Freesia Mosaic Virus

California Pest Rating for
Freesia Mosaic Virus
Pest Rating: B

Initiating Event:

On March 21, 2016, two samples of diseased Lilium sp. (lily) plants exhibiting leaf spots, were collected from a nursery in San Luis Obispo County, during a regulatory nursery inspection by San Luis Obispo County Agricultural officials, and sent to the CDFA Plant Pathology Laboratory for analysis.  Tongyan Tian, CDFA plant pathologist, identified two pathogens associated with the sample, namely, Freesia mosaic virus (FreMV) and Freesia sneak virus (FreSV). Freesia mosaic virus was assigned a temporary Q rating by the CDFA, whereas FreSV already has a permanent B rating.  Subsequently, all infected propagative plant material was destroyed.  The risk of infestation of FreMV in California is evaluated and a permanent rating is proposed here.

 History & Status:

Background:  Freesia mosaic virus is a plant virus belonging to the genus Potyvirus in the family Potyviridae, and is vectored by the potato aphid, Macrosiphum euphoribae and green peach aphid, Myzus persicae.   Freesia mosaic virus (FreMV) was originally reported from Freesia refracta, in Lisse, the Netherlands, by Van Koot et al. in 1954 (Brunt, et al., 1996 onwards; Van Koot et al., 1954).  This pathogen, along with few other plant virus pathogens, has been reported to naturally infect freesia plants (Van Koot et al., 1954; Bouwen, 1994).  In the Netherlands, Freesia mosaic virus was frequently found in field samples of freesia plants with and without symptoms of freesia leaf necrosis disease and, more or less frequently in double infections with Freesia sneak virus in the same plants (Vaira et al., 2006; Meekes & Verbeek, 2011).  Freesia leaf necrosis disease has been reported in Europe since the 1970s and double infections of FreMv and FreSV in freesia plants were first described as “severe leaf necrosis” or “complex disease” which is progressive and may cause death of plants before flowering (Van Dorst, 1973; Meekes & Verbeek, 2011).  The natural occurrence of FreMV has also been found in Peruvian lily in Italy, and besides its spread in Europe, the pathogen has been reported from Freesia spp. in India, Australia, Korea, and New Zealand (Bellardi, 1992; Brunt et al., 1996 onwards; Kumar, et al., 2008; Jeong et al., 2014).

In the USA, Freesia mosaic virus was reported from infected Freesia spp. in Virginia in 2009 (Vaira et al., 2009).  The pathogen was first detected in California, in symptomatic freesia plant samples collected during April 2014, from a nursery in San Luis Obispo County, and identified by Tongyan Tian, CDFA plant pathologist.  Subsequently, all infected plant material was destroyed.

Hosts: Freesia spp. F. refracta, (common freesia; Iradaceae) and Alstroemeria sp. (Peruvian lily; Alstroemeriaceae).  Freesia and Peruvian lily are monocots and although presently naturalized in several countries including the USA, both plant species are native to South Africa and South America respectively (Bellardi, 1992; Brunt et al., 1996 onwards). Freesia mosaic virus was also detected in Lily (Lilium sp.) by the CDFA (see ‘Initiating Event’) and is included as an associated host.

Symptoms:  Symptoms of Freesia mosaic virus-infected freesia plants include mild chlorosis. The pathogen may also be present in symptomless plants (Brunt et al., 1996 onwards).  Experimentally, Alstroemeria sp. plants that were mechanical inoculated FMV infested plant sap, failed to show symptoms three months after inoculation, although the virus was detected serologically (Bellardi, 1992).

Complex infections of Freesia mosaic virus and Freesia sneak virus may result in severe leaf necrosis showing symptoms of chlorotic spots and stripes that appear on the first leaf of freesia plants grown from corms, and later turn grey-brown and necrotic as the disease progresses rapidly often resulting in rot of corms, and death of plants before flower formation (Van Dorst, 1973).

Damage Potential: In California, nursery and private productions of freesia and lily plants may be impacted if infected with FreMV.

Transmission: In nature, Freesia mosaic virus is transmitted by the potato aphid, Macrosiphum euphorbiae and green peach aphid, Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between plants (Brunt et al., 1996 onwards).

Worldwide Distribution:  Asia: India, Korea; Europe: United Kingdom, Ireland, Italy, the Netherlands; North America: USA (Virginia); Australia; New Zealand (found, but with no evidence of spread) (Bellardi, 1992; Brunt, et al., 1996 onwards; Kumar et al., 2008; Jeong et al., 2014; Vaira et al., 2009).

Official Control: Freesia mosaic virus is on the ‘Harmful Organism List’ for Colombia, Georgia, Israel, Japan, Peru, and Taiwan (USDA-PCIT, 2016).  Currently, FreMV has a temporary Q-rating in California.

California Distribution: San Luis Obispo (nursery).

California Interceptions: There have not been any interceptions of Freesia mosaic virus-infected plants entering California.

The risk Freesia mosaic virus 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) Freesia mosaic virus is likely to establish wherever freesia and Peruvian lily and lily plants are grown in limited areas of California. These host plant species have limited production in state, mostly in the north coast and mountain regions, and few southern coast regions, as well as cultivated in nursery and private production sites – including home gardens.       

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) – Freesia mosaic virus is limited to Freesia spp. (Iradaceae), Alstroemeria sp. (Alstroemeriaceae), and Lilum spp. (Liliaceae).

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 Medium (2) Freesia mosaic virus has high reproductive potential.  In nature, its spread to non-infected plants is through aphid vectors, Macrosiphum euphorbiae and Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between 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 High (3) – Incidents of Freesia mosaic virus infections could lower plant value resulting in loss in market sales of nursery-grown freesia and lily plants.  The pathogen is vectored by the potato aphid and green peach aphid, Macrosiphum euphorbiae and Myzus persicae respectively.

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) – Plant infections caused by Freesia mosaic virus are likely to have a minimal impact on the overall environment but may significantly impact home gardening and ornamental plantings. The pathogen may impact California State and federal endangered western lily (Lilium occidentale) and Pitkin Marsh lily (L. pardalinum ssp. pitkinense (ref: State and Federally listed endangered, threatened, and rare plants of California, July, 2015, California Department of Fish and Wildlife, Biogeographic Data Branch, California Natural Diversity Database).

Consequences of Introduction to California for Freesia mosaic virus

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 Freesia mosaic virus to California = 10.

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.  Freesia mosaic virus-infected freesia plants have only been detected in a contained nursery environment in California.  Those plants were subsequently destroyed and therefore, the pathogen is not considered established in the State.

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.


Currently, the possible distribution of Freesia mosaic virus in California is not known.  Future confirmed detection of its in-state presence and distribution may affect its overall score and alter its current proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Freesia mosaic virus is B.


Bellardi, M. G.  1992.  Natural occurrence of Freesia mosaic virus in Alstroemeria sp.  Plant Disease 76:643. DOI: 10.1094/PD-76-0643B.

Bouwen, I.  1994.  Freesia leaf necrosis: some of its mysteries revealed.  Virus Diseases of Ornamental Plants VIII, Acta Horticulturae 377: 311-318.

Brunt, A.A., K. Crabtree, M. J. Dallwitz, A. J. Gibbs, L. Watson, and  E. J. Zurcher. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 16th January 1997.’ URL

Jeong, M. I., Y. J. Choi, J. H. Joa, K. S. Choi, and B. N. Chung.  2014.  First report of Freesia sneak virus in commercial Freesia hybrida cultivars in Korea.  Plant Disease 95:162.

Kumar, Y., V. Hallan, and A. A. Zaidi.  2008.  First finding of Freesia mosaic virus infecting freesia in India.  New Disease Reports 18:3.

Meekes, E. T. M., and M. Verbeek.  2011.  New insights in Freesia leaf necrosis disease.  Proceedings XIIth IS on Virus Diseases of Ornamental Plants; Editors A. F. L. M. Derks et al.  Acta Horticulturae  901, ISHA 2011.

USDA- PCIT.  2016.  USDA Phytosanitary Certificate Issuance & Tracking System. June 6, 2016. .

Vaira, A. M., V. Lisa, A. Costantini, V. Masenga, S. Rapetti, and R. G. Milne.  2006.  Ophioviruses infecting ornamentals and a probable new species associated with a severe disease in Freesia.  Proceeding XIth IS on Virus Diseases in Ornamentals, Ed. C. A. Chang.  Acta Horticulturae 722, ISHA 2006.

Van Dorst, H. J. M.  1973. Two new disorders in freesias.  Netherland Journal of Plant Pathology 79:130-137.

Van Koot, Y., D. H. M. van Slogteren, M. C. Cremer, and J. Camfferman.  1954.  Virusverschijnselen in freesia’s.  Tijdschrlfot over Planienziekten 60:157-192

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,[@]

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 Pest Rating: B

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