Apply 1 lb. of copper sulphate by weight for every 250,000 gallons of dugout water (see Table 1 to estimate dugout water capacities). There are several methods of applying copper sulphate. One is to tie the weighed amount of copper sulphate in a cloth bag (the pant-leg of an old pair of jeans works well). Attach the bag to the middle of a long piece of baler twine, and with the help of an assistant, drag the bag of copper sulphate back and forth over the surface of the dugout until the copper sulphate is dissolved. Alternatively, dissolve the copper sulphate in 6 or 8 litres of warm water. Spray the mixture over the surface of the dugout. Copper sulphate is corrosive. Clean all equipment immediately after spraying.
Apply copper sulphate later in the evening after the cattle have had their afternoon drink. That should prevent any accidental ingestion of copper sulphate by the animals. By morning, the copper sulphate will have mixed with the water and is safe for livestock to drink (wait 24 hours before using treated dugout water for human consumption.) If there are fish in the dugout, treat one-third of the dugout at a time with one-third of the weighed amount of copper sulphate. Spread the treatments over a period of three days.
Copper sulphate is particularly effective in controlling blue-green algae. This type of algae appears as grass clippings in the water. The clippings are slimy and will run through your fingers if you try to pick them up (other species of algae will feel solid or crumbly). Heavy concentrations of blue-green algae may look like a layer of solid green paint on the surface of the dugout. An iridescent sheen is sometimes reported. Blue-green algae can produce deadly toxins that damage the liver, nerves, lungs and hearts of livestock.
The rate of copper sulphate listed will provide good control of the blue-green algae, but exercise caution when treating heavy blooms of blue-green algae. A treatment of copper sulphate in these situations rapidly kill the algae. High concentrations of toxins may be released into the dugout water following treatment. The toxins can be lethal. Plan to utilize another source of water for 12 to 14 days after a treatment program to allow time for the toxins to dissipate.
Do not use more than the recommended amount of copper sulphate. Higher levels will destroy some of the beneficial organisms such as zooplankton that actively feed on algae. Plan to treat in the spring, mid-summer and early fall.
