Treesearch

Bait tests are very helpful for diagnosis of Phytophthora in for example soil, substrate, water, sediment, and rootball samples (Werres and others 2014). By attracting the motile zoospores of the Phytophthora species with the baits these pathogens can be separated from other organisms. Bait tests are simple and cost effective and - compared with other diagnostic techniques - they are much more independent on the varying sample quality. Furthermore, bait tests can be used for evaluating big sample quantities. Within the preparation of laboratory accreditation according to ISO standard...

The genus Phytophthora contains some of the most notorious plant pathogens affecting nursery crops. Given the recent emergence of the sudden oak death pathogen Phytophthora ramorum, particularly in association with Rhododendron spp., characterization of Phytophthora communities associated with this host in nursery environments is prudent. Many taxa may present symptoms similar to P. ramorum but we do not necessarily know their identity, frequency, and importance. Here, we present a survey of Phytophthora taxa observed from seven nurseries in the U.S. state of Oregon. Incidence and diversity...

Current regulations under the August 6, 2014 USDA APHIS Official Regulatory Protocol (Confirmed Nursery Protocol: Version 8.2) for Nurseries Containing Plants Infected with Phytophthora ramorum mandates the sampling of water in affected nurseries to demonstrate they are free of P. ramorum. Currently, detection of P. ramorum in these samples requires baiting periods followed by pathogen growth and/or expensive nucleic acid molecular detection methods. A rapid detection tool would greatly reduce the time, cost, and effort needed to demonstrate that nurseries are free of P. ramorum. To meet...

The National Ornamentals Research Site at Dominican University of California (NORS-DUC) is a research nursery that was established in 2009 to study invasive plant pathogens like Phytophthora ramorum, causal agent of sudden oak death and ramorum blight. In order to fulfill federal and state regulations, the possible movement of pathogens from the research site must be monitored using a sentinel plant system with host plants of P. ramorum (Rhododendron, Camellia, and Viburnum). Symptoms on the sentinel plants are studied using culturing, immunoassays, and sequence analysis. Symptom developmen...

Phytophthora ramorum, causal agent of sudden oak death (SOD) and ramorum leaf blight, remains a persistent problem of regulatory concern within the horticultural industry. Damages to nurseries have been realized as a result of enforced quarantine and sanitation efforts designed to prevent the spread and establishment of this invasive pathogen. Additionally, the introduction of P. ramorum to heritage gardens provides a treatment challenge when the goal to prevent local spread conflicts with the preservation of plant collections. There is a need for the development for alternative treatments...

Soilborne inoculum (infested leaf debris which has become incorporated into the soil) may be an important contributor to the persistence of the sudden oak death pathogen Phytophthora ramorum in recurrently positive nurseries. To initiate new epidemics, soilborne inoculum must not only be able to survive over time, but also be capable of producing sporangia during times favorable to infection of plant material at the soil surface. To accompany field studies of the epidemiological risk of soilborne inoculum in nurseries, laboratory assays were performed investigating how incubation of...

Phytophthora ramorum causes stem and bole cankers (sudden oak death) and foliar and twig dieback (ramorum blight) of susceptible plants. To date, more than 100 tree, shrub and herbaceous hosts of P. ramorum have been identified. In March 2015, plant samples were submitted to the CDFA Plant Pest Diagnostics Lab from the Marin Municipal Water District for disease analysis. The samples were collected near Bolinas Ridge in Marin County, CA in a maritime chaparral-live oak woodland forest with a history of P. ramorum and P. cinnamomi. The collectors noticed a large amount of unusual die-back in...

Microsatellite analysis initially identified genetic variations within the NA1 clonal lineage of Phytophthora ramorum; however, in Washington nurseries, the genetic population of P. ramorum has shifted and is now dominated by two other lineages, NA2 and EU1. In this study, recently identified markers that are more variable, and therefore more informative for the EU1 lineage, were used to reveal genetic diversity within the Washington P. ramorum EU1 population. Data from genotyping of DNA samples provided by the Washington State Department of Agriculture (WSDA) was combined with new...

A Phytophthora cactorum-infected nursery crop of Ceanothus thyrsiflorus was used to evaluate three Phytophthora monitoring methods. The Phytophthora detection level of three non-destructive sampling methods was quantified and compared to the detection level of destructive sampling. Non-destructive methods were (a) composite soil/root samples, pear-baited, (b) effluent samples, pear-baited, and (c) Agdia ImmunoStrip tests run on root samples. Time and expense of each method were also tracked. The baited soil/root sample method was the least labor intensive and most cost-effective method to...

Horticultural nurseries are under increasing pressure to reduce, remediate, and recycle irrigation water. A major constraint for reusing irrigation water is contamination by waterborne plant pathogenic Phytophthora and Pythium species. Current research is focused on helping plant nurseries monitor oomycete pathogens in their irrigation water to determine the need for water treatment, evaluate effectiveness of treatment options, and enable selection of cost-effective ways to disinfest water. A sensitive method to identify waterborne oomycetes present at low concentrations was needed. A...