the water, the concentration of the toxin or toxins and the amount of water ingested.
“Cyanobacteria can produce neuro and liver toxins,” says Michelle Mostrom, NDSU veterinary toxicologist. “Signs of neurotoxin poisoning can appear within five minutes to up to several hours after ingestion. In animals, symptoms include weakness, staggering, muscle tremors, difficulty in breathing, convulsions and, ultimately, death.”
Animals affected by liver toxins may exhibit weakness, pale-colored mucous membranes, mental derangement, bloody diarrhea and, ultimately, death.

Typically, livestock are found dead before producers observe symptoms. If cyanobacterial poisoning is suspected as the cause of death, producers should check the edges of ponds for dead wildlife.
Contact your local Extension agent for a sampling container or assistance in collecting samples.
Be sure to wear gloves because cyanobacteria can be toxic to humans. Collect a sample of the suspected cyanobacterial bloom from the surface of the water and deeper in the water. The sample should be kept cool but not frozen. Submit it to a Veterinary Diagnostic Laboratory or a commercial laboratory. The sample can be evaluated microscopically for algae, or the water can be analyzed for several of the toxins at commercial labs at a higher cost.
For more information on sample collection and submission, contact your local Extension agent.

Here are some ways producers can prevent cyanobacterial poisoning of livestock:
Reduce nutrient levels entering the water source by implementing a nutrient management plan or establishing buffer strips with perennial plant species.
Create a designated drinking area where the risk of cyanobacteria is minimal.
Fence off the pond and pump water from the pond to the water tank.
Use water from other sources following periods of hot, dry weather.
Add copper sulfate to the water if the source has a history of algae blooms.
Apply 2 pounds of copper sulfate per acre-foot of water, which is equal to a rate of 8 pounds per 1 million gallons. Livestock must be fenced out of treated water sources for 10 to 14 days. Use caution when using copper sulfate because it can impact wildlife, and algae toxins still may be present following treatment. Clean out any livestock troughs and pet water containers at least once a week to prevent algae build up.

Read more: “Cyanobacteria (Blue-green Algae) Poisoning >>.”

For additional help or questions related to blue-green algae, please contact North Carolina Cooperative Extension of Franklin County, 919-496-3344 or email