Try barley straw to control pond algae

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UNIVERSITY PARK, Pa. – The mother of all problems in ponds is excessive algae growth, according to water resources specialist Bryan Swistock, who recommends owners try a nontoxic method to control the choking green growth.

Backyard and ornamental ponds have become common in the last decade or so as more and more property owners add bodies of water to their landscaping. Pond sizes range from bathtub-sized containers to those covering acres, but they all can suffer from the same malady – algae growth that can cover everything with a thick green mat of goo.

Alternate method. “Traditional mechanical and chemical control methods are not always efficient or economical,” Swistock said. “In recent years, the use of barley straw has become more common as an alternative method for controlling excessive algae growth.”

This method has been extensively studied by scientists in Great Britain and has recently become widely known in the United States. When applied at the proper time and rate, barley straw is a successful algae control technique in Pennsylvania ponds, according to Swistock.

“Barley straw does not kill existing algae but it inhibits new growth,” he said. “The exact mechanism is poorly understood, but it seems that barley straw, when exposed to sunlight and oxygen, produces a chemical that inhibits algae growth. Barley straw does not reduce the growth of other aquatic plants.”

Best times. Barley straw is most effective when applied early in the year prior to the appearance of algae (fall through early spring). When applied to cold water (less than 50 degrees), it may take six to eight weeks for the straw to begin producing the active chemicals that inhibit algae growth.

If the straw is applied to warmer water (above 70 degrees), it may become effective in as little as one to two weeks.

In any case, barley straw remains effective for approximately six months after application.

“The most common application is two to three bales per surface acre of pond,” Swistock said. “The depth of water in the pond is not important. In ponds that are frequently muddy or those that have a history of heavy algae growth, two or three times this recommended dose may be required for the initial treatment.

“However, overdosing the pond with barley straw may cause fish kills because straw deoxygenates the water as it decays. This is especially a problem if the pond is overdosed with straw during a prolonged warm spell.”

How to apply. The straw is most effective when applied loosely in cages or netting.

It is best to anchor the straw packages to the bottom and provide a float to keep the straw near the surface of the pond where sunlight and oxygen are more prevalent.

Apply the straw at several locations around the pond, especially near the water source if a spring or stream feeds the pond. In small garden ponds, small nets or nylon stockings can be used to hold the small amounts of straw needed.

“Finding a local supplier of barley straw sometimes can be difficult,” Swistock said. “You might consult with private and government agencies that work with local farmers, like farm supply companies, cooperative extension offices and conservation district offices, to determine if barley straw is available locally.

“In addition, there are several suppliers available online – just type “barley straw” in your favorite search engine.”

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