California Pest Rating for
Phytophthora palmivora (E.J. Butler) E.J. Butler 1919 Coconut budrot
Pest Rating: B
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Posted by tn
Response to Janet Alexander
Comment: Conclusion and Rating Justification -We oppose the proposed rating because plant health in California wildlands, forests, horticultural settings, and agricultural settings would benefit from stronger regulatory protection from P. palmivora. The B rating would allow some regulatory protection against P. palmivora without imposing a regulatory burden. The B rating is warranted: this pathogen is considered one of the most damaging Phytophthora species, estimated by Brasier (et al. 2022) as causing over $1 billion per year in crop losses.
Response: There is a regulatory burden of increasing the rating from a C to a B. Under nursery cleanliness standards, if a block is found positive, the pathogen must be eradicated. Without curative treatments, this means that nursery blocks are destroyed. I agree it is a very damaging pathogen on some host, but those hosts are not widely grown in California. To date, no significant damage has been recorded in California.
Comment: We disagree with the assessment of distribution. To date this pathogen is not widespread in California. Although the species has been reported in the past in California based on morphological species determinations, Bourret et al. (2022) were only able to verify two instances of P. palmivora in California, the restoration isolate mentioned in the draft Pest Rating, as well as an isolate from an ornamental palm (Howea forsteriana) in Ventura Co.
Response: We have official records on multiple hosts from multiple counties over decades. I personally collected P. palmivora in Santa Barbara County in 2007, 2008, 2014 and 2016 from nurseries and landscape samples. We have made recent detections from nurseries in Santa Cruz, San Luis Obispo, Solano and Los Angeles counties, and landscapes in Orange County. Since the pathogen is in the nursery trades and has not been under regulation, these are enough detections to justify a score of Medium (-2)
Comment received 7/29/2022 from Janice Alexander
July 29, 2022
From: The California Oak Mortality Task Force and Phytophthoras in Native Habitats Work Group, California Forest Pest Council
To: Heather Scheck, California Department of Food and Agriculture
Regarding: California Pest Rating for Phytophthora palmivora. Proposed Pest Rating: C
We appreciate this opportunity to comment on the proposed California pest rating for Phytophthora palmivora. Our comments represent the views of The California Oak Mortality Task Force (www.suddenoakdeath.org) and The Phytophthoras in Native Habitats Work Group (www.calphytos.org), parts of the California Forest Pest Council (www.caforestpestcouncil.org). These groups endeavor to sustain California plant health and protect against pathogen introduction and spread.
For P. palmivora, the California Department of Food and Agriculture (CDFA) is proposing a pest rating of C: “An organism subject to no state enforced action outside of nurseries except to retard spread at the discretion of the county agricultural commissioner. Or, an organism subject to no state enforced action except to provide for pest cleanliness in nurseries.” Currently P. palmivora is a C rated pest, but its risk had not been formally assessed.
We oppose the proposed rating because plant health in California wildlands, forests, horticultural settings, and agricultural settings would benefit from stronger regulatory protection from P. palmivora. The B rating would allow some regulatory protection against P. palmivora without imposing a regulatory burden. The B rating is warranted: this pathogen is considered one of the most damaging Phytophthora species, estimated by Brasier (et al. 2022) as causing over $1 billion per year in crop losses.
As recognized in California’s pest risk assessment, P. palmivora has a wide host range including ornamentals, fruit and nut trees, and palms, many of which grow in California. The pest risk assessment lists many hosts, but a check of the USDA Agricultural Research Service, Mycological Database notes that others (e.g., apricot, Prunus, Türkölmez et al. 2015) are also known hosts. Examining the published reports shows that many important plant species that grow in California are known to be damaged by this pathogen.
We agree with your listed determination, “Consequences of Introduction to California for Phytophthora palmivora: High”. We disagree with the assessment of distribution. To date this pathogen is not widespread in California. Although the species has been reported in the past in California based on morphological species determinations, Bourret et al. (2022) were only able to verify two instances of P. palmivora in California, the restoration isolate mentioned in the draft Pest Rating, as well as an isolate from an ornamental palm (Howea forsteriana) in Ventura Co. Climate change (e.g., potential for increased monsoon rains in southern California), and an expanding agricultural and horticultural sector that is continually altering growing practices, all increase uncertainty and risk for future introduction and spread.
California is home to an incredible diversity of plants and production systems. Farms, nurseries, restoration areas, and landscapes must thrive alongside a population of approximately 40 million people. With so much to sustain, we urge a “B” rating for P. palmivora.
We appreciate your good work and accessibility. We would be happy to discuss this further, please contact me, Janice Alexander, Co-chairperson, Phytophthoras in Native Habitats Work Group, jalexander@ucanr.edu.
JANICE ALEXANDER
Co-chairperson, Phytophthoras in Native Habitats Work Group
Literature Cited
Bourret, T.; Fajardo, S.N.; Frankel, S.J; Rizzo, D. 2022. Cataloging Phytophthora species of agriculture, forests, horticulture, and restoration outplantings in California, USA: a sequence-based meta-analysis. Plant Disease. https://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-01-22-0187-RE.
Brasier, C.; Scanu, B.; Cooke, D. and Jung, T. 2022. Phytophthora: an ancient, historic, biologically and structurally cohesive and evolutionarily successful generic concept in need of preservation. IMA Fungus 13: 12. https://doi.org/10.1186/s43008-022-00097-z. See Supplementary Table 1, Examples of the ecological, economic, social and scientific impacts of selected Phytophthora species.
Türkölmez, Ş.; Çiftçi, O.; Canıhoş, E.; Serçe, Ç.U. and Derviş, S. 2015. Phytophthora crown and root rot of apricot Caused by Phytophthora palmivora in Turkey. Journal of Phytopathology. 163(6): 498-502.
Comment received 7/25/2022
July 22, 2022
To: Heather Scheck
From: Elizabeth Bernhardt, Ph. D., Tedmund Swiecki, Ph.D.
Re: California Pest Rating Proposal for Phytophthora palmivora (E.J. Butler) E.J. Butler 1919, Comment Period: 07/18/2022 through 09/01/2022
We offer the following comments for your consideration as you finalize the pest rating proposal.
5) Environmental Impact:
We agree with the selection of point A.
We believe that Point B should also be selected. Given its wide host range, which is not completely defined, this pathogen has the potential to directly affect one or more of California’s threatened or endangered plant species. In coastal habitats with high humidity, aerial infections may be possible. However, high humidity would not be necessary for the root/crown rot diseases, suggesting that a wider variety of species and habitats could be impacted, especially under warming conditions associated with climate change. Furthermore, given the wide host range of this pathogen, it is possible that introduction of this pathogen into a favorable habitat could impact threatened or endangered species by causing irreversible changes to critical habitat. Hence item C under this heading could reasonably be selected.
If B or both B and C were added, the Environmental impact score would be increased to 3. This would not change the overall consequences of introduction rating of High, but would increase the score to 14 points.
6) Post Entry Distribution and Survey Information:
We disagree with the selection of the medium rating. Current data do not support that this pathogen is widespread in California (Medium, -2 rating). Based on known occurrences, the scattered nursey detections would best be described by the “not established (0) known only from incursions” rating. We are unaware of any data, and none are presented in the PRP, indicating that this species is established in any given region or has a localized distribution in California.
Further, the last sentence in the Post Entry Distribution and Survey Information narrative is:
However, during comprehensive nursery surveys for Phytophthora spp., it is not a species that is commonly found (Rooney-Latham et al., 2019), likely due to environmental limitations.
This is not accurate as P. palmivora is not reported in Rooney-Latham et al., 2019. The statement should be revised to:
However, it has not been found during comprehensive nursery surveys for Phytophthora spp., Rooney-Latham et al., 2019; Yakabe et al. 2009 (reference below).
The reasons for P. palmivora’s scarcity in nursery stock are unclear, but could be due to environmental factors and/or the small number of introductions to date.
7) The final score
With the above changes to ratings noted, the overall score would be 14 rather than 11 as shown in the proposed PRP The final score should be higher than the 11 assigned. It should either be 13 or 14.
Conclusion and Rating Justification:
Based on the changes we recommend, the proposed rating for Phytophthora palmivora should be B. This more accurately reflects the potential for impact of this species.
Reference: Yakabe, L. E., Blomquist, C. L., Thomas, S. L., and MacDonald, J. D. 2009. Identification and frequency of Phytophthora species associated with foliar diseases in California ornamental nurseries. Plant Dis. 93:883-890.
Response to Elizabeth Bernhardt, Ph. D., Tedmund Swiecki, Ph.D
Comment: 5) Environmental Impact: We agree with the selection of point A. We believe that Point B should also be selected.
Response: agreed, this section allows for speculation, I will add a point for B and the score will increase to 3
Comment: 6) Post Entry Distribution and Survey Information. However, during comprehensive nursery surveys for Phytophthora spp., it is not a species that is commonly found (Rooney-Latham et al., 2019), likely due to environmental limitations. This is not accurate as P. palmivora is not reported in Rooney-Latham et al., 2019. The statement should be revised to: However, it has not been found during comprehensive nursery surveys for Phytophthora spp., Rooney-Latham et al., 2019; Yakabe et al. 2009 (reference below).
Response: I think it’s acceptable as written. It is not a species that is commonly found, but it has been found in nursery surveys by Phytophthora experts.
Comment: We disagree with the selection of the medium rating. Current data do not support that this pathogen is widespread in California (Medium, -2 rating). The reasons for P. palmivora’s scarcity in nursery stock are unclear but could be due to environmental factors and/or the small number of introductions to date.
Response: This is a difficult section to score. There have been detections made by taxonomic experts in nurseries in 7 counties in the Bay Area, Sacramento Valley, Coastal California, and Southern California. Because it has not been under regulation (with a C-rating), we must assume infected plants have been sold and put into landscapes. A lack of landscape detections implies this pathogen is not well adapted to California conditions, but we do not routinely survey landscapes. With so many detections over decades, I can’t justify rating it as a 0, only known from incursions, because it is in the nursery trades and has never been under eradication. And with so many Counties with detections, I can’t say its Low (-1), with a localized distribution. I am going to leave it as Medium (-2).
Comment: 7) The final score. With the above changes to ratings noted, the overall score would be 14 rather than 11 as shown in the proposed PRP The final score should be higher than the 11 assigned. It should either be 13 or 14.
Response: I have added 1 point under section 5, the new score is 12
Comment: Conclusion and Rating Justification: Based on the changes we recommend, the proposed rating for Phytophthora palmivora should be B. This more accurately reflects the potential for impact of this species.
Response: A final score of 12 can justify either a B or a C rating.