Progress 09/01/05 to 02/28/10
Outputs
OUTPUTS: Phytophthora species pose a growing threat to the nursery and floriculture industry as it increasingly depends on recycled water for irrigation. This project was to test a hypothesis that these pathogens decline along the water path from the runoff water entrance to exit or pump inlet and from the surface of the water column in containment basins and provide a foundation for crop health risk mitigation through pump house location and inlet placement. This was accomplished by surveying fourteen basins at five commercial nurseries in Virginia, two in North Carolina, and one each in Maryland and Pennsylvania regularly from 2005 to 2010 and performing series of assays in the lab. The major outputs from the water surveys included: (i) invention of a new deployment system that retained baits at designated locations and depths regardless of weather conditions and development of an improved baiting protocol that consistently provided the maximal recovery of pathogen diversity and population size; (ii) pathogen distribution patterns along the water paths from runoff entrance to exit or pump inlet, and at different depths of water columns; (iii) novel knowledge about how pathogen propagules settle at each step in multiple-step (basin) water recycling systems, whether all Phytophthora species are equally aquatic, and how individual species may respond to nutrients in the runoff water; and (iv) seasonal and diurnal fluctuation ranges and patterns of nine major parameters of water quality. The lab assays generated data essential to understand why (1) some species of Phytophthora decline more rapidly than other species along the water path and (2) contaminated irrigation water led to severe disease and damage to ornamental crops even at very low levels of pathogen density (often undetectable). The project concept and results were delivered to growers through numerous field demonstrations, learning modules and invited presentations at growers' meetings hosted by their local, regional (e.g., the Mid-Atlantic Horticulture Short Course) and national associations (the Society of American Florists). Dr. Hong developed a learning module on management of plant pathogens in irrigation water which is housed at the Green Industry Knowledge Center for Water, Nutrient and Plant Health Management (http://www.waternut.org/new/). The project results also have been disseminated to science communities through nine research articles, eleven abstracts, and many invited/keynote presentations. During the past 5 years, the Project Director alone was an invited speaker on biology and management of waterborne pathogens at five major universities and a number of regional (e.g., Virginia/West Virginia Annual Water Conference, Blacksburg, VA, 2007), national (Land Grant and Sea Grant National Water Conference in Hilton Head, SC, 2010) and international meetings (9th International Congress of Plant Pathology, Turin, Italy, 2008). These publications and presentations broadened and expedited the dissemination and application of the novel knowledge generated from this project. PARTICIPANTS: Dr. Gary Moorman, Professor of Plant Pathology, Pennsylvania State University (Co-PI); Dr. John Lea-Cox, Associate Professor of Horticulture, University of Maryland (Co-PI); Dr. David Ross, Professor of Agricultural Engineering, University of Maryland (Co-PI); Dr. Mannon Gallegly, Collaborator, West Virginia University; Dr. Sita Ghimire, Postdoctoral Associate, Virginia Tech; Dr. Ping Kong, Research Scientist, Virginia Tech; Dr. Zhihan Xu, Postdoctoral Associate, Virginia Tech; Miss Wei Hao, Graduate Student, Virginia Tech; Ms. Patricia Richardson, Research Specialist Sr., Virginia Tech; Collaborating Growers in Virginia, Maryland, Pennsylvania, North Carolina TARGET AUDIENCES: Plant pathologist, Mycologists, Ecologists, Horticulturists irrigation Specialists, Plant Health Care Profesionals, Growers, Policy makers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The genus Phytophthora was added to the list of water molds in 1944, but its aquatic habitat as a whole has received little attention until very recently. This project provided clear evidence supporting the hypothesis that Phytopthora populations decline along the water path in runoff containment basins. This project also produced several other major findings. (1) It provided an effective protocol for future aquatic ecology studies of these destructive pathogens. (2) A total of 32 distinct species including many new taxa and four species previously undocumented for irrigation water were identified. Four of these new taxa were named P. irrigata, P. hydropathica, P. aquatilis, and P. aquimorbida, respectively. P. pini, a defunct species, was resurrected. More new taxa are being described. (3) Zoosporic pH tolerance in aquatic environments varies greatly with species, challenging the general notion that Phytophthora species are water molds, at least in terms of zoospore activities. (4) Zoosporic behaviors are regulated by their extracellular products as demonstrated by P. nicotianae. Among these extracellular products is autoinducer-2, a signal molecule for interspecific communication within the bacterial world. (5) Water quality in irrigation runoff containment basins fluctuates dramatically with nine parameters in four distinct seasonal and two diurnal patterns. Each of these findings constitutes a major cornerstone of the aquatic ecology of Phytophthora species. The improved baiting protocol not only enhances the research quality and productivity of individual projects including this one, but also makes data collected from different geographic locations comparable, maximizing the aquatic ecology science advancement with limited available resources. Identification of new species and those previously undocumented for nursery irrigation water will help the plant pathology and mycology communities to identify the diversity of this group of plant pathogens in containment basins as well as in natural water ways. Discovery of pH intolerance of Phytophthora species and production of bacterial communication signal molecules by zoosporic pathogens provides new insight into pathogen biology and new horizons for crop health care innovation. Determination of fluctuation range and patterns of water quality in the containment basins provide a solid foundation for analytical studies of pathogen aquatic ecology. Most importantly, this project provides a new strategy for crop health risk mitigation by locating the pump inlet away from the runoff entrance. This strategy is environmentally-sound and economically-effective, requiring no or little extra capital investment for a life-time benefit. Numerous production facilities in the Mid-Atlantic region have used our project concept and data in design of new water recycling systems and modification of existing systems for minimal inoculum intake since the first project demonstration held in conjunction with the annual Field Day of the Virginia Nursery and Landscape Association in 2006. The water quality data also have become an important base for irrigation water quality management programming.
Publications
- Hong, C. X., Richardson, P. A., Ghimire, S. R., Hao, W., Kong, P., Moorman, G. W., Lea-Cox, J. L., and Ross, D. R. 2010. Two new homothallic species of Phytophthora from irrigation reservoirs and natural waterways in Virginia (Abstr.) Phytopathology (In press)
- Kong, P., and Hong, C. X. 2010. Zoospore density-dependent behaviors of Phytophthora nicotianae are autoregulated by extracellular products. Phytopathology (In press)
- Gallegly, M. E., Hong, C. X., Richardson, P. A., and Kong, P. 2010. Phytophthora pini, a valid distinct species (Abstr.) Phytopathology (In Press)
- Hong, C. X., Gallegly, M. E., Richardson, P. A., and Kong, P. 2010. Phytophthora pini resurrected to a distinct species status. Mycologia (In press)
- Kong, P., Lee, B. W. K., Zhou, Z. S., and Hong, C. X. 2010. Zoosporic plant pathogens produce bacterial autoinducer-2 that affects Vibrio harveyi quorum sensing. FEMS Microbiology Letters 303:55-60
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Progress 09/01/08 to 08/31/09
Outputs
OUTPUTS: While continuing data analysis and lab assays, we established two long-term water quality monitoring stations and developed methodology for identification of beneficial bacteria present in irrigation reservoirs this past year. The data analyses have resulted in nine publications, advancing the taxonomy of genus Phytophthora, pathogen aquatic ecology, and irrigation science. Specifically, we named Phytophthora hydropathica and resurrected a defunct species name Phytophthora pini. P. pini is a synonym of Phytophthora citricola I and this species is consistently isolated from irrigation reservoirs across locations and throughout the year. We also documented for the first time four species (Phytophthora insolita, Phytophthora polonica, Phytophthora pseudosyringae and Phytophthora sansomeana) in nursery irrigation water. We are working to name a number of other new taxa recovered through this project. Second, we reported the dramatic fluctuation of nine major water quality parameters in irrigation reservoirs. These data have already become an important base for irrigation water quality management programming and for prioritizing and planning lab studies on pathogen aquatic ecology. They also highlighted the needs of further investigations into water quality dynamics in irrigation reservoirs for crop health and production in the horticultural industry. Accordingly, we have established an additional long-term monitoring station in a pristine water reservoir at the same nursery for comparison purposes. Third, we found that zoosporic pH tolerance in aquatic environments varies greatly with species, challenging the general notion that Phytophthora species are water molds, at least in terms of zoospore activities. We also found that zoosporic plant pathogens produce autoinduce-2, a signal molecule for interspecific communication within the bacterial world. Fourth, we improved a research protocol for tracking the diversity and population dynamics of Phytophthora species in aquatic environments. We also developed an effective and efficient protocol for tracking microbial diversity and dynamics and identification of beneficial bacterial species in irrigation water. Finally, we actively reached out to the industry in addition to the science communities on our research progress. Notably, the Project Director (Dr. Hong) was an invited speaker on the latest water treatment technologies at the 2009 Mid-Atlantic Horticultural Short Course held in Virginia Beach, VA, January 25 to 30 (the Virginia Horticultural Foundation) and the 25th Annual Pest Management Conference, San Jose, CA, February 19 to 21 (the Society of American Florists). PARTICIPANTS: Dr. Gary Moorman, Professor of Plant Pathology, Pennsylvania State University (Co-PI) Dr. John Lea-Cox, Associate Professor of Horticulture, University of Maryland (Co-PI) Dr. David Ross, Professor of Agricultural Engineering, University of Maryland (Co-PI) Dr. Ping Kong, Research Scientist, Virginia Tech Dr. Sita Ghimire, Postdoctoral Associate, Virginia Tech Dr. Zhihan Xu, Postdoctoral Associate, Virginia Tech Dr. Mannon Gallegly, West Virginia University (collaborator) Miss Wei Hao, Graduate student Ms. Patricia Richardson, Research Specialist Sr., Virginia Tech Collaborating growers in Virginia, Maryland and Pennsylvania TARGET AUDIENCES: Plant pathologists, mycologists, horticulturists, irrigation specialists, agricultural engineers, policy makers, farmers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Cornerstones of aquatic ecology of plant destroyer Phytophthora species Relevance: Phytophthora species, generally regarded as "water molds", present a great threat to the horticultural industry as well as natural forests and this threat will continue to aggravate as the industry increasingly depends on recycled water for irrigation in the light of growing global water scarcity. However, little is known about the diversity of Phytophthora species and their aquatic ecology. The present project improved existing water assay technology, identified new species and taxa, documented the fluctuation range and pattern of water quality in irrigation runoff water containment basins and assessed their impacts on pathogen behaviors and survival. Response: We named two species and identified four known species that were not documented for irrigation water. We developed a protocol that provides the most effective and consistent detection of these pathogens in aquatic environments. In addition, we have determined the fluctuation range and pattern of water quality in the containment basins. Furthermore, we determined the zoosporic tolerance to pH in aquatic environments of seven Phytophthora species that are common in irrigation systems. We also found that zoosporic plant pathogens produce autoinducer-2 that regulates bacterial communal behaviors including aggregation and virulence. Moreover, we reached out to the science communities internationally and the horticultural industry nation-wide through nine publications and two presentations in addition to field days and other conventional and modern means of technology delivery. Impact: Each of the major findings produced through this project and reported here constitutes a major cornerstone of aquatic ecology of Phytophthora species. Identification of new species and those previously not documented for nursery irrigation water will help the plant pathology and mycology communities to identify the diversity of this group of plant pathogens in irrigation runoff water containment basins as well as in natural water ways. The improved baiting assay protocol not only enhances the research quality and productivity of individual projects including this one, but also makes data collected from different geographic locations comparable, maximizing the aquatic ecology science advancement with limited available resources. Determination of fluctuation range and patterns of water quality in the containment basins provide a solid foundation for analytical studies of pathogen aquatic ecology. Discovery of pH intolerance of Phytophthora species and production of bacterial communication signal molecules by zoosporic pathogens provides new insight into pathogen biology and a new horizon for crop health care innovation. Some of these findings also have immediate impacts on waterborne pathogen management. Specifically, the improved baiting protocol is a boost to waterborne pathogen monitoring and Phytophthora disease control in the horticultural industry.
Publications
- Hong, C. X. 2009. Re-circulating water without sacrificing crop health. Proceedings of 25th Pest Management Conference, San Jose, CA, February 19-21, 2009 (Society of American Florists), page 1-6
- Hong, C. X., Gallegly, M. E., Richardson, P. A., and Kong, P. 2009. Phytophthora pini resurrected to a distinct species status. FEMS Microbiology Letters (In press)
- Ghimire, S. R., Richardson, P. A., Moorman, G. W., Lea-Cox, J., Ross, D. S., and Hong, C. X. 2009. An in-situ bioassay for detecting Phytophthora species in irrigation runoff containment basins. Plant Pathology 58:577-583
- Hong, C. X., Gallegly, M. E., Richardson, P. A., Kong, P., Moorman, G. W., Lea-Cox, J. D., Ross, D. S. 2009. Phytophthora hydropathica, a new pathogen identified from irrigation water, Rhododendron catawbiense and Kalmia latifolia. Plant Pathology (In press)
- Hong, C. X., Lea-Cox, J. D., Ross, D. R., Moorman, G. W., Richardson, P. A., Ghimire, S. R., and Kong, P. 2009. Containment basin water quality fluctuation and implications for crop health management. Irrigation Science 27:485-496
- Hong, C. X., Richardson, P. A., Ghimire, S. R., Hao, W., Moorman, G. W., Lea-Cox, J. D., Ross, D. S., Kong, and P., Xu, Z. H. 2009. The first records of four Phytophthora species from nursery irrigation water in Virginia. Phytopathology 99:S54
- Kong, P., Lee, B. W. K., Zhou, Z. S., and Hong, C. X. 2009. Zoosporic plant pathogens produce bacterial autoinducer-2 that affects Vibrio harveyi quorum sensing. FEMS Microbiology Letters (In press)
- Kong, P., Moorman, G. W., Lea-Cox, J. D., Ross, D. S., Richardson, P. A., and Hong, C. X. 2009. Zoosporic tolerance to pH stress and its implications for Phytophthora species in aquatic ecosystems. Applied and Environmental Microbiology 75:4307-4314
- Xu, Z. H., Richardson, P. A., Kong, P., Hao, W., Moorman, G. W., Lea-Cox, J. D., Ross, D. S., and Hong, C. X. 2009. Exploring bacterial diversity in irrigation runoff water containment basins. Phytopathology 99:S145
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Progress 09/01/07 to 08/31/08
Outputs
OUTPUTS: While continuing to sample water we shifted our focus to data analysis and lab assays during this past year. The data analyses have resulted in nine publications in three areas that are critical to this project and future studies on pathogen aquatic ecology. The biggest surprise resulting from this project was the great diversity of Phytophthora species including many previously un-described species in the irrigation systems. We have completed morphological characterization and phylogenetic analyses of four new species and named the first two as Phytophthora irrigata and Phytophthora hydropathica, respectively in two publications. We are close to submitting another manuscript naming the other two. We also have collected most of the morphological and DNA sequence data required to name several additional new species. In addition, we identified four known species (Phytophthora insolita, P. polonica, P. pseduosyringae and P. sansomeana) that have not been documented previously for nursery irrigation water. The second biggest surprise was that water quality in irrigation runoff water containment basins fluctuates dramatically with nine parameters in four distinct patterns over time. This finding is essential to understand why recovery of Phytophthora species declines with distance from runoff entrance, a foundational hypothesis of this project to develop novel, ecologically-based water decontamination technology. It already has helped identify the major quality parameters to be examined in more details through lab assays and raised many new and important questions on aquatic ecology of plant pathogens. Another major accomplishment in data analyses is that we have clearly demonstrated that bait choices, deployment methods and exposure time affect recovery of Phytophthora species from the containment basins and subsequently formulated a protocol that provides the most efficient and consistent detection of these pathogens in aquatic environments. We also have made great progress in understanding aquatic ecology of plant pathogens through lab assays. We completed assays on zoosporic pH responses of seven selected species of Phytophthora. A full report is under internal review and will be submitted shortly for publication. We also identified some biological agents that stimulate plant infection by Phytophthora species and determined how zoospores communicate with one another and with other microbes in their vicinity. In addition, we actively reached out to the industry as well as the science communities on our project concepts and research progress. Notably, the project director (Dr. Hong) presented an invited talk at the 9th International Congress of Plant Pathology in Turin, Italy and accepted invitations to present the latest water treatment technologies at the 2009 Mid-Atlantic Horticultural Short Course to be held in Virginia Beach, VA, January 25 to 30 (the Virginia Horticultural Foundation) and the 25th Annual Pest Management Conference, San Jose, CA, February 19 to 21 (the Society of American Florists). PARTICIPANTS: Dr. Gary Moorman, Professor of Plant Pathology, Pennsylvania State University (Co-PI); Dr. John Lea-Cox, Associate Professor of Horticulture, University of Maryland (Co-PI); Dr. David Ross, Professor of Agricultural Engineering, University of Maryland (Co-PI); Dr. Ping Kong, Research Scientist, Virginia Tech; Dr. Sita Ghimire, Postdoctoral Associate, Virginia Tech; Dr. Zhihan Xu, Postdoctoral Associate, Virginia Tech; Dr. S. Umesha, Postdoctoral Associate, Virginia Tech; Dr. Mannon Gallegly, West Virginia University (collaborator); Ms. Patricia Richardson, Research Specialist Sr., Virginia Tech; Collaborating growers in Virginia, Maryland and Pennsylvania. TARGET AUDIENCES: Plant pathologists, Mycologists, Ecologists, Horticulturists, Irrigation specialists, Please health care professionals, Green industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Cornerstones of aquatic ecology of plant destroyer Phytophthora species Relevance: Phytophthora species, generally regarded as "water molds", present a great threat to the agricultural and horticultural industry as well as natural forests and this threat will continue to aggravate as the industry increasingly depends on recycled water for irrigation in the light of growing global water scarcity. However, little is known about the diversity of Phytophthora species and their aquatic ecology. The present project improves existing water assay technology, identifies known and unknown species and assesses their pathogenecity, and investigates the fluctuation range and pattern of water quality in irrigation runoff water containment basins. Response: We identified four known species (P. insolita, P. polonica, P. pseudosyringae and P. sansomeana) that were not documented for irrigation water, named two new species (P. irrigata and P. hydropathica) and collected required data to describe several additional new species. We also assessed pathogenicity of some existing and new taxa of Phytophthora species recovered from irrigation water. In addition, we clearly demonstrated that bait choices, deployment method and exposure time affect the recovery of Phytophthora species from containment basins and subsequently formulated a protocol that provides the most effective and consistent detection of these pathogens in aquatic environments. Furthermore, we have determined the fluctuation range and pattern of water quality in the containment basins. Moreover, we reached out to the science communities internationally and the horticultural industry nation-wide through three presentations and nine publications in five prestigious peer-reviewed journals, several in popular trade journals and newsletters in addition to field days and other conventional and modern means of technology delivery. Impact: Each of the major findings produced through this project and reported here constitutes a major cornerstone of aquatic ecology of Phytophthora species. Identification of new species and those previously not documented for nursery irrigation water will help the plant pathology and mycology communities to identify the diversity of this group of plant pathogens in irrigation runoff water containment basins as well as in natural water ways. The improved baiting assay protocol not only enhances the research quality and productivity of individual projects including this one, but also makes data collected from different geographic locations comparable, maximizing the aquatic ecology science advancement with limited available resources. Determination of fluctuation range and patterns of water quality in the containment basins provide a solid foundation for analytic studies of pathogen aquatic ecology. Some of these findings also have immediate impacts on waterborne pathogen management. Specifically, the improved baiting protocol is a boost to waterborne pathogen monitoring and Phytophthora disease control in the horticultural industry.
Publications
- 3. Ghimire, S. R., Richardson, P. A., Moorman, G. W., Lea-Cox, J., Ross, D. S., and Hong, C. X. 2009. Bait choices, deployment method and duration affect the recovery of Phytophthora species from irrigation runoff containment basins. Plant Pathology (in press).
- 4. Hong, C. X., Gallegly, M. E., Richardson, P. A., Kong, P., Moorman, G. W., Lea-Cox, J. D., and Ross, D. S. 2008. Phytophthora irrigata and Phytophthora hydropathica, two new species from irrigation water at ornamental plant nurseries. Phytopathology 98:S68.
- 5. Hong, C. X., Richardson, P. A., Ghimire, S. R., Kong, P., Moorman, G. W., Lea-Cox, J. D., and Ross, D. R. 2008. Water quality dynamics in irrigation runoff retention basins and its practical implications for plant health management. Phytopathology 98:S68.
- 6. Hong, C. X., and Moorman, G. W. 2008. Challenges, opportunities and obligations in biology and management of plant pathogens in irrigation water. Journal of Plant Pathology 90(2, supplement): 60 (Proceedings of the 9th International Congress of Plant Pathology, Turin, Italy, August 24 to 29, 2008).
- 7. Kong, P., and Hong, C. X. 2008. Searching for agents in recycled irrigation water that stimulate plant infection by Phytophthora species. Journal of Plant Pathology 90(2, supplement): 227 (Proceedings of the 9th International Congress of Plant Pathology, Turin, Italy, August 24 to 29, 2008).
- 8. Kong, P., Moorman, G. W., Lea-Cox, J. D., Ross, D. R., Umesha, S., Richardson, P. A., and Hong, C. X. 2008. Zoospore responses to environmental pH of seven Phytophthora species commonly isolated from irrigation reservoirs at ornamental plant nurseries. Phytopathology 98:S84.
- 9. Kong, P., and Hong, C. X. 2008. Quorum sensing operates in Phytophthora nicotianae Phytopathology 98:S85.
- 1. Hong, C. X., Gallegly, M. E., Richardson, P. A., Kong, P., Moorman, G. W. 2008. Phytophthora irrigata, a new species isolated from irrigation reservoirs and rivers in Eastern United States of America. FEMS Microbiology Letters 285:203-211.
- 2. Hong, C. X., Richardson, P. A., Kong, P. 2008. Pathogenicity to ornamental plants of some existing species and new taxa of Phytophthora from irrigation water. Plant Disease 92:1201-1207.
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Progress 09/01/06 to 08/31/07
Outputs
OUTPUTS: During this second year, we focused on three areas of the project. First, we continued water samplings at three locations in Virginia, representing three different types of recycling irrigation systems. Type (location) A involves a single retention basin with all runoff water returning to the basin through a single entrance and a pump house opposite to the runoff entrance. Type B involves three basins with all runoff water being captured in the top basin, and overflowed to the middle then lowest basin where irrigation water is drawn. Type C also involves three basins with a slightly different water flow path compared to that of Type B. All runoff water is captured in a sedimentation basin then overflowed to an irrigation reservoir. The third basin is a lake fed only by natural springs. The lake water is drawn as needed to feed the irrigation reservoir. These samplings have confirmed the horizontal and vertical distribution patterns of Phytophthora diversity and populations
in retention basins found the previous year. We went a few extra miles (beyond proposed research) and by taking advantage of the topographic characters of individual locations gained a lot of insight into some fundamental questions: (i) how pathogen propagules settle at each step in multiple-step (basin) recycling irrigation systems, and (ii) whether all Phytophthora species are equally aquatic and how individual species may respond to nutrients in the runoff water. Through continuous water quality monitoring, we observed dramatic fluctuations of chlorophyll readings, pH, dissolved oxygen, oxidation-reduction potential, total dissolved solids, conductivity, salinity and turbidity and their impacts on pathogen populations. We are analyzing data across locations and seasons, and formulating guiding protocols as proposed. With two years of field data in hand we have started writing for publications. Second, we have started laboratory assays to assess the impacts of individual water
quality parameters on pathogen survival beginning with pH and conductivity. Third, we actively reached out to the industry and communicated with stakeholders on our project concepts and research progress. Notably, we performed one on-site demonstration in conjunction with the Annual Field Day of Virginia Nursery and Landscape Association on August 17, 2006 and a mid-term stakeholder meeting on October 19 to 20, 2007. Through these events this project already has made significant positive impact on the nursery industry. We also identified a nursery in Maryland and performed one sampling at two runoff retention basins this summer to collect data for protocol validation.
PARTICIPANTS: Dr. Gary Moorman, Professor of Plant Pathology, Pennsylvania State University (Co-PI); Dr. John Lea-Cox, Associate Professor of Horticulture, University of Maryland (Co-PI); Dr. David Ross, Professor of Agricultural Engineering, University of Maryland (Co-PI); Dr. Ping Kong, Research Scientist, Virginia Tech; Dr. Sita Ghimire, Postdoctoral Associate, Virginia Tech; Ms. Patricia Richardson, Research Specialist Sr., Virginia Tech; Collaborating growers in Virginia, Maryland and Pennsylvania.
TARGET AUDIENCES: Nursery and Greenhouse industry; Other segments of irrigated agricultural crop production; USDA Forest Service; Water conservation and water quality protection
PROJECT MODIFICATIONS: We expanded the scope of research from single-retention-basin recycling irrigation to multi-step (basin) systems. We also included a natural lake in one of the commercial nurseries we sampled for comparative studies.
Impacts
Novel Research Stimulates Practice Changes in the Nursery and Floral Industry. Relevance: Phytophthora species in irrigation water present a great threat to the green industry as well as natural forests and this threat will continue to aggravate as the industry increasingly depends on recycled water for irrigation in the light of growing global water scarcity. Chlorination of irrigation water with either chlorine gas or liquid chlorine is the most cost-effective technology for water decontamination crucial to the health of the multibillion-dollar industry. However, there is a growing concern about potential health hazards associated with storage and use of this chemical because chlorine gas is explosive and liquid chlorine is corrosive. The present project investigates ecologically-based alternative technologies to reduce the risk of health hazards while improving crop health and profitability of the industry. Response: The research conducted in the first 2 years has
confirmed our hypothesis on the spatial distribution of Phytophthora populations in runoff retention basins although detailed guiding protocols are yet to be formulated and validated in the second phase of the project. In addition to using every field visit and all other conventional means of technology delivery we held two special events to communicate with stakeholders on the project concepts and research progress this past year. One was a demonstration on-site where we perform the most intensive water sampling, and continuously monitor water quality and weather conditions. This was held in conjunction with the Annual Field Day of the Virginia Nursery and Landscape Association (VNLA) on August 17, 2006. The other was a mid-term stakeholder meeting at the Virginia Tech's Hampton Roads AREC in Virginia Beach on October 19 to 20, 2007. Impact: Over 300 stakeholders from Virginia and neighboring states attended the on-site demonstration. They were very excited about the concept of
minimum pathogen intake by locating the pump house and inlet pipe depth away from the entrance where irrigation runoff water returns to the reservoirs, and considered the research demo enlightening. "We never thought about this approach for water decontamination and disease control" said many participating growers. Owners of several large nurseries asked the project director about relocating their pump houses and replacing inlets before leaving the Field Day. This demonstration was featured on the cover page of the September/October 2006 issue of VNLA Newsletter. More importantly, several local nurseries already have put our project concepts and research data into practice and expanded their sedimentation basins in size and depth to increase holding capacity and prolong settling time before runoff water overflows to irrigation reservoirs. Others re-routed the water path on their properties to avoid runoff water being pumped out immediately for irrigation. Following the recent mid-term
stakeholder meeting with local growers, regional and national representatives of the green industry, it is expected that many growers nationwide will soon start to benefit from this ongoing project as well.
Publications
- Hong, C. X. Richardson, P. A., Ghimire, G. R., Kong, P., Lea-Cox, J., Ross, D. S., Moorman, G. W. 2007. A Window to Reassess the Potential Impacts of Nutrients in Irrigation Runoff on Natural Water Resources. Proceedings of Virginia-West Virginia Water Conference, Blacksburg, VA (in press)
- Umesha, S., Kong, P., and Hong, C. X. 2007. Characterization of Phytopathogenic Bacteria from Irrigation Reservoirs at Two Commercial Nurseries in Eastern Virginia. Proceedings of Virginia-West Virginia Water Conference, Blacksburg, VA (in press)
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Progress 09/01/05 to 08/31/06
Outputs
This project is aimed at ecologically-based irrigation water decontamination technology. It consists of three distinct phases: technology generation, validation and dissemination among nursery entrepreneurs and professionals involved in the horticultural and landscape industries in the United States. During this first year we focused on the first two objectives investigating the diversity of Phytophthora species and spatial patterns of individual species present in runoff water retention basins to develop protocols to guide the selection of pump location and inlet placement depth for minimal pathogen intake. We began water sampling (baiting) in two retention basins at two commercial nurseries in eastern Virginia in August 2005 and sampled monthly through the winter except December. We used at least one other bait in addition to rhododendron leaves in order to increase the diversity of pathogen recovery. Baits were placed in surface water of 5 locations at 20-m
intervals beginning from a runoff entrance in each retention basin. Additional baits were placed in deep water at 0.5-m intervals from surface of two selected locations. Each baiting assay employed 2600 to 4600 leaf disks from which up to 800 isolates of Phytophthora were recovered and 225 isolates were subcultured and identified by colony PCR-SSCP. Representative isolates were examined morphologically to confirm their identities. Water profiles and water quality parameters were measured for each basin under investigation. We expanded water sampling to six additional retention basins at four other nurseries across the Commonwealth since February 2006. We also baited at one nursery and took a water sample from another nursery in North Carolina in July 2006. Overall a total of 35 distinct SSCP species were recovered, including P. cinnamomi, P. citricola, P. citrophthora, P. drechsleri (Dre I & II), P. megasperma (Meg I & II), P. nicotianae, P. palmivora, P. syringae, and several new
species. A declining pattern in the number of Phytophthora-infected baits with increasing distance from runoff entrance was observed in most retention basins with a single entrance. A similar pattern also was seen with depth from surface water in some retention basins. Specifically, Phytophthora species was not detected at 3.25 m or below at one retention basin. The diversity and populations of Phytophthora species recovered decreased as the winter progressed then increased with time as the spring started. A total of 11 SSCP species were detected at each of two nurseries in June 2006. We are analyzing water quality data in relation to Phytophthora recovery at each sampling location and date to identify the most important factors affecting diversity and spatial patterns of pathogen dispersal. We recently installed an automatic weather station recording temperature, relative humidity, rainfall, wind direction and speed at the nursery where we sample water monthly to get some insight
into how weather may affect water movement subsequently spatial pattern of pathogen dispersal in the basin. The first project meeting was held at the Virginia Tech in Virginia Beach, VA on February 14 to 15, 2006.
Impacts
Phytophthora species include a group of very common and damaging pathogens in nursery and greenhouse crops with direct plant losses in the billion dollars. Contaminated irrigation water is a primary source of inoculum for Phytophthora disease at production facilities, subsequently during transition, at retail centers and in the landscapes. This project aims to eliminate or mitigate this disease risk at production facilities by developing a protocol to guide selection of pump location and inlet placement depth with the minimum pathogen intake. The expected impacts of this novel water decontamination technology include: (1) increased profitability of the horticultural industry by reducing crop losses and fungicide expenses; (2) reduced fungicide usage to decrease chemical dependency and risk of fungicide release into the environment and improve worker health; (3) supply of healthy plants and improved aesthetical value of landscape; (4) increased adoption of recycling
irrigation to improve conservation and protection of water resources. This project already made a positive impact on the industry through a demonstration recently held at a nursery under investigation in conjunction with the Field Day of Virginia Nursery and Landscape Association. About 300 horticultural professionals attended this demonstration presenting our research goals and progress of the project. This research is mind-opening as we never thought about control of the most destructive diseases through selection of pump house location and inlet placement depth, said a participating and leading grower.
Publications
- Ghimire S. R., Richardson, P. A., Moorman, G. W., Lea-Cox, J. D., Ross, D., S. and Hong, C. 2006. Detection of Phytophthora species in a run-off water retention basin at a commercial nursery in plant hardiness zones 7b of Virginia in winter. Phytopathology 96:S40
- Ghimire S. R., Richardson, P. A., Moorman, G. W., Lea-Cox, J. D., Ross, D., S. and Hong, C. 2006 (first Draft). Spatial and temporal distributions of Phytophthora species in the surface water containment basins at two commercial nurseries in Eastern Virginia in winter months.
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