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Material type: Microbial
U.S. EPA Toxicity Category: III, "Caution"
USDA-NOP:
Considered nonsynthetic, allowed. Preventive, cultural,
mechanical and physical methods must be first choice for pest control,
and conditions for use of a biological material must be documented
in the organic system plan (NOP 2000).
Material description:
Bacillus
subtilis is a ubiquitous naturally
occurring saprophytic bacterium that is commonly recovered from
soil, water, air, and decomposing plant material. Under most conditions,
however, it is not biologically active and is present in the spore
form. Different strains of B. subtilis can be used as biological
control agents under different situations. There are two general
categories of B. subtilis strains; those that are applied to the
foliage of a plant, and those applied to the soil or transplant
mix when seeding.
The B. subtilis strain QST713 is a naturally occurring strain
that was isolated in 1995 by AgraQuest Inc. from soil in a California
peach orchard. This product is applied to foliage (NYDEC 2001).
In contrast, B. subtilis strain GB03 (Kodiak®) was discovered
in Australia in the 1930’s and is applied either as a seed
treatment or directly to soil. Neither strain is considered a genetically
modified organism.
How it works:
B. subtilis bacteria produce a class of lipopeptide
antibiotics including iturins. Iturins help B. subtilis bacteria
out-compete other microorganisms by either killing them or reducing
their growth rate (CPL 2002). Iturins can also have direct fungicidal
activity on pathogens.
B. subtilis products are made for many uses. For plant disease
control, these include foliar application and products applied
to the root zone, compost, or seed. When applied directly to seeds,
the bacteria colonize the developing root system, competing with
disease organisms that attack root systems (CPL 2002).
According to the manufacturer, B. subtilis inhibits plant pathogen
spore germination, disrupts germ tube growth, and interferes with
the attachment of the pathogen to the plant. It is also reported
to induce systemic acquired resistance (SAR) against bacterial
pathogens (NY DEC 2001). According to an Agraquest sales representative,
in the Serenade® product it is the lipopeptide activity that
gives disease control. Any living B. subtilis cells in this product
have only a minor effect (Cline 2004).
According to the manufacturer, the GB03 strain (Kodiak®) delivers
extended protection against disease pathogens through three distinct
modes of action:
- Colonies of B. subtilis take up space on the roots,
leaving less area or source for occupation by disease pathogens.
- Kodiak® feeds off plant exudates, which also serve as
a food source for disease pathogens. Because it consumes exudates,
Kodiak® deprives disease pathogens of a major food source,
thereby inhibiting their ability to thrive and reproduce.
- Kodiak® combats pathogenic fungi through the production
of a chemical (an iturin) that inhibits the pathogen's growth
(Gustafson 2004). Backman et al. (1997) reported that 60-75%
of the seed used for the US cotton crop was treated with Kodiak® for
suppression of Fusarium and Rhizoctonia pathogens.
Types of pests it controls:
Iturins are reportedly active against the fungus Sclerotinia
fruticola,
which causes rots of harvested stone fruit. B. subtilis has also
been tested for control of the pathogenic fungus Verticillium.
B. subtilis has been used in conjunction with Streptomyces
gramicifaciens for control of root rot in cucumber, corky rot of tomato and
carnation wilt. According to manufacturers, Norway maple inoculated
with B. subtilis also shows increased resistance to fungal diseases.
It is also claimed to suppress diseases caused by Fusarium
spp.
and Rhizoctonia spp (CPL 2002).
Formulations and Application Guidelines:
The labels require use of personal protective equipment (long-sleeved
shirt and long pants, gloves, shoes plus socks, dust/mist filtering
respirator) to mitigate the risk of dermal sensitivity and possible
allergic reactions.
Available strains:
QST 713 is a foliar application product predominantly used against
powdery mildew.
GB03 is a soil application or seed treatment product predominantly
used to control root-infecting fungi.
MBI 600 is used for soil application or seed treatment.
B. subtilis var. amyloliquefaciens strain FZB
24 is also used for soil application.
OMRI LISTED PRODUCTS:
Bacillus subtilis strain QST 713
Rhapsody® ASO
(Agraquest Inc)
Serenade® (Agraquest
Inc.)
Serenade® ASO (Agraquest
Inc)
Serenade® Garden Disease
Control Ready-To-Use (Agraquest Inc.)
Serenade® Garden
Disease Control Concentrate (Agraquest Inc.)
Bacillus subtilis strain
GB03
Kodiak® Concentrate Biological
Fungicide (Gustafson LLC)
References to OMRI listed products in this Guide are based on
the June 2004 edition of the OMRI Brand Name List. Please consult
www.omri.org for changes and updates in the brand name
product listings.
Non OMRI-listed products:
Bacillus subtilis GB03
Kodiak Flowable Biological Fungicide (Gustafson)
Kodiak Hb Biological Fungicide (Gustafson)
Companion (Growth Products, Ltd.) - liquid for turf, greenhouse,
nursery plus other microbes
Bacillus subtilis MBI 600
Histick N/T (Becker Underwood Inc.) - seed treatment also includes Bradyrhizobium japonicum
Subtilex Biological Fungicide (Becker Underwood)
Subtilex HB (Becker Underwood)
Pro-Mix With Biofungicide (Premier Horticulture, Inc) - potting mix
Bacillus subtilis var. amyloliquefaciens strain FZB 24
Taegro® (Earth Biosciences Inc.)
Reentry interval (REI) and pre-harvest
interval (PHI):
The EPA
Workers Protection Standard requires a minimum of 4 hours before
reentering a treated field. PHI (days to harvest) is zero.
Availability and Sources:
B. subtilis products are available in a number of strains and formulations.
The OMRI approved sources are generally available from pesticide
dealers.
Effect on the environment:
According to information submitted by the manufacturer and supported
by reviewers at NY DEC, when used as a seed inoculant both B.
subtilis and Bradyrhizobium japonicum (the naturally occurring
nitrogen fixing bacteria used in Histick) are ubiquitous in the
environment. The microbes used in this combination product are
not genetically modified, and this combination has been used
in the past by farmers with no reports of negative impacts on
crops. The USEPA required limited toxicological data and established
an exemption from tolerance for residues of Bacillus subtilis in or on all raw agricultural commodities when applied as a seed
treatment for growing agricultural crops (NY DEC 2000).
The US EPA Biopesticides and Pollution Prevention Division documents
indicate that B. subtilis MBI 600 is non-toxic/pathogenic to birds
or insects and no aquatic exposures are anticipated. No adverse
effects to fish or wildlife resources are likely through labeled
use of this product and no impact to groundwater is anticipated.
The Department's evaluation of non-target organisms found the
Serenade® Biofungicide product to be practically non-toxic
to mammals and birds. Label instructions are adequate to protect
aquatic organisms and bees. Modeling of maximum use rate applications
did not exceed toxicity thresholds for birds, mammals, or aquatic
organisms (NY DEC 2000).
Effect on human health:
In terms of human health, reviewers found the B. subtilis bacteria
to be relatively benign. It is not a known human pathogen or
disease causing agent. B. subtilis produces the enzyme subtilisin,
which has been reported to cause dermal allergic or hypersensitivity
reactions in individuals repeatedly exposed to this enzyme in
industrial settings. The oral, dermal and pulmonary acute toxicity
data, as well as eye and skin irritation data on the active ingredient
and/or the formulated product, indicate that neither the B.
subtilis strain QST713 nor the Serenade® Biofungicide product was
very toxic, irritating, pathogenic, or infective to laboratory
animals by the above noted routes of exposure. The Serenade® Biofungicide
product elicited a mild contact hypersensitivity response (tested
on guinea pigs) indicating that it is a potential skin sensitizer
(NY DEC 2001).
No toxicological effects were reported for B. subtilis MBI 600
following oral or dermal inhalation studies and no infectivity
or pathogenicity was observed. HiStick® N/T (based on data
for the formerly labeled product Epic®) may be somewhat irritating
to eyes and skin and may cause skin reactions from direct contact
(NY DEC 2000).
Efficacy
Serenade® —In the many tests done with Serenade®,
it gave good results against onion diseases, downey mildew in grapes,
and powdery mildew on greenhouse tomatoes. Other trials showed
poor to fair efficacy. It should be noted that trials against fireblight
in apples showed some efficacy, though low. This disease is notoriously
difficult to control, and even low levels are promising.
Serenade is often used and trialed in rotation or combination
with other fungicides such as copper products. Results from such
trials are not included here, because it is impossible to attribute
efficacy data from them directly to Serenade®. However, there
is some indication that this use of Serenade® may allow for
reduced rates or frequency of the companion fungicides.
Kodiak®--Kodiak seed treatment needs to be evaluated differently
from spray products directed against pathogens. In several of the
trials in our database, yield was used as a measurement of the
efficacy of the treatment. Kodiak showed significant yield increase
of 11 and 15% in two trials, and a non-significant increase of
28% in another. Since the cost of treatment is small, such increases
can be very worthwhile to the farmer, even though the numbers may
not be impressive.
In four studies, Kodiak® gave little or no visible control
of root rot pests, but in one it gave a significant 22% control
of Fusarium root rot in beans, and in another its use resulted
in an 81% stand increase in chickpeas. A summary of recent university
field trials of Serenade® and Kodiak® on fruit and vegetable
crops commonly grown in the Northeast was compiled for this fact
sheet. These university-based trials typically test products with
untreated buffer rows and other conditions that create unusually
severe pest pressure.
In the table below, “good control” means statistically
significant reductions in pest numbers or damage of 75% or more,
compared to an untreated control. “Fair control” includes
those with significant reductions of 50-74%, and any non-significant
reductions of over 50%. The “poor control” group includes
any results with less than 50% reduction.
The level of pest control obtainable is likely to be higher than
shown, on completely treated fields in which a good program of
cultural controls has also been implemented.
REFERENCES
Backman, PA, M. Wilson and J. F. Murphy. 1997. Bacteria
for Biological Control of Plant Diseases in Rechcigl and Rechcigl,
eds., Environmentally Safe Approaches to Crop Disease Control.
pp. 95-109. CRC Press.
Cline, D. 2004. Agraquest Inc. Personal communication.
CPL Scientific Publishing Services Ltd. 2001. Worldwide Directory
of Agrobiologicals web page dated 8-28-2002.
Gustafson LLC. Website accessed Feb.2004.
NOP. 2000. National Organic Program Regulators, 7CFR 205, 206(e)
http://www.ams.usda.gov/nop
NY DEC. 2000. M. Serafini. NY State Dept. of Environmental Conservation
NY DEC. 2001. M. Serafini, NY State Dept. of Environmental Conservation.
http://pmep.cce.cornell.edu/profiles/fung-nemat/aceticacid-etridiazole/bacillus_subtilis/bacillus_label_401.html |