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       <h1 class="title-bg">Introduction to seed treatment as a preventative measure</h1>
       <h1 class="title-bg">Compost “Teas” can Prevent Disease</h1>
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           <p>Options for reducing seed-borne pathogens in organic agriculture are limited to physical heat treatments and certain organic treatments, as synthetic pesticide protections cannot be used (Van der Wolf, Birnbaum, & Van der Zouwen, 2008). Saltwater and vinegar seed treatments represent organic options, while bleach is an synthetic compound that sterilizes seeds and can subsequently be washed off. Disinfecting seeds prior to sprouting helps prevents the possibility of plant disease epidemics by killing disease-causing organisms living within or on the surface of the seed (Munkvold, 2009). Preventative measures can decrease the probability of contamination in a field and reduce the use of pesticides to control plant epidemics that could have, with hindsight, been controlled through seed treatment.</p>  
           <p>Compost teas - an umbrella term that includes manure teas - are preventative measures: they reduce the possibility of plant infection from occurring. Preventative measures contrast with curative measures, with the latter aiming to address plant diseases as they occur within a field. Although the benefits of preventatives measure are not directly seen, these measures can save money and resources over time. Preventative measures can decrease the probability of pathogenesis in a field, reducing the need for insecticides to control plant epidemics that could have been controlled by preventative treatment in the first place.</p>


<p>Seed disinfection can kill seed-borne pathogens, or external pathogens living on the seed surface, while also protecting the seed, depending on the type of seed treatment (Munkvold, 2009; RPD, 1992). In addition to killing plant-pathogens, seed treatments can protect seedlings from common soil-inhabiting fungi that cause seed-rots (Munkvold, 2009; RPD, 1992). Finally, an effective seed treatment can reduce the need for multiple field applications of fungicides or bactericides later in the growing season (Mancini & Romanazzi, 2014). Aggravated use of pesticides is damaging to the local environment, economically costly, and posits a health hazard to farmers using these applications without respirators or advanced safety equipment. Subsistence farmers interested in minimizing pesticide use and improving crop health can use the preventative disinfection measures as outlined in this chapter. Within this encyclopedia, chapters on “Pesticide Seed Applications” provide more information on effective seed treatment technologies.</p>
 
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<p>Compost tea may reduce the need for multiple field applications of fungicides or bactericides later in the growing season. Aggravated use of pesticides is often damaging to the local environment and poses a health hazard to farmers using these applications without advanced safety equipment. Subsistence farmers interested in conserving crop health can consider compost teas as a safe preventative measure, although these teas are generally considered to be less effective than commercial pesticides.</p>
 
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      <h1 class="title-bg">Compost or Manure “Tea” Mechanism to Reducing Pathogenesis </h1>
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<p>Compost or manure “teas” - composed of compost, manures, and other organic materials - are organic approaches to reducing pathogens, most notably fungi and bacteria. There are multiple beneficial mechanisms that allow these teas to reduce pathogenesis of crops.
First, compost teas contain a variety of beneficial microbes in the compost or manure that outcompete pathogenic microbes for nutrients secreted by plants in both the roots and leaves (Ingham & Alms, 2003; Scheuerell, 2004). Plant exudates, both from roots and leaves, help grow disease-suppressing bacteria and fungi in the compost tea, fighting off pathogens (Ingham & Alms, 2003; Scheuerell & Mahaffee, 2002). Unfortunately pesticides and inorganic fertilizers can kill the beneficial microbes, leaving plant exudates for the disease causing microbes (Ingham & Alms, 2003).</p>
<p>Second, compost teas contain soluble nutrients that feed beneficial microbes within the teas themselves and also feed the plants after application of the “tea” (Ingham & Alms, 2003; Scheuerell, 2004). High nutrient concentrations promote beneficial microbe growth, plant resiliency, and increase retention of nutrients in the soil around the plants, reducing fertilizer demands (Ingham & Alms, 2003). Because of these mechanisms, compost teas are often sprayed onto the soil or used as a leaf spray (foliar).</p>
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      <h1 class="title-bg">Methods of Compost Tea Production and Application </h1>
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<p>Compost tea is produced by mixing compost (or manure in manure teas) with water and culturing for a defined period (Scheuerell, 2004). There are two major methods for producing these teas: actively aerating (aerated compost tea, ACT) or not (non-aerated compost tea, NCT) (Scheuerell, 2004). Finally, teas are made with or without additives that are intended to increase microbial population densities during production (Scheuerell, 2004). These are a number of other parameters besides the role of aeration that impact compost tea production and their suppressive properties (Scheuerell & Mahaffee, 2002). These include choice of compost feedstock, compost age, water ratio, fermentation time, added nutrients, temperature and pH, and these are outlined in table 1 (Scheuerell & Mahaffee, 2002). Each of these properties influences the suppressive capabilities of compost teas (Scheuerell & Mahaffee, 2002). Simple procedures/recipes can be found on wikihow (http://www.wikihow.com/Make-Manure-Tea).</p>
<p>A variety of parameters to consider for application are dilution ratio, equipment, timing, and rates of application (Scheuerell & Mahaffee, 2002). Application to soils and/or plants can be done with spray equipment and all types of irrigation systems, if useful (Steven J. Scheuerell). The application system determines the need for filtering compost tea and it should be noted that some filters could reduce microbial populations (Scheuerell, 2004). It should be noted that the research reflects that there is no one ideal compost tea and application factor for all host-pathogen systems (Scheuerell & Mahaffee, 2002.</p>
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<P><B>In summary</b>, these are several methods for producing compost or manure teas to choose from, depending on the scale of production and available financial resources for buying brewing equipment or constructing a homemade brewer (ATTRA, 1998). Methods include the Bucket-Bubbler, Tough, and Commercial Tea Brewer Methods (ATTRA, 1998). Two methods, found at ATTRA, are listed here and can be further researched if needed at ATTRA (ATTRA, 1998).
<P><B>First, the Bucket-Fermentation Method:</b> compost tea is made by immersing a burlap sack filled with compost into a tank with occasional stirring for 7-10 days, resulting in a compost water extract rather than a “brewed” compost tea (ATTRA, 1998). This is a hundreds of years old method for making basic watery compost tea (ATTRA, 1998).</P> 
<P><P><B>Second, the Commercial Tea Brewers:</b> These brewers contain a compost leachate basket with drainage holes placed in a tank with water and microbial food sources (ATTRA, 1998). A pump also supplies oxygen to aerate the compost tea while brewing in the tank (ATTRA, 1998). Although this method may be too expensive for a subsistence farmer, it may be affordable for a community.</P>
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      <h1 class="title-bg">Aerated and Non-aerated Compost Tea</h1>
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<p>As mentioned, the two major methods for producing compost teas are aerated compost tea (ACT) or non-aerated compost tea (NCT). This parameter is especially important because producing compost tea with or without aeration and nutrient additives was shown to affect total bacterial population counts as well as bacterial metabolically activity (Scheuerell, 2004). The main distinction between NCT and ACT is that NCT uses greater quantities of compost than ACT, usually without separate nutrient additives, and can be produced from several days to several weeks (Scheuerell, 2004). In contrast, ACT is aerated and uses composts, water, and nutrient additives to significantly increase microbial populations over a 12-36 hour period (Scheuerell, 2004). Compost is supplied aeration through technologies such as an aquarium pump (Lanthier & Advising, 2007). The higher oxygen supply stimulates growth of aerobic microbe populations that assist in compost tea disease suppression and nutrient supply, and these microbes may not survive low oxygen conditions (Lanthier & Advising, 2007).</p>
<p>Most research has focused on the plant disease control properties of compost tea, with most studies pointing to the efficacy of NCT as compared to ACT (Scheuerell, 2004). This review paper outlines the number of NCT studies that showed disease suppressive properties compared to ACT studies (Scheuerell & Mahaffee, 2002).</p>
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      <h1 class="title-bg">Case Studies</h1>
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<p>There are multiple examples in the literature to support the claims that both NCT and ACT can be effective in disease suppression (Scheuerell & Mahaffee, 2002; Martin, 2014; Haggag & Saber, 2007; Al-Dahmani, Abbasi, Miller, & Hoitink, 2003). Due to the volume of studies that reflect this, examples are outlined in table 2. Supposedly, like NCT, increasing the populations of both the total and active bacteria in ACT will generally lead to heightened plant disease suppression (Scheuerell, 2004). In one study, NCT used for seed sterilization prevented pea seeds from “damping-off” caused by the microbe Pythium ultimum and also helped the plant to grow after germination  (Scheuerell & Mahaffee, 2002). Although less research has been conducted on soil-borne disease suppression (as compared to foliar disease suppression) with compost teas, this is an often-practiced technique used by organic farmers (Scheuerell & Mahaffee, 2002</p>
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       <h1 class="title-bg">Solutions for Seed Disinfection: Bleach, Vinegar, & Saltwater </h1>
       <h1 class="title-bg">Critical Analysis and Summary</h1>
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          <p><b>Bleach</b></p>
<p>Use and application of compost teas in practice are rapidly expanding and outpacing the capacity for traditional scientific research to document the effects of these teas (Scheuerell, 2004). As with many biotechnologies, compost teas are not the single solution to complex problems, such as unsustainable farming, and often their efficacy is limited compared to commercial pesticides (Scheuerell, 2004). However, these teas may be integrated into organic farming systems as a carrier of plant nutrients and beneficial microbes to manage diseases, especially when pesticides use is not a possible solution. Subsistence farmers should be informed of how compost teas may impact their production systems (Scheuerell, 2004)</p>
<p>Sodium Hypochlorite, or commercial liquid laundry bleach, is a common choice for surface sterilization and it is readily available in many places. It can be diluted to proper concentrations needed for seed disinfestation from its original concentration of 5.25%-5.45% sodium hypochlorite (RPD, 1992). Seeds can be sterilized by immersion in a solution of 1 part bleach (~5.25% sodium hypochlorite) and 3 parts of water, for about two minutes (RPD, 1992), or 0.5% - 1.0% sodium hypochlorite for 10 minutes. This procedure works best when seeds are shaken periodically in the solution and then rinsed with water at least twice (Sauer & Burroughs, 1986). The time period and concentration may have to be adjusted for certain varieties, as optimal sterilization conditions that still allow for good seed germination can be different between seeds (Sweet & Bolton, 1979).</p>
<p>As some microbes in manure teas can be human pathogens, these “teas” must be used with caution. Microbes in compost teas are thought to be the most importance factor assisting in plant disease suppression despite a limited understanding of the microbes that provide this protection (Scheuerell & Mahaffee, 2002). This limit in knowledge, along with a lack of reporting standards, likely contributes to the variability in compost tea research findings (Scheuerell & Mahaffee, 2002).</p>  
<p>Bleach can be used for protection against fungus, and other clearing solutions have been used against viruses. Bleach soaks can also free seeds from root rot fungus and Fusarium wilt (RPD, 1992). Using a fine mesh or stringing bag, continuously agitate seeds for 40 minutes using 1 pint of liquid household bleach to 8 pints of water, and for each pound of seed treated, use 1 gallon (~3.78 Liters) of solution (RPD, 1992). Finally, use of the alkaline cleaning solid trisodium phosphate in solution can eliminate or reduce transmission of tobacco mosaic virus in pepper and tomato seeds (RPD, 1992).</p>
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<p>After treating multiple different species’ seeds with multiple different chemical seed treatments, Sweet and Bolton (1979) came to the conclusion that a 0.5% solution of calcium hypochlorite may be the most effective seed-sterilization agent when applied for 10 minutes. Calcium hypochlorite is known as chlorine powder or bleaching powder and is used in many water-treating activities and as a bleaching agent. Sweet and Bolton (1979) found that this solution was the least detrimental to the emerging seedlings while being easily prepared, safely handled, and convenient to store. Following application of bleach, seeds should be thoroughly rinsed with water, with three subsequent washes with water shown to be most effective (Sweet & Bolton, 1979).>/p>
<p>Sweet and Bolton (1979) also studied seed germination levels following each treatment and found that greater concentrations than 0.5% solution calcium hypochlorite and longer contact times reduced seed germination and did not improve the decontamination levels (Sweet & Bolton, 1979). They concluded that if seeds cannot be decontaminated with hypochlorite, than efforts could be shifted to find more effective seeds rather than a better sterilizer (Sweet & Bolton, 1979).</p>
<p><b>Vinegar</b></p>
<p>Since the development of synthetic pesticides, pesticide seed treatments have been used almost exclusively to control seed-borne pathogens (Borgen & Nielsen, 2001). Now, many alternative seed-disinfectants are being sought for heightened cost-effectiveness, accessibility, and to reduce the use of pesticides. One scientific study showed that some key organic acids, such as acetic acid (vinegar), at concentrations of 2.5% or higher reduce seed-associated bacteria (Van der Wolf et al., 2008). The researchers also showed that only organic acid to reduce seed germination at this concentration was propionic acid (Van der Wolf et al., 2008). In another study, researchers conducted trails in fields, disinfecting seeds with acetic acid, and found the treatments reduced common bunt (Tilletia tritici) in winter wheat by 91.5-96.2% without negatively effecting the seed germination (Borgen & Nielsen, 2001).</p>
<p>Vinegar is commonly considered to be useful as a sanitizing agent for household cleaning and home gardening due to its acidic nature, with potential for use by farmers who can access vinegar from fermented products. White distilled vinegar is considered as an eco-friendly organic fungicide and herbicide (Mancini, 2012). Thus, vinegar can be carefully applied to seeds in order to sterilize them. One method known for sterilization of seeds or beans is the immersion of dried seeds for 10 to 15 minutes into a bowl consisting of 1 tablespoon of apple cider vinegar to 1 quart of drinkable water (Mancini, 2012). Following immersion, a thorough rinsing of seeds for 5 minutes and subsequent drying prevents permanent seed damage from prolonged vinegar acidity (Mancini, 2012). Placing dry seeds in a netting bag with a tie and label simplifies this process (Mancini, 2012). Use of 1 tablespoon of white distilled vinegar in this process will have the same affect as the apple cider vinegar (Stouffer, 1999).</p>
<p>Sanitizing combinations of white distilled (or apple cider) vinegar with hydrogen peroxide, followed by subsequent washing with water, has also been shown to be an affective method for cleaning fruits and vegetables (Stouffer, 1999). It is considered to be ten times as effective as either solution alone (Stouffer, 1999). Use of clean sprayers filled separately with vinegar and hydrogen peroxide (never mixed) simplifies the cleaning process (Stouffer, 1999). Fruits and vegetables were sprayed first with vinegar, then immediately sprayed with hydrogen peroxide, shortly followed by a water rinse (Stouffer, 1999). The order of the vinegar or hydrogen peroxide application did not matter and neither is toxic in the small amounts remaining on washed products (Stouffer, 1999). Such methods could be applied to seed sterilization as affective bacterial killing agents on the seed surface. Finally, a recipe for preventing cross contamination of gardening tools is soaking tools in a half and half solution of white vinegar (50% vinegar and 50% water), which acts as a fungicide to kill any plant contaminants on these tools over a short time period (Martina, 2015).</p>
<p><b>Saltwater</b></p>
<p>Soaking in salt water is an effective disinfectant for seeds and is beneficial in the control of seed-borne fungi. One of the first seed-borne fungus discovered was Tilletia caries, which causes a covered smut of wheat, as described by Jethro Tull in 1733 (Kolotelo et al., 2001). Tull found that farmers whose wheat seed had been salvaged from the ocean was free of this smut, and this lead to the conclusion that salt water disinfected the wheat seed through its brining action (Kolotelo et al., 2001). </p>
<p>In high concentrations, salt water can act as an effective antimicrobial (Matsko, 2016). This is due to the cytolysis (cell reputing) of many bacterial cells that occurs due to the highly concentrated salt water. This is characteristic of hypertonic (high solute) solutions, and bacteria that are unable to live in such conditions. A sufficient method to create a salt-water disinfectant consists of the following steps. Add a teaspoon of salt into a clean cup of warm water and mix until all the salt is dissolved in the water (Matsko, 2016). Regular cooking salt will be effective (Matsko, 2016).</p>
<p><b>No one method may be perfectly effective as a disinfectant for any given seed variety</b></p>
<p>The most effective preventative measures to control seed-borne diseases are to only plant health seeds in the first place, preventing contamination, and to choose disease-resistant varieties (Borgen, 2004). However, in many situations it is often critical to reduce the degree of pathogen inoculum on seeds in order to prevent the infection of other plants and the spread of disease in fields (Kolotelo et al., 2001). There is a large micro-flora associated with seeds, but their effects on seeds are largely unknown (Kolotelo et al., 2001). Thus, it is safest to disinfect seeds as a reasonable preventative measure.</p>
<p>Attempts to attain seeds that are completely free from active bacteria and fungi usually results in failure because seed disinfectants are either too strong and damage the seed or are too weak to fully treat the seed (Wilson, 1915). Additionally, microbes located within the seeds are not released until germination (Sweet & Bolton, 1979). A more severe treatment will kill bacteria within the seed, but also cause more damage to the embryo (Sweet & Bolton, 1979). Some disinfectants are more effective than others, such as the three simple solutions outlined above. However, it should be recognized that no single surface disinfectant is perfect under every condition and each should be critically considered (Wilson, 1915; Sweet & Bolton, 1979). </p>
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      <h1 class="title-bg">Resources Moving Forward</h1>
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<p>ATTRA Sustainable Agriculture link is a quick guide to a variety of compost tea production systems. Retrieved from: https://attra.ncat.org/attra-pub/viewhtml.php?id=125</p>


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<p>ATTRA notes on compost teas. Retrieved from: https://attra.ncat.org/attra-pub/summaries/summary.php?pub=125 </p>
      <h1 style="background: #FBB03B;padding: 15px;font-weight: 600;color: #000;font-size: 22px;margin:unset;text-align:center;">Resources Moving Forward<h1>
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          <p>Seed handling guidebook. Although this resource was meant for tree seeds, its outlines and applications are useful for all species’ seed treatments. Retrieved from: https://www.for.gov.bc.ca/hti/publications/misc/seed_handling_guidebook_hi.pdf</p>


<p>Natural crop protection applications for fighting pest and pathogens in the tropics:
<p>Notes for compost teas and other pathogen treatments seen here: http://www.growseed.org/seedtreatments.html</p>
http://www.naturalcropprotection.margraf-verlag.de/overin.htm</p>


<p>Website full of organic treatments for seeds for the control of pests and pathogens in the tropics: http://www.oisat.org/control_methods/other_methods/seed_treatment.html</p>
<p>Compost Tea: Principles and Prospects For Plant Disease Control: good literature on ACT and NCT with tables. Retrieved from: http://www.tandfonline.com/doi/pdf/10.1080/1065657X.2002.10702095</p>


<p>Research book on pesticide seed treatments: Gullino, M. L., & Munkvold, G. (Eds.). (2014). Global Perspectives on the Health of Seeds and Plant Propagation Material (Vol. 6). Springer.</p>
<p>Outline of compost teas titled: Compost tea and its impact on plant diseases. Retrieved from: http://crophealth.com/wp/wp-content/uploads/2012/04/CropHealthcom-Sustainable-Compost-Tea-and-plant-diseases-2007-BCOrganicGrower-COABC.pdf</p>
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       <h1 class="title-bg">References</h1>
       <h1 class="title-bg">References</h1>
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           <p>1. Borgen, A., & Nielsen, B. (2001). Effect of seed treatment with acetic acid in control of seed borne diseases. In Proceedings of the BCPC Symposium No. 76:“Seed Treatment: Challenges & Opportunities” (Vol. 76). Farnham.</p>
           <p>1. Appropriate Technology Transfer for Rural Areas, ATTRA. (1998). Notes on Compost Teas. National Center for Appropriate Technology (NCAT). Retrieved from: https://attra.ncat.org/attra-pub/viewhtml.php?id=125</p>  
 
<p>2. Borgen, A. (2004). Strategies for regulation of seed borne diseases in organic farming. Seed Testing International-ISTA News Bulletin, 127, 19-21.</p>
<p>2. Al-Dahmani, J. H., Abbasi, P. A., Miller, S. A., & Hoitink, H. A. (2003). Suppression of bacterial spot of tomato with foliar sprays of compost extracts under greenhouse and field conditions. Plant disease, 87(8), 913-919.</p>
 
<p>3. Kolotelo, D., Steenis, E. V., Peterson, M., Bennett, R., Trotter, D., & Dennis, J. (2001). Seed handling guidebook. British Columbia Ministry of Forests, Tree Seed Centre.</p>


<p>4. Mancini, N. (2012). Controlling and Sterilizing Seeds. Organic gardening simplified. Retrieved from: http://www.organicgardeningsimplified.com/images/seeds/seeds.pdf</p>
<p>3. Gea, F. J., Navarro, M. J., & Tello, J. C. (2009). Potential application of compost teas of agricultural wastes in the control of the mushroom pathogen Verticillium fungicola. Journal of Plant Diseases and Protection, 116(6), 271-273.</p>


<p>5. Mancini, V., & Romanazzi, G. (2014). Seed treatments to control seedborne fungal pathogens of vegetable crops. Pest management science, 70(6), 860-868.</p>
<p>4. Haggag, W. M., & Saber, M. S. M. (2007). Suppression of early blight on tomato and purple blight on onion by foliar sprays of aerated and non-aerated compost teas. Journal of Food Agriculture and Environment, 5(2), 302.</p>
<p>6. Martina. (2015). Vinegar to keep your Garden Growing. Natural Clean. Retrieved from: http://naturally-clean.ca/vinegar-to-keep-your-garden-growing/</p>


<p>7. Matsko, C. M., Expert Reviewed. (2016). How to make a quick disinfectant for minor cuts and abrasions. Wikihow. Retrieved from: http://www.wikihow.com/Make-a-Quick-Disinfectant-for-Minor-Cuts-and-Abrasions</p>
<p>5. Ingham, E., & Alms, M. (2003). Compost tea. Soil Foodweb Incorporated.</p>


<p>8. Munkvold, G. P. (2009). Seed pathology progress in academia and industry. Annual review of phytopathology, 47, 285-311.
<p>6. Lanthier, M., & Advising, C. (2007). Compost tea and its impact on plant diseases. BC Organic Grower, 10(2), 8-11.</p>
<p>9. Sauer, D. B., & Burroughs, R. (1986). Disinfection of seed surfaces with sodium hypochlorite. Phytopathology, 76(7), 745-749.</p>


<p>10. Stouffer, J. (1999). Vinegar and Hydrogen Peroxide as Disinfectants. Tau Topics. Retrieved from: http://www.michaelandjudystouffer.com/judy/articles/vinegar.htm</p>
<p>7. Martin, C. C. S. (2014). Potential of compost tea for suppressing plant diseases. CAB Rev, 9(32), 1-12.</p>


<p>11. Sweet, H. C., & Bolton, W. E. (1979). The surface decontamination of seeds to produce axenic seedlings. American journal of botany, 692-698.</p>
<p>8. Scheuerell, S., & Mahaffee, W. (2002). Compost tea: principles and prospects for plant disease control. Compost Science & Utilization, 10(4), 313-338.</p>


<p>12. Report on Plant Disease (RPD) No. 915. (1992). Vegetable Seed Treatment. Department of Crop Sciences, University of Illinois at Urbana-Champaign.  
<p>9. Scheuerell, S. J. (2004, September). Compost tea production practices, microbial properties, and plant disease suppression. In International Conference on Soil and Compost Eco-Biology</p>
<p>13. Van der Wolf, J. M., Birnbaum, Y., Van der Zouwen, P. S., & Groot, S. P. C. (2008). Disinfection of vegetable seed by treatment with essential oils, organic acids and plant extracts. Seed science and technology, 36(1), 76-88.</p>


<p>14.Wilson, J. K. (1915). Calcium hypochlorite as a seed sterilizer. American journal of Botany, 2(8), 420-427.</p>
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Revision as of 00:39, 21 June 2022

7.8 - Manure tea field spraying and seed application


Nick Moroz, University of Guelph, Canada

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Suggested citation for this chapter.

Author name (2022) title of chapter. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Compost “Teas” can Prevent Disease

Compost teas - an umbrella term that includes manure teas - are preventative measures: they reduce the possibility of plant infection from occurring. Preventative measures contrast with curative measures, with the latter aiming to address plant diseases as they occur within a field. Although the benefits of preventatives measure are not directly seen, these measures can save money and resources over time. Preventative measures can decrease the probability of pathogenesis in a field, reducing the need for insecticides to control plant epidemics that could have been controlled by preventative treatment in the first place.


Compost tea may reduce the need for multiple field applications of fungicides or bactericides later in the growing season. Aggravated use of pesticides is often damaging to the local environment and poses a health hazard to farmers using these applications without advanced safety equipment. Subsistence farmers interested in conserving crop health can consider compost teas as a safe preventative measure, although these teas are generally considered to be less effective than commercial pesticides.

Compost or Manure “Tea” Mechanism to Reducing Pathogenesis

Compost or manure “teas” - composed of compost, manures, and other organic materials - are organic approaches to reducing pathogens, most notably fungi and bacteria. There are multiple beneficial mechanisms that allow these teas to reduce pathogenesis of crops. First, compost teas contain a variety of beneficial microbes in the compost or manure that outcompete pathogenic microbes for nutrients secreted by plants in both the roots and leaves (Ingham & Alms, 2003; Scheuerell, 2004). Plant exudates, both from roots and leaves, help grow disease-suppressing bacteria and fungi in the compost tea, fighting off pathogens (Ingham & Alms, 2003; Scheuerell & Mahaffee, 2002). Unfortunately pesticides and inorganic fertilizers can kill the beneficial microbes, leaving plant exudates for the disease causing microbes (Ingham & Alms, 2003).

Second, compost teas contain soluble nutrients that feed beneficial microbes within the teas themselves and also feed the plants after application of the “tea” (Ingham & Alms, 2003; Scheuerell, 2004). High nutrient concentrations promote beneficial microbe growth, plant resiliency, and increase retention of nutrients in the soil around the plants, reducing fertilizer demands (Ingham & Alms, 2003). Because of these mechanisms, compost teas are often sprayed onto the soil or used as a leaf spray (foliar).

Methods of Compost Tea Production and Application

Compost tea is produced by mixing compost (or manure in manure teas) with water and culturing for a defined period (Scheuerell, 2004). There are two major methods for producing these teas: actively aerating (aerated compost tea, ACT) or not (non-aerated compost tea, NCT) (Scheuerell, 2004). Finally, teas are made with or without additives that are intended to increase microbial population densities during production (Scheuerell, 2004). These are a number of other parameters besides the role of aeration that impact compost tea production and their suppressive properties (Scheuerell & Mahaffee, 2002). These include choice of compost feedstock, compost age, water ratio, fermentation time, added nutrients, temperature and pH, and these are outlined in table 1 (Scheuerell & Mahaffee, 2002). Each of these properties influences the suppressive capabilities of compost teas (Scheuerell & Mahaffee, 2002). Simple procedures/recipes can be found on wikihow (http://www.wikihow.com/Make-Manure-Tea).

A variety of parameters to consider for application are dilution ratio, equipment, timing, and rates of application (Scheuerell & Mahaffee, 2002). Application to soils and/or plants can be done with spray equipment and all types of irrigation systems, if useful (Steven J. Scheuerell). The application system determines the need for filtering compost tea and it should be noted that some filters could reduce microbial populations (Scheuerell, 2004). It should be noted that the research reflects that there is no one ideal compost tea and application factor for all host-pathogen systems (Scheuerell & Mahaffee, 2002.

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In summary, these are several methods for producing compost or manure teas to choose from, depending on the scale of production and available financial resources for buying brewing equipment or constructing a homemade brewer (ATTRA, 1998). Methods include the Bucket-Bubbler, Tough, and Commercial Tea Brewer Methods (ATTRA, 1998). Two methods, found at ATTRA, are listed here and can be further researched if needed at ATTRA (ATTRA, 1998).

First, the Bucket-Fermentation Method: compost tea is made by immersing a burlap sack filled with compost into a tank with occasional stirring for 7-10 days, resulting in a compost water extract rather than a “brewed” compost tea (ATTRA, 1998). This is a hundreds of years old method for making basic watery compost tea (ATTRA, 1998).

Second, the Commercial Tea Brewers: These brewers contain a compost leachate basket with drainage holes placed in a tank with water and microbial food sources (ATTRA, 1998). A pump also supplies oxygen to aerate the compost tea while brewing in the tank (ATTRA, 1998). Although this method may be too expensive for a subsistence farmer, it may be affordable for a community.

Aerated and Non-aerated Compost Tea

As mentioned, the two major methods for producing compost teas are aerated compost tea (ACT) or non-aerated compost tea (NCT). This parameter is especially important because producing compost tea with or without aeration and nutrient additives was shown to affect total bacterial population counts as well as bacterial metabolically activity (Scheuerell, 2004). The main distinction between NCT and ACT is that NCT uses greater quantities of compost than ACT, usually without separate nutrient additives, and can be produced from several days to several weeks (Scheuerell, 2004). In contrast, ACT is aerated and uses composts, water, and nutrient additives to significantly increase microbial populations over a 12-36 hour period (Scheuerell, 2004). Compost is supplied aeration through technologies such as an aquarium pump (Lanthier & Advising, 2007). The higher oxygen supply stimulates growth of aerobic microbe populations that assist in compost tea disease suppression and nutrient supply, and these microbes may not survive low oxygen conditions (Lanthier & Advising, 2007).

Most research has focused on the plant disease control properties of compost tea, with most studies pointing to the efficacy of NCT as compared to ACT (Scheuerell, 2004). This review paper outlines the number of NCT studies that showed disease suppressive properties compared to ACT studies (Scheuerell & Mahaffee, 2002).

Case Studies

There are multiple examples in the literature to support the claims that both NCT and ACT can be effective in disease suppression (Scheuerell & Mahaffee, 2002; Martin, 2014; Haggag & Saber, 2007; Al-Dahmani, Abbasi, Miller, & Hoitink, 2003). Due to the volume of studies that reflect this, examples are outlined in table 2. Supposedly, like NCT, increasing the populations of both the total and active bacteria in ACT will generally lead to heightened plant disease suppression (Scheuerell, 2004). In one study, NCT used for seed sterilization prevented pea seeds from “damping-off” caused by the microbe Pythium ultimum and also helped the plant to grow after germination (Scheuerell & Mahaffee, 2002). Although less research has been conducted on soil-borne disease suppression (as compared to foliar disease suppression) with compost teas, this is an often-practiced technique used by organic farmers (Scheuerell & Mahaffee, 2002

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Critical Analysis and Summary

Use and application of compost teas in practice are rapidly expanding and outpacing the capacity for traditional scientific research to document the effects of these teas (Scheuerell, 2004). As with many biotechnologies, compost teas are not the single solution to complex problems, such as unsustainable farming, and often their efficacy is limited compared to commercial pesticides (Scheuerell, 2004). However, these teas may be integrated into organic farming systems as a carrier of plant nutrients and beneficial microbes to manage diseases, especially when pesticides use is not a possible solution. Subsistence farmers should be informed of how compost teas may impact their production systems (Scheuerell, 2004)

As some microbes in manure teas can be human pathogens, these “teas” must be used with caution. Microbes in compost teas are thought to be the most importance factor assisting in plant disease suppression despite a limited understanding of the microbes that provide this protection (Scheuerell & Mahaffee, 2002). This limit in knowledge, along with a lack of reporting standards, likely contributes to the variability in compost tea research findings (Scheuerell & Mahaffee, 2002).

Resources Moving Forward

ATTRA Sustainable Agriculture link is a quick guide to a variety of compost tea production systems. Retrieved from: https://attra.ncat.org/attra-pub/viewhtml.php?id=125

ATTRA notes on compost teas. Retrieved from: https://attra.ncat.org/attra-pub/summaries/summary.php?pub=125

Notes for compost teas and other pathogen treatments seen here: http://www.growseed.org/seedtreatments.html

Compost Tea: Principles and Prospects For Plant Disease Control: good literature on ACT and NCT with tables. Retrieved from: http://www.tandfonline.com/doi/pdf/10.1080/1065657X.2002.10702095

Outline of compost teas titled: Compost tea and its impact on plant diseases. Retrieved from: http://crophealth.com/wp/wp-content/uploads/2012/04/CropHealthcom-Sustainable-Compost-Tea-and-plant-diseases-2007-BCOrganicGrower-COABC.pdf

References

1. Appropriate Technology Transfer for Rural Areas, ATTRA. (1998). Notes on Compost Teas. National Center for Appropriate Technology (NCAT). Retrieved from: https://attra.ncat.org/attra-pub/viewhtml.php?id=125

2. Al-Dahmani, J. H., Abbasi, P. A., Miller, S. A., & Hoitink, H. A. (2003). Suppression of bacterial spot of tomato with foliar sprays of compost extracts under greenhouse and field conditions. Plant disease, 87(8), 913-919.

3. Gea, F. J., Navarro, M. J., & Tello, J. C. (2009). Potential application of compost teas of agricultural wastes in the control of the mushroom pathogen Verticillium fungicola. Journal of Plant Diseases and Protection, 116(6), 271-273.

4. Haggag, W. M., & Saber, M. S. M. (2007). Suppression of early blight on tomato and purple blight on onion by foliar sprays of aerated and non-aerated compost teas. Journal of Food Agriculture and Environment, 5(2), 302.

5. Ingham, E., & Alms, M. (2003). Compost tea. Soil Foodweb Incorporated.

6. Lanthier, M., & Advising, C. (2007). Compost tea and its impact on plant diseases. BC Organic Grower, 10(2), 8-11.

7. Martin, C. C. S. (2014). Potential of compost tea for suppressing plant diseases. CAB Rev, 9(32), 1-12.

8. Scheuerell, S., & Mahaffee, W. (2002). Compost tea: principles and prospects for plant disease control. Compost Science & Utilization, 10(4), 313-338.

9. Scheuerell, S. J. (2004, September). Compost tea production practices, microbial properties, and plant disease suppression. In International Conference on Soil and Compost Eco-Biology

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