Marasmiellus Palmivorus

California Pest Rating for

Marasmiellus palmivorus (Sharples) Desjardin comb. prov.

Pest Rating: C

PEST RATING PROFILE

Initiating Event:

None. The risk of infestation of M. palmivorus in California evaluated and a permanent rating is herein proposed.

History & Status:

Background: Marasmiellus palmivorus is a Basidiomycete fungus in the order Agaricales. The species was described by Sharples in 1936, but, in the 1920s, was reported to have caused significant losses to oil palm and coconut in Malaysia 1920 (Pong et al., 2012). In 1980, specimens of the fungus from coconut and oil palm were initially identified as Marasmiellus semiustus, a species that is generally regarded synonymous with M. palmivorus (CABI, 2018). There has been confusion over the taxonomy of M. palmivorus and the species was previously attributed to the genus Marasmius (palmivorus). However, Hemmes and Desjardin (2002) and Wilson and Desjardin (2005), in their taxonomic revision of the genus, regarded the genus Marasmius as a synonym of Marasmiellus until further DNA phylogenetic analysis is done to support its accurate identification (Pong et al., 2012).

Marasmiellus palmivorus can be saprophytic on a range of dead and dying plant material, or parasitic on tropical plants. The species is reported to cause bunch rot disease on oil palm fruit, seeds, and seedlings in Malaysia (Almaliky et al., 2012; Pong et al., 2012), and is associated with leaf infection and bud rot of coconut, also causing embryo and shoot rot in germinating nuts and post-emergence damping off disease in Malaysia (Amaliky et al., 2013; CABI, 2018). Synonymous species of M. palmivorus have also been recorded on pineapple causing trunk and root rot, and root rot of maize and sugarcane (CABI, 2018). In Hawaii, M. palmivorus was listed as a wood-rotting basidiomycete fungus of native and exotic plant species (Gilbertson et al., 2002).

In California, during March 2017, Marasmiellus palmivorus was detected on ginger flower stems from a shipment of ginger cut flowers that originated in Hawaii and was intercepted in Humboldt County by Humboldt County Agricultural officials. The pathogen was identified at the CDFA Plant Pathology Lab and was given a Q rating, which resulted in the destruction of the shipment. The pathogen is not known to be established in California.

Disease Development: The fungus is normally saprophytic on decaying and dead materials. It spreads to a new food source by growth of its hyphal strands or rhizomorphs and requires plenty of moisture for growth and development. Not much is known of the biology of the fungus. It is presumed that the fungus becomes parasitic once it has attained a certain inoculum level as infection by a small amount of spores or mycelium is unlikely (Turner, 1981 in CABI, 2018).

Dispersal and spread: Infected plants including flowers, fruits, leaves, roots, stems, true seeds, wood, contaminated coconut seed-nuts, plant decaying and dead materials, windblown rain, water-splash, air-currents (CABI, 2018).

Hosts: Ananas comosus (pineapple), Alpini purpurata (red ginger), Cocos nucifera (coconut), Elaeis guineensis (African oil palm), Etlingera elatior (torch ginger), Hevea brasiliensis (rubber), Musa x paradisiaca (plantain), Zingiber officinale (ginger) (Almaliky et al., 2012, 2013; CABI, 2017; Farr & Rossman, 2017; Gilbertson et al., 2002).

Symptoms: Marasmiellus palmivorus causes bunch rot disease of oil palm in Malaysia. In pathogenicity tests conducted by Almaliky et al. (2012), symptoms in fruit included a wet, discolored soft rot that extended upward to the tip of the fruit; infected seeds showed pre-emergence damping off consisting of seed decay, reddish-brown discoloration of shoots and radicles, failure to germinate, and post-emergence damping off; infected seedling initially showed chlorosis that turn brown to black rot lesions on the base of lower leaves, and roots were usually soft, rotten, water-soaked and dark brown or black in color with white mycelia covering the roots and crowns partially. Seedlings reared in a greenhouse developed root and crown rot and leaf blight. Initial necrosis at the bases of leaves subsequently caused extensive discoloration, softening, rapid drying and wilting of leaves. Rotting of seedlings initiated near the soil line and moved downwards and upwards resulting in parts of stems and base of leaves turning brown to black in color. . Dense white mycelia were formed on the lower stem of base of seedlings. Basidiocarps (mushroom-like fruiting bodies) were formed at the base of seedlings near the crown. The fungus also caused post-emergence damping off on coconut seedlings in Malaysia (Almaliky et al., 2013). The researchers also showed that isolates from coconut were pathogenic to oil palm.

Damage Potential: In California, certain hosts, such as, ginger and plantain that are grown as ornamental plants by nurseries, small businesses, hobbyists, and private residents may be affected by the fungus if it were able to establish within high moisture environments.

Worldwide Distribution: Africa: Congo Democratic Republic, Nigeria; Asia: Brunei Darussalam, India (Andaman and Nicobar Islands), Indonesia, Malaysia; Central America and Caribbean: Trinidad and Tobago, North America: USA (Hawaii), South America: Colombia; Oceania: Fiji, Papua New Guinea (CABI, 2017; Farr & Rossman, 2017; Gilbertson et al., 2002).

Official Control: Marasmiellus palmivorus is on the ‘Harmful Organism’ lists for Guatemala, Nicaragua, and Peru (USDA-PCIT, 2017).

California Distribution: Marasmiellus palmivorus has not been reported from California.

California Interceptions: To date, Marasmiellus palmivorus has been detected once in a single shipment of ginger cuttings that were shipped from Hawaii and intercepted in Humboldt County.

The risk Marasmiellus palmivorus would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Marasmiellus palmivorus requires high amounts of moisture to grow and develop. It may be able to establish only in very limited areas of the State, if at all.

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

Score: 1

– 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 host range is limited to some tropical plants that include, pineapple, African oil palm, coconut, plantain, rubber, and ginger. It is also a saprophytic and feeds on dead and decaying material. Presently, its pathogenicity has only been reported on coconut and Oil palm.

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: Infected plants including flowers, fruits, leaves, roots, stems, true seeds, wood, contaminated coconut seed-nuts, plant decaying and dead materials, windblown rain, water-splash, air-currents.

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: Potential losses to oil palm in Malaysia have only been reported. Economic impact due to the fungus are largely not known. Most hosts of the fungus are not commercially grown in California. Other hosts, such as, ginger and plantain that are grown as ornamental plants by nurseries may be affected by the fungus if it were able to establish within high moisture environments.

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

Economic Impact: B

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: 1

– 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: Under high moisture environments, Marasmiellus palmivorus may impact ornamental plantings of host plants in home/urban gardens.

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 Marasmiellus palmivorus: Low (8)

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 ‘Not established’ in California.

Score: (0)

–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 = 8

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Marasmiellus palmivorus is C.

References:

Almaliky, B. S. A., M. A. Zainal Abidin, J. Kadir, and M. Y. Wong. 2012. Pathogenicity of Marasmiellus palmivorus (Sharples) Desjardin comb. prov. on oil palm Elaeis guineensis. Wulfenia 19: 1-17.

Almaliky, B. S. A., J. Kadir, M. Y. Wong, and M. A. Zainal Abidin. 2013. First report of Marasmiellus palmivorus causing post-emergence damping off on coconut seedlings in Malaysia. Plant Disease 97: 143.

CABI, 2017. Marasmius palmivorus (oil palm bunch rot) full datasheet. Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/34926

Farr, D. F., and A. Y. Rossman. 2017. Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved April 27, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Gilbertson, R. L., D. M. Bigelow, D. E. Hemmes, and D. E. Desjardin. 2002. Annotated check list of wood-rotting Basidiomycetes of Hawai’i. Mycotaxon 82: 215-239

Pong, V. M., M. A. Zainal Abidin, B. S. A. Almaliky, J. Kadir, and M. Y. Wong. 2012. Isolation, fruiting and pathogenicity of Marasmiellus palmivorus (Sharples) Desjardin (comb.prov.) in oil palm plantations in West Malaysia. Pertanika Tropical Agricultural Science 35 (S): 38-48.

USDA PCIT. 2017. USDA Phytosanitary Certificate Issuance & Tracking System. April 26, 2017, 5:04:18 pm CDT. https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

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.

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