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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Emerging Pests and Pathogens Research » Research » Research Project #435519

Research Project: Isolation, Identification, and Management of Phytophthora species in Nurseries and Greenhouses

Location: Emerging Pests and Pathogens Research

Project Number: 8062-22000-020-11-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2018
End Date: Aug 31, 2020

Our lab at Clemson University has been studying diseases of ornamental crops caused by Phytophthora spp. for many years. We have developed expertise in isolation from plants, soil, and water, identification of new host-pathogen associations, and management of these diseases. In this new NACA project, we will continue to study Phytophthora diseases of ornamental plants and to collaborate with colleagues around the country to share our expertise. We will use PRCR on lavender as a model system. Early detection and accurate identification of the species of Phytophthora attacking specific host plants are important first steps to effective disease management and to preventing new epidemics from starting. By identifying sources of primary inoculum (i.e., the inoculum that initiates infection and pathogenesis), one can take steps to prevent the pathogen from becoming established in a greenhouse or nursery, from spreading through a production facility, or from being moved to the landscape or field. However, once Phytophthora spp. are present in a nursery, greenhouse, or landscape, alternative management strategies need to be available—including fungicides, cultural practices, host resistance, etc. New, improved, and innovative disease management strategies are needed to prevent serious economic losses from diseases caused by Phytophthora spp. on both herbaceous and woody ornamental crops. Specific Objectives include: 1. Identify new host-pathogen associations for Phytophthora spp. on ornamental crops and continue to maintain a permanent collection of Phytophthora spp. from ornamental plants as a resource for future. 2. Improve detection methods of Phytophthora spp. in production facilities to prevent movement of these pathogens to landscapes and fields. 3. Evaluate management strategies for Phytophthora spp. on ornamental plants.

Objective 1. Identify new host-pathogen associations for Phytophthora spp. on ornamental crops. In working with growers and through collaborations with organizations and colleagues—including the Clemson University Plant and Pest Diagnostic Clinic (CU-PPDC), Bartlett Tree Research Lab (BTRL) in Charlotte, NC, the US Lavender Growers Association (USLGA), Marge Daughtrey at Cornell University, and diagnosticians at other universities—we will receive samples of diseased ornamental plants and cultures of Phytophthora species from ornamental plants. We will add isolates to our already our extensive collection for long-term storage and will then use this collection to identify new host-pathogen associations. Currently, we are focusing on Phytophthora spp. on lavender and unique and exotic species of Phytophthora. Isolates will be identified using molecular characters, and molecular identities will be validated and confirmed using traditional morphological and physiological characters. Experiments to confirm pathogenicity in new host-pathogen associations will be conducted in the greenhouse. Objective 2. Improve detection methods of Phytophthora spp. in production facilities. Production of ornamental crops is a multi-step process—with plugs, cuttings, and liners produced at one location and plants for wholesale or retail sale grown at another location. Therefore, it is possible that inocula of Phytophthora spp. are being moved along with propagation material used to produce both woody and herbaceous ornamental plants. In collaboration with USLGA as well as local nurseries and greenhouses, we will target several plant species and sample plugs at or coming from production facilities. Plants in production trays and flats will be assayed for Phytophthora spp. using several different methods being studied in our laboratory. Our goal is to detect these plant pathogens at the source—before they are moved out of the nursery or greenhouse. Objective 3. Evaluate management strategies for Phytophthora spp. on ornamental plants. Minimizing losses to diseases in commercial production facilities requires effective disease management strategies. Strategies for managing Phytophthora diseases in nurseries, greenhouses, landscapes, and fields continues to be a challenge. Using an established host-pathogen system, we will evaluate new fungicides that have been developed recently or are under development and compare these to some of the standard products already in the marketplace. We also will evaluate registered biofungicides for efficacy against PRCR on lavender plants. In addition, we will screen cultivars of floriculture plant species for resistance to P. nicotianae. Host plant resistance has the potential to effectively manage Phytophthora diseases over the long term in landscapes and fields. We are working with commercial flower companies to develop annual vinca plants that are resistant to P. nicotianae, which causes Phytophthora foliage blight and root rot.