FY11-12 Research Projects

The following projects are underway at the National Ornamentals Research Site at Dominican University of California (NORS-DUC). They have been funded with this Fiscal Year 2011-2012 farm bill monies, pending completion and approval through the California Pesticide registration.

If NORS-DUC is funded through the farm bill next fiscal year, additional monies will be made available for research. See Call for Proposals.

TITLE: Use of Trichoderma to Remediate Phytophthora ramorum-Infested Soil
RESEARCHERS: Timothy Widmer,
USDA/ARS, Fort Detrick, MD 21702, Phone: (301) 619-7338, Fax: (301) 619-2880,  [email protected]; Nina Shishkoff, Foreign Disease Weed Science Research Unit, USDA/ARS, Fort Detrick, MD 21702, Phone: (301) 619-2877, Fax: (301) 619-2880, [email protected]
AMOUNT: $18,770.00 (permit pending)

Phytophthora ramorum has been repeatedly detected in nurseries even after the removal of infected plants and sanitation of the growing area.  Although methods, such as chemical fumigation, oxidation, and heat treatment, exist to sterilize soil they are often costly, impractical, and raise health and environmental concerns.  It is the purpose of this study to repeat an on-going study to examine methods to remediate P. ramorum-infested soil that are environmentally friendly, safe and effective.  The field site will be infested with a known amount of P. ramorum propagules and then partitioned off using fiberglass, circular microplots.  A specific treatment will then be applied to the microplots in replication.  These treatments will be: 1) a non-treated control; 2) a commercially-registered chemical treatment; 3) a commercially-available biological control agent; 4) a different commercially-available biological control agent; and 5) an experimental fungal isolate of Trichoderma that was demonstrated to reduce P. ramorum populations to non-detectable limits in the laboratory.  Over the course of the experiment, soil samples will be taken within each microplot and the populations of P. ramorum and the biological control agents will be monitored.  It is the hope that the biological control agents will be effective in reducing or eliminating the populations of P. ramorum.


TITLE: The Risk of Asymptomatic Phytophthora ramorum Infection on Fungicide-Treated Rhododendron
RESEARCHERS: Gary Chastagner and Marianne Elliott,
Washington State University, Research and Extension Center, Puyallup, WA 98371, Phone - Gary: (253) 445-4528; Phone - Marianne: (253) 445-4596, [email protected], [email protected] 
AMOUNT: $14,934.00 (permit pending)

A number of systemic and contact fungicides have been shown to be effective in controlling Phytophthora ramorum development on several nursery crops.  One of the concerns about using fungicides to manage this pathogen on nursery stock relates to the possibility that fungicides are masking symptom development, thus making it more difficult to detect infected plants during routine visual inspections and increasing the risk of spreading this pathogen on asymptomatic infected plants. Results from earlier artificial inoculation studies have indicated that Subdue MAXX and Insignia fungicides may pose a high risk of masking symptom development on rhododendron foliage. This research project will determine the risk that fungicide applications will mask symptom development on rhododendrons under commercial production practices and determine how long suppression of symptom development lasts following the cessation of fungicide treatments.


TITLE: Potential Efficacy of a Copper Fungicide for Preventing Establishment and Dissemination of Phytophthora ramorum in Ornamental Plant Nurseries
RESEARCHER: Steven Jeffers,
Department of Entomology, Soils, & Plant Sciences, Clemson University, Clemson, SC 29634, Phone: (864) 656-7157, [email protected]
AMOUNT: $5,500.00 (permit pending)

Phytophthora ramorum has been brought to nurseries in the eastern United States by the shipment of infected and infested ornamental plants. Consequently, this pathogen poses a real threat to forests in the eastern USA because native plant species are susceptible and the environment is conducive.  We repeatedly have found P. ramorum at ornamental plant nurseries throughout the southeastern states, and it has become established in some of these nurseries.  Currently, management options for P. ramorum at a nursery are very limited once the pathogen has become established in field soil; therefore, an effective mitigation strategy for soil is needed. Our hypothesis is that a topical application of a copper-based fungicide to the soil surface may be an option.  Most copper fungicides are only weakly soluble in water so they withstand weathering for long periods, and copper is relatively immobile in the soil profile.  Recently, research in our laboratory has demonstrated that relatively low concentrations of copper ions are lethal to propagules of Phytophthora spp.  Consequently, we propose to apply a topical, prophylactic application of a copper-based fungicide to the soil surface in a nursery bed to determine if propagules of P. ramorum washing or splashing out of infested containers that come into contact with copper residues on the soil surface are affected.  Likewise, we will determine if a topical application of copper fungicide to the soil surface affects the ability of an established population in soil from splashing onto healthy plants and initiating new infections. 


TITLE: Effect of Fungicides and Biocontrol Agents on Sporulation and Persistence of Phytophthora ramorum on Nursery Hosts
RESEARCHERS: Steve Tjosvold,
University of California Cooperative Extension (UCCE), Watsonville, California   95076, General Office: (831) 763-8040, Direct Office: (831) 763-8013, Fax:  (831) 763-8006, [email protected]; Gary Chastagner and Marianne Elliott, Washington State University Research and Extension Center, Puyallup, WA 98371, Phone - Gary: (253) 445-4528; Phone - Marianne: (253) 445-4596, [email protected]; [email protected]
AMOUNT: $41,766.00 (permit pending)

Phytophthora ramorum is the causal agent of Sudden Oak Death (SOD) and can infect many commonly grown nursery crops. Once P. ramorum is introduced into a nursery on a host, its local spread and establishment is primarily dependent on sporangia and zoospores production for its spread.  Nursery operators commonly use fungicides to prevent the establishment of Phytophthora diseases, although current research only supports the use of fungicides for preventing infection. It is still unknown, however, what effect fungicide treatments have on sporulation, spread, and persistence of the pathogen on established infections.  With this additional knowledge, fungicide treatments could more effectively be used to prevent the spread and establishment of the pathogen in nursery operations. This research will evaluate activity of foliar applied fungicides and biocontrol agents to inhibit sporulation and reduce pathogen persistence in ornamental hosts.


TITLE: Solarizatin to Eliminate Phytophthora ramorum from Nursery Beds
RESEARCHER: Jennifer L. Parke,
Department of Crop and Soil Science and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97330, Phone: (541) 737-8170, Fax: (541) 737-5725, [email protected] 
AMOUNT: $34,718.00 (permit pending)

Elimination of Phytophthora ramorum from infested nursery soil continues to be one of the most formidable challenges in limiting the persistence and spread of this pathogen. Although soil fumigants are effective under controlled lab conditions, there are reasons they often cannot be used in nurseries: restrictions on application of fumigants near roads, homes, and schools, and ineffective fumigant penetration of nursery beds in container nurseries, which typically consist of compacted soils topped with a layer of gravel or rock.  Previous research on the distribution of P. ramorum in the soil profile, and studies on the effects of elevated soil temperature on P. ramorum viability, indicate that soil solarization has potential for decontaminating infested nursery soils.   Soil solarization is a widely used means of decontaminating soil in several agricultural production systems, and was effective in eliminating P. ramorum from field soil in a small preliminary study. However, solarization of nursery beds typical of container nurseries has not been tested. Recent improvements in plastic films which could optimize solarization of nursery beds have also not been tested.  The objective of the proposed research is to determine the effectiveness of six different solarization treatments on the survival of P. ramorum in nursery beds typical of a container nursery. In two field trials conducted during summer 2011-2012, P. ramorum inoculum buried at three different depths in the soil profile will be recovered after 2,4, 6, and 8 weeks.  Soil temperature at each depth will also be determined.  Data analysis will include determination of temperature x time parameters most critical in influencing pathogen survival, which can be used to predict solarization effectiveness in different locations.  Results of this study will inform APHIS about the feasibility of including soil solarization as a treatment option in the Confirmed Nursery Protocol.


TITLE: Episodic Abiotic Stress and Ramorum Blight in Nursery Ornamentals: Impacts on Symptom Expression and Chemical Management of Phytophthora ramorum in Rhododendron
RESEARCHER: Richard M. Bostock,
Department of Plant Pathology, University of California, Davis, CA 95616, Phone:  (530) 752-0308, Fax: (530) 752-5674, [email protected]
AMOUNT: $15,875.00 (permit pending)

For all plant diseases caused by Phytophthora spp. water status of the host and the environment critically influences disease occurrence and severity.  Water potential influences pathogen behavior and the formation and activity of infective propagules.  Importantly, water stress and other abiotic stresses, including transient episodes of soil salinity, root hypoxia associated with waterlogged soils, and low temperatures affect host physiology to increase vulnerability of roots and shoots to disease.  Previous work has shown that zoospores of P. ramorum readily infect roots of Rhododendron sp. and Viburnum tinus and that a brief episode of salt stress predisposes roots to infection to significantly increase disease severity.  There is evidence that root infections may play a role in the disease cycle of ramorum blight in some hosts, and it is likely that such infections can remain cryptic.  Thus, a better understanding of specific edaphic and abiotic factors that contribute to disease development from soilborne infections will inform and guide management decisions.  These factors could have a large effect on inoculum thresholds necessary for disease, the extent and significance of root infections in various hosts, the consistency and reliability of pathogenicity tests for the assessment of host resistance, and the efficacy of chemical treatments to manage disease.  The proposed research will examine abiotic factors – nitrogen fertility, waterlogging, water deficit, and chilling – that are encountered in nurseries as potential triggers for disease development arising from low inoculum levels or cryptic root infections.  We will assess the importance of these stresses as they may contribute to rapid development of ramorum blight in seemingly healthy nursery plants, such as might occur following shipment and planting.  The proposed studies will focus on Rhododendron sp., a good model and important host for ramorum blight in ornamentals.  We will also examine the impact of mild episodic stress on the efficacy of selected chemicals for managing ramorum blight, including plant activators that induce host resistance.  The proposed research will suggest measures to complement or refine disease management practices.


TITLE: Risk of Root-to-Root Spread of Phytophthora ramorum in Ornamental Production Nurseries
RESEARCHERS: Gary Chastagner and Marianne Elliott,
Washington State University Research and Extension Center, Puyallup, WA 98371, (253) 445-4528, Phone - Gary: (253) 445-4528; Phone - Marianne: (253) 445-4596, [email protected], [email protected]; Steve Tjosvold, University of California Cooperative Extension (UCCE), Watsonville, California 95076, General Office: (831) 763-8040, Direct Office: (831) 763-8013, Fax: (831) 763-8006, [email protected]; Nina Shishkoff, Foreign Disease Weed Science Research Unit, USDA/ARS, Fort Detrick, MD 21702, Phone: (301) 619-2877, Fax: (301) 619-2880, [email protected]
AMOUNT: $37,507.00 (permit pending)

Laboratory studies have shown that Phytophthora ramorum is able to colonize and infect root systems of a number of plants. Studies have also shown that this pathogen is able to sporulate on infected root tissues of Viburnum, Camellia and Rhododendron. The epidemiological significance of root infections in production nurseries is unknown. We are proposing to examine the root-to-root spread of P. ramorum on Viburnum tinus in ground or raised beds at the NORSDUC research site. This research will provide a better understanding of the risk associated with this pathway of spread.


TITLE: Development and application of an epidemiological framework for management of Phytophthora ramorum on Rhododendron in nursery settings

RESEARCHERS: Niklaus J. Grunwald, Horticultural Crops Research Laboratory, USDA ARS, 3420 NW Orchard Ave., Corvallis, OR 97330, Phone: (541) 738-4049, Fax: (541) 738-4025, [email protected]; Jennifer L. Parke, Dept. of Crop and Soil Science, 3017 Agriculture and Life Sciences Building, Oregon State University, Corvallis, OR 97330, Phone: (541) 737-8170, Fax: (541) 737-5725, [email protected]; Christopher A. Gilligan, School of Biological Sciences, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, U.K., [email protected],
AMOUNT: $103,460 (permit pending)

Epidemiological theory provides a useful toolbox to identify criteria for invasion of pathogens in nursery settings.  Using a combination of intensive experimentation and established epidemiological theory the current project aims to develop and test the epidemiological framework necessary for evaluating different management scenarios within nurseries for the sudden oak death pathogen Phytophthora ramorum. Work will include development and validation of a spatially-explicit epidemiological model for invasion by P. ramorum within nurseries to screen potential management scenarios and, once developed, evaluation of different management scenarios for control of P. ramorum in nursery settings.