Question: I started a wildlife pond that will not be using a filter this year because I will be attracting dragonfly larva. Unfortunately, now I have algae in the pond. What are your views on using barley straw to control the algae growth?
Answer: Excessive algae growth is the most common problem for ponds. Brawley straw being used as an algaecide is becoming more popular and easier to purchase locally. Small bales or compressed pellets can be found at garden centers or nurseries. Many homeowners have had success in controlling algae with the use of barley straw, but the research has been inconclusive.
Barley straw began to be used as an algaecide in England in 1990 for large reservoirs and canals. It was believed the fungi that decompose barley in water release a chemical that prevents the growth of the algae. Research has been inconclusive as to whether the barley being decomposed is releasing the chemical or if the chemical is a metabolic product produced by the fungi. Its use is more often described as preventing the growth of the algae rather than killing already existing algae. Also, not all types of algae seem to be controlled equally.
Overall evidence does suggest water clarity will be improved over time with the use of the barley straw.
According to the University of Delaware, two bales of barley straw per acre of pond surface will control algae. For smaller ponds, follow the manufacturer's recommendations. The amount is approximately 0.8 ounces of straw per 10 square feet of surface area. It is recommended the barley straw be placed in a monofilament bag or sack and secured so it stays at water surface. The best time to apply the straw is in early spring.
It takes one to two weeks at 68 degrees to be effective, and eight weeks at cooler temperatures. Early applications will minimize a heavy buildup of the algae.
Very muddy pond water will reduce the barley's effectiveness. A higher dose should be used with these heavy sediment waters, but not excessive; 1.7 ounces per 10 square feet. Do not exceed 3.3 ounces per 10 square feet. The decomposition of the straw requires oxygen and sunlight. Too much straw will reduce the oxygen amounts in the water. Once the straw begins to work, it will control algae for about four to six months.
Using barley straw is an inexpensive and environment-friendly first option for algae control. If it is not successful other options are available.
Mona Bawgus is a certified master gardener and consumer horticulturist with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330. Email: firstname.lastname@example.org