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Controlling Pond Algae

with Barley Straw  


To properly reclaim and maintain water quality in a lake or pond, diffuser based aeration and beneficial bacteria treatments are the most effective combination. Barley straw can be effective at controlling algae in certain situations, but it doesn't address the underlying problem of low oxygen and high nutrient levels and over the long term it is not an effective water management solution.

Algae are microscopic, free-floating plants which comprise a critical component of a lake's food web. They are fed upon by tiny animals called zooplankton which are an important food source for fish. Algae color the water green or brown, and uncontrolled growth can lead to nuisance surface scums, poor water clarity, noxious odors and an overall reduction in the lake's recreational value. Excessive levels or "blooms" of algae occur when nutrients, especially phosphorus, are abundant. After taking steps to reduce the amount of phosphorus entering a lake, it may be desirable to control the algae growth directly. Typically this is accomplished by treating the lake with copper-containing compounds such as Cutrine Plus or copper sulfate. These treatments are effective short-term controls of algae, but they are also toxic to non-target organisms that are important food sources for fish such as zooplankton and insect larvae. Re-application of these chemicals is usually necessary several times each year and the long-term buildup of copper in the lake sediments is an environmental and health concern.

            Barley straw has been proven to be an effective natural way to control algae growth in dugouts.  As the straw decomposes, it releases a chemical which inhibits algal growth. This method may be a good alternative to using copper-containing compounds since it is not known to have toxic effects on rooted aquatic plants, zooplankton, insect larvae or fish. It appears to be a cost-effective and environmentally acceptable way to control algae in ponds and lakes.

When to Apply the Straw

The decomposition process is temperature dependent and occurs faster in warmer water. When the water temperature is below 50 deg F, it takes approximately six to eight weeks for the decomposing straw to produce enough of the growth inhibiting chemical to effectively control algae. However, it only takes one to two weeks when the water temperature is above 68 deg F. Once the straw begins to produce sufficient amounts of the chemical, it is likely to control algae for four to six months. Therefore, straw should be applied right after the ice is off in order to control summer algal growth.

Amount of Straw to Apply

The amount of straw required to control algal growth depends on the surface area of the lake. Lakes with a history of algae problems should be treated at a rate of 225 pounds of barley straw per surface acre. This rate is equivalent to about 0.8 ounces of straw per 10 square feet of surface area. Lower doses can be tried, but should not fall below 90 pounds of straw per acre or 0.3 ounces per 10 square feet.

The effectiveness of the straw is reduced by sediments suspended in the water (i.e. "muddy" water). Therefore, a higher dose may be required in "muddy" lakes or lakes with extremely severe algae problems. In these types of lakes, apply 450 pounds per acre (1.7 oz per 10 square feet), but do not exceed 900 pounds per acre (3.3 oz per 10 square feet). The decomposition of the straw requires oxygen, and applying excessive amounts (greater than 900 lbs per acre) of straw could reduce the oxygen content of the water to levels that stress or kill fish.

   Example:  Determining the amount of straw required to treat a

                    1/4 acre pond.  (One acre is 43,560 square feet)

     1. The surface area of the pond is 1/4 acres.

     2. The selected dose is 225 pounds of straw per acre.


     3. Multiply the area of the pond (in acres) by the

         amount of straw required per acre to calculate the

         total amount of straw required to treat the whole 

         pond (1/4 acres x 225 lbs/acre = 56.25 lbs).

     4. To calculate the number to bales needed to treat 

         the pond, divide the total amount of straw required

         to treat the whole pond by the weight of a single

         bale of barley straw. For this example, assume one

         bale weighs 45 pounds. However, the size and

         weight of bales can be highly variable.  It is

         recommended that the approximate weight of the

         bales be determined at the time of purchase.

         (56.25 lbs, 45 lbs/bale = 1.25 bales).

How to Apply the Straw

1. The straw bales must first be broken apart. Bales are packed too tightly and do not allow adequate water movement through the straw.

2. The loose straw should be placed in some form of netting.  We suggest the type used for wrapping trees, or snow fencing will also work.  This netting can be used to construct straw-filled tubes of various lengths depending on how much straw you need.  Loose woven sacks (e.g., onion sacks) can be used in small ponds that require low doses.

3. Use floats to suspend the straw-filled netting in the upper 1 to 2 feet of the pond. The straw will lose its effectiveness if it sinks below this depth. Water movement near the surface will keep the straw well oxygenated and distribute the growth inhibiting chemical throughout the upper portion of the pond. This ensures that the chemical is produced where the majority of the algae are growing and away from the bottom sediments which will inactivate the chemical. Therefore, it is recommended that floats be inserted inside the netting at the same time the netting is filled with straw. The netting is then anchored into place using rope attached to bricks.

Where to Apply the Straw

In order to improve the distribution of the growth inhibiting chemical, place several small quantities of straw around a pond. Place each net of straw roughly equidistant from other nearby nets and the shore. The placement of the nets does not need to be exact and practical considerations such as corridors for boating and angling may influence the location of the nets.

Some Info obtained from Purdue University and University of Nebraska


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Max Menard