Tag Archives: fungi

Fungi, Plant Pathogens

Melampsoridium hiratsukanum S. Ito ex Hirats. f., (Alder Rust)

California Pest Rating
Melampsoridium hiratsukanum S. Ito ex Hirats. f.,
(Alder Rust)
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

The pest rating of Alder Rust has been raised by certain counties and related nurseries due to its increased spread within California.  Currently, Melampsoridium hiratsukanum has a temporary Q rating that is herein reconsidered for a permanent rating.

History & Status:

Background:  Three Melampsoridium species are reported as causing foliar rust on alder (Alnus spp.) namely, M. alni, M. betulinum and M. hiratsukanum. Confusion has existed on the distinct identity of the species as all three are morphologically similar.  This confusion has caused doubt about the authenticity of many older records.  However, since the late 1990s, the use of DNA analysis has confirmed the identities of the three species. Melampsoridium hiratsukanum belongs to the family Pucciniastraceae in the order Pucciniales.  The species was first described on Manchurian alder (A.hirsuta) from Hokkaido in Japan in 1927.

Disease cycle:  Melampsoridium hiratsukanum is a heteroecious rust that produces two different fruiting bodies (uredinia and telia) on the leaves of its main host alder (Alnus spp.) and two different fruiting bodies (spermagonia and aecia) on its alternate host larch (Larix sp.).  On alder, the fungal species forms uredinia which give rise to urediniospores.  These spores are produced repeatedly and form the major stage for reproduction and dispersal.  Urediniospores are the only spores that re-infect their same host plant repeatedly.  Later, the pathogen produces the sexual, overwintering fruiting body structure or telia which give rise to thick-walled teliospores.  During the following spring, teliospores germinate forming a basidium which produces haploid basidiospores.  Basidiospores may infect young needles of larch (Larix spp.) and develop to form spermogonia – which form pycniospores or spermatia and receptive hyphae.  Following fertilization of spermatia and compatible receptive hyphae, dikaryotic mycelium is produced which forms aecia that produce aeciospores. Aeciospores may infect alder but not other larch or Larix spp. On infection, aeciospores produce more dikaryotic mycelium that this time forms uredinia that produce urediniospores thereby completing the life cycle.

The fungal pathogen may also exhibit a shortcut life cycle especially where the alternate aecial host (Larix spp.) is not present.  In such situations, the life cycle of the pathogen is completed on alder alone without the need of the alternate host and is therefore, reproduces and spreads only through the production of urediniospores.  Such may be the situation with the occurrence of the disease on alder plants in California nurseries.  The pathogen has not been reported on an alternate host in California.  It is likely that the urediniospores re-infect fresh alder leaves thereby enabling their survival and perpetuating the disease through a rapid build-up of inoculum.  Such a shortcut life cycle is known for many rust fungi with alternate hosts and is assumed to occur in Austria and Hungary (NOBANIS, 2007; Szabo, 2002).

Dispersal and spread:  Alder may be infected by aeciospores, or as discussed above for California, it may be infected with urediniospores produced in other alder plants.  Also, it may survive as mycelium infecting buds or with urediniospores.  The rust fungus spreads from plant to plant mainly by windblown spores.  Urediniospores are formed repeatedly and in abundance and may be transmitted over several hundred kilometers by strong winds and then washed down by rain on to host plants that are readily infected.  Aeciospores are also capable of long distance dispersal.  Over the past 10 years, the introduction and rapid spread of the pathogen in Europe was most likely due mainly to dry airborne spores, although specific distances have not been reported (Lane et al., 2013).  Infected nursery stock or plantings also provide a means for long distance spread of the pathogen which is capable of surviving in bud scales in dormant buds.

Hosts:  Alder (Alnus spp.), Black, European or common alder (Alnus glutinosa), Manchurian alder (A. hirsuta), Grey or Speckled alder (A. incana), Red alder (A. rubra) (EPPO, 2014), white alder (A. rhombifolia) (Blomquist et al., 2014); Larch (Larix spp.), Dahurian larch (L. gmelinii), Siberian larch (L. russica) (EPPO, 2014) and White or Downy birch (Betula pubescens) (Lane et al., 2013).  Experimental hosts: European larch (L. decidua), Tamarack or American larch (L. laricina) (Lane et al., 2013).

Symptoms and damage potential:  Infected white alder leaves exhibit numerous small orange-yellow uredinia pustules on the lower leaf surfaces, with corresponding yellow to orange spots on the upper surface.  Later, leaves turn dark brown and curl inwards with the production of telia.  Infected leaves often turn yellow, die and sometimes drop prematurely. The disease causes considerable damage to alder foliage in late summer causing them to be easily distinguished from a distance.  Repeated infections can cause defoliation and crown thinning leading to tree death (Lane et al., 2013).

Worldwide Distribution: Records of the detection of M. hiratsukanum prior to 2005 may be dubious due to taxonomic difficulty that existed in distinguishing it from other closely related species, viz. M. alni and M. betulinum without using molecular analysis.  Many records prior to 2005 may have been of M. betulinum (Lane et al., 2013).  Nevertheless, it is probable that M. hiratsukanum originated in Eastern Asia and has spread to temperate regions of Europe and North America.  Reliable records of the global distribution of M. hiratsukanum (EPPO, 2014) include:

Asia: China, Japan, Nepal (Adhikari & Manandha, 1989; EPPO, 2014)

Europe: Austria, Czech Republic, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lithuania, Norway, Poland, Romani, Russia, Slovakia, Switzerland, Turkey, Ukraine, UK.

North America: Canada, USA (California and Oregon:  Bloomquist et al., 2014; Pscheidt & Ocamb, 2013).  Most likely, it is widespread in nurseries of western US coastal states (Blomquist 2014: pers. comm.)

Official Control: Currently, there are no reports of official control imposed against Melampsoridium hiratsukanum.

California Distribution:  Melampsoridium hiratsukanum is most likely widespread on alders in California nurseries (Blomquist 2014: pers. comm.). The pathogen has been in California since 1931 and a first published report was issued in 2014 of its detection in white alder from a nursery in Santa Cruz County (Blomquist et al., 2014).  However, disease symptoms on trees caused by the pathogen have not been found in California wild lands – mainly due to the absence to high moisture conditions necessary for the perpetuation of the disease in its natural habitat.

California Interceptions:  The pathogen has been in California since in the 1931 as evident by a sample that was submitted to the Federal Herbarium in Beltsville, MD.  However, this sample had been misidentified, and later, when it was correctly identified the revised identification was never published.  The pathogen has also been found in several locations in California Central Valley.

The risk Alder Rust would pose to California is evaluated below.

 Consequences of Introduction: 

 1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is High (3):  Melampsoridium hiratsukanum is already established and suspected to be widely distributed wherever alder is grown in California nurseries.  The pathogen has not been found in California wild lands.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1): The host range is mainly limited to alder and larch trees. Only a few records of its occurrence on birch are from Europe (U.K.).  In California, the pathogen has only been found on alder.     

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3): Alder Rust has high reproduction and dispersal potential via windblown spores that are capable of being transmitted by strong winds over distances of several hundred kilometers.  Also they may be spread over long distances via infected nursery stock

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is Medium (2): Trees infected with Melampsoridium hiratsukanum could cause significant loss of foliage, thereby generally reducing their yield and value in nursery productions.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2): Alder rust has been in California since 1931, although the pathogen was misidentified.  Although it is difficult to find nursery alder trees that are not infected with the pathogen, according to Dr. Cheryl Blomquist (CDFA, pers. comm.), this rust pathogen has not been found in the wild lands, and no significant impact to California’s environment has been reported.  Nevertheless, it may cause significant concern for home/urban gardens or ornamental settings.

Consequences of Introduction to California for Alder Rust:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 11 (Medium).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Medium (-2).  Melampsoridium hiratsukanum is widespread in California nurseries, but has not been detected in wild lands.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 8.

Uncertainty:

 While Melampsoridium hiratsukanum has been in California since 1931, it was not possible to distinguish it from M. alni and M. betulinum based on morphology alone.  The latter two species have been reported earlier from California.   It may well be those earlier detections are, in fact, M. hiratsukanum which have yet to be molecularly differentiated.  If this is determined to be so, then it will only strengthen the proposed C rating for this pathogen, as also will its detection in California’s wild land habitats.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Alder Rust is C.

References:

Agrios, G. N.  2005.  Plant Pathology Fifth Edition.  Elsevier Academic Press, USA.  922 p.

Blomquist, C. L., H. J. Scheck, J. Haynes, P. W. Woods and J. Bischoff.  2014.  First published report of rust on white alder caused by Melampsoridium hiratsukanum in the United States.

EPPO.   2014.  Melampsoridium hiratsukanum (MELDHI).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int.

Lane, C., S. Matthews Berry and H. Anderson.  2013.  Rapid pest risk analysis for Melamsoridium hiratsukanum.  The Food & Environment Research Agency, Version 3, March, 2013.

NOBANIS.  2007.  Melampsoridium hiratsukanum.  NOBANIS – Invasive Alien Species Fact Sheet.  http://www.nobanis.org/files/factsheets/Melampsoridium_hiratsukanum.pdf.

Pscheidt, J. W. and C. M. Ocamb.  2013.  Pacific Northwest Plant Disease Management Handbook.  URL: pnwhandbooks.org/plantdisease/node/2616.

Szabo, I.  2002.  First report of Melampsoridium hiratsukanum on common alder in Hungary.  Plant Pathology, 51:804.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

 Pest Rating:  C

Posted by ls

Fungi, Plant Pathogens

Puccinia crepidis-japonicae (Lindr.) Dietel (Rust)

California Pest Rating for
Puccinia crepidis-japonicae (Lindr.) Dietel
(Rust)
Pest Rating: D 
PEST RATING PROFILE
Initiating Event:

Recently, the USDA NPAG (New Pest Advisory Group) reported and evaluated the detection of Puccinia crepidis-japonicae in Gainesville, Florida, thereby, marking the first record of this pathogen in the USA.  Subsequently, the risk and consequences of its introduction to, and establishment in California is assessed here and a permanent rating is proposed.

History & Status:

Background:  In February 2015, the fungal rust pathogen, Puccinia crepidis-japonicae, was discovered on the exotic weed Youngia japonica (oriental false Hawksbeard) in Florida (USDA NPAG, 2015).  The pathogen primarily attacks weed plants.  While P. crepidis-japonicae is reported to attack plant genus Prenanthes, the host Y. japonica was originally described under the genus name Prenanthes japonica. Therefore, it is likely that the pathogen may be limited to the host belonging to Youngia spp.  This common host, Youngia spp., is present in southern California, and Y. japonica grows there as a garden weed at the edge of lawns and planting beds.

Puccinia crepidis-japonicae has not been reported from California. However, there is a very early record of a different species belonging to the same group, namely, P. crepidis-acuminatae P. Syd. & Syd., which was detected on naked-stem Hawksbeard, (Crepis runcinata which is now a synonym of Youngia runcinata) and tapertip Hawksbeard (Crepis acuminata, synonym of Y. acuminata) in California (Blasdale, W. C. 1919: A preliminary list of the Uredinales of California. University of California Publications in Botany, 7:101-157).

Puccinia crepidis-japonicae is not considered an economically damaging pathogen as it is associated with non-economically important plants. Pereira et al., 2002 suggested that P. crepidis-japonicae may play a significant role as a biocontrol agent against its weed host.  In Florida, the possibility of using this exotic rust against the exotic host, Youngia japonica, is being considered (USDA NPAG, 2015).  However, it is not known if the pathogen kills its host since it needs the latter in order to live as a parasite.

Disease cycle:  The complete life cycle and climate requirements for disease development for Puccinia crepidis-japonicae are not known.  In general, rust pathogens require living host plants to complete a life cycle.  The life cycle may be completed in one or two hosts – and this is not known for P. crepidis-japonicae. Rusts attack only certain genera or varieties of plants.  This appears to be the case for P. crepidis-japonicae. Rusts may have a short cycle (microcyclic) producing only two different spores: teliospores and basidiospores, or a long cycle (macrocyclic) producing five different spores: teliospores, basidiospores, spermatia, aeciospores, and urediniospores. Only urediniospores and teliospores are reported for P. crepidis-japonicae, so this pathogen may be macrocyclic. Urediniospores infect host plants and can rapidly spread to cause new and multiple infections of host plants (Agrios, 2005).

Dispersal and spread:  The pathogen is spread from plant to plant mainly by windblown spores.  Urediniospores can be transported over several hundred kilometers by strong winds and washed down by rain to available hosts.  Insects, animals, humans, and rain may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Hosts: Asteraceae – Prenanthes sp. (rattlesnake root), Youngia fusca, Y. japonica (oriental false Hawksbeard), Y. tenuifolia, Y. japonica (originally cited as Crepis japonica which is now a synonym of Y. japonica) (Farr & Rossman, 2015).

Symptoms and damage potential:  Puccinia crepidis-japonicae primarily attacks weed plants (e.g., Youngia japonica) producing dark brown, irregularly oval-shaped leaf lesions containing urediniospores (Pereira et al., 2002).

Worldwide Distribution: Asia: China, Korea, Japan, Yoron Islands; North America: United States; Oceania: Australia, New Caledonia; South America: Brazil (Farr & Rossman, 2015; USDA NPAG, 2015; Pereira, et al., 2002; Zhuang, 1989).

In the United States, it has only been reported from Florida (USDA NPAG, 2015).

Official Control: Puccinia crepidis-japonicae is not listed as a harmful organism by any country (PCIT, 2015).  No official control of this pathogen is reported.

California Distribution: Puccinia crepidis-japonicae is not present in California.

California Interceptions:  None reported.

The risk Puccinia crepidis-japonicae Rust would pose to California is evaluated below. 

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is Low (1):  If introduced, Puccinia crepidis-japonicae is likely to establish under favorable environmental conditions in limited areas within southern California where its common host, Youngia spp. is present.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1): The host range is limited to weed plants in the genus Youngia spp. in the family Asteraceae. 

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3): Puccinia crepidis-japonicae has both high reproduction and dispersal potential through the production of abundant, infective urediniospores and the ease of their spread by winds, insects, animals, humans, and rain to non-infected host plants.  

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A.  The pest could lower crop yield.

B.  The pest could lower crop value (includes increasing crop production costs).

C.  The pest could trigger the loss of markets (includes quarantines).

D.  The pest could negatively change normal cultural practices.

E.  The pest can vector, or is vectored, by another pestiferous organism.

F.  The organism is injurious or poisonous to agriculturally important animals.

G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is Low (1): Puccinia crepidis-japonicae is not considered an economically damaging pathogen as it is associated with non-economically important plants or weeds.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B.  The pest could directly affect threatened or endangered species.

C.  The pest could impact threatened or endangered species by disrupting critical habitats.

D.  The pest could trigger additional official or private treatment programs.

E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Low (1): None.

Consequences of Introduction to California for Puccinia crepidis-japonicae Rust:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 7

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is: Not established (0).

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 7.

Uncertainty:

Details of the life cycle and complete host range are unknown.  However, it is unlikely this knowledge will significantly alter the proposed rating for Puccinia crepidis-japonicae.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Puccinia crepidis-japonicae Rust is D.

References:

Agrios, G. N.  2005.  Plant Pathology Fifth Edition.  Elsevier Academic Press, USA.  922 p.

Farr, D.F., & Rossman, A.Y. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved August 31, 2015, from http://nt.ars-grin.gov/fungaldatabases/

Pereira, O. L., J. R. P. Cavallazzi and R. W. Barreto.  2002.  First report of Uredo crepidis-japonicae and Septoria crepidis on Crepis japonica in Brazil. Fitopathológicas Brasileira 27 (3):319.

USDA NPAG.  2015.  NPAG report Puccinia crepidis-japonicae (Lindr.) Dietel: Rust.  USDA/APHIS/ PPQ/CPHST/PERAL NPAG Report 20150615.docx. 6 pg.

Zhuang, J. Y. 1989. Rust fungi from the desert of northern Xinjiang. Acta Mycologica Sinica 8(4):259-269.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Pest Rating: D

Posted by ls

Fungi, Plant Pathogens

Colletotrichum cymbidiicola Damm, P. F. Cannon, Crous, P. R. Johnst. & B. Weir, 2012

California Pest Rating for
Colletotrichum cymbidiicola Damm, P. F. Cannon, Crous, P. R. Johnst. & B. Weir, 2012
Pest Rating: B
PEST RATING PROFILE
Initiating Event:    

In April 2014, during an inspection of a nursery in San Diego County, California, Pat Nolan, plant pathologist, San Diego County, observed black spots on leaves of greenhouse-grown cymbidium orchids and submitted symptomatic foliar samples to the CDFA Plant Pathology Laboratory for pathogen diagnosis.  Suzanne Latham, plant pathologist, CDFA analyzed the samples and detected Colletotrichum cymbidiicola in cultures of the symptomatic leaves.  The identity of the associated pathogen was later confirmed by the USDA APHIS National Identification Services.  This detection marked a first record of C. cymbidiicola in the USA (Bethke, 2014).  Follow-up samples collected in June and August from the same nursery, also tested positive for C. cymbidiicola.  Subsequently, the nursery destroyed symptomatic plants and administered sanitary and fungicidal treatment measures to protect remaining plants from future infections.  Trace-back investigations revealed that the San Diego orchids originated in a nursery in Humboldt County.  However, C. cymbidiicola was not detected in orchid samples collected from the Humboldt nursery greenhouse.  A few months later, in June 2014, C. cymbidiicola was detected again in cymbidium orchids in a small, residential nursery in Santa Clara County, however, no trace-back information was available.   Recently, on May 7, 2015, more C. cymbidiicola was detected in orchids from the original nursery in San Diego County.    Therefore, there is a need to reevaluate the current temporary pest rating of C. cymbidiicola for the proposal of a permanent rating.

History & Status:

Background:  Colletotrichum cymbidiicola is a fungus species belonging to the complex species group C. boninense which was originally described in 2003 as a segregate of the vastly morphological and physiological variable C. gloeosporioides complex (CABI, 2014; Morikwaki et al., 2003).  In the past, isolates of C. boninense were often identified as C. gloeosporioides.  However, after segregation from C. gloeosporioides, researchers found that C. boninense actually comprised of a complex of several species and by 2012, through molecular phylogenetic analyses of 86 strains of C. boninense, Damm et al. (2012) were able to recognize 18 species within the C. boninense complex including C. cymbidiicola based on DNA sequence data and morphology.  Colletotrichum cymbidiicola is associated with orchids and is specific at plant genus level.

Hosts: Cymbidium spp. (orchids) (Damm et al., 2012).

Symptoms:  Anthracnose symptoms are expressed as dark spots or lesions in infected orchid leaves, petioles and blossoms.  Initial symptoms include brown discolorations which are irregularly shaped sunken lesions that turn to dark brown with concentric brownish black fruiting bodies (acervuli).  Leaf wilting may occur often resulting in dieback and reduction in plant quality.  As in orchids infected with Colletotrichum gloeosporioides, symptoms may be most common on orchid leaves when stressed plants are damaged by cold and hot temperatures, sun, wind, chemicals and mechanical damage.

Damage Potential:  Anthracnose disease caused by Colletotrichum cymbidiicola can result in reduced plant quality and growth.  Estimates of yield/crop loss due to this pathogen have not been reported although severe outbreaks of orchid anthracnose have been reported in India (Chowdappa, et al., 2014).  Nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum cymbidiicola has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which result in fruiting bodies (acervuli) that bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Condia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Australia, India, Japan, New Zealand, USA (California) (Chowdappa et al., 2014; Damm, et al., 2012; Farr & Rossman, 2015).

Official Control:  Colletotrichum cymbidiicola is considered a new record in North America and reportable to the USDA.

California Distribution: San Diego and Santa Clara Counties (see ‘Initiating Event’).

During the 1980s, CDFA plant pathologists identified C. gloeosporioides in Cymbidium sp. (Alex French, California Plant Disease Host Index 2nd edition).  The site of detection generally includes the southern coastal counties. Details of that specific record are not currently available.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. cymbidiicola.  It is, therefore, possible that this detection may have included C. cymbidiicola. No eliminative action would have been taken against C. gloeosporioides as the species is known to be widespread in California.  However, since that detection and until the 2014-2015 detections noted above in ‘Initiating Events’ there have been no reports of Colletotrichum sp. on cymbidium orchids in California.

California Interceptions:  Colletotrichum cymbidiicola has not been intercepted in quarantine plant shipments imported to California.

The risk Colletotrichum cymbidiicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is Medium (2) – Similar to other species of Colletotrichum, C. cymbidiicola requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California. On the other hand, the pathogen could establish in limited regions with conducive climates within California. Of particular importance is the ability for  C. cymbidiicola to effectively infect and spread to host plants grown under conducive climate conditions in nurseries.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1) – Presently the host range of Colletotrichum cymbidiicola is limited to orchids, Cymbidium sp.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A.  The pest could lower crop yield.

B.  The pest could lower crop value (includes increasing crop production costs).

C.  The pest could trigger the loss of markets (includes quarantines).

D.  The pest could negatively change normal cultural practices.

E.  The pest can vector, or is vectored, by another pestiferous organism.

F.  The organism is injurious or poisonous to agriculturally important animals.

G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is High (3) – Under suitable climates, the pathogen could lower plant growth and value and trigger the loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B.  The pest could directly affect threatened or endangered species.

C.  The pest could impact threatened or endangered species by disrupting critical habitats.

D.  The pest could trigger additional official or private treatment programs.

E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The pathogen could significantly impact cultural practices, home or ornamental plantings of orchids.

Consequences of Introduction to California for Colletotrichum cymbidiicola:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum cymbidiicola to California = (11).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Low (-1).  Colletotrichum cymbidiicola has been found in nursery greenhouses in two coastal counties: San Diego and Santa Clara.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10.

Uncertainty:

The detection and distribution of Colletotrichum cymbidiicola in other orchid-growing California counties is not known.  Subsequent results from those detections may alter the proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum cymbidiicola is B.

References:

Bethke, J. A.  2014.  First detection of Colletotrichum cymbidiicola in California and water supply update.  UCNFA News, University of California, Division of Agriculture and Natural Resources.  http://ucanr.edu/sites/UCNFAnews/Regional_Report_San_Diego_and_Riverside_Counties/Summer_2014__First_detection_of_Colletotrichum_cymbidiicola_in_California/# .

Chowdappa, P., C. S. Chethana,  R. P. Pant and P. D. Bridge.  2014.  Multilocus gene phylogeny reveals occurrence of Colletotrichum cymbidiicola and C. cliviae on orchids in North East India.  Journal of Plant Pathology, 96:327-334.

Damm, U., P. F. Cannon, J. H. C. Wouldenberg, P. R. Johnston, B. S. Weir, Y. P. Tan, R. G. Shivas and P. W. Crous.  2012.  The Colletotrichum boninense species complex.  Studies in Mycology 73:1-36; www.studiesinmycology.org .

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/ .

Kitterly, W. R., and A. P. Keinath.  1996.  Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’.  Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Moriwaki, J., T. Sato and T. Tsukiboshi.  2003.  Morphological and molecular characterization of Colletotrichum boninense sp. nov. from Japan.  Mycoscience 44:47-53.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Pest Rating: B

Posting by ls

Fungi, Plant Pathogens

Colletotrichum asianum Prihastuti, L. Cai & K. D. Hyde, 2009

California Pest Rating for
Colletotrichum asianum Prihastuti, L. Cai & K. D. Hyde, 2009
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

During July, 2014, mango fruit exhibiting spots or lesions were intercepted by the CDFA Dog Team in Santa Clara County and samples of symptomatic fruit were sent to the CDFA Plant Pathology Laboratory for diagnosis.  The associated anthracnose fungal pathogen, Colletotrichum asianum, was identified by Suzanne Latham, CDFA plant pathologist and later confirmed by USDA.  Subsequently, the fruit was destroyed and the shipment was traced back by the USDA to Florida and C. asianum was detected in fruit still on the tree.  This detection marked the first report of the pathogen in the USA (USDA, 2015).  Since its first detection and during April and June 2015, C. asianum continued to be detected in mango fruit shipments destined for Alameda, Butte, Los Angeles, Merced, Riverside, Sacramento, San Joaquin, and Santa Clara Counties.  The shipments were intercepted at USPS distribution facilities by Dog Teams.   On July 7, 2015, C. asianum was found to be associated with necrotic spots in mango leaves of plants in a nursery in Imperial County.  This was the first detection of the pathogen from leaves. In all cases of interceptions mentioned afore, subsequent to the detection of C. asianum, all fruit and plant shipments were received from Florida and either destroyed or rejected from entering California.  Currently, C. asianum has a temporary ‘Q’ rating.  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is proposed herein.            

History & Status:

Background:  Colletotrichum asianum was first reported to be associated with coffee berries (Coffea arabica) in northern Thailand (Prihastuti et al., 2009).  The pathogen is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides complex and is generally identified from other species of the complex only with DNA sequences (Prihastuti et al., 2009; Weir et al, 2012).

Hosts: Mangifera indica (mango) and Coffea arabica (coffee) (Prihastuti et al., 2009; Weir et al., 21012).

Symptoms:  Initially, small, dark brown circular spots are produced on mango fruit and leaves infected with Colletotrichum asianum.  These spots increase rapidly in size and coalesce to form dark depressed anthracnose lesions in ripened fruit (Krishnapillai & Wilson Wijeratnam, 2014). Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves which often result in dieback and reduction in plant quality.

Damage Potential:  Anthracnose disease caused by Colletotrichum asianum can result in reduced plant quality and growth, fruit production and marketability.  Estimates of yield/crop loss due to this pathogen have not been reported.  Nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum asianum has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Conidia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Africa: South Africa; Asia: Japan, Sri Lanka, Thailand, Philippines; South America: Brazil, Colombia, Panama; Australia; North America: Florida (Farr & Rossman, 2015; Krishnapillai & Wilson Wijeratnam, 2014; Lima et al., 2013; Prihastuti et al., 2009; Sharma et al., 2013; USDA, 2015; Vieira et al., 2014; Weir et al., 2012).

Official Control:  In California C. asianum is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

California Distribution: Colletotrichum asianum is not established in California (see “Initiating Event”).

California Interceptions:  During 2015, Colletotrichum asianum has been intercepted several times mainly in shipments of mango fruit and less frequently in mango plants (leaves) that originated in Florida (see ‘Initiating event’).

The risk Colletotrichum asianum would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is Medium (2) – Similar to other species of Colletotrichum, C. asianum requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California. Also limiting is the very narrow host range of C. asianum comprising mango and coffee.  Coffee is not cultivated in California and mango has limited production in the foothills of southern California or warm locations in the Coachella Valley.  It is also grown in residential backyards and few nurseries, either as fruit or nursery stock.  The pathogen could establish within these limited regions under conducive climates.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1) – The host range of Colletotrichum asianum is limited to mango and coffee.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A.  The pest could lower crop yield.

B.  The pest could lower crop value (includes increasing crop production costs).

C.  The pest could trigger the loss of markets (includes quarantines).

D.  The pest could negatively change normal cultural practices.

E.  The pest can vector, or is vectored, by another pestiferous organism.

F.  The organism is injurious or poisonous to agriculturally important animals.

G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is High (3) – Mango fruit production, in particular, can be limited by its susceptibility to anthracnose under wet conditions. Therefore, under suitable climates, the pathogen could lower plant growth, fruit production and value and trigger the loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B.  The pest could directly affect threatened or endangered species.

C.  The pest could impact threatened or endangered species by disrupting critical habitats.

D.  The pest could trigger additional official or private treatment programs.

E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The pathogen could significantly impact cultural practices or home garden plantings.

Consequences of Introduction to California for Colletotrichum asianum:

Add up the total score and include it here. (Score)

-Low = 5-8 points

  -Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum karstii to California = (11).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is not established (0).  Colletotrichum asianum is not established in California.  All instances of interception of C. asianum-infected mango fruit and plants were either rejected or destroyed. 

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11.

Uncertainty:

Periodic surveys need to be conducted to confirm the presence/absence of C. asianum in commercial and private production regions within California.  Subsequent results may alter the herein proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum asianum is B.

References:

CABI.  2015.  Colletotrichum asianum basic datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/

Kitterly, W. R., and A. P. Keinath.  1996.  Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’.  Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Krishnapillai, N., and R. S. Wilson Wijeratnam.  2014.  First report of Colletotrichum asianum causing anthracnose on Willard mangoes in Sri Lanka.  New Disease Reports, 29:1. http://dx.doi.org/10.5197/j.2044-0588.2014.029.001 .

Lima, N. B., M. V. de A. Batista, MAde Morais Júnior, M. A. G. Barbosa, S. J. Michereff, K. D. Hyde, M. P. S. Câmara.  2013. Five Colletotrichum species are responsible for mango anthracnose in northeastern Brazil. Fungal Diversity, 61:75-88. http://rd.springer.com/article/10.1007/s13225-013-0237-6.

Prihastuti, H., L. Cai, H. Chen, E. H. C. McKenzie, and K. D. Hyde.  2009. Characterization of Colletotrichum species associated with coffee berries in northern Thailand. Fungal Diversity 39: 89-109.

Sharma, G., M. Gryzenhout, K. D. Hyde, A. K. Pinnaka, and B. D. Shenoy.  2015.  First report of Colletotrichum asianum causing mango anthracnose in South Africa.  Plant Disease, 99:725.  http://dx.doi.org/10.1094/PDIS-08-13-0837-PDN .

USDA. 2015.  Email from John H. Bower, USDA ,APHIS, PPQ, PHP to Nick Condos, CDFA, subject: Colletotrichum asianum on mango from CA and from the source tree in FL (first records for Continental US), dated April 30, 2015 6:26 am.

Vieira, W. A. S., S. J. Michereff, M. A. de Morais Jr., K. D. Hyde, and M. P. S. Câmara.  2014.  Endophytic species of Colletotrichum associated with mango in northeastern Brazil.  Fungal diversity, 67:181-202.

Weir, B. S., P. R. Johnston, and U. Damm.  2012.  The Colletotrichum gloeosporioides species complex.  Studies in Mycology, 73:115-180. DOI:10.3114/sim0011.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

PEST RATING:  B

Posted by ls 

Fungi, Plant Pathogens

Tranzschelia mexicana M. Scholler & M. Abbasi

California Pest Rating for
Tranzschelia mexicana M. Scholler & M. Abbasi
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

During April, 2015, Heather Scheck, plant pathologist, Santa Barbara County Agricultural Commissioner’s office detected symptoms of rust on capulin cherry nursery stock growing in a nursery in Santa Barbara County.  Cheryl Blomquist, CDFA plant pathologist, examined infected leaf samples and identified the associated rust pathogen Tranzschelia mexicana.  This pathogen was first found in Santa Barbara in 2014 in 4 year old cherry trees grown in a residential backyard garden.

History & Status:

Background:  Tranzschelia mexicana is a fungal pathogen that causes rust in capulin cherry trees.  The pathogen was originally described from Mexico and thus named to indicate its natural distribution in southern Mexico.  It is assumed that this pathogen requires two different kinds of hosts to complete its life cycle (also called a host alternating rust) and is macrocyclic (i.e., produces urediniospores, teliospores and basidiospores on main host and spermatia and aeciospores on an alternate host).  However, the alternate host as well as spermogonia and aecia (fruiting structures producing spermatia and aeciospores respectively) are unknown for T. mexicana. Furthermore, Blomquist et al. (2015) did not detect telia in rust-infected capulin cherry leaves that were collected from trees in Santa Barbara County, California, during October and November 2014 and January 2015 and thereby, deduced that the fungal species does not form telia.  This is not unusual for host alternating rusts when aecial hosts (alternate hosts) are not present in regions. Scholler et al., suggest that Anemone mexicana – a plant native to the Valley of Mexico – might be the aecial host for the capulin rust pathogen.  Nevertheless, it is likely that T. mexicana has spread without its aecial host via production of urediniospores only (Scholler et al., 2014).

Hosts: Capulin/Mexican black cherry, (Prunus salicifolia, Rosaceae) is the only reported host for Tranzschelia mexicana (Scholler et al., 2014; Blomquist et al., 2015).

Symptoms: Tranzschelia mexicana causes yellow spots on the upper side of leaves and brownish pustules on the underside.  Entire infected trees are susceptible to high infestations although fewer pustules may be present in younger leaves than older leaves.  Severe infestations may cause defoliation and reduced plant stands (Blomquist et al., 2015).

Damage Potential:  Capulin cherry is not a commercially cultivated crop in California, however, a small percentage of nursery stock plants are sold in the retail market.  Infections of this rust pathogen could negatively impact production and value of plants in private residences, public parks, amusement parks, and other environments. Rusted capulin cherry leaves are not only aesthetically unsightly but also negatively impact plant growth.  Severe infestations of rust can result in defoliation and reduction in plant growth, vigor and stand.  Containment and management of the rust pathogen can be difficult as infected leaves produce masses of air-borne spores enabling long-range spread and infection.

Transmission:  The pathogen is spread from plant to plant mainly by windblown spores.  Urediniospores can be transported over several hundred kilometers by strong winds and washed down by rain to available hosts.  Insects, animals, humans, and rain may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Worldwide Distribution: North America: Mexico, USA (California – CDFA pest detection records); South America: Colombia, Ecuador (Scholler et al., 2014). It is assumed that the distribution of the capulin rust pathogen extends beyond the above mentioned distribution in the Americas where capulin cherry is cultivated.

Official Control: None reported.

California Distribution:  Capulin rust pathogen, Tranzschelia mexicana, has been detected in residential backyard and nursery environments in Santa Barbara County (see ‘Initiating Event’).

California Interceptions:  There have been no quarantine interceptions of Tranzschelia mexicana was intercepted in California.

The risk Tranzschelia mexicana would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
– High (3) likely to establish a widespread distribution in California.

Risk is High (3) – Tranzschelia mexicana is able to establish wherever capulin cherry trees are grown in California.  Capulin cherry (Prunus salicifolia) is a rare fruit and is grown in many low chill regions in California for its flowers and edible fruit.

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range.

Risk is Low (1) – Currently the host range of Tranzschelia mexicana is limited to capulin cherry (Prunus salicifolia). The alternate host for this pathogen is not known. Blomquist et al (2015) did not find symptoms of rust on several peaches, apricots and other Prunus spp. that were growing on the same property with rust-infested capulin cherry trees.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

-Low (1) does not have high reproductive or dispersal potential
-Medium (2) has either high reproductive or dispersal potential
– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The infective spores of Tranzschelia mexicana namely, urediniospores, are produced in abundance and are spread to healthy plants mainly by wind. Insects, animals, humans, rain, and infected nursery plants also aid in its spread.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

-Low (1) causes 0 or 1 of these impacts
-Medium (2) causes 2 of these impacts
– High (3) causes 3 or more of these impacts.

Risk is High (3) – Severe infestations of the capulin cherry rust pathogen could result in defoliation and reduction of plant growth, vigor and stand, and loss of markets. Nursery plantings are at risk being significantly impacted by the introduction of this pathogen. Without eradicative action subsequent to detection of bamboo rust-infected plants within greenhouse environments, there is the risk of further spread to the outside environment. The spread of the rust pathogen would be difficult to manage due to its effective means of windblown transmission.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur
– Medium (2) causes one of the above to occur
– High (3) causes two or more of the above to occur.

Risk is High (3) – Capulin cherry plantings for aesthetic and rare fruit production value by private growers may be impacted by the capulin cherry rust pathogen subsequently triggering additional treatment programs.

Consequences of Introduction to California for Tranzschelia mexicana

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Tranzschelia mexicana to California = (13).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluationis Low (-1): Presently, Tranzschelia mexicana is only established in Santa Barbara, California.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 12

Uncertainty:

Future detection surveys for Tranzschelia mexicana in nurseries and established capulin cherry plantings are needed to gain further information of the probable introduction, establishment and distribution of this pathogen in California.  This information could alter the proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Tranzschelia mexicana is B.

References:

Agrios, G. N.  2005.  Plant Pathology (Fifth Edition).  Elsevier Academic Press, USA.  922 p.

Blomquist, C. L., M. Scholler and H. J. Scheck.  2015.  Detection of rust caused by Tranzschelia mexicana on Prunus salicifolia in the United States.  Plant Disease (Accepted for publication).

California Rare Fruit Growers, Inc.  1997. Capulin cherry Prunus salicifolia HBK. Fruit Facts. http://www.crfg.org/pubs/ff/capulin-cherry.html .

Scholler, M., M. Abbasi and F. Friedrich.  2014.  Tranzschelia in the Americas revisited: two new species and noted on the Tranzschelia thalictri complex.  Mycologia, 106: 448-455. DOI: 10.3852/12-260.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health@cdfa.ca.gov.

PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Podosphaera caricae-papayae

California Pest Rating for
Podosphaera caricae-papayae
Pest Rating: B
PEST RATING PROFILE
Initiating Event: 

In March 2014, Podosphaera caricae-papayae, a powdery mildew fungal pathogen, was identified by morphological and sequence analyses by Suzanne Latham, plant pathologist, CDFA. The symptomatic papaya leaf sample was collected from an ornamental container nursery in Santa Barbara County by County Agricultural plant pathologist, Heather Scheck. The identity of the pathogen was confirmed by USDA APHIS PPQ Mycologist, Megan Romberg.  Subsequently, the nursery destroyed the infected papaya plants.  In May 2014, the same pathogen was detected on papaya plants, grown in a commercial papaya fruit production nursery greenhouse at a different location within Santa Barbara County.  The detection of powdery mildew of papaya in Santa Barbara County marks a first record for North America.  Initially, the fungal pathogen was assigned a Q rating which is reassessed herein for the proposal of a permanent rating.

History & Status:

Background:    Podosphaera caricae-papayae was originally described by Tanda and Braun in 1985 as Sphaerotheca caricae-papayae.  However, in 2000 the species was placed in the genus Podosphaera based on molecular sequence analysis by Braun and Takamatsu (Romberg, 2014).  Complications in taxonomic classification of the species exist over the accurate linkage of the sexual or teleomorph stage to the asexual or anamorph stage of the pathogen and further molecular and morphological studies are needed to determine the correct taxonomic position of P. caricae-papayae.  In the original description of the species, the teleomorph stage, Sphaerotheca, was linked to the anamorph stage, Oidium caricae (Liberato et al., 2004).  However, later this linkage was proven inaccurate and O. caricae was rejected as the anamorph stage, thereby leaving the classification of an asexual stage for P. caricae-papayae unresolved.  The exact distribution is unknown because it is unclear which records of “O. caricae” actually belong to P. caricae-papayae.  In 2012, P. caricae-papayae was synonymized with the morphologically similar species P. xanthii – the pathogen causing powdery mildew on cucurbits (Braun & Cook, 2012).  The synonymy of P. xanthii and P. caricae-papayae is in question given recent molecular work (Takamatsu et al., 2010).  P. caricae-papayae is only known from infected seedlings of papaya in Australia, China, India, Japan, New Zealand and California (USA).  Greenhouse infections of papaya plants in California were reported as being caused by “cucurbit powdery mildew”.  Infections of mature papaya plants in the field have never been reported.

The infected papaya plants recently detected in California only bear the anamorph stage which morphologically resembles the anamorph stage of P. caricae-papayae that was described by Tanda and Braun in 1985 (Romberg, 2014).  Furthermore, molecular sequence analysis revealed that the sequences from both California detections are identical to a sequence of P. caricae-papayae from Thailand that was used by Takamatsu et al., (2010) in their phylogenetic analyses of the genus Podosphaera (Latham, 2014; Romberg, 2014).  Unfortunately, no morphological information of the Thailand isolate is available to compare with the California isolate.  The sequence from Thailand is the only P. caricae-papayae sequence deposited in GenBank and therefore, analytical sequence comparisons of isolates of P. caricae-papayae from California and Thailand with those from other reported regions are lacking.  Nevertheless, the Thailand sequence is different from other Podosphaera species sequences in Genbank, including the cucurbit powdery mildew, P. xanthii.   Further molecular and morphological studies which would include more isolates will help determine the correct taxonomic position of P. caricae-papayae within the genus Podosphaera in the family Erysiphaceae of the order Erysiphales (Takamatsu et al., 2010).

Powdery mildew of papaya is on obligate parasite.  The fungus grows on the surface of plant tissue and invades by sending feeding organs (haustoria) into the plants epidermal cells only in order to obtain nutrients.  Mycelium produces conidiophores on the plant surface.  Each conidiophore produces chains of conidia (spores) that are dispersed by air currents.  Powdery mildew thrives in warm and humid environments. Low light levels, high humidity, moderate temperature and rainfall enhance disease development in papaya (Cunningham & Nelson, 2012). Generally, disease can be severe in warm and dry climate as long as the relative humidity is high enough to enable condial germination and infection.

Hosts: Carica papaya (papaya).

Symptoms:  Powdery mildew infects papaya plants of all ages however seedlings in greenhouses are more susceptible than field grown plants.  The pathogen frequently infects young immature leaves, petioles, pedicels, peduncles, and unripe fruit. Early on, the undersides of leaves become speckled with small water-soaked spots with white to grayish powdery fungal patches usually near the leaf veins.  Yellow-green spots develop on the corresponding upper sides.  Soon the patches grow in size and coalesce, and fungal growth may grow on the upper leaf surface and veins.  In severe infections, leaves become necrotic, curl and drop prematurely.  Mildew patches also develop on immature fruit and can cover the entire fruit, eventually resulting in deformed fruit (Cunningham & Nelson, 2012).

Damage Potential:  Infections can result in prematurely defoliated trees, mildewed and deformed fruit causing significant if not, total losses in plant growth and crop yield.   Deformed fruit is not marketable resulting in lowered sales.  Infections occurring in plants grown in greenhouse can result in severe spread and loss in production if left unmanaged.

In California, there is no commercial acreage under cultivation for papaya. Production is limited to ornamental and fruit production nursery greenhouse and residential gardens for ornamental purposes in southern California counties.  Under those environments, loss in production is possible if not managed.

Transmission:  Conidia (spores) are primarily dispersed by wind currents.

Survival:  During cool weather, condia production ceases and powdery mildew fungi overwinter as cleistothecia (a sexually produced, closed, fruiting body) and mycelium in dormant plant tissue. However, only the asexual stage has been found in California greenhouses.  Constant greenhouse growth conditions could perpetuate the anamorphic stage of the fungus.

Worldwide Distribution: The true distribution of the California isolate of P. caricae-papayae is currently not known.  Molecular sequence analyses remain unknown for reported isolates of P. caricae-papayae from Australia, China, India, Japan, and New Zealand.  The sequence of the isolate from Thailand is the only one deposited in GenBank, and is identical to the sequence of the California isolate.

Official Control:  There is no record of official control against this pathogen.

California Distribution: The pathogen has only been detected in greenhouses of two nurseries at two different locations in Santa Barbara County.

California Interceptions:  There are no records of Podosphaera caricae-papayae having been intercepted in papaya imported to California.

The risk Podosphaera caricae-papayae would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
– High (3) likely to establish a widespread distribution in California

Risk is Low (1) – Of what is currently known, Podosphaera caricae-papayae will only infect papaya and therefore, is limited to wherever papaya is cultivated.  In California, where there is no major cultivation of papaya, plants are propagated in greenhouses for fruit production and ornamental plantings in residential and urban environments of southern counties.  As evident in the recent detection in Santa Barbara, the pathogen is capable of establishing in nursery grown papaya.  

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

Risk is Low (1) – The host range is limited to Carica papaya (papaya).

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– Low (1) does not have high reproductive or dispersal potential
– Medium (2) has either high reproductive or dispersal potential
– High (3) has both high reproduction and dispersal potential

Risk is High (3) – Under suitable climate conditions, airborne conidia are produced in abundance and readily spread by wind currents to non-infected sites.  Within and outside greenhouse environments, the pathogen is capable of rapidly spreading to non infested papaya plants as well as other sites where papaya is grown.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts
– Medium (2) causes 2 of these impacts
– High (3) causes 3 or more of these impacts

Risk is High (3) – The pathogen can potentially cause significant losses in plant growth and crop yield. Powdery mildew infections of papaya fruit could lower crop yield and value causing significant losses in production.  This would result in loss of markets, and change in cultivation practices to prevent the spread of inocula to non-infected, healthy plants.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur
– Medium (2) causes one of the above to occur
– High (3) causes two or more of the above to occur

Risk is High (3) – Although limited to papaya, occurrence of the pathogen in nursery and outside environments could significantly impact home/urban gardening and/or ornamental plantings, as well as result in the imposition of additional official or private treatments to mitigate effects of infection.

Consequences of Introduction to California for Podosphaera caricae-papayae:

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of P. caricae-papayae to California = (11).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.
–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Low (-1).  The pathogen was only detected within nursery greenhouses in Santa Barbara, California.  Measures were taken to destroy infested plants.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10

Uncertainty:

To date, the detection of P. caricae-papayae in California is limited to two in-greenhouse sites in Santa Barbara County.  There have not been any additional detections, surveys or reports of new infestations in papaya production nurseries and/or outside environments to provide further knowledge of the presence of this pathogen. Further comparative molecular analyses against reported international isolates of the pathogen may provide information of its global distribution and clarity of its taxonomic classification, however, it’s separation from P. xanthii (present in California) has already been proven (see ‘Background’).

While the host range and distribution of the pathogen within California is currently known to be limited, the potential of incurring significant damage due to infection by P. caricae-papayae places the limited distribution of instate papaya nursery ornamental and production plants at medium risk and, therefore, warrants assignment of a B rating.  Future detections of P. caricae-papayae could indicate a wider distribution than presently known and result in a lower rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Podosphaera caricae-papayae is B.

References:

Braun, U. and R. T. A. Cook.  2012.  Taxonomic manual of the Erysiphales (Powdery Mildews).  Centraalbureau voor Schimmelcultures, vol. 11, 707 p.

Cunningham, B and S. Nelson.  2012.  Powdery mildew of Papaya in Hawai’i.  College of Tropical Agriculture and Human Resources University of Hawai’I at Mānoa.  Plant disease, PD-90.

Latham, S.  2014.  Email to John Chitambar, CDFA: sent July 3, 2014.

Liberato, J. R., R. W. Barreto and R. P. Louro.  2004. Streptopodium caricae sp. nov., with a discussion of powdery mildews on papaya, and emended descriptions of the genius Streptopodium and Oidium caricae.  Mycological Research 108:1185-1194.

Romberg, M. K.  2014.  Email from M. K. Romberg, APHIS-USDA, to Suzanne Latham, CDFA: sent March 26, 2014.

Takamatsu, S., S. Ninomi, M. Harada and M. Havrylenko.  2010.  Molecular phylogenetic analyses reveal a close evolutionary relationship between Podosphaera (Erysiphales: Erysiphaceae) and its rosaceous hosts.  Persoonia, 24, 38-48.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Colletotrichum boninense Moriwaki, Toy. Sato & Tsukib. 2003

California Pest Rating for
Colletotrichum boninense Moriwaki, Toy. Sato & Tsukib. 2003
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

During February 2015, the fungal pathogen Colletotrichum boninense was detected in infected Aglaonema commutatum (Aglaonema/Chinese evergreen) cuttings in a nursery in Vista, San Diego County, California.  The plants were part of an incoming nursery shipment from Fallbrook, San Diego County, California and originated in a nursery in Costa Rica. A month later, the pathogen was detected twice in San Diego in two different shipments of Aglaonema sp. plants: one sent to the Vista nursery by the same shipper as before, and the other sent by a different shipper to a different nursery.  The latter two shipments had also originated in Costa Rica.  The pathogen was cultured from leaf spots, sequenced, and identified by Suzanne Latham, CDFA plant pathologist.  This detection was considered a new US record and reportable by the USDA. The species identity was confirmed by the USDA PPQ National Mycology Laboratory.  Consequently, the shipment of plants was destroyed.   A permanent rating for Colletotrichum boninense is proposed herein.        

History & Status:

Background:  Colletotrichum boninense was first discovered associated with Crinum asiaticum var. sinicum (Amaryllidaceae) in the Bonin Islands, Japan (Moriwaki et al., 2003).  These scientists also found the species in Japan to be associated with several other hosts plants of different plant families.  Furthermore, C. boninense was originally described in 2003 as a segregate of the vastly morphological and physiological variable C. gloeosporioides complex (CABI, 2014; Morikwaki et al., 2003).  Prior to its segregation as a species, isolates of C. boninense were often identified as C. gloeosporioides.  However, after the segregation, researchers found that C. boninense actually comprised of a complex of several species and by 2012, through molecular phylogenetic analyses of 86 strains of C. boninense, Damm et al. (2012) were able to recognize 18 species within the C. boninense complex including C. boninense in its strict sense (s. str.) based on DNA sequence data and morphology.  The current proposed rating is for C. boninense s. str.

Hosts: Host plants of C. boninense s. str. are very diverse and include members in the plant families Amaryllidaceae, Bignoniaceae, Podocarpaceae, Proteaceae, Solanaceae and Theaceae (Damm et al., 2012).  The CDFA 2015 detection of C. boninense s. str. on Aglaonema commutatum would also include the family Araceae.

The range of host plants for Colletotrichum boninense s. str. is not well understood from reports published prior to 2012 as many of those reports refer to the broad C. boninense complex (sensu lato).  Subsequently, those reported hosts would need to be molecularly verified to be C. boninense s. str.  and include members of the genera Bletilla, Camellia, Capsicum, Cattleya, Clivia, Coffeae, Crinum, Cucumis, Cymbidium, Dacyrarpus, dendrobium, Dracaena, Eucalyptus, Hippaestrum, Leucospermum, Oncidium, Pachira, Panax, Passiflora, Pleione, Protea, Prunus, and Solanum (Farr & Rossman, 2015).

Symptoms:  Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves often resulting in dieback and reduction in plant quality.

Damage Potential:  Anthracnose disease caused by Colletotrichum boninense can result in reduced plant quality and growth.  Estimates of yield/crop loss due to this pathogen have not been reported.  Nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum boninense has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Condia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Australia, Brazil, China, Colombia, Japan, Korea, the Netherlands, New Zealand, South Africa, and Zimbabwe (Farr & Rossman, 2015).

Except for Japan, Australia, and New Zealand where the presence of Colletotrichum boninense s. str. was verified (Damm et al., 2012), reports from other countries should be independently verified for C. boninense s. str.

The 2010 report of Colletotrichum boninense in Florida, USA, reported by Tarnowski & Ploetz,  is now not considered to be C. boninense s. str. but actually a different species within the C. boninense species complex (personal communication: Aaron Kennedy, National Identification Services, USDA-APHIS-PPQ-PM). The Florida report was published before the C. boninense complex was split into several species in 2012.

Official Control:  Colletotrichum boninense is considered a new USA record and reportable to the USDA.

California Distribution: There is no official record of the establishment of Colletotrichum boninense in California however during the early 1980s, CDFA plant pathologists identified C. gloeosporioides in Camelia japonica (Theaceae) and other hosts in the plant family Araceae which are included as host for C. boninense s. str.  These detections were made in northern and southern coastal counties.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense.  It is, therefore, possible that these detections may have included C. boninense s. str. (Suzanne Latham and Cheryl Blomquist, CDFA, personal communication).  No eliminative action would have been taken against C. gloeosporioides as the species is known to be widespread in California.

California Interceptions:  Colletotrichum boninense has been intercepted at least thrice in shipments of Algaonema sp. from Costa Rica (see ‘Initiating event’).

The risk Colletotrichum boninense would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
– High (3) likely to establish a widespread distribution in California

Risk is Medium (2) – Similar to other species of Colletotrichum, C. boninense requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California. Limited regions with conducive climates within California could enable the pathogen to establish.  In particular, C. boninense s. str. can effectively infect and spread to host plants grown under conducive climate conditions in nurseries.

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

Risk is High (3) – The host range of Colletotrichum boninense s. str. is very diverse and includes member in the plant families Amaryllidaceae, Bignoniaceae, Podocarpaceae, Proteaceae, Solanaceae, Theaceae, and Araceae.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– Low (1) does not have high reproductive or dispersal potential
– Medium (2) has either high reproductive or dispersal potential
– High (3) has both high reproduction and dispersal potential

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts
– Medium (2) causes 2 of these impacts
– High (3) causes 3 or more of these impacts

Risk is High (3) – Under suitable climates, the pathogen could lower plant growth and value and trigger the loss of markets.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur
– Medium (2) causes one of the above to occur
– High (3) causes two or more of the above to occur

Risk is Medium (2) – The pathogen could significantly impact cultural practices, home gardening or ornamental plantings.

Consequences of Introduction to California for Colletotrichum boninense:

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum boninense to California = (13).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is not established.  However, while there is no official record of the establishment of Colletotrichum boninense in California, during the 1980s, CDFA plant pathologists identified C. gloeosporioides in Camelia japonica (Theaceae) and other hosts in the plant family Araceae which are included as host for C. boninense s. str.  These detections were made in northern and southern coastal counties.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense.  It is, therefore, possible that these detections may have included C. boninense s. str.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 13.

Uncertainty:

The possibility that the 2013 detection of C. gloesporoides may have included the now segregate species, C. boninense st. str. and that the latter may already be established in California, can only be ascertained through survey and testing of infected host plants particularly in suspect counties included in early detection reports of C. gloeosporioides .  Subsequent results may alter the herein proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum boninense s. str. is B.

References:

CABI.  2014.  Colletotrichum boninense datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

Damm, U., P. F. Cannon, J. H. C. Wouldenberg, P. R. Johnston, B. S. Weir, Y. P. Tan, R. G. Shivas and P. W. Crous.  2012.  The Colletotrichum boninense species complex.  Studies in Mycology 73:1-36; www.studiesinmycology.org

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/

Kitterly, W. R., and A. P. Keinath.  1996.  Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’.  Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Moriwaki, J., T. Sato and T. Tsukiboshi.  2003.  Morphological and molecular characterization of Colletotrichum boninense sp. nov. from Japan.  Mycoscience 44:47-53.

Tarnowski, T. L. B. and R. C. Ploetz.  2010.  First report of Colletotrichum boninense, C. capsici, and a Glomerella sp. as causes of postharvest anthracnose of passion fruit and Florida.  Plant Disease 94:786. http://dx.doi.org/10.1094/PDIS-94-6-0786C .

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Colletotrichum petchii Damm, P. F. Cannon & Crous, 2012

California Pest Rating for
Colletotrichum petchii Damm, P. F. Cannon & Crous, 2012
Pest Rating: B
PEST RATING PROFILE
Initiating Event:    

In January 2015, the fungal pathogen Colletotrichum petchii, was detected in infected potted Dracaena deremensis (corn plant) in a nursery in Vista, San Diego County, California.  The plants were shipped from a nursery in Keaau, Hawaii. The pathogen was cultured from infected leaves and identified by Suzanne Latham, CDFA plant pathologist.  This detection was considered a new US record and reportable by the USDA. The species identity was confirmed by the USDA PPQ National Mycology Laboratory.  Consequently, the shipment of plants was destroyed.   A permanent rating for Colletotrichum petchii is proposed herein.        

History & Status:

Background:  Colletotrichum petchii was originally discovered in 1925 by Petch and described under a previously existing name, Colletotrichum dracaenae that was detected in dark brown patches on leaves of Dracaena brauni (syn. D. sanderiana) in Sri Lanka.  However, Damm et al., (2012) published the name C. petchii to replace C. dracaenae Petch 1925 which was an illegitimate name according to the International Code of Nomenclature for fungi. [The legitimate name for C. dracaenae is the same name but described by Allescher: C. dracaenae Allesch., 1902.]

The more recent development of species-specific molecular diagnostic tests, particularly since the early 2000s, resulted in changes in taxonomy and nomenclature of fungi within the genus Colletotrichum and eventually led to the recognition of Colletotrichum petchii.  During 2003 to 2012, prior to its being legitimately named, C. petchii was included as a strain of the species C. boninense.  However, researchers indicated that C. boninense actually comprised of a complex of several species.  Then by 2012, through molecular phylogenetic analyses of 86 strains of C. boninense, Damm et al. were able to recognize C. petchii as a separate species. Furthermore, C. boninense was originally described in 2003 as a segregate of the vastly morphological and physiological variable C. gloeosporioides complex (CABI, 2014; Morikwaki et al., 2003).  In the past, isolates of C. boninense were often identified as C. gloeosporioides (Damm et al., 2012).

Hosts: Dracaena spp., Dracaena aletriformis (syn. D. latifolia).D. braunii, D. fragrans (syn. D. deremensis), D. sanderiana,

Symptoms:  Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves often resulting in dieback and reduction in plant quality.

Damage Potential:  Anthracnose disease caused by Colletotrichum petchii can result in reduced plant quality and growth.  Estimates of yield/crop loss due to this pathogen have not been reported.  Nursery production of Dracaena as potted plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum petchii has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Condia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Sri Lanka, Italy, China, Netherlands, Germany, and USA.

Official Control:  Colletotrichum petchii is considered a new USA record and reportable to the USDA.

California Distribution: There is no official record of the establishment of Colletotrichum petchii in California, however in 2013 CDFA plant pathologists identified C. gloeosporioides in Dracaena warnickii plants grown in a nursery in San Luis Obispo County, California.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense and C. petchii.  It is, therefore, possible that this detection may have included C. petchii (Suzanne Latham, CDFA, personal communication).  No eliminative action would have been taken against the 2013 nursery detection of C. gloeosporioides which is known to be widespread in California.

California Interceptions:  Colletotrichum petchi has been intercepted once in shipment of potted Dracaena deremensis from Hawaii (see ‘Initiating event’).

The risk Colletotrichum petchii would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
– High (3) likely to establish a widespread distribution in California

Risk is Medium (2) – Similar to other species of Colletotrichum, C. petchii requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California. Limited regions with conducive climates within California could enable the pathogen to establish.  In particular, C. petchii can effectively infect and spread to host plants (Dracaena spp.) grown under conducive climate conditions in nurseries.

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

Risk is Low (1) – The host range of Colletotrichum petchi is limited to Dracaena spp.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– Low (1) does not have high reproductive or dispersal potential
– Medium (2) has either high reproductive or dispersal potential
– High (3) has both high reproduction and dispersal potential

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts
– Medium (2) causes 2 of these impacts
– High (3) causes 3 or more of these impacts

Risk is High (3) – Under suitable climates, the pathogen could lower plant growth and value and trigger the loss of markets.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur
– Medium (2) causes one of the above to occur
– High (3) causes two or more of the above to occur

Risk is Medium (2) – The pathogen could significantly impact cultural practices, home gardening or ornamental plantings.

Consequences of Introduction to California for Colletotrichum petchii:

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum petchii to California = (11).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is not established.  However, while there is no official record of the establishment of Colletotrichum petchii in California, in 2013 CDFA plant pathologists identified C. gloeosporioides in Dracaena warnickii plants grown in a nursery in San Luis Obispo County, California.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense and C. petchii.  It is, therefore, possible that this detection may have included C. petchii (Suzanne Latham, CDFA, personal communication).

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

 Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11.

Uncertainty:

The possibility that the 2013 detection of C. gloesporoides may have included the now segregate species, C. petchii and that the latter may already be established in California, can only be ascertained through survey and testing of infected host plants particularly in San Luis Obispo County and neighboring counties.  Subsequent results may alter the herein proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum petchii is B.

References:

CABI.  2014.  Colletotrichum boninense datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

Damm, U., P. F. Cannon, J. H. C. Wouldenberg, P. R. Johnston, B. S. Weir, Y. P. Tan, R. G. Shivas and P. W. Crous.  2012.  The Colletotrichum boninense species complex.  Studies in Mycology 73:1-36; www.studiesinmycology.org

Kitterly, W. R., and A. P. Keinath.  1996.  Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’.  Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Moriwaki, J., T. Sato and T. Tsukiboshi.  2003.  Morphological and molecular characterization of Colletotrichum boninense sp. nov. from Japan.  Mycoscience 44:47-53.

Petch, T.  1925.  Additions to Ceylon fungi. III. Annals of the Royal Botanical Gardens. Peradeniya 9:313-328.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Phytophthora niederhauserii Abad & J. Abad, 2014

California Pest Rating for
Phytophthora niederhauserii Abad & J. Abad, 2014
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

None.  A permanent rating for Phytophthora niederhauserii is proposed herein.

History & Status:

Background: In 2003, Abad and Abad reported the discovery of a Phytophthora species associated with necrotic collars, stems and roots of arborvitae (Thuja occidentalis L.) and English ivy (Hedera helix L.) grown in greenhouses in North Carolina.  They named the species, P. niederhauseria and submitted the ITS (Internal transcribed spacer) genetic sequences on GenBank-NCBI before publishing an official description of the species.  Soon other researchers from around the globe found that they were working with the same species based on the similarity of their test ITS sequences with that of P. niederhauseria in GenBank.  The species was discovered in 13 countries and associated with ornamentals, fruit trees and native plants.  However, it was only recently, that an official description of the species was published and the name, P. niederhauserii was validated (Abad et al., 2014).

Hosts: Abad et al., (2014) isolated P. niederhauserii from 33 plant hosts in 25 families from various countries.  A number of shrubs and herbaceous ornamental plants are hosts of the pathogen.  Few agricultural crops are also included.  Thuja occidentals (arborvitae), Hedera helix (English ivy), Abies nordmanniana, Acacia dealbata (Mimosa), Banksia baxteri, Banksia prionotes (acorn banksia), Banksia speciosa, various Begonia hybrids,  Callistemon citrinus, Ceanothus sp., Chamaecyparis lawsoniana, Cistus monspeliensis, C. salviifolius (sageleaf rockrose),  Grevillea olivacea, Heuchera sp. Iris sp. Juniperus sp., Kalanchoe blossfeldiana (kalanchoe), Manihot esculenta, Metrosideros villosa, Peperomia clusiifolia,Pistacia lentiscus, Plumbago sp., Prunus dulcis (almond), Punica granatum, Rhododendron catawbiense (catawba rhododendron), Sinningia speciosa (gloxinia), Spathiphyllum sp., Vitis vinifera (grape), and Xanthorrhoea australis (Farr & Rossman, 2014; Abad et al., 2014).

Symptoms:  Generally, Phytophthora niederhauserii infestations cause symptoms of root and stem collar necrosis resulting in wilting and leaf desiccation or drop in host plants.  In Norway, symptoms of P. niederhauserii infestation on greenhouse-potted begonia, gloxinia and ivy included necrotic roots and stems with necrosis extending to the leaves via the petioles.  Wilting of the entire plant was observed in gloxinia and ivy. In kalanchoe, only root discoloration and stunted plant growth are apparent (Herrero et al., 2008).  In Spain, symptoms on almonds included leaf chlorosis and drop, wilting, cankers and gum exudation.  In spring, symptoms included failure to leaf-out, death of scion and rootstock sprouts (Pérez-Sierra et al., 2010). The pathogen caused collar and root necrosis in boxwood associated with severe wilting and desiccation of foliage (Józsa et al., 2010).

Damage Potential: Quantitative economic losses in plant production due to Phytophthora niederhauserii have not been reported, however, infestations may result in significant damage and loss in production and stands of host plants by causing root and crown/basal stem rots of infected plants. Nursery ornamentals and plants grown in natural ecosystems are particularly affected. Infections may lead to death of the plant.  Generally, annual plants and young seedlings of trees may be killed by the disease within a few days, weeks or months (Agrios, 2005). The pathogen can potentially cause crown rot in grapes – as detected in South Africa and in almonds in Turkey (Abad et al., 2014).       

Disease Cycle: Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as thick-walled, resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  During spring, the oospores and chlamydospores germinate to produce motile spores (zoospores) that swim around in soil water and roots of susceptible hosts. The pathogen infects the host at the soil line causing water soaking and darkening of the trunk bark. This infected area enlarges and may encircle the entire stem of small plants which wilt and eventually die.  On large plants and trees, the infected, necrotic area may be on one side of the stem and become a depressed canker below the level of the healthy bark.  Collar rot canker may spread down the root system. Roots are invaded at the crown area or at ground level.   Mycelium and zoospores grow in abundance in cool, wet weather causing damage where the soil is too wet for normal growth of susceptible plants and low temperatures (15-23°C) prevail (Agrios, 2005).

Transmission:  Infected soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites.

Worldwide Distribution:  Widespread.  Thirteen countries, namely, Australia, Hungary, Israel, Italy, Japan, the Netherlands, Norway, South Africa, Spain, Taiwan, Turkey, the United Kingdom and the USA (Abad et al., 2014).

In the USA, Phytophthora niederhauserii has been found in California, North Carolina, South Carolina (Robayo-Camacho et al., 2009; Farr & Rossman, 2014).

Official Control:  None reported.

California Distribution: Phytophthora niederhauserii has been detected in Santa Barbara County and counties within the San Joaquin Valley namely, Kings, Fresno, Kern, Merced, Stanislaus, Madera, San Luis Obispo and Tulare counties (CDFA Plant Pathology Database, 2007; Schmidt et al., 2012).

California Interceptions:  The pathogen has not been intercepted in quarantine shipments of plants.

The risk Phytophthora niederhauserii would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
– High (3) likely to establish a widespread distribution in California

Risk is High (3) – Phytophthora niederhauserii has already been detected in few nurseries in California and has been reported (Schmidt et al., 2012) as an aggressive pathogen of almonds in the San Joaquin Valley of California.  Within California, it is likely to establish in cool, wet climates in susceptible hosts.

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

Risk is Medium (2) –Currently at least 33 plant species in 25 families have been reported as hosts of the pathogen.  A number of shrubs and herbaceous ornamental plants are included. Few agricultural crops (almonds and grapes) are also included.  The latter are grown as major crops in California.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– Low (1) does not have high reproductive or dispersal potential
– Medium (2) has either high reproductive or dispersal potential
– High (3) has both high reproduction and dispersal potential

Risk is High (3) – Phytophthora niederhauserii is primarily spread artificially via infested soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts
– Medium (2) causes 2 of these impacts
– High (3) causes 3 or more of these impacts

Risk is High (3) – The pathogen could lower crop yield, increase production costs and cause loss of market of infected nursery stock and agricultural crops. The capability of the pathogen to survive and spread in infected soils and irrigation water could require changes in normal cultivation practices of host plants.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur
– Medium (2) causes one of the above to occur
– High (3) causes two or more of the above to occur

Risk is High (3) – A number of plants in natural ecological habitats are hosts to the pathogen.  Subsequently, natural plant communities, ecosystems, threatened or endangered species as well as home/urban gardening and ornamentals may be negatively impacted.

Consequences of Introduction to California for Phytophthora niederhauserii:

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Phytophthora niederhauserii to California = (14).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is High (-3). In California, Phytophthora niederhauserii has been detected in Santa Barbara County and the San Joaquin Valley counties.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11.

Uncertainty:

Statewide surveys specifically for Phytophthora niederhauserii have not been conducted to include all nursery sites and natural ecosystems (e.g., restoration sites) as well as almond and grapevine cultivation sites.  Subsequent data generated may result in the addition of new host plant species and further distribution of the pathogen within California.  All this may alter the current proposed rating of P. niederhauserii.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora niederhauserii is B.

References:

Abad Z. G, and J. A. Abad.  2003.  Advances in the integration of morphological and molecular characterization in the genus Phytophthora: the case of P. niederhauseria sp.nov. Phytopathology 408 93:S1.

Abad, Z. G., J. A. Abad, S. O. Cacciola, A. Pane, R. Faedda, E. Moralejo, A. Pérez-Sierra, P. Abad-Campos, L. A. Alvarez-Bernaola, J. Bakonyi, A. Józsa, M. L. Herrero, T. I. Burgess, J. H. Cunnington, I. A. Smith, Y. Balci, C. Blomquist, B. Henricot, G. Denton, C. Spies, A. Mcleod, L. Belbahri, D. Cooke, K. Kageyama, S. Uematsu, I. Kurbetli and K. Keğirmenci.  2014.  Phytophthora niederhauserii sp. nov., a polyphagous species associated with ornamentals, fruit trees and native plants in 13 countries.  Mycologia, 106 (3): 431-447.

Agrios, G. N.  2005.  Plant Pathology fifth edition.  Elsevier Academic Press, Massachussetts, USA.  922 p.

Farr, D.F., & Rossman, A.Y.  2014.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved November 10, 2014, from http://nt.ars-grin.gov/fungaldatabases/

Jo´zsa A, J. Bakonyi, L. Belbahri, ZA Nagy, A. Szigethy, G. Boha´r and S.Woodward. 2010. A new species of Phytophthora reported to cause root and collar rot of common boxwood, Nordmann fir and Port Orford cedar in Hungary. Plant Pathology 59:1166–1167.

Pe´rez-Sierra A, A. Leo´n, LA A´ lvarez, S.Alaniz, M. Berbegal, J. Garcı´a- Jime´nez, P. Abad-Campos. 2010. Outbreak of a new Phytophthora sp. associated to severe decline of almond trees in eastern Spain. Plant Disease 94:534–541.

Robayo-Camacho E, Hwang J, Jeffers SN.  2009.  A diversity of species of Phytophthora found on floriculture crops.  Phytopathology 99:S109, doi:10.1094/PHYTO-99-1-0109

Schmidt, L. S., R. G. Bhat, D. A. Kluepfel and G. T. Browne.  2012.  Resistance to Phytophthora in new rootstocks for almond and stone fruits.  Phytopathology, 102:S4.106.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Phytophthora siskiyouensis Reeser & E. M. Hansen, 2008

California Pest Rating for
Phytophthora siskiyouensis Reeser & E. M. Hansen, 2008
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

In October 2014, Suzanne Latham, CDFA plant pathologist detected the oomycete, Phytophthora siskiyouensis which was isolated from a diseased alder tree with a bleeding trunk canker in Mill Valley, Marin County, California.  A few months earlier, the pathogen had been detected in some diseased Italian alder trees in Richmond, Contra Costa County, and originally in 2006 from a large planting of Italian alder trees in Foster City, San Mateo County. These detections in California first noted the capability of P. siskiyouensis to cause detrimental disease in alder. Subsequently, there is a need to reevaluate the current status and pest rating of P. siskiyouensis for the proposal of a permanent rating.

History & Status:

Background: Since the discovery of Phytophthora ramorum, causal organism for the Sudden Oak Disease, there has been an increase of surveys throughout the world, for Phytophthora spp. which resulted in the identification of several new species, including P. siskiyouensis.  Phytophthora siskiyouensis was first discovered in 2007 in streams and soils in native forest within sudden oak death epidemic regions of coastal southwest Oregon (Reeser, et al., 2007).  It appears to occur naturally in native forests in south west Oregon and was later found associated with a blighted myrtlewood shoot growing near ground level, and infrequently from tanoak bark cankers.  Furthermore, it was found in Oregon nurseries as a pathogen of alder planting stock but was not observed to cause disease on red alder in natural environments where it was detected in soil and streams (Hansen, et al., 2011; Reeser, et al., 2007).

In California, Phytophthora siskiyouensis was first found associated with bleeding trunk cankers in dying Italian alder trees in Foster City, San Mateo County (Rooney-Latham et al., 2009). In pathogenicity tests, the pathogen was confirmed to be pathogenic on Italian alder trees and potentially pathogenic to red and white alder trees.  Furthermore, it was only detected in tree bark and vascular tissue lesions and not from associated soil and root samples of the diseased trees.  The pathogen was also reported to be associated with dying alder trees in a garden in Melbourne, Australia, but as in California, was not detected in soil around the diseased trees (Smith et al., 2004).  Presently, it is not known if Phytophthora siskiyouensis is endemic to or was introduced to California.

Hosts: Presently, the full range of Phytophthora siskiyouensis is not known.  Reported hosts include, Italian alder (Alnus cordata), European common alder (A. glutinosa), White alder (A. rhombifolia), tanoak (Notholithocarpus densiflorus), California bay laurel/Myrtlewood (Umbellularia californica), and in forest streams or soil (Hansen, et al., 2011; Rooney-Latham et al., 2009; Smith et al., 2004). In pathogenicity tests, Smith et al., (2004) determined that P. siskiyouensis was a potential weak pathogen of Citrus, Acacia, and Eucalyptus seedlings.

Symptoms:  The pathogen causes collar rot in Italian alder trees.  Predominant symptoms produced on alder trees include sparse foliage, dieback in the canopy, and bleeding cankers on the trunks. Canker form primarily at the bases of trunks near the soil line and extend upwards.  Few isolated cankers may form about 2 meters above the soil line.  Trunks may have several small spots or large areas with bleeding lesions which are dark-brown to black on the outer bark.  Below the outer bark, diseased, dark orange-brown tissue is present.  A cinnamon-brown margin is separates cream-colored healthy tissue from diseased tissue which extends through the bark to the vascular cambium and sapwood interface.   Trees with large cankers may show dieback of the canopy however, cankers are not always produced on trees showing dieback (Rooney-Latham, et al., 2009; Sims, 2012). Reeser et al., (2007) noted that in Oregon the pathogen was associated with occasional symptoms on a variety of plants.

Damage Potential: Currently, there are no reports on quantitative economic losses in plant production caused by Phytophthora siskiyouensis. While infected native trees in Oregon occasionally resulted in apparent symptoms on a variety of associated plants, including trunk cankers on tanoaks, the pathogen was found to kill alder trees in California and Australia.  Infestations may result in significant damage and loss in production and stands of host plants by causing collar rot of infected plants. The full host range for this pathogen is yet not known, nevertheless, nursery alders in particular, and plants grown in natural ecosystems are particularly affected.  In general for Phytophthora spp., young seedlings of trees and annual plants may be killed within a few day, weeks or months (Agrios, 2005).

Disease Cycle: Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as thick-walled, resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  During spring, the oospores and chlamydospores germinate to produce motile spores (zoospores) that swim around in soil water and roots of susceptible hosts. The pathogen infects the host at the soil line causing water soaking and darkening of the trunk bark. This infected area enlarges and may encircle the entire stem of small plants which wilt and eventually die.  On large plants and trees, the infected, necrotic area may be on one side of the stem and become a depressed canker below the level of the healthy bark.  Collar rot canker may spread down the root system. Roots are invaded at the crown area or at ground level.   Mycelium and zoospores grow in abundance in cool, wet weather causing damage where the soil is too wet for normal growth of susceptible plants and low temperatures (15-23°C) prevail (Agrios, 2005).

Transmission:  The pathogen may be spread to non-infected sites through infected plants, nursery and planting stock, seedlings, soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment and tools.

Worldwide Distribution:  North America: USA; Oceania: Australia.

In the USA, Phytophthora siskiyouensis has been found in California and Oregon (CABI, 2014).

Official Control:  None reported.

California Distribution:  Phytophthora siskiyouensis has been detected on alder in Contra Costa, Marin, and San Mateo Counties (see ‘Initiating Event’).

California Interceptions:  The pathogen has not been intercepted in quarantine shipments of plants.

The risk Phytophthora siskiyouensis would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
– High (3) likely to establish a widespread distribution in California

Risk is High (3) – Phytophthora siskiyouensis has already been detected in few counties.  Within California, it is likely to establish in cool, wet climates in susceptible hosts.  Thus far it has only been detected in alder trees in California.

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

Risk is Low (1) – The full host range of Phytophthora siskiyouensis is yet not known.  Reported hosts include, Italian alder, European common alder, white alder, tanoak, and California bay laurel.  It has also been detected in forest streams or soil in Oregon.  Experimentally, it has been shown to be a weak pathogen of Citrus, Acacia and Eucalyptus seedlings.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– Low (1) does not have high reproductive or dispersal potential
– Medium (2) has either high reproductive or dispersal potential
– High (3) has both high reproduction and dispersal potential

Risk is High (3) – Phytophthora siskiyouensis is primarily spread artificially via infested soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites. Thus far, in California, the pathogen has not been isolated from roots and associated soil of infected alder trees.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts
– Medium (2) causes 2 of these impacts
– High (3) causes 3 or more of these impacts

Risk is High (3) – Although quantitative economic losses in plant production have not reported, the potential for infected alder  plants to result in collar rot, trunk cankers, and shoot dieback could decrease stands on non-infected plants, increase production costs and cause loss of market of infected  nursery stocks. The potential for the pathogen to survive and spread in infected soils and irrigation water could require changes in normal cultivation practices of host plants.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur
– Medium (2) causes one of the above to occur
– High (3) causes two or more of the above to occur

Risk is Medium (2) – Currently, the host range and geographic distribution of P. siskiyouensis are not fully known.  The few known host plants (see ‘Hosts’ above) can be found in natural ecological habitats as well as in nursery environments.  Alder trees are particularly affected by this pathogen.  Subsequently, under favorable climate conditions, natural plant communities and ecosystems, as well as home/urban gardening and ornamentals may be negatively impacted.

Consequences of Introduction to California for Phytophthora siskiyouensis:

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Phytophthora siskiyouensis to California = (12).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.
–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Low (-1). To date, Phytophthora siskiyouensis has been detected in three California coastal counties (Contra Costa, Marin and San Mateo Counties) on alder (Alnus sp.) under similar climate (north coastal environment).

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11.

Uncertainty:

The full host range and in-state distribution of Phytophthora siskiyouensis is not currently known.  To date, in California, the pathogen has only been detected from alder trees in three northern coastal counties.  Continued statewide surveys for Phytophthora spp. occurring in nurseries and natural ecosystems (e.g. restoration sites) will contribute to the present knowledge of this pathogen group as well as that of P. siskiyouensis.  Also, it is not known if P. siskiyouensis is endemic to California or was introduced. Related information gained through further research may affect the current proposed rating of P. siskiyouensis.  

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora siskiyouensis is B.

References:

Agrios, G. N.  2005.  Plant Pathology fifth edition.  Elsevier Academic Press, Massachussetts, USA.  922 p.

CABI.  2014.  Phytophthora siskiyouensis datasheet (basic) report.  Crop Protection Compendium.  www.cabi.org/cpc/

Farr, D.F., & Rossman, A.Y.  2014.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved November 10, 2014, from http://nt.ars-grin.gov/fungaldatabases/ .

Hansen, E. M., P. Reeser and S. Rooney-Latham.  2011.  Phytophthora siskiyouensis.  Forest Phytophthoras 1(1). doi: 10.5399/osu/fp.1.1.1826

Reeser, P. W., E. M. Hansen and W. Sutton.  2007.  Phytophthora siskiyouensis, a new species from soil, water, myrtlewood (Umbellularia californica) and tanoak (Lithocarpus densiflorus) in southwestern Oregon.  Mycologia 99:639-643.

Reeser, P. W., Sutton, W., and Hansen, E. M. 2008. Phytophthora species causing tanoak stem cankers in southwestern Oregon. Plant Dis. 92:1252.

Rooney-Latham, S., C. L. Blomquist, T. Pastalka and L. R. Costello.  2007.  First report of Phytophthora siskiyouensis causing disease on Italian alder in Foster City, California.  Phytopathology 97:S101.

Rooney-Latham, S., C. L. Blomquist, T. Pastalka and L. Costello.  2009.  Collar rot on Italian alder trees in California caused by Phytophthora siskiyouensis.  Online. Plant Health Progress doi:10.1094/PHP-2009-0413-01-RS. http://www.plantmanagementnetwork.org/pub/php/research/2009/alder/ .

Sims, L.  2012.  Alder (Alnus spp.) – Collar Rot {Phytophthora Canker}.  PNW Plant Disease Management Handbook Printed page URL: pnwhandbooks.org/plantdisease/node/6703 http://pnwhandbooks.org/plantdisease/node/6703/print

Smith, I. A., Cunnington, J., and Pascoe, I. 2004. Another new? species of Phytophthora on alder down under (Australia). P. of the IUFRO Res. Work. Gr. Conf. on Phytophthora Forests and Natural Ecosystems. 11-17 September 2004. Freising, Germany.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Kweilingia divina (Syd.) Buriticá 1998

California Pest Rating for
Kweilingia divina (Syd.) Buriticá 1998
Pest Rating: A
PEST RATING PROFILE
Initiating Event: 

In December 2014, Kweilingia divina was detected in a quarantine interception of bamboo leaves showing symptoms of rust, imported from Florida to California.  The detection was made by Contra Costa Agricultural Commissioner’s office inspector and the associated pathogen was identified by Suzanne Latham, CDFA plant pathologist. This rust fungus had also been intercepted in 2006 by Los Angeles County in a similar shipment of bamboo from Hawaii.  All infected plants were destroyed.  The risk of introduction and establishment of Kweilingia divina in California is evaluated here and a permanent rating is proposed.

History & Status:

Background:  The bamboo rust fungal pathogen, Kweilingia divina was originally ascribed as the type species of the genus Dasturella (D. divina) which was detected in infected bamboo leaves (Bambusa sp.) in 1943 (Mundkur & Kheswalla, 1943).  However, in 1998, Dasterulla divina was renamed Kweilingia divina.

Kweilingia divina requires two different kinds of hosts to complete its life cycle (heteroecious), producing two types of specialized spores on each host, namely urediniospores and teliospores on bamboo and spermatia (pycniospores) and aeciospores on its alternate host, Catunaregam spinosa (mountain pomegranata). The pycnial and aecial state are not known in the New World (Farr & Rossman, 2015).

Hosts: Several species of bamboo including, Bambusa balcooa, B. bambos, B. domestica, B. multiplex, B. mutabilis, B. oldhami, B. polymorpha, B. tulda, B. shimadai, B. tuldoides, B. vulgaris, Dendrocalamus brandisii, D. hamiltonii, D. latiflorus, D. longispathus, D. strictus, Ischurochloa stenostachya, Ochlandra scriptoria, O. travancorica, Oxtenanthera sp.,O. abyssinica, O. nigrociliata, Phyllostachys bambusoides,Pleioblastus sp., Pseudoxytenanthera ritcheyi, Pseudosasa japonica var. usawai, P. usawai, Shibataea kumasaca,  Thyrsostachys oliveri, T. sianensis, and the alternate, non-bamboo host Catunaregam spinosa (Blomquist et al., 2009; Cummins, 1971; Nelson & Goo, 2011; Farr & Rossman, 2015).

Symptoms: On bamboo, initial symptoms of infection are the presence of water-soaked, pinhead-sized flecks on the lower surface of leaves.  Soon yellowish-orange to brown, elongate, interveinal, linearly aligned fruiting structures (uredinia) develop and produce urediniospores.  On the corresponding side of the upper leaf surface, grayish-brown to dark brown lesions with yellowish halos for along the parallel veins.  Numerous lesions may develop on a leaf surface or coalesce to form larger areas of tan-colored necrotic blight. Over time, brownish black linear structures (telia) develop within the lesions on the lower leaf, either inside old, degenerating uredinia or separately.  Severely infected leaves defoliate prematurely (Nelson & Goo, 2011).  The alternate host, Catunaregam spinosa is not present in California but is native to tropical Southeast Asia and tropical Africa.

Damage Potential:  Bamboo is not a main cultivated crop in California.  However, bamboo plants are grown and sold mainly as nursery ornamentals and commercial plantings in private residences, public parks, amusement parks, and other environments.  The bamboo rust disease is a threat to these limited yet economically important regions where bamboo is grown in California.  Rusted bamboo leaves are not only aesthetically unsightly but also negatively impact plant growth.  Severe infestations of bamboo rust can result in defoliation and reduction in plant growth, vigor and stand.  Once established in California, containment and management of the rust pathogen will be difficult as infected leaves produce masses of air-borne spores enabling long-range spread and infection.

Transmission:  The pathogen is spread from plant to plant mainly by windblown spores.  Urediniospores can be transported over several hundred kilometers by strong winds and washed down by rain to available hosts.  Insects, animals, humans, and rain may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Worldwide Distribution: Asia: India, China, Hong Kong, Japan, Pakistan, Taiwan, Malaysia; Africa: Cote d’Ivoire, Ghana, Nigeria,    North America: Mexico, USA; Oceania: Australia, New Calendonia, Samoa; Caribbean Islands: Cuba, Dominican Republic, Jamaica, Puerto Rico, Trinidad and Tobago, West Indies, Virgin Islands; Central America: Costa Rica; South America: Brazil, Guyana, Colombia, French Guiana (Farr & Rossman, 2015).

In the USA it has been reported from the Hawaiian Islands (Oahu, Hawaii, Kauai, and Maui).  The detections in California resulted in the eradication of the disease (Blomquist et al., 2009; Nelson & Goo, 2011).

Official Control: None reported.

California Distribution:  Bamboo rust pathogen, Kweilingia divina, is not established in California.  All 2006 and 2014 intercepted shipments of infected bamboo plants were destroyed (see ‘Initiating Event’).

California Interceptions:  Kweilingia divina was intercepted in Los Angeles in 2006 and in Contra Costa County in 2014.

The risk Kweilingia divina would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

Risk is High (3) – Kweilingia divina is able to establish a widespread distribution in California wherever bamboo is grown.

2)  Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

Risk is Low (1) – The host range of Kweilingia divina is mainly limited to several species of bamboo. The alternate host does not exist in California.

3)  Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.

 Risk is High (3) – The infective spores of Kweilingia divina namely, urediniospores, are produced in abundance and are spread to healthy plants mainly by wind. Insects, animals, humans, rain, and infected nursery plants  also aid in its spread.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.
B.  The pest could lower crop value (includes increasing crop production costs).
C.  The pest could trigger the loss of markets (includes quarantines).
D.  The pest could negatively change normal cultural practices.
E.  The pest can vector, or is vectored, by another pestiferous organism.
F.  The organism is injurious or poisonous to agriculturally important animals.
G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

Risk is High (3) – Severe infestations of the bamboo rust pathogen could result in defoliation and reduction of plant growth, vigor and stand, and loss of markets. Nursery plantings are at risk being significantly impacted by the introduction of this pathogen. Without eradicative action subsequent to detection of bamboo rust-infected plants within greenhouse environments, there is the risk of spread to the outside environment. The spread of the rust pathogen would be difficult to manage due to its effective means of windblown transmission.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.  The pest could directly affect threatened or endangered species.
C.  The pest could impact threatened or endangered species by disrupting critical habitats.
D.  The pest could trigger additional official or private treatment programs.
E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

Risk is High (3) – Outbreaks of the disease could have significant impact on established bamboo ecosystems. Commercial bamboo plantings in public parks, resorts and plantings in private residences may be impacted by the bamboo rust pathogen subsequently triggering additional treatment programs.

Consequences of Introduction to California for Kweilingia divina

Add up the total score and include it here. (Score)

-Low = 5-8 points
-Medium = 9-12 points
-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Kweilingia divina to California = (13).

6)  Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation: Kweilingia divina is not established in California (0). 

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 13

Uncertainty:

Future detection surveys for Kweilingia divina in nurseries and established bamboo groves are needed to gain further information of the probable introduction, establishment and distribution of this pathogen in California.  This information could alter the proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Kweilingia divina is A.

References:

Blomquist, C. L., J. M. McKemy, M. C. Aime, R. W. Orsburn and S. A. Kinnee.  2009.  First report of bamboo rust caused by Kweilingia divina on Bambusa domestica in Los Angeles County, California.  Plant Disease 93: 201. http://dx.doi.org/10.1094/PDIS-93-2-0201A

Cummins, G. B. 1971.  The rust fungi of cereals, grasses and bamboos.  Springer-Verlag New York Inc.  570 p.

Farr, D. R., and A. Y. Rossman.  2015.  Fungal databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 18, 2015, from http://nt.ars-grin.gov/fungaldatabases/

Johnson, G. I.  1985.  Rust (Dasturella divina) of Bambusa spp. in Australia.  Australasian Plant Pathology 14:54-55.

Mundkur, B.B., and K. F. Kheswalla. 1943. Dasturella: A New Genus of Uredinales. Mycologia 35:201–206.

Nelson, S., and M. Goo.  2011.  Kweilingia rust of bamboo in Hawaii.  College of Tropical Agriculture and Human Resources, University of Hawaii at Mānoa. Plant Disease PD-74.

Responsible Party:

Dr. John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Pest Rating: A

Posted by ls

Fungi, Plant Pathogens

Colletotrichum orbiculare (Berk. & Mont.) Arx 1957

California Plant Pest Rating for
Colletotrichum orbiculare (Berk. & Mont.) Arx 1957
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None. A permanent rating for Colletotrichum orbiculare is proposed herein.

History & Status:

Background: Colletotrichum orbiculare is a fungal pathogen causing anthracnose disease of cucurbit plants particularly watermelon, cantaloupe, and cucumber. The species is often known by its synonymized scientific name, Colletotrichum lagenarium and belongs to the taxonomic family Glomerellaceae, within the phylum Ascomycota. C. orbiculare is the asexual (anamorph) stage of the pathogen. The sexual stage (telemorph) with the name Glomerella lagenarium has been reported but is rarely found in nature. Two distinct populations of the pathogen are known: one from watermelon (race 1) and the other from cucumber and melon (race 1 and 3) (Sitterly & Keinath, 1996).

Hosts: The pathogen commonly attacks members of the family Cucurbitaceae, especially melon and watermelon. Hosts include Althaea officinalis (marsh-mallow), Artocarpus heterophyllus (jackfruit), Benincasa hispida (wax gourd), Citrullus lanatus (watermelon), Cucumis melo (melon), Cucumis sativus (cucumber), Cucurbita maxima (giant pumpkin), C. moschata (pumpkin), C. pepo (ornamental gourd), Momordica charantia (bitter gourd) and Trichosanthes cucumerina var. anguinea (snake gourd) (CABI, 2014).

Symptoms: Host plants infected with Colletotrichum orbiculare exhibit symptoms of anthracnose and fruit rot. In California, except for seedless watermelon, anthracnose is unusual on cucurbit crops and can cause leaf, fruit, and/or stem lesions. On cucurbits, leaf spots are usually large (>10 mm diameter) and tan to pale brown with distinct margins. However on watermelon, these foliage lesions are dark brown to black. Brown or black lesions appear on fruit. These lesions grow to 20-30 mm diameter, become sunken, wrinkled and dark, with concentric rings of sub-surface, tiny, black, saucer-shaped asexual structures that containing spores or conidia (acervuli). In wet weather, pink or orange spores ooze from these asexual structures (CABI, 2014; UCIPM, 2008). Fruit is susceptible to infection approximately at the time of ripening and severely infected fruits are often tasteless or bitter and usually invaded by soft rotting bacteria and fungi (Agrios, 2005).

Damage Potential: Anthracnose disease caused by Colletotrichum orbiculare has recently been considered to be particularly important wherever cucurbits are cultivated under highly controlled conditions. High infections may cause formation of numerous leaf lesions and vine defoliation resulting in poor quality fruit and yield loss (Egel, 2014). Watermelon artificially inoculated with C. orbiculare (as C. lagenarium) caused up to 63% losses in yield (CABI, 2014).

Disease Cycle: The species has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on cucurbit plant residue in soil, on infected volunteer plants, and on or in cucurbit seed. During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers. Conidia are transmitted to host plants. Humid, wet, rainy weather is necessary for infection to occur. Condia germinate and grow optimally at 22-27°C and 100% relative humidity for 24 hours. These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem in transplants grown under controlled environments of greenhouses. Condia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue up to 72 hours after deposition. Symptoms are produced about 96 hours after infection. The sexual stage (telemorph) is rarely found in nature (Sitterly & Keinath, 1996).

Transmission: Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution: Colletotrichum orbiculare is widely distributed throughout the world and has been reported from several countries in Asia, Africa, North America, South America, Central America and Caribbean, Europe and Oceania. In the USA it has been found in Alabama, California, Colorado, Connecticut, Florida, Hawaii, Illinois, Indiana, Iowa, Kansas, Louisiana, Maryland, Minnesota, Mississippi, Nebraska, North Carolina, North Dakota, Oklahoma, Pennsylvania, South Carolina and Texas (CABI, 2014; Farr et al., 1989).

Official Control: Currently Israel, Chile and Jordan include Colletotrichum orbiculare on their Harmful Organism List.

California Distribution: in California, Colletotrichum orbiculare has been detected in a greenhouse in Tehama County (Koike et al., 1991).

Historically, it has also been detected in southern coastal region counties which include: San Benito, Monterey, San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Orange and San Diego Counties (K. F. Baker Herbarium, CDFA in The California Plant Disease Host Index by A. M. French, 1989).

Details of the south coastal region detections are not available. Given the absence of reports on the field detection of the pathogen in California, it is likely that the south coastal region detections were mainly limited to greenhouses. On the other hand, those south coastal counties would share a similar climate including higher incidence of rainfall and wind driven rain necessary for infection and establishment of the disease.

California Interceptions: The pathogen has not been intercepted in quarantine shipments of plants.

The risk Colletotrichum orbiculare would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

Risk is Low (1) – Colletotrichum orbiculare requires humid, wet, rainy weather for conidia to infect host plants. This is a main reason why the pathogen has not been able to fully establish and spread under dry field conditions in California. It has, however, been detected in controlled greenhouse environments.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

Risk is Moderate (2) – Although the host range for Colletotrichum orbiculare is mainly limited to members of the family Cucurbitaceae, plants, the cultivation of cucurbits, mainly melon and watermelon, is in significant acreage and of major importance in California.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively. They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A.   The pest could lower crop yield.
B.   The pest could lower crop value (includes increasing crop production costs).
C.   The pest could trigger the loss of markets (includes quarantines).
D.   The pest could negatively change normal cultural practices.
E.   The pest can vector, or is vectored, by another pestiferous organism.
F.   The organism is injurious or poisonous to agriculturally important animals.
G.   The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

Risk is High (3) – Under suitable climates, the pathogen could lower crop yield, value and trigger the loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A.   The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.   The pest could directly affect threatened or endangered species.
C.   The pest could impact threatened or endangered species by disrupting critical habitats.
D.   The pest could trigger additional official or private treatment programs.
E.   The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The pathogen could significantly impact cultural practices, home gardening or ornamental plantings.

Consequences of Introduction to California for Colletotrichum orbiculare:

Add up the total score and include it here. (Score)

–  Low = 5-8 points
–  Medium = 9-12 points
–  High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum orbiculare to California = (11).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–  Not established (0) Pest never detected in California, or known only from incursions.
–  Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
–  Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
–  High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Medium (-1). Colletotrichum orbiculare has been reported from counties in the California’s south coastal region however, details of those detections are not available. Given the absence of reports on the field detection of the pathogen in California, it is likely that the south coastal region detections were mainly limited to greenhouses. Nevertheless, those south coastal counties would share a similar climate including higher incidence of rainfall and wind driven rain necessary for infection and establishment of the disease.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score: Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10.

Uncertainty:

As discussed above, there is little to no verifiable evidence of the occurrence of Colletotrichum orbiculare in field environments within California. Such information may strengthen or lower the proposed rating for this pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose of cucurbits pathogen, Colletotrichum orbiculare is B.

References:

Agrios, G. N. 2005. Plant Pathology (Fifth Edition). Elsevier Academic Press, USA. 922 p.

CABI. 2014. Colletotrichum orbiculare datasheet report. Crop Protection Compendium. www.cabi.org/cpc/

Egel, D. S. 2014. Vegetable diseases: Anthracnose of cucumber, muskmelon, and watermelon. Purdue Extension BP-180-W, Purdue University. https://www.extension.purdue.edu/extmedia/BP/BP-180-W.pdf

Farr, D. F, G. F. Bills, G. P. Chamuris and A. Y. Rossman. 1989. Fungi on Plants and Plant Products in the United States. St. Paul, Minnesota, USA: APS Press, 1252 pp.

Kitterly, W. R., and A. P. Keinath. 1996. Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’. Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Koike S. T., T. E. Tidwell, D. G. Fogle and C. L. Patterson. 1991. Anthracnose of greenhouse-grown watermelon transplants caused by Colletotrichum orbiculare in California. Plant Disease, 75(6):644.

UCIPM. 2008. Cucurbits anthracnose pathogen: Colletotrichum lagenarium. UCIPM Online, Statewide Integrated Pest Management Program, University of California Agriculture & Natural Resources. http://www.ipm.ucdavis.edu/PMG/r116101411.html

Responsible Party:

Dr. John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Pest Rating: B

Posted by ls