Barley straw for algae control by cam67257


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Barley straw for algae control
Successful use of barley straw for controlling algae in water gardens and
small pools has led many to suspect that barley might be effective on pond
and lake algae.

Carole A. Lembi, Ph.D.

   The use of barley for algae control        been somewhat slow to initiate
was developed in the early 1990s in           research on barley, some studies have
England, where it is widely used in many      been conducted.
bodies of water, including large reser-
voirs and canals. It is thought that fungi    Purdue University and
decompose the barley in water, which          University of Maryland
causes the release of a chemical that pre-       Laboratory studies at Purdue
vents the growth of algae. The specific       University and the University of
chemical (or chemicals) has not been          Maryland also found that algal
identified (oxidized polyphenolics and        species vary in their susceptibility to
hydrogen peroxide are two decomposi-          barley straw.
tion products that have been suggested),         In larger studies in stock tanks (out-
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                                                                                                                          Key points
and it is not clear whether the chemical      doors) and in plastic cylinders (in the
is exuded from the barley itself or           greenhouse) at Purdue, we sometimes
whether it is a metabolic product pro-                                                     ■ Barley straw has been
                                              observed a decrease in phytoplanktonic
duced by the fungi. The activity of bar-                                                     used in England to control
                                              growth (the microscopic algae that
ley straw is usually described as being                                                      algae in ponds, lakes and
                                              color the water green), but we often
algistatic (prevents new growth of algae)                                                    other bodies of water
                                              noticed an increase in mat-forming
rather than algicidal (kills already exist-                                                  since the early 1990s.
                                              algae on the surface of the water.
ing algae).                                                                                ■ The means by which
   Laboratory studies conducted by                                                           barley controls algae
                                              University of Nebraska
English researchers suggest that barley                                                      is still unknown.
                                                 Researchers at the University of
will not control the growth of all species                                                 ■ Results of barley straw
                                              Nebraska initiated a field study in April
of algae. In fact, studies do not agree on                                                   studies in the United
                                              2000. They applied barley to a lake that
which species are controlled by barley.                                                      States have been mixed.
                                              had a history of noxious phytoplankton
Field evidence from England suggests                                                       ■ Because barley is not
                                              blooms (blue-green algae). The barley
that using barley will usually improve                                                       a registered pesticide,
                                              did not control the blooms, and in fact,
water clarity over time because algal                                                        it can be used only as
                                              it might have enhanced algal growth.
populations are reduced.                                                                     a “home remedy” on
                                                                                             private property.
                                              Iowa State University
Research in the United States                    Researchers applied barley straw to
  Although U.S. researchers have              plastic enclosures in a pond in spring

                                                                                                            February 2002 ■ GCM

                                                                                  2001. No effects on algae were found.        different water-quality conditions and
                                                                                  Barley applications to several separate      algal populations.
                                                                                  ponds appeared to reduce algae growth;          Clearly, the use of barley is not a
                                                                                  however, it is uncertain whether the         process that is going to produce the
                                                                                  pond tests are valid because, unlike the     same rapid, visible results as an algicide
                                                                                  plastic enclosure tests, they were not       application. Results with barley, accord-
                                                                                  replicated and did not include               ing to the English researchers, can take
                                                                                  untreated controls.                          several months.

                                                                                  University of Florida and                    U.S. EPA
                                                                                  North Carolina State University                  After the city of Lakeville, Minn.,
                                                                                     The University of Florida and North       applied barley to a lake in spring 2000
                                                                                  Carolina State University conducted          and achieved improved water clarity, a
                                                                                                 additional studies several    number of lake associations in
                                                                                                 years ago.                    Minnesota were anxious to begin using
                                                                                                     In Florida, a small-      barley straw as an alternative to tradi-
                                                                                                 scale study found that        tional pesticides. Members of the
                                                                                                 predigestion of the straw     Minnesota Department of Natural
                                                                                                 (incubation in water) for     Resources were concerned that not
                                                                                                 about a month was neces-      enough was known about the potential
                                                                                                 sary for activity. As shown   effects of barley. They questioned
                                                                                                 in the English studies, the   whether it provides consistent control
                                                                                                 liquor did not reduce         and whether they could approve its
                                                                                                 existing algal populations    use in “public” waters. The agency asked
                                                                                                 but did prevent algae         the U.S. EPA, which regulates pesticide
                                                                                                 from growing.                 use, for guidance.
                                                                                                     It was concluded that         The EPA said that barley is legally
                                                                                                 the amount of straw           considered a pesticide if it is claimed to
                                                                                                 needed, if extended to a      control algae (a pest). However, barley
                                                                                                 pond scale, was too large     has not been tested or registered for use
                                                                                                 to be practical in Florida,   as a pesticide. Therefore, it cannot be
                                                                                                 particularly because its      sold as a pesticide to control algae.
                                                                                                 ponds and lakes are warm,         This ruling has serious implications
                                                                                                 shallow and have a long       for certified commercial applicators
                                                                                                 growing season. Several       (individuals who have been state
                   Photo by Carole Lembi

                                                                                                 pond trials conducted         certified to apply aquatic pesticides
                                                                                                 there were unsuccessful.      for hire) and lake management special-
                                                                                                     In North Carolina, two    ists. These individuals cannot recom-
                                                                                                 trials were conducted on      mend or apply — and garden shops and
                                           Mat-forming algae are common                          farm ponds with no effect     nurseries cannot legally sell — barley
                                           problems in ponds and shallow lakes.   on mat-forming algae.                        for algae control. These actions would
                                                                                                                               be the same as distributing an unregis-
                                                                                  Results                                      tered pesticide.
                                                                                      In summary, results from barley              For the homeowner working on his
                                                                                  research in this country have not            own pond, barley qualifies as a “home
                                                                                  been overwhelmingly positive. Whether        remedy” and does not come under EPA
                                                                                  we are dealing with algal species, water     authority. Pond owners who wish to
                                                                                  conditions, climatic conditions or           purchase barley and apply it to ponds
                                                                                  other factors that differ from those of      on their own property themselves are
                                                                                  the typical English water body is            free to do so. However, a person who
                                                                                  simply not known at this time.               lives on a public lake cannot apply bar-
                                                                                  Furthermore, dosages have not been           ley because the lake is public property
                                                                                  tested in replicated field studies under     and managed by state government. EPA

                GCM ■ February 2002
                                                                                                                                             E S E A R C H
does not provide guidance on which           be treated at a rate of 225 pounds of
ponds/lakes are private vs. public, and      barley straw (about five bales) per sur-
how this distinction is made likely varies   face acre of water. This rate is equiva-
among states.                                lent to about 0.8 ounces of straw per 10
    EPA acknowledges that some prod-         square feet of surface area. Lower doses
ucts have multiple uses and that it is       can be tried, but should not fall
legal to advertise, sell and apply a prod-   below 90 pounds of straw per acre or 0.3
uct based on its nonpesticidal uses, even    ounces per 10 square feet.
if the product also has pesticidal uses.         The water
Selling or applying barley straw without     should be rela-
claiming algae control is therefore legal.   tively shallow,
The obvious alternative reason for the       perhaps 4 to
application of barley is that it might act   5 feet deep.
as a water clarifier. Is this a legitimate   Barley        may
way to justify the use of barley? Until      work in deeper
further clarification is obtained from       waters as well,
EPA, this is a matter for the individual     but maximum
to decide.                                   depths       have
                                             not been deter-
How to use barley                            mined.
   Before using barley as a “home rem-           The effec-
edy,” contact the state Department of        tiveness of the
Agriculture to determine the legal status    straw is re-
                                                                                                          Photos courtesy of Steve McComas
of using barley straw for algae control in   duced by sedi-
your area. The following information is      ments suspended in the water.                For treatments of larger ponds, barley
taken from guidelines provided by the        Therefore, a higher dose may be              straw can be repacked using a
                                                                                          Christmas tree baler to feed the straw
University of Nebraska, which are based      required in muddy lakes or lakes with        into a mesh bag.
on English recommendations.                  extremely severe algae problems. In
                                             these types of lakes, the dosage is 450
When to apply the straw                      pounds per acre (1.7 ounces per 10
    The decomposition process depends        square feet) to 900 pounds per acre (3.3
on temperature and occurs faster in          ounces per 10 square feet). The decom-
warmer water. When the water temper-         position of the straw requires oxygen,
ature is below 50 F, it takes approxi-       and the application of excessive
mately six to eight weeks for the decom-     amounts (greater than 900 pounds per
posing straw to produce enough of the        acre) of straw could reduce the oxygen       Sources of netting
growth-inhibiting chemical to effec-         content of the water to levels that stress
tively control algae. However, it only       or kill fish.
takes one to two weeks when the water                                                                Standard netting
temperature is above 68 F.                   Example: To determine the amount of                   Aquatic Eco-Systems Inc.
    Once the straw begins to produce         straw required to treat a 5-acre lake,                      Apopka, FL
sufficient amounts of the chemical, it is    multiply the surface area of the lake (5                 (407) 866-3939
likely to control algae for about four to    acres) by the selected dose (225 pounds
six months. Straw should be applied in       of straw per acre):                                  Christmas tree netting
mid-to-late April to control summer                                                                 The Campbell Co. Inc.
algal growth in ponds and lakes in                  5 acres × 225 pounds/acre                           Wautoma, WI
Nebraska (or sites at similar latitudes).           = 1,125 pounds of straw.                          (800) 242-2019

How much straw?                              How to apply the straw                                    Kelco Industries
   The amount of straw required to              Tight bales prevent the thorough                        Milbridge, ME
control algal growth depends primarily       distribution of oxygen, which is                         (800) 343-4057
on the surface area of the lake. Lakes       required to decompose the straw.
with a history of algae problems should      Anything that increases aeration in the

                                                                                                                    February 2002 ■ GCM

                                                            body of water, like an aerator, may help      Results
                                                            in the decomposition process.                    Effects of the barley straw treat-
                                                                Bales must be broken apart and the        ment are not immediate. If barley
                                                            barley loosely placed into some form of       works as an algistat, it will prevent new
                                                            netting. For larger lakes and ponds, wrap     growth, but it may not kill off what is
                                                            the straw in the cylindrical netting com-     already present. Presumably, early treat-
                                                            monly used for wrapping Christmas trees.      ments, perhaps in March or April,
                                                            This netting can be used to construct a       applied before the algae start to grow,
                                                            straw-filled tube about 65 feet long, con-    will help this situation.
                                                            taining about 110 pounds of straw.               The alternative is to control existing
                                                            Loosely woven sacks (for example, onion       algal populations, either manually or
                                                                                    sacks) can be used    chemically, and then to apply the barley
                                                                                    in small ponds        to prevent new growth. According to J.
                                                                                    that require low      Newman, who has conducted some of
                                                                                    doses.                the research in England, the activity of
                                                                                        Floats    sus-    barley builds up to a maximum at about
                                                                                    pend the straw-       six months after treatment and then
                                                                                    filled netting in     ceases. At that time, new barley should
                                                                                    the upper 3 to 4      be introduced into the system.          ■
                                                                                    feet of the lake.
                                                                                    The straw will
                                                                                    lose its effective-                   Acknowledgments
                                                                                                              Partial funding for research conducted at
                                                                                    ness if it sinks      Purdue University was provided by the Indiana
                                                                                    below this depth.     Value-added Grant Fund, Office of the
                                                                                    Floats should be      Commissioner of Agriculture. The following indi-
                                                                                                          viduals contributed information for this article:
                    For treatments of small ponds, barley
                                                                                    inserted inside       Dan Terlizzi, University of Maryland, College
                    straw can be repacked into 50-pound     the netting at the same time the netting      Park; John Holz, University of Nebraska, Lincoln;
                    onion mesh bags. These bags hold        is filled with straw. The netting is then     Joe Morris and Joe Boylen, Iowa State University,
                    about 7 pounds of barley straw.                                                       Ames; Ken Langeland, University of Florida,
                                                            anchored into place using rope attached       Gainesville; Stratford Kay, North Carolina State
                                                            to bricks or concrete-filled buckets.         University, Raleigh; Steve Enger and David
                                                                Water movement near the surface           Wright, Minnesota Department of Natural
                                                                                                          Resources, St. Paul; Steven McComas, Blue Water
                                                            will keep the straw well oxygenated and       Science, St. Paul, Minn. Information in this article
                                                            distribute the growth-inhibiting chemi-       is also available at
                                                            cal throughout the upper portion of the       Pubs/APM/APM-1-W.pdf. For a copy of EPA’s
                                                                                                          written response to questions about barley, please
                                                            lake. This ensures that the chemical is       contact Carole Lembi by e-mail (lembi@btny.
                                                            produced where the majority of the   and send a fax number.
                                                            algae are growing and away from the
                                                            bottom sediments that will inactivate         1. ACR-Centre for Aquatic Plant Management.
                                                            the chemical.                                    Information Sheet 3: Control of algae with
                                                                                                             strw.sht (verified Nov. 26, 2001).
                                                            Where to apply the straw
                                                               Placing several small quantities of        2. Holz, J.C. 2000. Controlling pond algae with
                                                            straw around a lake is recommended to            barley straw. NF00-429 Lake Water Quality
                                                                                                             Extension Program, Nebraska Cooperative
                                                            improve the distribution of the growth-          Extension, Institute of Agriculture and
                                                            inhibiting chemical. Each net of straw           Natural Resources, University of Nebraska,
                                                            should be roughly equidistant from               Lincoln.
                                                                                                             wildlife/NF429.htm (verified Nov. 26, 2001).
                                                            other nearby nets and the shore. Net
                                                            placement does not need to be exact,
                                                            and practical considerations such as
                                                            corridors for boating and angling may
                                                            influence the location of the nets. In
                                                            small ponds, where only one net of            Carole A. Lembi, Ph.D. (e-mail: lembi@btny.pur-
                                                                                                , is a professor of botany in the department
                                                            straw is required, place it in the center     of botany and plant pathology at Purdue University
                                                            of the body of water.                         in West Lafayette, Ind.

                GCM ■ February 2002

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