Compost tea and additives causing pathogens

[mdvpc]

Take a look at this article:

http://www.foodconsumer.org/777/8/Re...post_Tea.shtml

The article states that adding things like kelp can promotes bacteria, including pathogens. I have frequently added kelp to my compost tea while brewing. I think I will add it when I am finished brewing and just before I spray.

[beeman]

I suppose the answer is to make certain that e coli are not in the compost to start with.
My information is that E coli comes from manure, both human and animal. As I don't use either in my compost, then there should not be an increase of pathogens in the Tea.

[Blueaussi]

Can you be assured that no cockroaches or peromyscus or squirrels scampered across your compost pile?

And, say, weren't you the one who was advocating going out in the woods and digging up leaf litter to brew compost teas?

[beeman]

Originally Posted by Blueaussi

And, say, weren't you the one who was advocating going out in the woods and digging up leaf litter to brew compost teas?

NOTE TO SELF. Revert to lurker mode, or else you'll wake the troll.

[mdvpc]

I contacted Patricia Milner, who was one of the USDA scientists that did the research in my first link.

Here is the original article. She told me in an email that molasses specifically was one of the additives that was a problem in growth of pathogens during brewing.

1
National Organic Standards Board
Compost Tea Task Force Report
April 6, 2004
Introduction
In 2003, the National Organic Standards Board convened a Compost Tea
Task Force to review the relevant scientific data and report their
recommendations on ‘What constitutes a reasonable use of compost tea?’ The
Task Force was composed of 13 individuals (Appendix B) with knowledge and
expertise in organic farming practices, organic certification, EPA pathogen
regulations, compost, compost tea production and analysis, plant pathology, food
safety and environmental microbiology. Throughout their discussions, members
consistently acknowledged the growing interest among certified organic and
conventional growers to use compost teas, and the need to develop effective
biologically-based tools to manage plant fertility, pests, and diseases. A major
focus of the Task Force was concern about the potential for compost tea to
contaminate edible plants with human pathogens as regulated in Section
205.203 of the USDA National Organic Program Final Rule. Addressing potential
contamination by human pathogens required an examination of compost tea
production and use practices, along with the underlying science relative to
human pathogen contamination of crop plants.
Use of the terms compost and vermicompost in this report refer to the
definitions set forth in the NOSB Compost Task Force report of April, 2002
(NOSB, 2002). These definitions are printed in the glossary below, along with
additional terminology and definitions used in this report. Hereafter in this report,
‘compost’ shall refer to both compost and vermicompost. Likewise, ‘compost tea’
shall refer to both compost tea and vermicompost tea.
Background
Compost tea practitioners are largely responsible for developing the wide
array of compost tea production practices and uses of compost tea in plant pest,
disease, and fertility management programs (reviewed in Brinton, 1995; Brinton
et al, 1996; Diver, 1998 and 2001; Ingham, 2003; Quarles, 2001; Scheuerell and
Mahaffee, 2002; Touart, 2000). In comparison to the extensive experiences
reported by practitioners, relatively few peer-reviewed reports describe scientific
studies on the production and use of compost teas; most research reports relate
to the efficacy of compost teas for plant disease control (reviewed in Weltzien,
1991; Scheuerell and Mahaffee, 2002). Because much of the available
information on compost tea practices and effects has not been rigorously or
scientifically documented, this report attempts to distinguish between existing
2
practitioner-based knowledge [practice] and scientific knowledge that is
supported by controlled, replicated experiments [science].
A primary reason for producing compost tea is to transfer microbial biomass,
fine particulate organic matter, and soluble chemical components of compost into
an aqueous phase that can be applied to plant surfaces and soils in ways not
possible or economically feasible with solid compost. While compost tea is made
in a variety of ways, all methods are similar in having water as the first, and
compost as the second, most abundant starting materials. Compost tea
production methods diverge based on several properties, particularly the intent to
maintain a minimum level of dissolved oxygen. Other distinguishing factors are
the ratio of compost to water, addition of supplemental nutrients designed to
increase microbial biomass (in this report termed ‘compost tea additives’), and
the duration of the production process. At the time this committee gathered
information to review (2003-2004), the predominant compost tea production
method practiced in the United States is commonly termed actively aerated
compost tea, which is the product of the following general process. Usually
compost is filled into a porous container, which is then suspended in a watercontaining
vessel, typically 1 part compost to 10-50 parts water. Constant
mechanical energy input is used to provide aeration either by air injection directly
into the water or by re-circulation of the water, typically for 12-24 hours. Compost
tea additives, such as molasses, yeast extract, algal powders, when included,
substantially increase microbial biomass in the aqueous phase from
microorganisms extracted from the compost. Often actively aerated compost
teas are made using one of many commercially produced “brewers”, however,
many home-made brewers are also in use.
A second form of compost tea is termed either non-aerated compost tea or
passively aerated compost tea, and is the product of the following general
process. Typically 1 part compost is mixed with 3-10 parts water in an open
container, where it remains with or without daily stirring, for at least several days,
often for 1 to 3 weeks. Compost tea additives are infrequently added to nonaerated
compost tea.
For the purposes of distinguishing compost tea production practices that have
the potential to support growth of bacterial pathogens, this report considers any
mixture of compost and water that is held for longer than one [1] hour before
initiating application to be a form of compost tea. Any mixture of compost and
water that is held for less than one hour before initiating application is considered
a compost extract (see Glossary herein for a definition of compost extract; see
Scheuerell and Mahaffee, 2002, for a discussion).
Before use, compost teas are typically filtered to a degree necessary to avoid
plugging the sprayer or irrigation system used for application. Spray adjuvants
are sometimes added immediately prior to application.
Background issues associated with human pathogen contamination
The National Organic Program (NOP) specified composting standards for
manure and mandated a 90/120 day pre-harvest interval for land application of
3
non-composted manure. These requirements were established to reduce the
potential for transfer of human pathogens to food crops from raw manure. Timetemperature
criteria for thermophilic composting provides a basis for this
disinfection process that further reduces pathogens (PFRP), however, meeting
the criteria does not guarantee the complete destruction of all pathogens in every
particle of compost. The number of human pathogens surviving may be so low
that they are undetectable by standard laboratory procedures used in quality
assurance testing. This does not mean that the process was deficient, but simply
indicates that the test cannot guarantee a pathogen-free result for the entire
mass, and that the test has limits of sensitivity. It does show that the pathogen
content of the organic mass is substantially less than it was prior to composting.
With both the time-temperature exposure data and before/after composting test
results, compost producers can document that their process meets the standards
for pathogen limits established for use and general distribution of composted
fecal-matter as a soil amendment (US EPA, 1993; FDA, 1998).
For compost tea, the use of compost tea additives to encourage growth of
beneficial, nonpathogenic microbial populations from compost can have nontarget
effects, i.e., the additives can likewise support growth of bacterial human
pathogens from undetectable to easily detectable numbers, in liquid microbial
cultures, as preliminary investigations have demonstrated (discussed further
below). This is the basis for concern about compost tea production practices that
use compost tea additives to increase microbial populations; thereby potentially
posing a risk of contaminating crop plants with human pathogens due to
introduction of pathogenic bacteria (Patricia Millner, personal communication).
The concern is similar to that of EPA’s Solid Waste bureau and other State
regulating bodies which restrict re-introduction of fresh decomposable substrates
into composts that have previously met heat standards, owing to risk of pathogen
regrowth. These concerns led the NOP to state that compost tea does not satisfy
ξ205.203 Soil fertility and crop nutrient management practice standard (c) The
producer must manage plant and animal materials to maintain or improve soil
organic matter content in a manner that does not contribute to contamination of
crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or
residues of prohibited substances (NOSB Compost Task Force
Recommendation, 2002; as amended by the NOP). However, there is not
unanimous agreement on these and other data, which the Task Force was aware
of, suggesting that the evidence of dangers from pathogens is inconsistent.
Although concern exists, there have been no reported cases of food borne
illness from the use of compost tea, but there have been no epidemiological
health/microbial studies done to evaluate this effect. Because gastrointestinal
disease cases in the US are notoriously underreported and of unknown cause
(Mead et al., 1999), lack of evidence cannot be used to support evidence of no
problem. The committee acknowledges that proactive protective measures
should be considered when the contamination of fresh produce with human
pathogens is an issue. For compost tea, averting the theoretical possibility of
contaminating crops with human pathogens can be approached by implementing
measures that reduce the potential for pathogens to enter compost tea
4
production systems, and perform quality assurance testing to demonstrate that a
specific compost tea production system produces compost tea that meets
microbiological quality guidelines.
Glossary and definitions
A brief list of relevant terms used in this report is provided below.
• Composting. A managed process in which organic materials, including
animal manure and other residuals, are decomposed aerobically by
microbial action. “Thermophilic” composting refers to the time-limited,
self-heating process in which heat generated by microbial respiration is
retained in the mass of a pile or windrow such that vulnerable pathogenic
microorganisms are destroyed. Compost is defined by the NOSB Compost
Task Force (NOSB, 2002) as “Compost, in addition to that described in
section 205.203 (c) (2), is acceptable if (i) made only from allowed
feedstock materials, except for incidental residues that will not lead to
contamination, (ii) the compost undergoes an increase in temperature to
at least 131 degrees F (55 degrees C) and remains there for a minimum of
3 days, and (iii) the compost pile is managed to ensure that all of the
feedstock heats to the minimum temperature.”
See also Vermicompost below.
• CFU. Colony-forming unit; a term used in microbiology to express the
number of microbes in a sample that produced colonies on nutrient agar in
petri plates.
• Compost extract. Any mixture of compost and water, additives, and
adjuvants that is not held for more than one hour before use. Compost
extracts lack sufficient holding time for microorganisms to multiply and
grow significantly.
• Compost leachate. Liquid that has leached through a compost pile and
collects on the ground, compost pad, or collection ditches, puddles, and
ponds.
• Compost tea additives. Materials separate from compost and water that
are added in the process of making compost tea that are presumed to
sustain and enrich microbial growth. These are distinct from spray
adjuvants that are tank mixed immediately prior to application of compost
tea. Examples include but at not limited to the following: molasses, yeast
extract, fish-based products, kelp, and green plant tissue.
• Disease vector. Animals including rodents, flies, and birds that are
capable of transferring human pathogens to other materials.
5
• Manure extract. Water suspension containing raw, non-disinfected
manure; when the suspension is maintained for several hours or more it is
sometimes referred to as manure tea.
• Microorganism. Bacteria, fungi (molds, yeasts), protozoans, helminths,
and viruses. The terms microbe and microbial are also used to refer to
microorganisms.
• Pathogen. A microorganism capable of causing disease or injury; used to
refer to “plant” or to “human” pathogens. Parasite and parasitic refer to
infectious protozoans and helminths. Helminth and helminth ova refer to
parasitic worms, e.g., roundworms, tapeworms, Ascaris, Necator, Taenia,
and Trichuris, and ova (eggs) of these worms. (See Appendix A for a list
of pathogens of concern).
• Indicator organism. A microorganism that is used for monitoring whether
a certain set of pathogens might be present.
• Potable water. Water suitable for human consumption.
• Sanitize. To treat equipment and surfaces by a process that is effective in
destroying or substantially reducing the numbers of microorganisms of
public health concern, as well as other undesirable microorganisms.
Sanitizing agents are described and defined in 21 CFR 178.1010.
• Spray adjuvants. Any material added to compost tea immediately prior
to application of compost tea. These may include materials that are
designed for wetting & sticking agents, plant nutrients, and those materials
that sustain and enrich microbial growth, but because of the short time
frame between addition and application, there is a very low probability of
multiplying undesirable microorganisms in the spray tank.
• Vermicomposting. Process of worms digesting organic matter to
transform the material into a beneficial soil amendment. Vermicompost is
defined by the NOSB Compost Task Force (NOSB, 2002) as:
“Vermicompost is acceptable if (i) made from only allowed feedstock
materials, except for incidental residues that will not lead to contamination,
(ii) aerobicity is maintained by regular additions of thin layers of organic
matter at 1-3 day intervals, (iii) moisture is maintained at 70-90%, and (iv)
duration vermicomposting is at least 12 months for outdoor windrows, 4
months for indoor container systems, 4 months for angled wedge systems,
or 60 days for continuous flow reactors. “
See also Compost above.
6
Compost tea applications
Compost tea practitioners have developed a range of compost tea uses and
applications methods. A brief description of the most common uses and
application methods for compost tea follows. This information was used to
develop an understanding of compost tea applications that could pose an
increased potential of contaminating food crops with human pathogens.
Applications to above ground plant parts.
• Foliar spray. Applied through irrigation system or sprayer to aboveground
plant parts.
• Stubble digester/green manure inoculant. Applied to crop residues
or cover crops, usually after mowing and before incorporation into the
soil
Applications to soil and soil-less potting media.
• Soil. Application to unplanted or planted fields. For unplanted fields,
applied through irrigation system (drip, micro sprinklers, sprinkler line,
gun, wheel line, center pivot) or tractor mounted/pulled sprayer. For
planted fields, applied as a directed spray to areas of bare soil or
through drip irrigation systems.
• Soil-less media. Use to moisten media before planting or as a postplant
drench.
Seed treatment. Soak seeds or propagation material (e.g., potato) before
planting.
Odor suppressant. Applied to manure collection/handling areas or to ground
surrounding compost piles to reduce production of odors.
Plant responses to compost tea
Grower testimonials constitute the majority of evidence that supports the use
of compost tea as a beneficial agricultural production tool. Most testimonials
have described impacts on plant growth or disease suppression. Relatively few
rigorous scientific studies have examined the use of compost tea for plant
disease suppression. The following information summarizes plant responses to
compost tea and was used by the Task Force to identify areas of study that
should receive greater scientific attention.
Positively impact plant vigor and growth. A growing number of organic and
conventional growers are using compost tea because they have observed yield
7
and/or production efficiency gains (Schmitz, 2002; Diver, Ingham, Scheuerell,
personal communication).
• Postulated direct mechanisms include plant response to nutrients or
phytohormone/growth promoting chemicals in the compost tea.
• Postulated indirect mechanisms include altering composition and/or
populations of plant associated microorganisms that cause a direct
effect, or over time, moderation of the chemical, physical or biological
properties of the rhizosphere/phyllosphere. Examples would be soil
structure, pH, or reducing the effect of deleterious (nonpathogenic)
microorganisms.
Plant disease management
• Practitioner-based knowledge [Practice]
There have been a large number of grower testimonials in recent years
suggesting that compost tea has improved their ability to manage plant
diseases (Diver, Ingham, Scheuerell, personal communication).
Grower experiences have indicated that both non-aerated and aerated
compost tea can suppress the incidence and/or severity of foliar and
root rot diseases.
• Science-based knowledge [Science]
• Some replicated scientific studies have indicated that both nonaerated
and aerated compost tea can suppress the incidence
and/or severity of foliar and root rot diseases, while others have
observed no significant effect (reviewed in Scheuerell and
Mahaffee, 2002; Weltzien, 1991).
• Lack of consistency of disease suppression by compost tea is
postulated to be caused by variability in raw materials, the
production process, nutrients and other materials tank mixed before
application, application method and timing, pathogen pressure, and
environmental conditions. The committee had limited data available
to review (see Scheuerell, 2002; Scheuerell and Mahaffee, 2002;
Weltzien, 1991).
Potential Microbial Hazards Associated with Compost Tea
There are many variables in the production and application of compost tea
that could affect the probability of contaminating crops with human pathogens. In
addition, plant properties and environmental conditions greatly affect survival of
8
human pathogens. This section of the report discusses factors associated with
compost tea production, plant properties, and environmental conditions that
could affect the contamination of crops with human pathogens. This information
was used by the Task Force to identify data gaps and guide the development of
recommendations.
Transfer or multiplication of pathogenic organisms
• Compost tea production factors. In general, pathogens that go
into the process might come out at the same, lower, or higher
levels. Processes or materials that have a high probability of
increasing human pathogens during compost tea production are of
greatest concern.
• Compost feedstocks and composting process used
[Science]
Feedstocks such as manure have a high probability of
containing pathogenic organisms. These types of materials can
be processed to reduce populations of indicator microbes and
pathogens to acceptable levels by using approved PFRP’s. For
example, Lung et al. (2001) recently reported that after
composting cow manure E. coli and Salmonella were not
detected after 72 hours at 45 degrees C. All data brought to the
Task Force support the notion that compost tea made from
compost and vermicompost, as defined by the NOSB Compost
Task Force (NOSB, 2002), does not represent a risk if compost
tea additives are not used.
• Compost stability. [Science]
Compost stability is the reactivity of composting materials, most
commonly measured as the rate of oxygen consumption and/or
rate of carbon dioxide respiration. Stability is known to affect
the potential for Salmonella re-growth in composting biosolids
(Soares et al , 1995; Soares, 1996; Skanavis and Yanko, 1994;
Yanko, 1987; Yanko et al., 1995 ). Stability affects the relative
quantity of nutrients originating from the compost that support
the growth of a wide range of microorganisms, including some
human pathogenic bacteria. Data is lacking on the relationship
between human pathogen growth potential in compost tea and
compost stability.
• Water quality [Science]
9
Potable water quality is necessary to prevent the introduction of
pathogens.
• Sanitation [Practice]
Cleaning procedures for production and application equipment.
No standards exist, but sanitizing agents should be used to
maintain equipment free of microbial biofilms between uses, and
accidental contamination from wind-borne dust should be
avoided.
• Disease vector access [ Science]
Rodents, flies, and birds need to be excluded from the materials
used to produce compost tea.
• Brew time and temperature. [Practice]
Affects the theoretical maximum number of bacterial divisions
that can occur during compost tea production.
• Compost tea additives. [Practice and Science]
Materials other than water and compost added at the start of the
compost tea making process to increase microbial
biomass/populations. It should be noted that as of March 30,
2004, only one of the studies (Duffy et al, 2004) discussed
below has been published in a peer-reviewed scientific journal.
• Duffy (et al 2004) related the growth of E. coli O157:H7 and
Salmonella Thompson to concentration of molasses added to 2
types of compost with water in sealed flasks that were rotary
shaken for 72 hours (Duffy et al, 2002). Re-growth of either
pathogen was not detected when 0, 0.05, or 0.2% vol/vol
molasses was added. Re-growth of E. coli and Salmonella was
observed when 0.5 or 1.0% molasses was added, with 0.5%
molasses supporting greater re-growth of Salmonella than E.
coli. For Salmonella, composted chicken manure supported 100
times more re-growth than composted dairy manure when 0.5 or
1.0% molasses was added; potentially due to the greater
concentrations of inorganic nutrients in the composted chicken
manure. This indicates that pathogen re-growth can be
dependent on the concentration of compost tea additive used.
In addition, the significant interaction between compost source
and additives on the re-growth potential of human pathogens in
this study indicates the need to test individual batches of
compost with defined concentrations of compost tea additives
10
for compost tea quality assurance testing. The nature of the
production method used in the Duffy et al paper has been
challenged as not relating to any compost tea production
practice (Elaine Ingham, personal communication).
• Data presented by Bess (et al, 2002) at the 2002 International
Symposium Composting and Compost Utilization, May 6-8,
Columbus, Ohio, addressed the issue of increasing populations
of bacterial pathogens through the addition of compost tea
additives. The report indicated that E. coli increased to various
degrees with different microbial culture nutrients when
incompletely composted material that contained detectable
populations of E. coli was used in an aerated compost tea
brewer (Bess et al, 2002).
• Initial experiments presented to the Task Force by Pat Millner
and Will Brinton and duplicated in two microbiological labs
simultaneously, indicated pathogen growth could occur in
compost teas when very low concentrations of molasses were
used in combination with a compost substrate seeded with very
low numbers of human pathogens (‘trace’ concentration, also
referred to as ‘undetectable’ by common laboratory analysis).
This resulted in growth of the pathogens in the compost tea to a
quantity detectable by common laboratory procedures (Millner
and Brinton, Manuscript Report to Task Force).
• Other experiments were discussed that showed vermicompost
with relatively high populations of E. coli resulted in variable
amounts of E. coli growth depending on the concentration of
molasses used as a compost tea additive (Elaine Ingham,
personal communication). Related experiments using a mined
humus material (no detectable E. coli) in place of compost
resulted in no growth of E. coli over a range of molasses
concentrations used as a compost tea additive (Elaine Ingham,
personal communication). Other tests that utilized compost sold
as part of an aerated compost tea production system or
compost that had had below detectable levels of E. coli did not
show an increase in E. coli even when compost tea additives
were used (Scheuerell and Millner, personal communication;
Brinton, personal communication).
• Crop/environmental factors [Practices available, no Science
available that directly addresses compost tea use under agronomic
conditions]
• Pre-harvest interval
• Climate – temperature, humidity, precipitation
11
• Crop architecture – UV protected sites, moisture availability,
plant exudates
• Crop cleaning, processing, cooking. Crops that are dried and
then cooked before consumption, such as grain crops, are not
considered to be a significant source of human pathogens.
Factors Associated with Human Pathogens
The following are factors associated with human pathogens that the Task Force
considered while developing recommendations.
• Actual pathogens present. The presence or growth potential of
many pathogens has not been thoroughly evaluated for different
compost teas.
• Contamination level of compost teas. Available research has used
non-stable compost with readily detectable populations of human
pathogens or compost artificially inoculated with human pathogens.
For artificially inoculated compost, research has demonstrated a high
degree of variability in final pathogen populations across replications of
the same compost tea production treatment (Scheuerell and Millner,
personal communication). Data currently relate to pathogens
suspended in the tea, rather than the number that survive on the
surface of edible fresh produce after tea is directly applied to plant
surfaces.
• Pathogen survival. In the environment pathogen populations typically
decline over time, unless deposited in a site with all conditions
conducive for survival or growth. For example, Liao (2003)
demonstrated that human pathogens present in dairy manure were not
detectable 70 days after application to potato production fields. In a
review of published data on the survival of human pathogens on plant
surfaces, Epstein (1997) indicated that most studies found bacterial
pathogens to survive for <1 day to a maximum of 35 days on plants,
and the longest cited survival time of any pathogen was 68 days.
• Crop architecture and exudate profile. Potential for the crop to
enable pathogen survival or growth. Lettuce and apples are the
best known examples for harboring bacterial pathogens in sites
protected from environmental stress and likely releasing sufficient
nutrients to support pathogen metabolic activity.
• Environment. Particularly important for above ground portions of
plants. Ultraviolet radiation and dessication are the two most
important environmental factors causing pathogen destruction.
12
Little is known about interactions with other microorganisms on
plant surfaces under field conditions.
• Pre-harvest interval. If the decimal reduction time is known for a
crop and general environment, then the interval between the last
compost tea application and harvest can be used to compute the
amount of pathogen reduction expected during that pre-harvest
interval.
• Post-harvest treatments. Removing part of the plant, sanitizing, and
processing activities can leave unaffected, spread or kill individual
pathogen cells. This depends on a number of factors including plant
type, washing system, sanitizing system, cutting of plant tissue, and
most importantly thermal processing.
Data Gaps [Science needed]
• Cost-benefit analysis. Developing a cost-benefit analysis of compost tea
use will require confirming compost tea production and application
methodologies that consistently provide a positive, measurable crop
response. If benefits were quite certain, then the cost of incorporating the
compost tea program compared to other production choices could be
quantified.
• Ecology of human pathogens
• We lack an understanding of the population dynamics of human
pathogens when occurring in diverse microbial mixtures with active
predation by higher trophic levels. The microbial diversity and
competition found during compost tea production could inhibit or
destroy human pathogenic bacteria.
• Influence of water temperature and production duration on pathogen
growth. For compost tea production, combining relatively low water
temperatures with short production durations may provide conditions
not suitable to significantly increase human pathogenic bacteria that
have evolved optimal growth rates associated with warm-bodied
animals.
• Survival of human pathogens on crop plants, under field conditions,
when inoculated at realistic levels. In addition, diverse microbial
competition for resources and/or antagonism and predation by other
organisms on crop plants could affect duration of survival in crop
environments.
• Internalization of pathogens into plants. Laboratory and greenhouse
studies have shown incorporation of E. coli into plant tissue is possible
when inoculated with very high populations of pathogenic bacteria.
Whether this occurs on crop plants, under field conditions, or in relation
13
to compost teas containing a realistic level of contamination has not
been researched. If internalization of pathogens is an issue, on what
plants and under what conditions needs to be determined.
• Pre-harvest application interval. The aforementioned data gaps
preclude a meaningful assessment of appropriate pre-harvest interval
recommendations.
• Compost Stability. Role of compost stability in the potential for compost
to support the growth of pathogenic bacteria during compost tea
production.
• Feedstocks. Role of different feedstocks used to make compost in the
potential for compost to support the growth of pathogenic bacteria during
compost tea production.
• Phytotoxic reaction [Practice]. Potential for compost tea to cause
phytotoxic reactions, particularly in relation to the compost tea production
practice used. There are few reports of adverse effects (Diver and
Ingham, personal communication). Theoretical concerns of phytotoxicity
are based on soluble salt levels or potential accumulation of phytotoxic
microbial metabolites during compost tea production. Potential for
phytotoxic reactions could be affected by tea concentration, dose, crop,
and environmental conditions. If a concern exists, like any agricultural
material, the tea should be tested on a small portion of the crop and
observed.
• Dissolved oxygen content. The relevancy of measuring oxygen content
of compost teas as a stand-alone indicator of potential pathogen growth is
uncertain given than E. coli and other potential pathogens are facultative
organisms (capable of growth in presence of oxygen).
Recommendations
1. Potable water must be used to make compost tea and for any dilution before
application.
2. Equipment used to prepare compost tea must be sanitized before use with a
sanitizing agent as defined by 21 CFR 178.1010.
3. Compost tea should be made with compliant compost or vermicompost, using
the NOSB Compost Task Force Guidelines set forth on April 18, 2002, for
thermal compost and vermicompost, or compost as defined in section
205.203 (c) (2) of the NOP rule. For compost tea, this applies to 100% plant
feedstock materials in addition to manure feedstocks because non-manure
compost feedstocks may harbor high levels of fecal bacteria (Epstein, 1997).
14
4. Compost tea made without compost tea additives can be applied without
restriction.
5. Compost tea made with compost tea additives can be applied without
restriction if the compost tea production system (same compost batch,
additives, and equipment) has been pre-tested to produce compost tea that
meets the EPA recommended recreational water quality guidelines for a
bacterial indicator of fecal contamination (US EPA, 2000). These indicators
and the passing criteria are Escherichia coli (126 CFU/100ml) or enterococci
(33 CFU/100ml). At least two compost tea batches must be tested using
accepted methodology (APHA-AWWA-WEF, 1999; US EPA, 2000), with the
average population of indicator bacteria across compost tea batches used as
the measurement of passing. Each new batch of compost would require that
the system quality assurance pre-test be conducted again as indicated. After
it passes again, compost tea from the system can be used without restriction.
If compost tea made with compost tea additives has not been pre-tested for
indicator bacteria, its use on food crops is restricted to the 90/120 day preharvest
interval. Crops not intended for human consumption, ornamental
plants, and grain crops intended for human consumption are exempt from
bacterial testing and 90/120 day pre-harvest interval restrictions. In the view
of the Task Force, educating producers about the potential for contamination
and its impacts on public health and marketing, as well as how this
recommended quality assurance testing system would avoid potential
contamination will provide compelling incentives for producers to follow the
rules.
6. Compost extracts - any mixture of compost, water, additives, and adjuvants
that is not held for more than one hour before use - may be applied without
restriction.
7. Raw manure extracts or teas may be applied to the soil with a 90/120 day
pre-harvest restriction, foliar applications are prohibited.
8. Compost leachate may be applied to the soil with a 90/120 day pre-harvest
restriction, foliar applications are prohibited.
9. Compost tea is not allowed for the production of edible seed sprouts.
10. The emerging national acceptance of compost tea as a biologically-based
crop production tool by organic as well as conventional growers clearly
indicates the need for further scientific investigation to validate the benefits
and concerns of compost tea use. The Task Force unanimously urges USDA
and its agencies to strongly support additional research on the potential for
crop contamination and plant disease/pest control by compost tea. There is
15
an urgent national need to address critical data gaps, uncertainties, and
variability in existing data that limited the evaluation of potential crop
contamination by the current task force. Data are urgently needed to provide
science-based recommendations on how compost tea production and
application practices impact potential crop contamination, while at the same
time preserve the means for improving plant health and vigor. Critical issues
requiring further data include compost quality, compost tea additives,
temperature and duration of compost tea production, and the population
dynamics of human pathogens in microbially diverse agro-ecosystems
relative to pre-harvest intervals for application of compost tea.
16
REFERENCES
American Public Health Association, American Water Works Association, Water
Environment Federation. 1999. Standard methods for the examination of water
and wastewater [CD-ROM]. 20th edition. New York.
Bess, V. H., R. B. S. Manes, and J. L. Snodgrass. 2002. E. coli survival in
compost tea using different nutrient substrates. Proceedings 2002 International
Symposium Composting and Compost Utilization.
Brinton, W.F. 1995. The control of plant pathogenic fungi by use of compost teas.
Biodynamics Jan/Feb:12-5.
Brinton, W.F, A. Trankner, M. Droffner. 1996. Investigations into liquid compost
extracts. Biocycle 37(11):68-70.
Diver, S. 1998. Compost Teas for Plant Disease Control. ATTRA, Fayetteville,
AR. http://attra.ncat.org/attra-pub/comptea.html
Diver, S. 2001. Notes on Compost Teas: A 2001 Supplement to the ATTRA
publication Compost Teas for Plant Disease Control. ATTRA, Fayetteville, AR.
http://attra.ncat.org/attra-pub/compost-tea-notes.html
Duffy, B., C. Sarreal, R. Subbarao, and L. Stanker. 2004. Effect of molasses on
Regrowth of E. coli O157:H7 and Salmonella in compost teas by B. Duffy, C.
Sarreal, S. Ravva and L. Stanker Compost Science and Utilization, Vol. 12
(1):93-96.
Epstein, E. 1997. Pathogens, p. 213-245 In: The Science of Composting.
Technomic Publishing Co., Inc., Lancaster, PA.
FDA, 1998. Guidance for Industry: Guide to Minimize Microbial Food Safety
Hazards for Fresh Fruits and Vegetables. Federal Register, October 29, 1998
Vol. 63(209):58055-58056. http://www.foodsafety.gov/~dms/prodguid.html.
Ingham, E.R. 2003. The Compost Tea Brewing Manual, 3rd Edition. Soil Food
Web, Inc., Corvallis, OR.
Liao, Ching-Hsing, C. Wayne Honeycutt, Tim S. Griffin and John M.
Jemison. 2003. Occurrence of gastrointestinal pathogens in soil of potato
field treated with liquid dairy manure. Food, Agriculture & Environment
Vol.1(2):224-228.
Lung, A.J., C.M. Lin, J.M. Kim, R. Marshall, R. Nordstedt, N.P. Thompshon and
C.I. Wei. 2001. Destruction of Escherichia coli 0157:H7 and Salmonella
17
enteridtidis in cow manure composting. Journal of Food Protection 64:
9:1309-1314.
Mead, P.S., Slutsker, L., Dietz, V., McCaig, L.F., Bresee, J.S., Shapiro, C.,
Griffin, P.M. and Tauxe, R.V. 1999. Food-related illness and death in the United
States. Emerging Infectious Diseases 5:607-625.
NOSB, 2002. Compost Task Force Recommendation, as amended by the NOP.
http://www.ams.usda.gov/nosb/archive...endations.html
OMRI, 2003. OMRI update. Vol. 5(3):1,6.
Quarles, W. 2001. Compost tea for organic farming and gardening. The IPM
Practitioner 23(9):1-8.
Scheuerell, S. 2002. Compost teas and compost amended container media.
Ph.D. Dissertation. Oregon State University, Corvallis, OR.
Scheuerell, S. and W. Mahaffee. 2002. Compost tea: Principles and prospects
for plant disease control. Compost Science and Utilization 10(4):313-338.
Schmitz, J. 2002. Compost teas work on center pivot farm. Capitol Press. Nov.
29, 2002, p. 20.
Skanavis, C. and Yanko, W. A. 1994. Evaluation of composted sewage sludge
based soil amendments for potential risks of Salmonellosis. Journal of
Environmental Health 56(7):19-23.
Soares, H., B. Cardenas, D. Weir, M. Switzenbaum. 1995. Evaluating pathogen
regrowth in biosolids compost. BioCycle. June:70-74
Soares, H. 1996. Pathogen Indicator Regrowth Potential as a Method to Evaluate
Compost Stability. Ph.D. Dissertation. University of Massachusetts, Amherst,
MA.
EPA (U.S. Environmental Protection Agency). 1993. Federal Register: February
19, 1993. 40 CFR Parts 257, 403, and 503. The Standards for the Use or
Disposal of Sewage Sludge. Final Rules. EPA 822/Z-93/001. U.S. Environmental
Protection Agency.
US EPA, 2000. Improved Enumeration Methods for the Recreational Water
Quality Indicators: Enterococci and Escherichia coli. United States Environmental
Protection Agency. Office of Science and Technology, Washington, DC.
EPA/821/R-97/004.
18
Weltzien, H. C. 1991. Biocontrol of foliar fungal disease with compost extracts, p.
430-450. In: J. H. Andrews and S. S. Hirano (eds.), Microbial Ecology of Leaves.
Springer-Verlag, New York.
Touart AP. 2000. Time for compost tea in the Northwest. Biocycle 40(10):74-7.
Yanko, W.A. 1987 Occurrence of Pathogens in Distribution and Marketing
Municipal Sludges. NTIS PB88-154273-AS. Springfield, VA.
Yanko, W.A., A.S. Walker, J.L. Jackson, L.L. Libao, and A.L. Garcia. 1995.
Enumerating Salmonella for compliance with pathogen regulations. Water
Environment Research 67:364- 370.
19
Appendix A
Public Health (Food and Waterborne) Pathogens of Concern in
Animal Manure
Major Concern
Minor Concern Intermediate
E. coli 0157:H7
Listeria monocytogenes
Salmonella
enterpathogenic E. coli
Yersinia enterocolitica
Campylobacter jejuni
Leptospira
Cryptosporidium parvum
Giardia lamblia
Ascaris lumbricoides
Ascaris suum
Hymenolepis nana
Necator americanus
Taenia saginata
Toxocara canis
Trichuris trichiura
Enteroviruses
Rotaviruses
Orthomyxovirus (Influenza A)
Bacillus cereus
Brucella
Citrobacter spp.
Clostridium perfringens
Coxiella burnetii
Enterobacter spp.
Erysipelotrix rhusiopathiae
Francisella tularensis
Klebsiella spp.
Mycobacterium tuberculosis
Mycobacterium avium spp.
Proteus spp.
Pseudomonas aeruginosa
Serratia spp.
Staphylococcus
Streptococcus spp.
Helicobacter
Aeromonas
Burkholderia
Legionella pneumophilia
Toxoplasma gondii
Endotoxins
Enterotoxins
Antibiotic resistance
Paramyxovirus (Newcastle)
Parapox (Orf)
• Not all pathogens are necessarily present in all manures, all the time.
In terms of emerging diseases, Taylor et al. (2001) reported that there are 1415
infectious agents that affects human, including 217 viruses and prions, 538
bacteria and rickettsia, 307 fungi, 66 protozoa, 287 helminths. Of these 868
(61%), are zoonotic, i.e. transmissible between humans and animals, 175
pathogenic spp. are associated with diseases considered to be ‘emerging’
Taylor et al. (2001) show that zootic pathogens are more likely to be emerging
than existing and that protozoa and viruses are most likely to emerge and
helminths are least likely. They found no association between the disease
transmission route and emergence.
Taylor, L.H., Latham, S.M., Woolhouse, M.E.J. 2001. Risk factors for human
disease emergence. Phil. Trans. Royal Soc. London B 356: 983-989.
20
Appendix B
Compost Tea Task Force Members
Dr. Eric Sideman, Chair
Maine Organic Farmers and Gardeners Association
Dennis Holbrook, Co-Chair until he resigned from the NOSB
National Organic Standards Board, Farmer
Dr. Owusu Bandele
Food for Thought Organic Farm
National Organic Standard Board, Chair of Crop Committee
Dr. Will Brinton
Woods End Research Laboratory
Esper K. Chandler
Texas Plant & Soil Lab
Steve Diver
ATTRA – National Sustainable Agriculture Information Service
Dr. Clive Edwards
The Ohio State University
Dr. Elaine Ingham
Soil Foodweb, Inc.
Dr. Rosalie Koenig
National Organic Standard Board, Chair of Material Committee and Co-
Chair of Task force replacing Dennis Holbrook
Dr. Frederick Magdoff
University of Vermont
Dr. Patricia Millner
USDA/ARS
Dr. Steven Scheuerell
Oregon State University
Ms. Zea Sonnabend
California Certified Organic Farmers
21
Dr. Larry Zibilske
USDA/ARS

[beeman]

I will risk waking the troll.......
Oh boy! That's a great deal of reading. I didn't see anything to make me stop using/making Activated Compost Tea. I still maintain, keep your compost clean will prevent any problems with E coli and other pathogens.
The benefits far outweigh the risks.
Thanks for posting that.

[mdvpc]

Bee:

It IS a lot of reading and stuff to digest.

Glad you found it of interest.

[Blueaussi]

Originally Posted by beeman

I will risk waking the troll.......

You keep substituting personal attacks for facts. If you don't have any facts that support your position, why don't you just say so?

As I pointed out before, the method of brewing compost tea that you described is favorable to the production of several pathogens. Unless you quarantine your compost in some fashion, it is exposed to various sorts of insects, amphibians, reptiles, birds, and animals (mostly rodents, but probably some insectivores, and one rather notorious marsupial). All those beasties excrete, and they're not very discriminating about where they do, um...doo. And most of them are capable of carrying pathogens that can infect humans.

Now, you said the way to make sure that no E. coli is present in the compost tea is to make sure no E. coli is present in the compost, and that you don't use manure in your compost and therefor have no risk of E. coli in your compost tea.

So, I will ask you again, how do you know that one or some of the native beasties in your area haven't contributed any special surprises to your compost? Can your recognize the poo of all or any of them, and how the poo would look in a moldering pile of vegetable matter?


Were it me, I would have checked with my local health department to see if there were any recent cases of pathogen transmission to a human from one of the afore mentioned creatures, google a bit for any reliable information on research into the likelihood of one of them carrying a pathogen, then I would make an informed choice about the risk of exposing myself or anyone I shared produce with to a pathogen cultured in my homemade compost tea. And, if questioned, instead of denying the possibility with an airy hand wave and a serious snit, I would post my chain of logic and risk assessment procedure, and emphatically assert that this was my own informed choice, and that the questioner should do their own risk assessment and make their own informed decision. But that's just me.

[David Marek]

I just finished reading Teaming With Microbes and am excited about looking for materials to start making AACT this year. My recipe so far includes kelp and molasses. My compost piles usually heat up to 155-160 F (enough to cook a hamburger, although I've never tried it). Sometimes birds poop on the tomatoes so I wash them off. The alternative is to buy grocery store vegetables from CA grown with grey water.

Aren't the additives supposed to encourage fungal and bacterial growth? Does plain sugar help the process?

I am a home grower, not a commercial producer, but I often share produce with friends and neighbors. Thanks for the info.

David

[beeman]

Originally Posted by David Marek

Aren't the additives supposed to encourage fungal and bacterial growth? Does plain sugar help the process?David

Good, another convert!
You're right about additives, but shush don't talk about it, there are others on this forum with extremely different viewpoints.
Sugar is not as effective as molasses, it's more refined and all the goodness has gone.

[ALLGOLD]

Now, without adding fuel to the fire-may the debate continue.
Please excuse my ignorance but is tea made from the castings of red wriggler good or bad for toms?
For this too is doo

[dustdevil]

NOTE TO SELF. Issue diapers in appropriate sizes to all living organisms, so they don't poo on my tomatoes and compost pile.

[Blueaussi]

Originally Posted by ALLGOLD

Now, without adding fuel to the fire-may the debate continue.
Please excuse my ignorance but is tea made from the castings of red wriggler good or bad for toms?
For this too is doo

It's very good for tomatoes. I have never seen any information that suggested that earthworms carry zoonotic pathogens. And most folks keep their earthworm compost set ups covered in some way, so it isn't as likely to be invaded by any of the dangerous doo-ers.

And, you know, compost tea that does contain some uninvited poo is most likely not going to be dangerous. It's the whole brewing and bubbling process that gives the pathogens time to multiply to dangerous levels that has the potential for harm.

[ALLGOLD]

Got it
Closed systems are a safer bet for all concerned
Mix it up
Use it
Don’t brew it.

Thanks Blueaussi

[riceke]

I can remember as a young man serving my country in the orient watching young oriental boys and women carrying with what seemed to be a yoke across their backs with buckets of some liquid sloshing as they walk to the rice fields. Watched them pour it in the rice paddies. Come to find out it was human waste both liquid and solid of nature.

Also, my father tending his tomatoes would scoop out some strange liquid out of a 5 gallon can in the garden and pour it around his tomatoes. He told me that he would take some horse manure, put it in a burlap bag and soak it in collected rainwater. That was his fertilizer.

Now why is it today, that E coli is contaminating everything we eat when before using the same stuff that it comes from was used as fertilizer and at least no one in our family or others that I knew of that used the same technique got sick from it?