Evaluation of Chemical Agents for the Control of Phytophthora ramorum and Other Species of Phytophthora on Nursery Crops

2008 ◽  
Vol 9 (1) ◽  
pp. 26 ◽  
Author(s):  
Robert G. Linderman ◽  
E. Anne Davis
Keyword(s):  
Foliar Application ◽  
Management Strategies ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Detached Leaf ◽  
Chemical Agents ◽  
Mycelial Plug ◽  
Previously Treated ◽  
Nursery Crops ◽  
Leaf Test

Phytophthora diseases occur frequently in nurseries, and the recent incidence of ramorum blight, caused by P. ramorum, on nursery crops has underscored the need for improved management strategies against all Phytophthora diseases. We evaluated several chemicals that target Oomycete pathogens, inoculating detached rhododendron or lilac leaves removed from plants previously treated with various chemicals, or chemically-treated leaves on intact plants. Results indicated that Subdue MAXX (drench or foliar application) was the most effective chemical in suppressing infections caused by all species of Phytophthora tested (P. ramorum, P. citricola, P. citrophthora, and P. nicotianae) except P. citrophthora; with P. ramorum, it was active for at least 6 weeks after spray application. More chemicals were effective when sporangial rather than mycelial plug inoculum of P. ramorum was used, including Aliette, Ranman, Stature DM, and Fenamidone. All chemicals tested were fungistatic, not fungicidal. These tests indicate that several materials inhibit infection by Phytophthora species, and that the detached leaf test is effective in evaluating efficacy of chemical agents for the suppression of Phytophthora pathogens from nurseries. Accepted for publication 10 November 2007. Published 11 February 2008.

scholarly journals Response of Selected Nursery Crop Plants to Inoculation with Isolates of Phytophthora ramorum and Other Phytophthora Species

2006 ◽  
Vol 16 (2) ◽  
pp. 216-224 ◽  
Author(s):  
R.G. Linderman ◽  
E.A. Davis ◽  
J.L. Marlow
Keyword(s):  
Plant Species ◽  
The United States ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Experimental Conditions ◽  
Pathogen Virulence ◽  
Detached Leaves ◽  
Nursery Crops ◽  
Relative Differences ◽  
Selection Of

Many nursery crops are susceptible to root and foliage diseases caused by numerous species of Phytophthora. Phytophthora ramorum causes sudden oak death of trees and ramorum leaf blight and shoot dieback on numerous nursery plants, including rhododendron (Rhododendron spp.), viburnum (Viburnum spp.), pieris (Pieris spp.), and camellia (Camellia spp.) in Europe, the United States, and British Columbia, Canada. We sought to evaluate relative susceptibility of a selection of ornamental nursery crops by inoculating detached leaves with several species of Phytophthora known to infect rhododendrons, and to compare the relative virulence on those species to isolates of P. ramorum. The results indicated that many plants were susceptible under these experimental conditions, while others were not. On a given host, symptoms caused by all species of Phytophthora were identical except for differences in pathogen virulence. Plant species were identical except for differences in pathogen virulence. Plant species within genera or cultivars within species varied in susceptibility to isolates of P. ramorum and other species of Phytophthora. Phytophthora ramorum, P. citricola, P. citrophthora, and P. nicotianae were the most virulent pathogens on most of the host plants inoculated. Some plants were susceptible to several species of Phytophthora, while others were susceptible only to P. ramorum. Inoculation of detached leaves of `Nova Zembla' rhododendron, lilac (Syringa vulgaris), or doublefile viburnum (Viburnum plicatum var. tomentosum) under controlled conditions with different species of Phytophthora or isolates of P. ramorum (both mating types) indicated significant relative differences in species or isolate virulence.

scholarly journals Diversity of Foliar Phytophthora Species on Rhododendron in Oregon Nurseries

Plant Disease ◽  
2015 ◽  
Vol 99 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
B. J. Knaus ◽  
V. J. Fieland ◽  
K. A. Graham ◽  
N. J. Grünwald
Keyword(s):  
Community Structure ◽  
Plant Pathogens ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Recent Emergence ◽  
Nursery Crops ◽  
The U.S

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 of Phytophthora communities differed significantly among nurseries and among seasons within nursery. The taxa P. syringae and P. plurivora were widespread and detected at most of the nurseries sampled. Nine other taxa were also detected but were found either in a single nursery or were shared among only a few nurseries. Characterization of the Phytophthora communities present in nurseries is an important step toward understanding the ecology of these organisms as well as an aid to nursery managers in determining what risks may be present when symptomatic plants are observed. This study builds on an increasing literature, which characterizes Phytophthora community structure in nurseries.

Detection of oomycide-insensitive Phytophthora isolates in Maryland ornamental nurseries and Mid-Atlantic landscapes provide data for reconsidering management strategies

2021 ◽  
Author(s):  
Justine Beaulieu ◽  
Johanna Del Castillo Munera ◽  
Yilmaz Balci
Keyword(s):  
Growth Rate ◽  
Mycelial Growth ◽  
Management Strategies ◽  
Resistance Management ◽  
Phytophthora Species ◽  
Oak Forests ◽  
Relative Growth ◽  
Off Label ◽  
Potting Media ◽  
Almost All

Five Phytophthora species comprising a total of 243 isolates (77 P. cinnamomi, 23 P. citrophthora, 18 P. multivora, 18 P. pini, and 107 P. plurivora) were screened for sensitivity to mefenoxam, fosetyl-Al, dimethomorph, dimethomorph + ametoctradin and fluoxastrobin using amended agar assays. Mefenoxam-insensitive isolates were detected within P. cinnamomi (4%), P. multivora (11%), and P. plurivora (12%) even at approximately 2.5x the recommended label rate. These isolates were also insensitive to higher (off-label) concentrations of fluoxastrobin. Concentrations of dimethomorph (400 g/mL) and dimethomorph + ametoctradin (100 g/mL) were mostly effective in mycelial growth inhibition, but two P. plurivora isolates were insensitive, suggesting that resistance management is required. All mefenoxam-insensitive isolates were sensitive to fosetyl-Al at the label rate. Surprisingly, the populations of P. cinnamomi from mid-Atlantic oak forests included insensitive isolates. With almost all species, isolates recovered from asymptomatic hosts (e.g., soil/potting media collected of randomly selected asymptomatic hosts) had a significantly greater relative growth rate when compared to isolates recovered from symptomatic hosts (e.g., isolates recovered from lesions or wilted plants). These findings suggest that mefenoxam should no longer be used to manage oomycetes in Maryland ornamental nurseries and that the use of fluoxastrobin should be limited.

scholarly journals First Report of Phytophthora ramorum on Viburnum bodnantense in Belgium

Plant Disease ◽  
2003 ◽  
Vol 87 (2) ◽  
pp. 203-203 ◽  
Author(s):  
D. De Merlier ◽  
A. Chandelier ◽  
M. Cavelier
Keyword(s):  
The Netherlands ◽  
Plant Protection ◽  
Morphological Characteristics ◽  
Pcr Primers ◽  
Selective Medium ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Pathogenicity Test ◽  
First Report ◽  
Root Necrosis

In the past decade, a new Phytophthora species inducing shoot canker on Rhododendron and dieback of Viburnum has been observed in Europe, mainly in Germany and the Netherlands, and California. This new pathogen has been named Phytophthora ramorum (3). In May 2002, a diseased Viburnum plant (Viburnum bodnantense) from the Plant Protection Service (Ministry of Agriculture, Belgium) was submitted to our laboratory for diagnosis. Symptoms included wilting, leaves turning from green to brown, discolored vascular tissues, and root necrosis. The plant came from a Belgian ornamental nursery that obtained supplies of stock plants from the Netherlands. Pieces of necrotic root tissue were excised, surface-disinfected, and transferred aseptically to a Phytophthora selective medium. P. ramorum was identified based on morphological characteristics, including the production of numerous, thin-walled chlamydospores (25 to 70 µm in diameter, average 43 µm) and deciduous, semi-papillate sporangia arranged in clusters. Radial growth after 6 days at 20°C on V8 juice agar was 2.8 mm per day. Random amplified microsatellite markers (RAMS) (2) from the total genomic DNA of the Belgian strain (CBS 110901) were similar to those of P. ramorum reference strains (CBS 101330, CBS 101332, and CBS 101554). Using PCR primers specific for P. ramorum, the identification was confirmed by W. A. Man in't Veld (Plantenziektenkundige Dienst, Wageningen, the Netherlands) (1). A pathogenicity test was carried out on three sterile cuttings of Rhododendron catawbiense (3). Brown lesions were observed on the inoculated cuttings after 6 to 7 days. None of the three uninoculated cuttings showed symptoms of infection. P. ramorum was reisolated from lesion margins on the inoculated cuttings. To our knowledge, this is the first report of the fungus from Belgium. Since our initial observation, we have found P. ramorum in other Belgian nurseries on R. yakusimanum. References: (1) M. Garbelotto et al. US For. Ser. Gen. Tech. Rep. PSW-GRT. 184:765, 2002. (2) J. Hantula et al. Mycol. Res. 101:565, 1997. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.

scholarly journals First Report of Phytophthora hydropathica Causing Wilting and Shoot Dieback on Viburnum in Italy

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1582-1582 ◽  
Author(s):  
S. Vitale ◽  
L. Luongo ◽  
M. Galli ◽  
A. Belisario
Keyword(s):  
Natural Infection ◽  
Morphological Characteristics ◽  
Leaf Tissue ◽  
The United States ◽  
Selective Medium ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Width Ratio ◽  
Morphological Identification ◽  
First Report

The genus Viburnum comprises over 150 species of shrubs and small trees such as Laurustinus (Viburnum tinus L.), which is one of the most widely used ornamental plants in private and public gardens. Furthermore, it commonly forms stands of natural woodland in the Mediterranean area. In autumn 2012, a survey was conducted to determine the presence of Phytophthora ramorum on Viburnum in commercial nurseries in the Latium region where wilting, dieback, and death of twigs were observed on 30% of the Laurustinus plants. A Phytophthora species was consistently recovered from soil rich in feeder roots from potted Laurustinus plants showing symptoms. Soil samples were baited with rhododendron leaves. Small pieces of leaf tissue cut from the margin of lesions were plated on P5ARPH selective medium (4). Pure cultures, obtained by single-hypha transfers on potato dextrose agar (PDA), were petaloid. Sporangia formation was induced on pepper seeds (3). Sporangia were almost spherical, ovoid or obpyriform, non-papillate and non-caducous, measuring 36.6 to 71.4 × 33.4 to 48.3 μm (average 53.3 × 37.4 μm) with a length/width ratio of 1.4. Chlamydospores were terminal and 25.2 to 37.9 μm in diameter. Isolates were considered heterothallic because they did not produce gametangia in culture or on the host. All isolates examined had 30 to 35°C as optimum temperatures. Based on these morphological characteristics, the isolates were identified as Phytophthora hydropathica (2). Morphological identification was confirmed by internal transcribed spacer (ITS), and mitochondrial partial cytochrome oxidase subunit 2 (CoxII) with BLAST analysis in the NCBI database revealing 99% identity with ITS and 100% identity with CoxII. The sequences of the three isolates AB234, AB235, and AB236 were deposited in European Nucleotide Archive (ENA) with the accession nos. HG934148, HG934149, and HG934150 for ITS and HG934151, HG934152, and HG934153 for CoxII, respectively. Pathogenicity tests were conducted in the greenhouse on a total of six 1-year-old shoots cut from V. tinus plants with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis into the phloem. Controls were treated as described above except that sterile PDA plugs replaced the inoculum. Shoots were incubated in test tubes with sterile water in the dark at 24 ± 2°C. After 2 weeks, lesions were evident at the inoculation points and symptoms were similar to those caused by natural infection. P. hydropathica was consistently re-isolated from the margin of lesions, while controls remained symptomless. In the United States in 2008, P. hydropathica was described as spreading from irrigation water to Rhododendron catawbiense and Kalmia latifolia (2). This pathogen can also attack several other horticultural crops (1), but to our knowledge, this is the first report of P. hydropathica causing wilting and shoot dieback on V. tinus. References: (1) C. X. Hong et al. Plant Dis. 92:1201, 2008. (2) C. X. Hong et al. Plant Pathol. 59:913, 2010. (3) E. Ilieva et al. Eur. J. Plant Path. 101:623, 1995. (4) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986.

scholarly journals Effect of Temperature and Moisture Period on Infection of Rhododendron ‘Cunningham's White’ by Phytophthora ramorum

2009 ◽  
Vol 99 (9) ◽  
pp. 1045-1052 ◽  
Author(s):  
Paul W. Tooley ◽  
Marsha Browning ◽  
Kerrie L. Kyde ◽  
Dana Berner
Keyword(s):  
The United States ◽  
Phytophthora Ramorum ◽  
Effect Of Temperature ◽  
Optimum Temperature ◽  
Detached Leaf ◽  
Wide Range ◽  
Effects Of Temperature ◽  
Gradient Plate ◽  
Whole Plants ◽  
Moisture Conditions

We investigated the temperature and moisture conditions that allow Phytophthora ramorum to infect Rhododendron ‘Cunningham's White’. Most experiments were performed with a single P. ramorum isolate from the NA1 clonal lineage. For whole plants incubated in dew chambers at 10 to 31°C, the greatest proportion of diseased leaves, 77.5%, occurred at the optimum temperature of 20.5°C. Disease occurred over the entire range of temperatures tested, although amounts of disease were minor at the temperature extremes. For whole plants exposed to varying dew periods at 20°C and then incubated at 20°C for 7 days, a dew period as short as 1 h resulted in a small amount of disease; however, at least 4 h of dew were required for >10% of the leaves to become diseased. Moisture periods of 24 and 48 h resulted in the greatest number of diseased leaves. In detached-leaf, temperature-gradient-plate experiments, incubation at 22°C resulted in the greatest disease severity, followed by 18°C and then 14°C. In detached-leaf, moisture-tent experiments, a 1-h moisture period was sufficient to cause disease on 67 to 73% of leaves incubated for 7 days at 20°C. A statistical model for disease development that combined the effects of temperature and moisture period was generated using nonlinear regression. Our results define temperature and moisture conditions which allow infection by P. ramorum on Cunningham's White rhododendron, and show that P. ramorum is able to infect this host over a wide range of temperatures and moisture levels. The results indicate that P. ramorum has the potential to become established in parts of the United States that are outside its current range.

scholarly journals Management Strategies for Conservation of Tanoak in California Forests Threatened by Sudden Oak Death: A Disease-Community Feedback Modelling Approach

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1103
Author(s):  
João A. N. Filipe ◽  
Richard C. Cobb ◽  
Maëlle Salmon ◽  
Christopher A. Gilligan
Keyword(s):  
Disease Management ◽  
Community Dynamics ◽  
Management Strategies ◽  
Phytophthora Ramorum ◽  
Ecological Impacts ◽  
Control Measures ◽  
Forest Community ◽  
Forest Composition ◽  
Cumulative Impact ◽  
Modelling Approach

We use a new modelling approach to predict the cumulative impact of Phytophthora ramorum on the dynamic distribution of tanoak (Notholithocarpus densiflorus) and other tree species in coastal-Californian forest-communities. We explore the effectiveness of disease-management strategies for the conservation of tanoak at stand level. Forest resources are increasingly threatened by emerging pathogens such as P. ramorum, a generalist that kills hosts and has altered ecosystems in the USA and Europe. In coastal California, P. ramorum has the greatest impact on tanoak through leaf sporulation and lethal bole infections, but also sporulates on the common overstory-tree bay laurel (Umbellularia californica) without significant health impact. Such epidemiological differences impede host-species coexistence and challenge pathogen management. For most disease-impacted natural systems, however, empirical evidence is still insufficient to identify effective and affordable pathogen-control measures for retaining at-risk host populations. Yet, landscape-scale tree mortality requires swift actions to mitigate ecological impacts and loss of biodiversity. We apply a mathematical model of the feedback between disease and forest-community dynamics to assess the impacts of P. ramorum invasion on tanoak under stand-scale disease-management strategies by landowners aiming to retain tanoak and slow disease progression: (1) removal of inoculum through reduction of bay laurel abundance; (2) prevention of tanoak infection through chemical protection (acting epidemiologically like a vaccine); and (3) a combination strategy. The model results indicate that: (1) both bay laurel removal and tanoak protection are required to help maintain tanoak populations; (2) treatment effectiveness depends on forest composition and on threshold criteria; (3) sustainable tanoak conservation would require long-term follow-up of preventive treatments; (4) arresting basal sprouting upon tree removal may help to reduce inoculum. These findings suggest potential treatments for specific forest conditions that could be tested and implemented to reduce P. ramorum inoculum and disease and to conserve tanoak at stand level.

scholarly journals Occurrence of Phytophthora Species in Commercial Nursery Production

2016 ◽  
Vol 17 (2) ◽  
pp. 64-75 ◽  
Author(s):  
Corina Junker ◽  
Patrick Goff ◽  
Stefan Wagner ◽  
Sabine Werres
Keyword(s):  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Water Recycling ◽  
Infection Rates ◽  
Sand Filter ◽  
Detection Rates ◽  
Water And Sediment ◽  
Nursery Production ◽  
Slow Sand Filter ◽  
Soil Substrates

Two commercial woody ornamental nurseries were sampled for the presence of Phytophthora species over a period of three years between 2011 and 2014. The samples were taken every two months at different propagation (greenhouses, plastic tunnels) and cultivation (container stands) areas as well as from nearby pathways and from a water recycling system with a slow sand filter. Furthermore, different materials like soil, substrates, residues, wind-carried leaves, water and sediment were sampled. In total, 12 known Phytophthora species could be detected. Further, three isolates did not match any of the known species. Phytophthora ramorum, P. gonapodyides, and P. plurivora were the species with the highest detection rates. Phytophthora ramorum could be detected during all seasons of the year. In total, the puddles on the pathways had the highest percentage of positive detections. Residues, wind-carried leaves and water and sediment from the water runoffs were also good places for Phytophthora survival. In both nurseries, the plant samples showed very low infection rates. Ideas for surveys and management are discussed. Accepted for publication 14 March 2016. Published 11 April 2016.

Adaptation of a Phytophthora ramorum Real-Time Polymerase Chain Reaction Assay Based on a Mitochondrial Gene Region for Use on the Cepheid SmartCycler

2010 ◽  
Vol 11 (1) ◽  
pp. 28
Author(s):  
K. E. Sechler ◽  
M. M. Carras ◽  
N. Shishkoff ◽  
P. W. Tooley
Keyword(s):  
Real Time ◽  
Mitochondrial Gene ◽  
Cross Reactivity ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Rt Pcr ◽  
Field Samples ◽  
Symptomatic Tissue ◽  
Polymerase Chain ◽  
High Degree

Detection of Phytophthora ramorum in US commercial nurseries has led to a number of quarantine regulations. Methods such as real-time PCR (RT-PCR) provide rapid and reliable detection that can supplement attempts to culture P. ramorum from symptomatic tissue. We adapted and optimized a previously described mitochondrial gene-based RT-PCR assay for use with a Cepheid SmartCycler v.1 and ready-to-use lyophilized PCR beads. The detection limit was 10 fg of P. ramorum genomic DNA. No cross-reactivity was observed on the SmartCycler for seven additional Phytophthora species tested, which included species known to cross-react in other assays as well as recently described species Phytophthora foliorum and P. kernoviae. The SmartCycler assay described here was used to detect P. ramorum in a set of 2008 California field samples with a high degree of accuracy. Accepted for publication 13 October 2009. Published 13 February 2010.

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