Progress 10/01/06 to 09/30/08
Outputs
OUTPUTS: Our research into the mechanisms behind disease suppression has focused on understanding the observed changes in zoospore attraction induced by vermicompost microbes. We have confirmed our preliminary results that microbially modified seed exudates attract fewer zoospores that control seed exudates and are continuing work in this system to determine if the change in zoospore behavior is due to the presence of a toxin or the absence of a key chemical attractant. We have also explored alternative methods of introducing vermicompost microbes into horticultural production systems, namely non-aerated compost extracts. A systematic evaluation of preparation methods revealed that high initial ratios of vermicompost to water led to extracts with high electrical conductivity, low dissolved oxygen and high pH. Extracts made with lower initial vermicompost to water ratios (i.e. below 1:25) were not phytotoxic and some batches were mildly suppressive towards Pythium aphanidermatum on cucumber. This result needs to be confirmed with multiple batches of non-aerated compost extract. New collaborations have arisen from work on this project between researchers in Applied Economics and Management and Horticulture at Cornell and 7 NY vegetable and fruit growers. On-farm trials and greenhouse work at Cornell are investigating the economic viability of practical applications of vermicompost in horticultural production systems. We have found that for most vegetable crops, amending potting media with 10% vermicompost and blood meal leads to higher seedling biomass than commercially available certified organic mixes. In field trials with cut flower species, vermicompost amended potting media provided no suppression of root rots identified as Pythium spp., which emphasizes the importance of understanding the mechanism behind suppression before we can predict how different composts will perform in the field. Outreach to the scientific community included the following talks: 1) Modification of seed exudates by seed colonizing microbes from vermicompost alters pre-infection behavior of Pythium aphanidermatum zoospores. American Phytopathological Society, Minneapolis, MN; 2) Vermicompost: Horticultural applications and impacts on plant associated microbial communities, Department of Crop and Soil Sciences seminar, Cornell. Outreach to growers and the general public included the following talks / events: 1) Suppressing plant diseases with vermicompost. NC State Vermicomposting Workshop, Raleigh, NC; 2) Development of biocontrol products from vermicomposted cow manure. Public Engagement and Science Communication Symposium, Center for Life Science Enterprise, Cornell; 3) Special discussion on potting media amendments, Organic Production and Marketing Program Work Team, Cornell and 4 NY county extension offices (via video conference). Additionally members of the project team met and discussed the project with multiple representatives from Syngenta and Life Science Partners, venture capitalists who are considering investing in RTS, the vermicomposting business we collaborate with in western NY. PARTICIPANTS: Graduate students: Allison Jack; Technicians: Eric Carr, Betsy Leonard; Partner organization: RT Solutions, Tom Herlihy, president TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
If the observed changes in zoospore behavior can be directly linked to the observed suppression of disease, the interaction between seed-colonizing vermicompost microbes and Pythium aphanidermatum zoospores could become a new model experimental system for understanding how complex microbial communities can prevent soil-borne plant diseases. Over the course of this project, vegetable growers have been increasingly adopting vermicompost as a potting media amendment for plant nutrition. Elzinga & Hoeksema Nurseries in Michigan has one of the nation's largest certified organic greenhouses and is using exclusively vermicompost and vermicompost extracts made by our industry collaborators in western NY in their plant fertility program. They've incorporated its use into their conventional greenhouses as well. We currently have 7 on-farm field trials in NY and have been able to successfully network with other researchers and growers who are interested in working with this material. Now that vermicompost is being more widely adopted in the horticulture industry as a nutrient source, it is even more imperative that we better understand its effects on plant health. Increased adoption over the long term could result in decreased synthetic fertilizer and pesticide use in the horticultural and cut flower industries. The dairy associated with the vermicomposting facility has been able to fundamentally change their manure management practices as a result of changes in their waste stream. The facility diverts a large volume of separated solids, leaving the dairy with only liquid effluent. Liquid effluent, as opposed to manure slurry, can be pumped through hoses and subsurface injected directly behind a plow instead of transported load by load in heavy manure spreading trucks. Coyne Dairy now has their 7 M gallon lagoon capped with a methane flare which generates income through a carbon trading scheme. The vermicomposting facility is currently seeking venture capital to expand its operations and could become a national model for environmentally sound and economically viable manure management under the newly enacted CAFO legislation.
Publications
- No publications reported this period
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Progress 10/01/06 to 09/30/07
Outputs
Our work thus far has demonstrated that vermicomposted dairy solids protect cucumber seeds and seedlings from Pythium damping off. Amending soil with 40% v:v vermicompost results in almost complete plant protection. Amendment with sterilized vermicompost results in high disease, indicating that the observed suppression is due to a biological factor. Zoospores of all oomycete plant pathogens are highly sensitive to changes in soil moisture. The disease suppression bioassays involve a modified apparatus to control soil matric potential, which has led to highly replicable results in experiments using P. aphanidermatum zoospores as inoculum. We have furthered our understanding of how vermicomposts protect germinating cucumber seeds from infection by focusing on fundamental aspects of zoospore pre-infection behavior. Transplant bioassays show that zoospores reach the surface of germinating cucumber seeds within 1-2 days. We hypothesize that seed colonizing microbes
interfere with one of the zoospore pre-infection stages; homing, encystment, or germination. To test the first stage, homing, we used seed colonizing microbial communities from suppressive vermicompost to modify cucumber seed exudates. Zoospores have the ability to sense chemicals released into the soil by germinating seeds, called seed exudates. Zoospores exhibit a chemotactic response, actually swimming towards these exudates which we measured with a novel zoospore attraction assay. In our preliminary and ongoing experiments, unmodified cucumber seed exudate attracted a large number of Pythium zoospores, while modified exudate attracted a much lower number of zoospores. In addition to our research activities, the project team hosted two small field days at the vermicomposting facility in Avon, NY intended to network with other Cornell researchers and extension staff interested in compost and vermicompost. Members of the project team discussed ongoing disease suppression research in
an online educational/promotional video with one of the project collaborators (http://www.wormpower.net/worm-castings/worm-castings-video.php). Other outreach activities included: 1) Vermicompost Production and Use, Small Farm Expo, Augusta NJ 2006, 2) Vermicompost Production and Use for Plant Disease Suppression, Agroecological Perspectives Seminar Series, Cornell 2006, 3) The World Beneath Our Feet: Exploring Soil Life, Master Gardener Training Cornell 2007, and 4) Compost Microbiology, Tompkins County Cornell Cooperative Extension 2007. Consulting services included working with a project collaborator, Tom Herlihy, to develop a literature review for the lay audience explaining the complexities of compost mediated suppression of plant diseases entitled: Current scientific understanding of controlling plant diseases with composts, vermicomposts and compost teas. Misinformation on this topic abounds in grower communities and is disseminated by commercial testing facilities. Current
information was compiled and synthesized for a non-scientific audience as a tool to facilitate dialogue between scientists and commercial growers and composters.
Impacts
Our current results indicate that microbes from suppressive vermicompost may be modifying seed exudates in such a way that they interfere with zoospore homing behavior and thus reduce disease. If this phenomenon can be verified, it would be the first documentation of this type of mechanism for compost-mediated plant disease suppression. Further understanding of this mechanism will greatly narrow the search for the microorganisms responsible for this interaction. These findings have broad implications for agricultural practices. Pythium aphanidermatum has over 50 crop hosts, causing extensive damage in vegetable and ornamental production systems. Establishing vermicompost as an effective pesticide alternative is expanding existing markets for recycled livestock manures. Our collaborator, RT Solutions, is currently producing over 10 tons of vermicomposted dairy solids a week and shipping to vegetable, berry and wine growers across the country. Wider adoption of
vermicomposting as a manure management technology could be an important step in removing livestock manure from fragile watersheds and creating jobs in rural areas. To predict disease suppression, many growers rely on commercial testing of composts which is not always based on sound science. Our increased understanding of compost mediated disease suppression will aid the development of novel and accurate testing methods. Working with growers, cooperative extension and the compost industry, we are promoting scientific literacy and generating an open dialogue on the microbiological testing of composts.
Publications
- No publications reported this period
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Progress 10/01/06 to 12/31/06
Outputs
Our work is aimed at understanding the mechanisms by which various thermogenic and vermicomposted substrates suppresses Pythium damping-off diseases. Studies have focused on seedling diseases incited by Pythium aphanidermatum and Pythium ultimum. Microcosms were used to establish the suppressiveness of vermicomposted dairy manure to Pythium aphanidermatum damping-off of cucumber seedlings. Amending soil with 20 percent (v:v) vermicompost significantly (p less than 0.0001) increased cucumber seedling survival when inoculated with 50 mL of a 3x105 mL-1 suspension of P. aphanidermatum zoospores. Disease suppression at water potentials between -2 and -8 kPa did not differ. In experiments with P. ultimum, a cured thermogenic biosolids compost was used to evaluate the effects of water potential, crop species and microbial activity on suppression of Pythium ultimum. Compost-induced suppressiveness was expressed on three test hosts, cucumber, wheat, and pea. Initial
experiments revealed strong impacts of water potential on suppressiveness of compost. Water potentials higher than -2 kPa did not support suppressiveness. Suppressiveness was observed only at water potentials between -2 and -4 kPa and was lost upon autoclaving. From a series of transplant experiments, we observed that microbial communities colonizing seeds of cucumber and wheat between 8 and 16 hr after sowing induced high levels of suppressiveness, fully explaining the suppressiveness observed after 7 days. These results point to the importance of water potential in modulating disease suppressiveness and the possible involvement of seed-colonizing microbial communities in the suppression of Pythium damping-off.
Impacts
Our research will provide a means of understanding how composts suppress diseases and how key microbial communities accomplish this suppressiveness. Through our work, we will be able to more accurately predict compost suppressiveness, increase their overall efficacy, and, once implemented by growers, reduce fungicide inputs. This project will enhance collaborations between compost producers and growers by allowing the two to work together to develop compost products that would best meet the needs of both industries. Many beneficial economic impacts would arise from an increase in compost use for disease control. The production of both peas and cucumbers are greatly affected by seed decay and root rots. However, no biological control practices are currently available for either crop. Effective biological control of seed-infecting pathogens could substantially lower the cost of fungicide inputs and increase yield bringing an economic benefit to the grower. Since some
fungicides have been shown to negatively impact soil's natural suppressiveness towards damping-off, compost use as a pesticide alternative would lead to the preservation and even enhancement of indigenous suppressive communities in soils. In the longer term, the positive impacts of compost use on soil health may lead to a reduction in other plant diseases, thus reducing the need for many other fungicides.
Publications
- No publications reported this period
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