Control of Botrytis by Compost Tea Applications on Grapes in Oregon Vineyards

Final Report for SW00-039

Project Type: Research and Education
Funds awarded in 2000: $141,572.00
Projected End Date: 12/31/2003
Region: Western
State: Oregon
Principal Investigator:
Shepard Smith
Sunbow Farm/Soil Foodweb Inc
Co-Investigators:
Elaine Ingham
Soil Foodweb Inc/ Southern Cross University
Elaine Ingham
Sustainable Studies Institute
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Project Information

Abstract:
Use of Foliar Compost Tea Applications to Protect Against Fungal Diseases

Use of foliar applications of compost tea to control mildew and botrytis was successful in reducing fungicide applications by 85% to 93% in both 2001 and 2002. Both years exhibited unusually intense mildew incidence, but low botrytis incidence. In 2001, the weekly plot in one vineyard required no fungicide application, while untreated controls showed mildew outbreaks by the second or third week of June, and were put into tea treatments immediately and were not repeated in year two. In both years, in the bi-monthly compost tea treatments, mildew outbreaks occurred in the last week of August or the first week of September. The outbreak spread from the bi-monthly treatment to the weekly tea treatment. Mildew outbreaks were controlled by fungicide (potassium hydroxide) application in both years. In severe mildew years, it would be reasonable to apply fungicide in the last week of August, while using compost tea containing adequate fungal biomass the rest of the summer. Once the outbreak of mildew was controlled by fungicide, compost tea was adequate in controlling mildew and botrytis. Initial lab studies showed that control of botrytis required a minimum of 5% fungal biomass to be applied to the leaves, and that this level of fungal coverage on leaf surfaces required a minimum of 2 ug of active fungal biomass per ml of compost tea. Foliar applications of compost tea alone were not adequate to completely replace use of fungicides. Use of other chemical applications (Roundup, copper sulfate) in the vineyard prevented any improvement in soil life, even though foliar fungicide applications were reduced. Maintaining quality tea production, based on adequate fungal biomass in the tea was difficult. Maintaining aeration was critically important in preventing bacteria from attacking and consuming fungi in the tea. The machine used was critically important. In year one, the compost tea machine used was difficult to clean (up to two hours to clean; the machine is no longer commercially available), while in the second year, the machines used took only 20 minutes to routinely clean. Effects of different recipes on tea biology were assessed, showing that fungal foods were required to obtain the fungal component on the leaf surface that would allow adequate coverage and protection of the plant surfaces from pathogen growth. The likely mechanism of action was coverage by the non-pathogen organisms, and growth of these organisms, thus leaving no space or food or un-occupied infection sites free for pathogen growth.

Project Objectives:

To assess the ability of different compost teas to reduce disease in grapes.

The proposal was to focus on botrytis, but in the two years of the study, botrytis was not a significant disease factor. Mildew was a significant factor, and thus, this became a study of whether compost tea could control mildew, instead of botrytis.

This study focused on foliar applications of compost tea alone, without any attempt to alter the soil or the litter in the vineyards.

Can disease control be obtained with just foliar applications of the needed biology — biology that has disappeared and no longer exists in the vineyards because of the toxic chemical applications and high fertilizer use in previous years and that may still be on-going in these orchards?

One objective was to assess recipes for compost tea to improve fungal biomass in the tea, to achieve the results seen in the lab studies.

Introduction:
Defining Actively Aerobic Compost Tea

Early on in the study it became apparent that we needed to define the kind of compost tea being used. Compost tea makers through the ages have not differentiated the different ways of making compost tea. VERY different results can be the result, so we need to recognize the benefits, and dangers, inherent in the teas made by these different methods.

Actively Aerated Compost Tea (AACT).

Aeration must be adequate to extract the maximum amount of soluble nutrients, and to maintain oxygen in aerobic concentrations in order to produce a tea high in aerobic bacteria and fungi, and with maximum extraction of protozoa and nematodes. The more diverse the community of microorganisms extracted and grown under aerobic conditions, the greater the disease suppression and the better nutrient retaining the tea will be. The greater the concentration of nutrients extracted, the more food there is to grow beneficial bacteria and fungi in the tea during the brewing cycle and after the tea is sprayed out.

It is CRITICAL to understand that tea must remain aerobic. If too great a concentration of food resources for the bacteria and fungi are added, the growth of the organisms will be so rapid that they will consume oxygen more rapidly than oxygen can be added into the tea. The tea will go anaerobic, and then human pathogens can grow in the tea.

Any compost tea machine can be caused to go anaerobic if too much microbial food is added, too much compost, and aeration is lacking.

Compost tea is used to add bacteria, fungi, protozoa, and nematodes to the soil or onto foliage. Compost tea also contains soluble nutrients that feed the organisms in the tea and may feed plants. Use compost tea any time organisms in the soil or on the plants are lower than optimum levels. Chemical-based pesticides, fumigants, herbicides, and some synthetic fertilizers kill the beneficial microorganisms that encourage plant growth, either in the soil or on foliage. Compost teas improve the life in the soil and on plant surfaces and help plants take up the nutrients they require, and suppress diseases at the same time as building soil structure, and reduce erosion and loss of nutrients into drinking water. High quality compost tea will inoculate the leaf surface and soil with beneficial microorganisms, instead of destroying them.

Given a good set of organisms (see Compost Tea Standards for what those numbers are), the following benefits can be brought about:

·Improved plant growth,

·Reduced application rates of chemical pesticides, herbicides, and fertilizers,

·Reduced impacts of chemical-based pesticides, herbicides and fertilizers on beneficial microorganisms in the ecosystem,

·Occupation of infection sites on the plant surface so pathogens cannot infect the leaf,

·Improved uptake of plant nutrients through influences on stomata,

·Increased numbers of organisms on and around plants to compete with disease-causing organisms, reducing disease incidence,

·Retention of microorganisms in soil or on leaf surfaces, resulting in an increase in retention of nutrients,

·Increased plant nutritional quality,

·Reduced production costs,

·Reduced application of toxic chemicals, thus reducing run-off into lakes and streams,

·Reduced toxic impacts on humans and pets.

Fermentative Compost Tea (FCT)

This tea selects for growth of facultative anaerobic organisms that can suppress certain diseases and prevent growth of certain organisms through an antibiotic – inhibitory set of interactions

Long-Brewing Compost Tea (LBCT)

Starts aerobic usually, moves through an anaerobic phase, but then returns to aerobic by the end of the brewing process.

Not-Aerobic Compost Tea (NACT)

Anaerobic bacteria grow for the most part, resulting in production of some toxic materials that can be useful for preventing the growth of particular organisms. This version of compost tea probably needs to be registered as a bio-pesticide as very toxic material can be produced. However, this should possibly be labeled as bio-pesticide, since highly toxic material can be produced, and should be tested accordingly.

Given the decrease in funding that was imposed at the beginning of this study, we had to make choices about what to remove from the outline of work. We could not produce and test all the different categories of compost given above, and so we concentrated on AACT, and different food resources and application rates of tea.

Cooperators

Click linked name(s) to expand
  • Tom Broadly
  • Kevin Chambers
  • Dai Crisp
  • Terry Grove

Research

Materials and methods:

Site Descriptions
Vineyards. Three sites were used, Reed and Reynolds Vineyard in Carlton, OR, (Willakenzie soil, 17 acres, elevation 335 feet), Wren Vineyards in King’s Valley, OR (Willakenzie soil, 400 feet elevation) and Broadly vineyard, outside Monroe, OR (Dayton soil, 350 feet elevation). Three plots of each treatment were placed on each vineyard. On each sample date, three replicate samples will be removed from each treatment. Within each vineyard, sites were chosen for uniformity of plants, similar slope position, similar soils, the same grape cultivar and root stock. Pinot Noir will be the grape on Wren and Equinox Vineyards, while Gewurtz is in the plots on Reed and Reynolds vineyard.

This proposal focused on finding the most effective tea for reducing fungal diseases, in particular botrytis, and powdery mildew. In lab testing, powdery mildew was easier to control than botrytis with compost teas. But, in the field in both years, botrytis was never a problem, since environmental conditions did not favor botrytis growth.

The following treatments were performed:
1. Normal vineyard practices will be performed on one treatment (the majority of the vineyard). All treatment data will be compared to these control rows to determine effect of the tea treatments on diseased grapes.
2. Fungal-dominated compost, 25 gal brews, 1 quart molasses, 24 hour brew times, highly aerobic tea, applied once a week.
3. As above, but applied twice a month.

Tea Production.
Two different actively aerated compost tea machines were used in the course of this study. In year one, a Microb-BrewerÔ was used, but proved to be extremely time intensive to clean. When absolutely spotless, the machine produced very good tea, as determined by fungal activity in the tea, but had to be cleaned after each tea brew. Cleaning could take up to four hours.

In the second year, EPM machines were used, and produced acceptable, but not great, teas, as assessed by active fungal biomass in the tea. Cleaning for the machine was approximately 20 to 40 minutes, depending on the recipe of material used in the tea.

Tea recipes always contained molasses and Maxi-Crop or Acadian kelp. The major problem remained adequate fungal biomass in the tea. Several different materials were used to try to improve compost tea fungal biomass and activity. HydraHume AN as a humic acid gave best fungal growth, as did oatmeal, feathermeal, and chitin.

Tea Application.
Reed and Reynolds and Broadly vineyards used Cimi sprayers (Gearmore) to apply tea. A pull-behind, air blast sprayer was used on the Wren vineyard to apply teas to the foliage and grape zones on each spray date.

It was necessary to allow Reed and Reynolds and Wren to choose when to begin applications in the spring, relative to weather and ability of the grower to get to the application. At Wren, application before June was prevented until spring irrigation equipment, which was used to reduce frost damage, was removed from the vineyard.

Teas were applied approximately two weeks before bud break in order to establish the microbial community on plant surfaces.

Tea was sprayed every 7 days, or every 14 days, depending on weather conditions. Given reductions in budget, coverage of the leaf surfaces and grapes (when present) was restricted to limited times.

The length of time coverage is maintained through seasonal changes was assessed by taking leaf samples immediately before, immediately after, and on days 3, 6, 9, and 12 post-spray. This allowed determination of differences in survival of bacteria and fungi in the different treatments and which recipe significantly influences “stickiness” of the organisms.

Assessment Methods

Leaf Assay.
Samples for leaf and grape surface assessment were taken as soon as possible after tea application. Leaf samples were taken from inner plant positions that are hard for spray to reach, and from outer leaves on the sun-ward side of the vine where sunlight is likely to reduce effectiveness of the protective biofilm.

Organisms.
The normal groups of soil/foliar organisms were assessed in teas, compost, and soil, including total and active bacteria, total and active fungi, protozoa, and nematodes. We monitored the foodweb in the soil 6 inches from the vine stem in the spring and the fall in order to determine the impacts of the tea sprays on the soil foodweb. Organisms numbers were assessed in samples taken from the compost (three independent subsamples assessed from each compost) at the start of the brewing cycle. Three independent subsamples were taken from the tea when it was moved from the brewer and put into the spray tank. On the first sample date, three independent subsamples were taken from the nozzles of the sprayers as they sprayed material out onto leaf material in the vineyard.

Disease Incidence.
The number of leaves or grapes infected with either mildew or botrytis, based on visual symptoms (discoloration, presence of hyphae) will be counted in randomly determined areas within each plot.

Statistical Analysis.
Data will be assessed using F-protected ANOVA, but will be stratified by within plot, between plot, and between vineyard analysis. The most important comparisons are between the controls, using conventional chemical methods of control of foliar disease, and each individual tea tested. However, determination of which tea was most effective at reducing disease is also desirable information, as different teas might be most effective in different sites, or in different vineyards. Since replicated samples will be taken from each plot within each site, and there are three sites, spatial assessment can be analyzed.

Research results and discussion:

Field Notes

Year One:
1. Initial soil samples were taken, initial soil foodweb documented.

2. Teas produced were not as fungal as they should have been. The Microb-Brewers were not capable of making tea at the levels documented in the lab studies to be needed.

3. Reduction in fungicide use still significant but mildew showed up in vineyard #1 in the control with no application of any control measure within the first three weeks of the study, and was put into weekly tea application treatment.

4. Last week of August mildew showed up in all the bi-monthly treatments and fungicide applications were required. Growers were reimbursed for the use of the fungicide and time to apply, despite the fact that they would have to have been applying fungicide weekly to avoid mildew through the season.

5. Fungicides would have to have been applied a minimum of 14 times in the normal season, and were used only once (up to three applications of the fungicide to get problem under control, however, in one vineyard).

6. Reduction in fungicide use between 13 out of 14 sprays, to 17 out of 20 sprays.

Year Two:
1. Soil sample taken in spring revealed no significant difference in soil biology between controls and treatments. Growers had not stopped using Roundup, copper sulfate, or soil insecticides on the soil.

2. Using 100 gal compost tea machines from EPM, tea was now at least in adequate levels for fungi, based on the pre-trial work.

3. Difficulty was experienced in getting cooperation from Vineyard #1. Teas were not sent in, leaf samples were not received despite all efforts.

4. First week of September mildew showed up in the bi-monthly treatment just as in the first year. This spread to the weekly tea treatment.

5. Fungicides were applied to both treatment areas to deal with the mildew. Mildew was more difficult to reduce throughout the valley in this year. Most growers used a minimum of 18 tea sprays, in the tea treatments, tea was applied 8 times in the bi-monthly treatments, with 3 fungicide applications. In the weekly tea treatment, tea was applied 14 times, with one fungicide treatment .

Year Three:
1. Soil samples revealed no significant difference in soil organism numbers.

2. Analysis of data, writing paper

3. Short-term experiment on anaerobic tea comparison with aerobic tea.

4. Paper on field work submitted for publication to Applied Soil Ecology.

5. Paper in preparation on the initial tea study to document percent coverage levels.

Initial Leaf Study

Establishment of Coverage of Leaf Surfaces with Botrytis-spore applied grape leaves

Concentration of Botrytis spores in Spore suspension, as determined by Microscopic Observation: 25,000,000 spores per ml (SD of 2700 spores per ml).

Coverage was determined by assessing whether there was an organism, or spore, within a 10 um2 area. Given that any organism could germinate and grow, and usually did if active, one cell within a 10 um2 area was considered to have control of this area. Each 10 um2 area with one or more cell present was considered to be covered.

To achieve 70% coverage of the leaf surfaces with Botrytis, 25 grape leaves (approximately 60 cm2 area leaf surface) received 10 ml of the above spore suspension sprayed onto the surface with a hand-held bottle sprayer. Leaves were examined (Table 1 below), and documented to have at least one spore in 70% of the 10 cm2 areas observed on the leaf surface. In approximately 10% of the areas observed, more than one Botrytis spore occurred in the 10 um2 area, but this did not alter coverage determination.

Leaves were randomly chosen from the set of 25 leaves sprayed and placed into groups. Leaves in the first group received 10 sprays of a compost tea, the second group received 9 sprays, group 3 received 8 sprays, and so forth to the leaf surface that received 10 sprays of sterile buffer used to suspend the tea, but without any tea organisms present. The leaf surfaces were assessed for the biology present (Table 2 below).

AB stands for Active Bacterial Biomass, TB means total bacteria, AF measn active fungi, TF means total fungi. ND means not detectable.

Table 1. Microbial Biomass for Tea #1. AB means Active bacterial biomass, TB means total bacterial biomass, AF means active fungi, TF means total fungi, (all of these are in micrgrams per mL of tea), F means flagellate numbers, A means Amoebae Numbers, C means ciliate numbers

Microbial Biomass or Numbers
Tea #1 AB TB AF TF F A C
Before
Appli-
cation 3.5 1,154 2.3 11.1 210 1,092 2

Table 2. Percent coverage of 5 leaves treated with increasing application of tea to achieve this coverage. Coverage was determined by the number of 10 um2 areas with at least one individual of bacteria or fungal hyphae present. Average variability was 14% for active bacterial coverage and 6% for active fungi. Many readings were zero for fungi. Coverage can be greater than 100%, because areas can have both bacteria and fungi. AB means Percent Coverage by Active Bacteria, AF means Percent Coverage by Active Fungi.

Desired
Coverage AB AF
100% 92 7
90% 80 8
80% 74 6
70% 66 5
60% 57 4
50% 42 2
40% 35 3
30% 22 2
20% 18 1
10% 11 None detected
No tea,
water 3 None detected

Within three weeks, botyrtis growth had become evident on all but the leaves above 70% coverage with the organisms from the compost tea.

This experiment was repeated with a slight variation. Fungal coverage was controlled more carefully.

Table 3. Microbial Biomass for Tea #2. Key as for Table 1

AB TB AF TF F A C
Tea #2 4.6 682 6.2 15.7 782 770 23
Tea #3 5.1 994 1.2 6.3 2,022 832 18

Table 4. Percent coverage of leaves (number of 10 um2 areas with at least one individual of bacteria or fungal hyphae present). Average variability was 5% for active bacterial coverage, and 3% for active fungi. Coverage can be greater than 100%, because areas can have both bacteria and fungi. Leaves with no tea application had 3% bacterial coverage, no active fungi were detected. Same Key as for Table 2.
Tea
Treat-
ment AB AF
Hi Bacteria, High Fungi (Tea 2; 10 sprays)
1 92 7
2 92 8
3 92 7
4 92 8
5 92 8
Hi Bacteria, Low Fungi (Tea 3, 9 sprays)
1 75 2
2 71 3
3 73 2
4 75 2
5 70 2
Medium Bacteria, High FungiTea 2; 6 sprays)
1 66 5
2 68 6
3 64 6
4 65 6
5 66 6
Low Bacteria, Low Fungi (Tea 3, 5 sprays)
1 61 2
2 59 3
3 60 2
4 58 1
5 59 2

All leaves in the high bacteria, high fungal, or the medium bacteria, high fungal coverage groups showed no disease within the 3 week period. All the leaves in the high bacteria, low fungal group, or the low bacteria, low fungus groups showed botrytis growth. These results suggest that fungal coverage is a critical component in protection of leaf surfaces from fungal pathogens.

Compost Tea that does not contain adequate fungal biomass to attain 5% coverage of the leaf surface will not be as capable of occupying the leaf surface and preventing the growth of other fungal species. Activity, and then growth of the fungi over the surface of the leaf, is critical in maintaining the displacement of competing species fungi, particularly disease fungi.

From this study, it was clear that coverage of the leaf surface, with a minimum of 5% fungal coverage, resulted in best control of botrytis.

Table 5. Length of time tea organisms remain on leaves after tea application

Time
since Percent Coverage
Application (sum of bacterial and fungal)

In general, during the cooler, moister time of the year, growth of the organisms occurred on the leaves, survival and activity remained longer, and the initial populations of organisms on the leaves was greater. As the summer progressed, and leaves became waxier, moisture more limiting, the populations initially on the leaves was lower than earlier in the summer, the teas were not as high in organisms after first spraying, and did not increase in number, nor survive as long as previously in the summer.

Possibly one reason for failure of the protective ability of the teas in late summer was the rapid reduction in activity on the leaf surfaces as temperature increased and humidity decreased.

Please see attached submitted paper to read about the results from the field trials and pathogen incidence.

Conclusions

1.Use of compost tea can reduce pesticide applications by as much as 95%, at least as much as 85% reduction in chemical use, and these results were observed for both years of the study.

2. Use of foliar applications of tea alone will not be adequate to replace use of fungicides.

3. Use of other chemical applications in the vineyard prevented any improvement in soil life in the soil, even though foliar fungicide applications were reduced.

4. Maintaining quality tea production was not simple. Fungal biomass in the tea was difficult to maintain. Growers need help to manage quality compost tea. Machines used are critically important. Maintaining aeration is critically important in keeping the fungi in the tea.

5. Each year, bi-monthly foliar applications alone allowed mildew to escape. Weekly tea applications would have maintained mildew control, except the mildew from the bi-weekly applications moved into the weekly tea treatment, and fungicides were required.

6. Once the outbreak of mildew was controlled by fungicide, tea was adequate in controlling mildew and botrytis.

7. Need to treat soil, and especially the litter in the fall to prevent over-wintering by the fungal diseases.

8. Grower cooperation was very difficult to obtain. They do not consider that because this is science, methods cannot change once they have been established. Year two had to be done the same as year one to show that the approach used had consistent year-to-year results. Growers wanted changes in year two, and were thus not interested in continuing the study if they had to keep the approach the same in year two as in year one.

Research conclusions:
Impact of Results

Reduction in fungicide use by 85% minimum, typically by 93%, and in one case by 100% during the summer of 2001, in the weekly tea application plot in one vineyard, indicates significant possible benefit of compost teas as alternatives to chemical pesticides.

Long-term use of compost tea still needs to be investigated. Will pathogen resistance develop? Will continued use result in complete displacement of fungal pathogens. Could insects be discouraged, as well bacterial diseases?

These results are of great interest to the people not certain about the usefulness of compost tea. There has been a significant amount of hype about compost tea, and this research will give some better expectations of what is possible with disease prevention by compost tea.

Many growers are experiencing excellent results, similar to the results being shown in this work. By also applying compost tea to the soil, and improving the beneficial life in the soil, combating the disease, compaction and lack of nutrient uptake by plants in compacted conditions, even greater reduction in disease may be possible.

Some of this data show that the quality of tea is important, although the data here are incomplete with respect to what exactly happened with each tea application. Early tests showed that coverage is critical. More work needs to be performed along this line.

We receive reports of at least one per week, and often five or six per week, of people using tea and having great results. On rare occasion, we have someone who, like the growers in the study being reported, insist on continuing use of herbicides, insecticides, and other materials that kill the biology added by the tea. When toxic chemical inputs are not reduced (defining what that means can be significantly different between cooperators), use of compost tea is not as effective. The simple fact is that pesticides and herbicides kill a significant set of non-target organisms. Reducing not only fungicides but other toxic chemicals and levels of fertilizer must go hand-in-hand with compost tea usage. For this reason, use of actively aerated compost tea both as foliar and soil drench applications combined is recommended.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:
Publications and Outreach

In every seminar, workshop, public address, or class that Dr. Ingham has been involved in during the last year, the SARE grant has been mentioned, and usually described to some extent. With the publication of the two papers, one of which has already been submitted to journal (attached), and the second whose data are given above, our understanding of the limitations of foliar compost tea applications without soil applications, and the limitations that poorly made compost present, will be much more clearly understood by the scientific and grower communities alike.

In each seminar given at Soil Foodweb, a field component is included. We will be starting a project with several urban developers where 275 acres of land in Salem, One will be developed in a sustainable manner, and will include the use of compost and compost tea to maintain the community parks, green areas and communities gardens in sustainable production.

Each month in the Soil Foodweb electronic magazine, compost tea information is given out. The SARE grant papers will be summarized in this monthly publication, and these summaries will be sent to ATTRA, to SANET, and to the compost tea listserve.

Educational Efforts.
The information obtained from this study has been presented in numerous seminars and viticultural classes. Presumably, these results will provide proof of when and how compost tea can be used, and when its effectiveness is questionable.

Classes. Soil Foodweb Inc. and the Soil Foodweb Advisors trained by soil foodweb (approximately 50 individuals around the world) participate in and are responsible for a large number of seminars, workshops, symposia, invited talks, and grower group presentations. The results from this research have been presented in these arenas. Approximately 15,000 people a year have been made aware of this research.

Manual. Soil Foodweb Inc. publishes the only existing manual about compost tea production (The Compost Tea Brewing Manual), in which the SARE results appear. Currently, nearly 2000 manuals have been distributed by SFI and related businesses. The manual will be updated with information from this research.

Publications. Results of this research project have been submitted to Applied Soil Ecology, the journal of the Soil Ecology Society. Summaries of this research will be given to grape grower and compost industry journals.

Project Outcomes

Project outcomes:
Economic Considerations

The simplest economic analysis is to examine the costs the growers asked for re-imbursement to the grant for the sprays they used to deal with their mildew outbreaks. These were approximately $500/ac per fungicide application for the vineyard, including labor, supplies, sprayer costs, and the fungicide itself.

If fungicide had been applied every week during the summer, starting the first full week of June when, each year, the mildew alert went out from Oregon State University (Dr. Jay Pscheidt), and if the sprays had been performed weekly until color change, 20 to 21 fungicide sprays per vineyard per summer would have been applied. Botrytis prevention was minimal each year, so we will disregard that cost.

The cost of the fungicide was then 20 times $500, or a total of $10,000, minimum (labor and fungicide cost).

Compost tea reduced costs for the growers from $10,000 per vineyard to $500 to $1500 per vineyard for the fungicide, depending on whether one or three applications of the fungicide was required to kill the mildew outbreak. The costs of the compost tea applications were $3/gallon, at 5 gallons per acre ($15 for the tea per application), plus $100 application cost per application, for a total of $115 per ac per application. At 19 to 20 applications per summer, the cost of applying compost tea was $2,300 as opposed to $10,000 for the fungicide.

If compost tea was also used to replace the biology needed to compete with, inhibit, and consume insects, weeds, and other pests (studies need to be performed to show the precise method for achieving these results in different systems), application of the compost tea to soil at 20 gallons/ac, would result in vineyard costs of an additional $320. This is considerably below the cost of pesticide, herbicide, and fungicide applications. Even if one or two chemical sprays had to be applied, and especially if growers could know in advance when those sprays were likely to be needed, the cost of growing crops would be seriously reduced.

Compost tea is not a health hazard. In all the spraying that has been done in the last 5 years, no reports of negative reactions have been reported from a well-made, AEROBIC compost tea, or compost. It is always wise to use precautions when spraying material that could be inhaled, however. The mist produced when spraying compost tea is much like light dew, and we breathe in the organisms in the air all the time. Even when spraying water in a commercial setting, however, it is wise to protect against inhaling too much vapor.

Several medical doctors have considered the potential risk of compost tea spraying, and the view the potential risk as extremely slight, given the caveat that it is always wise to avoid direct and willful efforts to put oneself in the way of anything not completely tested. They consider that the likelihood of harm from the pesticide sprays still being used for insects and weeds in the vineyards were of much greater hazard and risk than the compost tea.

Reduction in health concerns and insurance costs should be considered when using compost tea, since it is clear that the toxic chemicals are hazards, and these can be reduced if use of compost tea is encouraged.

The major concern with compost and thus compost tea is the quality of the compost available to the grower. As has been shown in the initial studies with compost tea on leaf materials, coverage with fungi and bacteria is of critical importance. If the compost was not made properly, then the organisms will not be present in the compost. Assessment of microbial biomass using chloroform fumigation methods will not, however, assess the important factors of what biology is present. Chloroform fumigation cannot differentiate between bacteria, fungi, protozoa, or nematodes, and also includes a large component of organic matter solublilized by the chloroform. This cannot be accounted for using a non-chloroformed control. In addition, organisms growing on the dead microbial biomass do not utilize dead fungal hyphae, and there fore the fumigation misses the fungal biomass completely. This method then is not appropriate, therefore, to assess compost tea or compost additions.

Plate count methods are not appropriate either, as they miss approximately 99.9% of the bacterial and fungal species present in soil, compost, or compost tea. Therefore, compost tea needs to be assessed using rapid (3 minute staining time to assess activity) direct determination methods.

Farmer Adoption

Compost tea is already being used, and proving to be highly effective in many field trials. Poor quality tea production plagues the industry. At least two machines being sold commercially, which are purported to make compost tea, which do not produce compost tea with the biology shown to be needed in this study. One “compost tea machine” apparently does not even use compost in the production process. How can this be compost tea?

Shepard Smith, the main field cooperator for this study, has started a Compost Tea Center in Philomath, Oregon. We are working with approximately 25 Compost Tea Centers around the United States.

Adoption of Actively Aerated Compost Tea technology is rapid and highly successful, IF people have compost with excellent numbers of aerobic bacteria, fungi, protozoa and nematodes present in the compost. They need to be able to extract the full diversity of those organisms into the tea, and grow the beneficial organisms in aerobic conditions.

Testing of over 150 different Actively Aerated Compost Teas made using adequate aeration (documented through the brewing cycle, not “guessed at”) shows no detectable E. coli in those tea brews. Other teas, which drop into anaerobic conditions, and which used poorly made compost that contained E. coli in the compost, had E. coli present in the tea, but usually at levels less than irrigation water requirements.

This technology shows a great deal of promise and potential, which must be carefully nurtured so that people not interested in maintaining standards, just out for a quick dollar, are not allowed to mis-represent compost tea that actually gives the benefits possible by returning excellent biology, the full, highly diverse foodweb, back to the soil and to the plant surfaces.

Recommendations:

Areas needing additional study

Standards for compost tea are needed. Extensive study on the different conditions to produce quality tea, the effects of different starting materials, and the impacts these materials have on human pathogens that might be present in poorly made compost need to be investigated. More extensive understanding of aeration of tea during production is needed. In conjunction with the work performed for the SARE grant, SFI investigated effects of aeration on molasses concentration and E. coli survival when less than optimal compost was used as starting material. This work is summarized in the additional submitted paper attached to this report.

What is the effect of inadequate aeration on survival of E. coli in compost tea? Presence of molasses is clearly not the critical factor. Presence of E. coli in the compost used is critical, and this is where testing is required. If compost tea is adequately aerated, and adequate aerobic organisms are present, E. coli and other human pathogens will not be able to compete with these organisms adequately. In these cases, we find that E. coli, even when in relatively high numbers at the beginning of the tea brew, are lower and at times not detectable at the end of the brew.

Still, it is preferable not to have to risk that aeration and growth of the bacteria and fungi and protozoa in the tea brew are adequate to deal with these pathogens. It is preferable to make good compost, where human pathogen numbers are low and will always be out-competed and consumed by the aerobic organisms in the tea brew.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.