Controlling pond algae has been a problem for pond owners, as long as there have been ponds. The technique of using barley straw for ponds was developed in England, where it is widely used in many bodies of water, including large reservoirs and canals to naturally eliminate pond algae. It is thought that naturally occurring microbes in the pond water decompose the barley straw, which causes a chemical to be released that provides pond algae control, by prohibiting the growth of the algae. The specific chemical(s) has not been identified. Oxidized polyphenolics and hydrogen peroxide are two decomposition products that have been suggested. It is not clear whether the chemical is exuded from the barley straw itself, or if it is a metabolic product produced by the pond microbes. The activity of barley straw is thought to be more “algistatic” (preventing the growth of new algae in pond water) rather than “algicidal” (killing already existing algae). Lab studies have suggested that barley straw will not control the growth of all species of algae. Some studies claim certain types of algae are susceptible to barley straw, while other studies claim those algae are not susceptible. The field evidence from England does suggest that in most cases, barley straw can be a pond clarifier (water clarifier), claiming water clarity will improve over time, due to a reduction in algal populations.
Research In The U.S.
American researchers have been somewhat slow to initiate research on using barley for ponds. Some studies have been conducted and will be summarized here. Results of research at Purdue University have been inconsistent. The first studies were conducted in the laboratory, and we were able to show that some algal species were indeed susceptible to barley straw, but others were not. A similar study at the University of Maryland also showed that algal species vary in their susceptibility. Researchers at the University of Nebraska initiated an actual field study, and applied pond barley to a lake that had a history of noxious phytoplankton blooms (blue-green algae). The barley did not control the algae blooms, and in fact may have enhanced algal growth. On the other hand, the application of barley by the city of Lakeville to a lake in Minnesota seemed to provide algal control. Pond water clarity improved in the year of treatment compared to previous years. Additional studies were conducted at the University of Florida, and at North Carolina State University. In Florida, a small-scale study found that pre-digestion of the barley straw (incubation in water) for about a month was necessary for activity. English studies suggest the effect was algistatic rather than algicidal. In other words, existing algal populations were not controlled, but were prevented from growing. The conclusion from this study was that the amount of barley straw needed was too large to be practical as a pond clarifier. Several pond trials conducted in Fl were unsuccessful. In North Carolina, two trials were conducted on farm ponds, with no effect on filamentous “mat-forming” algae, which often appears as slime in ponds, and can be found on rocks and weeds under the surface. A barley study was initiated by researchers at Iowa State University. In this case, plastic enclosures were installed in a lake. Some were treated with barley and others were not. The Minnesota Department of Natural Resources allowed the treatment of several ponds in the Twin Cities area, testing pond water clarity. The conclusions drawn from these studies were not overwhelmingly positive. Whether we are dealing with algal species, water conditions, climatic conditions, or other factors that differ from those of the typical English water body is simply not known. Furthermore, dosages have not been tested in replicated field studies under different water quality conditions and algal populations. Pond owners remain hopeful in finding a natural way to turn cloudy pond water into clear pond water. In the meantime, the use of barley straw as a natural pond cleaner is not a process that will produce rapid, visible results like applying a chemical algaecide would. However, many pond owners refuse to use toxic chemicals in their pond water. Especially if the pond is used for fishing or swimming.
Many pond owners have given up on the use of barley straw in ponds, because of the inconsistent results and the many months of time it takes to finish the barley straw treatment. They have instead turned to beneficial pond bacteria for natural pond cleaning. Beneficial pond bacteria will eliminate murky water caused by organic wastes, as well as reduce bottom-sludge (muck) that is the result of organic wastes building up over time. Since pond bacteria is not a chemical pesticide it does not require an aquatic applicators license to apply. Many pond owners choose pond bacteria products for their natural pond maintenance. Pond muck removal done with large equipment is very intrusive to the pond’s eco system and very costly for the pond owner. Pond bacteria can do the same thing without disrupting the ecosystem and in a very cost-effective way. Pond sludge removal is especially problematic in older ponds. As long as the pond muck is organic, pond bacteria will consume it as their food source and naturally eliminate it.
Epa’s Views On Barley
The Environmental Protection Agency (EPA) has the responsibility of maintaining the health of our nation’s bodies of water. It is also the agency that regulates the use of pesticides in the United States. All pesticides must undergo thorough testing for their potential to cause adverse effects on non-target species, human health, and the environment. A pesticide that is approved by the EPA receives a registration number. Only registered products can legally be used as pesticides. After the apparently successful Lakeville, Minnesota test, several lake associations in that state were anxious to begin using barley straw as an alternative to traditional pesticides. Members of the Minnesota Department of Natural Resources were concerned that not enough was known about the potential effects of barley. They questioned whether it provides consistent control and whether they could approve its use in “public” waters. They asked EPA for guidance on this matter, and the EPA’s response is summarized as follows: The EPA defines a pesticide as “any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.” If a claim is made that barley straw “controls” algae (a pest), it is legally considered a pesticide in the eyes of the EPA and requires EPA registration. Therefore, barley cannot be sold as a pesticide to control algae. Neither can beneficial pond bacteria products. This has serious implications for certified commercial applicators and lake management specialists that have been state certified to apply aquatic pesticides. These individuals cannot recommend or apply barley or pond bacteria for algae control. Their application of barley or pond bacteria into a pond, for the purpose of algae control, would be the same as if they were distributing an unregistered pesticide. Likewise, garden shops and nurseries cannot legally sell barley straw for the stated or implied purpose of algae control. The EPA acknowledges that some products have multiple uses and that it may be legal to advertise, sell, and apply a product based on its non-pesticidal uses, even if the product also has pesticidal uses.
