Ramularia salviicola Tharp

California Pest Rating  for
Ramularia salviicola Tharp
Pest Rating: C

 


PEST RATING PROFILE
Initiating Event:

On April 14, 2017, sage (Salvia sp.) plants showing symptoms of leaf spots were detected in a nursery in San Luis Obispo County by County Agricultural officials.  A sample of diseased leaves was sent to the CDFA Plant Pathology Laboratory for diagnosis.  On April 24, 2017, Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen, Ramularia salviicola associated with the diseased leaf tissue.  The pathogen was assigned a temporary Z rating as it has been recorded earlier in California, but never assigned a rating.  Subsequently, the consequences of introduction and establishment of R. salviicola in California are assessed and a permanent rating is proposed herein.

History & Status:

Background:   Ramularia salviicola is a fungal pathogen that causes leaf spot disease in host plants.  This pathogen was first discovered on Salvia farinacea in Austin Texas (Tharp, 1915).   Since then, it has only been reported from California on black sage, hummingbird sage and an unknown sage species (French, 1989).

Hosts:  Ramularia salviicola is only known to infect Salvia spp. (sage) in the family Lamiaceae: Salvia farinacea (mealycup sage), S. mellifera (black sage), Salvia sp. (sage), S. spathacea (hummingbird sage) (Braun, 1998; Farr & Rossman, 2017).

Symptoms:  Leaf spots are produced on both sides of living leaves.  Spots are subcircular to irregular, 1-10 mm in diameter, occasionally coalescing, brown with indefinite margin or with a diffuse yellowish halo, and sometimes divide into zones (Braun, 1998).

Disease development and spread: While there is a paucity of information reported on the specific biology of Ramularia salviicola, it is likely to be similar to that of other species within the genus.  Clusters of conidiophores arise from leaf lesions (spots) producing conidia (asexual spores) on living leaves.  Conidia are airborne and are spread accordingly to nearby plants.  It is also likely that, similar to other Ramularia species causing leaf spot disease, R. salviicola is transmitted as mycelium within the integument of seed and by movement of infested soil (Daughtrey et al., 1995),

Dispersal and spread: Infected plants and nursery stock, seeds, airborne conidia (Daughtrey et al., 1995).

Damage Potential: Quantitative losses due to Ramularia salviicola have not been reported.  Reduction in photosynthetic area due to leaf spotting can be expected as well as leaf wilt, premature leaf drop, and reduced tree vigor may result.  Leaf spot damage caused by R. salviicola may significantly impact commercial production and marketing of nursery ornamental plants, as well as private productions.  Black sage and hummingbird sage are perennial shrubs that are native to California and confined mainly to the southern and central coastal counties (Calflora, 2017).  Several other species of Salvia are also cultivated throughout California, but have not yet been reported as hosts of the pathogen.

Worldwide Distribution: North America: USA (California, Texas) (Braun, 1998; Farr & Rossman, 2017).

Official Control:  No official control for Ramularia salviicola has been reported.

California Distribution:  Southern coastal counties including, San Luis Obispo County.

California Interceptions:  None.

The risk Ramularia salviicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: In California, Ramularia salviicola has already become established in southern coastal regions where its hosts, black sage and hummingbird sage, are mainly cultivated. While the pathogen has not been reported from other regions it is likely to establish a larger but limited part of the State.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– 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.

2) Known Pest Host Range: The pathogen has only been found on Salvia

Evaluate the host range of the pest.

Score: 1

Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Ramularia salviicola has high reproductive and dispersal potential. The pathogen is likely to be transmitted through movement of infected plants and nursery stock, integuments of seed and airborne conidia.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– 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.

4) Economic Impact: Ramularia salviicola causes leaf spot in sage plants.  While there is no information on quantitative crop loss caused by this pathogen, leaf spot disease could lower crop value and cause loss of markets.  Use of preventive chemical sprays and other control measures could increase production costs.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: B, C

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.

Economic Impact Score:  2

– 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.

5) Environmental Impact:  The pathogen could significantly impact ornamental plantings in home/ urban, public gardens and other recreational environments.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

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.

Environmental Impact Score: 2

– 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.

Consequences of Introduction to California for Ramularia salviicola:  Medium (10)

Add up the total score and include it here.

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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.

Evaluation is High (-3).

Score: -1

-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.

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:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Ramularia salviicola is C.

References:

Braun, U. 1998. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 2.  IHW-Verlag 2: 439.

Calflora.  2017.  Information on California plants for education, research and conservation. [web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

Daughtery, M. L., R. L. Wick, and J. L. Peterson.  1995.  Cyclamen stunt and Ramularia leaf spot of Cyclamen and Primula.  In Compendium of Flowering Potted Plant Diseases.  APS Press, The American Phytopathological Society.  Page 20.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved June 5, 2017, from http://nt.ars-grin.gov/fungaldatabases/

French, A.M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).


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.

Comment Period: CLOSED

June 29, 2017 – August 13, 2017


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Pest Rating: C


Posted by ls