Algae in Lakes, Ponds, Reservoirs, and Irrigation Channels

copper sulfate pentahydrate2

Rate 0.25 to 2 ppm suspended in burlap bags, poured directly into water of irrigation channels, injected into the water column, or applied over water surface of impoundments.

Time Apply early in spring and at 2- to 3-week intervals thereafter.

Remarks Safe in potable and irrigation water. Do not wait until a severe algae problem develops before applying. Efficacy reduced with low water temperatures and hard water.

Caution May be toxic to fish and aquatic invertebrates (especially trout); treat 1/2 to 1/3 of the water at a time and wait a minimum of 10 to 14 days between treatments.

Site of action Plant cells

Chemical family Inorganic

2 Copper compounds are not allowed for aquatic use in Washington, except under the NPDES general permit for Irrigation Districts.

dimethylamine salts of endothall (Hydrothol)

Rate 0.05 to 0.3 ppm (for general algal control); 0.3 to 1.5 ppm (for increased longevity or use on difficult to treat species of algae). Sprayed on the water, injected below surface or granular application.

Time Apply when algal growth appears.

Remarks Liquid and granular formulations. Apply if algae in the irrigation channel must be removed to allow water delivery. However, water-use restrictions apply. See Caution below.

Caution Toxic to fish and wildlife. Fish may be killed at dosages above 0.3 ppm. Not for use in brackish/salt water. Minimum 600 ft setback from functioning potable water intakes. Do not use treated water for irrigation or agricultural sprays on food crops, watering livestock, or domestic purposes within 7 to 25 days following treatment, depending on concentration applied. Do not treat more than 1/10 of lake or pond at one time with concentrations higher than 1.0 ppm. Marginal or sectional treatments rather than an overall treatment is recommended.

Site of action Not well understood

Chemical family None generally recognized

hydrogen peroxide (GreenClean Liquid)

Rate 1 to 30 gal per surface acre.

Time Apply when algal growth appears; apply early in the day during calm, sunny weather.

Remarks May not penetrate surface mats or blooms; second application may be required to treat bottom-growing algae. No use restrictions. OMRI listed.

Caution Excessive amounts of decaying algae can deplete dissolved oxygen, potentially leading to fish kills; consider treating 1/2 to 1/3 of area at a time.

Site of action Oxidizing agent

Chemical family None generally recognized

lanthanum-modified bentonite clay (Phoslock)

Rate Based on amount of soluble phosphorus. Contract Registrant for recommendations

Remarks Phoslock is not an algaecide. But by removing phosphorus from the water column proliferation of algae, particularly blue green algae, is reduced.

Caution The maximum application rate is 80 ppm when applied to drinking water

Site of action Permanently binds free reactive phosphorus

Chemical family None generally recognized

sodium percarbonate (GreenClean)

Rate 30 to 170 lb per acre-foot (heavy algal growth); 3 to 17 lb per acre-foot (low algal growth/maintenance) broadcast manually or by a mechanical spreader. Liquid solutions may also be applied via surface treatment.

Time Apply when algal growth appears; apply early in the day during calm, sunny weather.

Remarks Short residual time; no use restrictions for swimming, fishing, irrigation, stock watering, following treatment. Uniform applications required for optimal results as these products only control algae in direct contact with granules/liquid.

Caution NOT intended for use in drinking water. Toxic to birds. Do not bring in contact with other pesticides, cleaners or oxidative agents.

Site of action Oxidizing agent after dissociating in water into sodium carbonate and hydrogen peroxide (H2O2).

Chemical family None generally recognized

sodium carbonate peroxyhydrate (GreenCleanPRO)

Rate 20 to 90 lb per acre foot (heavy algal growth); 2 to 9 lb per acre-foot (low algal growth/maintenance) broadcast granules or suspended in burlap bags. Liquid solution may also be applied via surface treatment or injection.

Time Apply when algal growth appears; apply early in the day during calm, sunny weather.

Remarks Short residual time; no use-restrictions for swimming, fishing, irrigation, stock watering, drinking or domestic use following treatment. Uniform applications required for optimal results as these products only control algae in direct contact with granules/liquid. Liquid applications may not penetrate surface mats or blooms; second application may be required to treat bottom-growing algae.

Caution Avoid drift to adjacent crops where IPM strategies are in use as this product is toxic to bees, other beneficial insects and birds. Avoid use in shallow waters during amphibian breeding season. Excessive amounts of decaying algae can deplete dissolved oxygen, potentially leading to fish kills; consider treating 1/2 to 1/3 of area at a time.

Site of action Oxidizing agent after dissociating in water into sodium carbonate and hydrogen peroxide (H2O2)

Chemical family None generally recognized