Ciborinia camelliae
(flower blight)

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Identity

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Preferred Scientific Name

• Ciborinia camelliae L.M. Kohn

Preferred Common Name

• flower blight

Other Scientific Names

• Sclerotinia camelliae H.H. Hansen and H.E. Thomas, 1940
• Sclerotinia camelliae Hara, 1919

International Common Names

• English: petal blight; sclerotinia blight: Camellia spp.

EPPO code

• SCLECA (Ciborinia camelliae)

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Fungi
•         Phylum: Ascomycota
•             Subphylum: Pezizomycotina
•                 Class: Leotiomycetes
•                     Subclass: Leotiomycetidae
•                         Order: Helotiales
•                             Family: Sclerotiniaceae
•                                 Genus: Ciborinia
•                                     Species: Ciborinia camelliae

Notes on Taxonomy and Nomenclature

Top of page C. camelliae belongs to the inoperculate Discomycetes in the family Sclerotiniaceae. It was first described from Japan by Hara (1919) as Sclerotinia camelliae. Hansen and Thomas (1940) found the fungus in California, USA in 1938 and named it S. camelliae. Their description was not validly published because they did not provide a Latin description. They later concluded that the fungus they had described was the same as that originally described by Hara (Thomas and Hansen, 1946). Kohn (1979) placed the fungus in the genus Ciborinia based on the presence of host tissue in the sclerotial medulla and noted that the sclerotial medulla in the genus Sclerotinia is free of host tissue. Kohn and Nagasawa (1984) concluded that S. camelliae Hara and Ciborinia camelliae Kohn are synonyms, and that accommodated in Ciborinia, C. camelliae Kohn is the correct name.

Description

Top of page Sclerotia black, discoid, occurring singly or aggregate, 12 x 10 x 2 mm. Remains of petal tissues embedded within cortex and medulla of the sclerotium. Apothecia stipitate-cupulate, arising from sclerotia on or in the soil. Stipe variable in length, 2-100 x 1-2 mm. Receptacle 5-18 mm diameter, cupulate at first, becoming discoid to plano-convex. Hymenium buff to dull cinnamon when young, becoming dull umber to dark brick at maturity (Rayner, 1970). Asci 120-145 x 6-10.5 Ám, cylindrical, 8-spored. Ascospores hyaline, one-celled, ovate to obovate, bi-guttulate to multi-guttulate, uni-nucleate, 7.5-12.5 x 4.0-5.0 Ám. Microconidia catenate, brown-walled, globose to obovate, 2.5-4.0 Ám. A detailed illustrated description with comparisons of American and Japanese isolates is given by Kohn and Nagasawa (1984).

Variations in published morphological measurements exist for sclerotia and ascospores. Hansen and Thomas (1940) list sclerotia up to 20 x 30 mm and Gill (1954) gives dimensions of 12-25 mm diameter. Ascospore measurements of Hansen and Thomas (1940) were 5.3-7.0 x 2.5-3.5 Ám and are smaller than those listed by Kohn and Nagasawa (1984). Yoshimi (1979) described a large-spored form of the fungus with ascospores 12-13 x 6-8 Ám.

Distribution

Top of page Flower blight was first reported from Japan in 1919 (Hara, 1919) and was probably carried to the USA with imported plants where it was first observed in 1938 (Hansen and Thomas, 1940). The disease is now widespread in the USA and probably occurs wherever camellias are grown as landscape plants. The disease is also known to occur on greenhouse-grown plants in the USA in areas too cold for their outdoor production. Flower blight was found in New Zealand in 1993 (Stewart and Neilson, 1993) and more recently in England (Cook, 1999; Scott, 1999), France, Germany and Switzerland (Peper, 1999), Spain and Portugal (Mansilla et al., 1999a, 1999b).

See also CABI/EPPO (1998, No. 184).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Risk of Introduction

Top of page Quarantine regulations were adopted in 1949 to prevent movement of camellia flowers and blooming plants with soil into the southern states of the USA from the states of California, Georgia and Oregon where flower blight was known to occur (Brown, 1954). Concern was so great about flower blight spread that the state of Georgia quarantined an individual homeowner's property (Wilby, 1954). These regulations proved useless as flower blight continued to spread and now occurs throughout the southern states of the USA.

C. camellia is on the EPPO A1 list of quarantine pests although it is now known to occur in several European countries including the UK (Taylor and Long, 2000). In areas where the fungus does not occur, it was recommended that camellia flowers, plants with open flowers and plants with soil should not be imported from areas or countries where C. camellia does occur (Brooks, 1979).

Hosts/Species Affected

Top of page The only hosts of C. camelliae are species of Camellia. C. japonica is the main host reported in Japan (Iriyama, 1980), European countries and New Zealand (Taylor and Long, 2000) and the USA (Farr et al., 1989). It is presumed that C. reticulata and its hybrids are also hosts because they are grown in the same areas and bloom at the same time as C. japonica, although there are no published reports on their susceptibility.

Growth Stages

Top of page Flowering stage

Symptoms

Top of page Camellia flowers are the only parts of the camellia plant affected. First symptoms are few to many tan to brown specks on flower petals that rapidly enlarge and coalesce during periods of favourable temperature and moisture conditions. Petals with developing infected areas may appear netted due to the dark-brown colour of vascular elements that stand out against the lighter brown of the inter-veinal areas (Haasis and Winstead, 1954). Infected petal tissue is soft and slippery when rubbed between thumb and forefinger. When completely blighted, the whole flower or individual petals fall from the plant. Flowers may become infected while still in the bud stage when petal tissue becomes exposed at the bud tip. Infected flowers retain their shape and firmness for many days after they have fallen. Under moist conditions the fungus forms masses of microconidia that appear as black liquid droplets or streaks on fallen flowers. After the flowers are completely blighted, the fungus produces compound sclerotia at the base of intact flowers or simple sclerotia at the base of individual petals. Compound sclerotia may mimic petal arrangement in form. Sclerotia are dark-brown to black in colour (Hansen and Thomas, 1940).

List of Symptoms/Signs

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Biology and Ecology

Top of page The disease cycle begins with germination of sclerotia in or on the soil or beneath leaf litter. In the southern USA, sclerotia are dormant during summer and autumn, but are active from late December to April and may remain viable for up to 5 years (Baxter and Epps, 1981). A single aggregate sclerotium may produce one to 12 apothecia (Haasis and Winstead, 1954; Baxter and Fagan, 1975). Ascospores are forcibly discharged during changes of humidity and carried by air currents to camellia flowers where they initiate infections. Clouds of spores can sometimes be seen being discharged into the air when the mulch beneath plants is removed. Spores may be carried at least several kilometres (Zummo and Plakidas, 1960) and possibly up to 20 km and remain infective (Taylor and Long, 2000). Ascospores are the only source of inoculum so there is no secondary disease spread from infected to healthy flowers. Sclerotia are formed within 12-15 days after blighted flowers and petals fall to the ground (Plakidas, 1961), and this completes the disease cycle. Microconidia that are formed on fallen flowers have no infective role, but are believed to function in the sexual process.

Flower infections can occur at 8oC, but disease development may be very slow. Infections are more numerous and symptoms develop faster at temperatures from 12° to 16°C. Heavy flower infection occurs at 20°C, but at 24°C infection no longer takes place (Haasis and Winstead, 1954). A similar temperature response was also observed for vegetative growth of C. camelliae when grown in culture. Growth occurred over a range of 8-20°C. The fungus made little or no growth at 24° and 28°C and was killed after 8 days at 32°C (Haasis and Winstead, 1954).

Means of Movement and Dispersal

Top of page Natural dispersal of C. camelliae ascospores is by wind-borne ascospores (Hansen and Thomas, 1940; Gill, 1954; Taylor and Long, 2000). The fungus can be moved long-distance on infected cut flowers, on plants with open flowers and as sclerotia in soil accompanying camellia plants.

Seedborne Aspects

Top of page Ciborinia camelliae is not seedborne.

Plant Trade

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Impact

Top of page In North America, C. camelliae causes severe damage to camellia flowers on landscape plants in the southern USA. Flower blight is considered to be the most serious disease of camellias and can occur on plants grown in greenhouses and on cut flowers at camellia shows. Flower losses in landscape plantings may range from 43% to 84% in a given year (Holcomb, 1990) and were 95% in a 40-year-old camellia garden (Holcomb, 1997).

Diagnosis

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The fungus is easy to isolate and grow in culture (Holcomb, 1980; Kohn and Nagasawa, 1984). Sections from blighted petals (2-4 mm²), disinfected in 70% ethyl alcohol for 1-3 min, often yield pure cultures of the fungus when incubated on acidified potato-dextrose agar. In culture, mycelium is at first white to cream coloured, later turning grey and forming masses of black microconidia and scattered, flat, black sclerotia that are attached to the mycelium. Cultures of the fungus can be stored for up to 14 years on sterilized wheat seeds in parafilm-sealed, screw-capped bottles (Holcomb, 1994).

A diagnostic protocol is given in OEPP (2003).

Detection and Inspection

Top of page Disease can be detected by inspecting flowers for the presence of brown spots and blight. Grey mycelium is often present at the base of freshly fallen, blighted flowers. Fallen, blighted flowers and petals have sclerotia or developing sclerotia present.

Similarities to Other Species/Conditions

Top of page Camellia flower blight may be confused with cold or frost damage on flowers. Flowers damaged by blight or cold turn a brown colour. Cold damaged petals have a firm leathery texture when rubbed between thumb and forefinger. Flower blight damaged petals are generally soft and slippery, especially at early infection stages, when tested in the same manner.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

There is no satisfactory method for controlling camellia flower blight at present. Plant quarantine measures were not successful in preventing its spread in the USA. Cultural methods such as collecting diseased flowers and the use of various mulches are of limited value unless practised on a community-wide basis (Young and Milbrath, 1950; Zummo and Plakidas, 1960; Baxter and Epps, 1981). Host plant resistance has offered little hope as all C. japonica cultivars appear to be susceptible (Baxter and Berly, 1956; Baxter and Epps, 1981; Taylor and Long, 2000). Fungicide soil applications to prevent sclerotial germination may be useful in some situations, such as isolated plantings, but in general must be practised community-wide (Anzalone and Plakidas, 1958; Baxter and Epps, 1981). The use of flower protectant fungicides such as triadimefon can reduce blight by 50%, but the level of control is not great enough to justify their use (Holcomb, 1983, 1990, 1991, 1997). There is no indication that a satisfactory control procedure will be developed in the near future.

References

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Alford DM; Sinclair JB; Pirone TP, 1961. Spread and distribution of camellia flower blight in Louisiana. Plant Disease Reporter, 45:856-857.

Anzalone L; Plakidas AG, 1958. Control of flower blight of camellias in Louisiana with fungicides. Plant Disease Reporter, 42:804-806.

Baxter LW; Berly JA, 1956. Flower blight of camellia in South Carolina. Plant Disease Reporter, 40:831.

Baxter LW; Epps WM, 1981. Camellia flower blight caused by Ciborinia camelliae Kohn. American Camellia Yearbook, 1981:107-113.

Baxter LW; Fagan SG, 1975. Camellia flower blight - 1975. American Camellia Yearbook, 1975:91-95.

Brooks A, 1979. Camellia flower blight. The Garden, Journal of the Royal Horticultural Society, 104:214-216.

Brown AC, 1954. Camellia flower blight. American Camellia Yearbook, 1954:34-40.

CABI/EPPO, 1998. Distribution maps of quarantine pests for Europe (edited by Smith IM, Charles LMF). Wallingford, UK: CAB International, xviii + 768 pp.

Cochran JH, 1962. A report of the occurrence of camellia flower blight in Mississippi. Plant Disease Reporter, 46:617.

Cook R, 1999. Fight the blight. Horticulture Week August, 12:20-21.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

European and Mediterranean Plant Protection Organization, 2003. Diagnostic protocols for regulated pests. Ciborinia camelliae. Bulletin OEPP, 33(2):257-264.

Farr DF; Bills GF; Chamuris GP; Rossman AY, 1989. Fungi on Plants and Plant Products in the United States. St. Paul, Minnesota, USA: APS Press, 1252 pp.

Gill DL, 1948. Camellia flower blight in the south. Plant Disease Reporter, 32:317-318.

Gill DL, 1954. Camellia flower blight. Camellian, 5(4):12-13,15,25.

Haasis FA; Winstead NN, 1954. Some characteristics of two Sclerotinia pathogens and their relationship to flower blight of camellia. American Camellia Yearbook, 1954:22-33.

Hansen HH; Thomas HE, 1940. Flower blight of camellias. Phytopathology, 30:166-170.

Hara K, 1919. A sclerotial disease of camellia (Camellia japonica). Dainppon Sanrin Kaiho, 436:29-31.

Holcomb GE, 1980. Maintenance of Sclerotinia camellip cultures on sterilized wheat. Plant Disease, 64(11):1008

Holcomb GE, 1983. Camellia flower blight: comments on the fungus, its relatives and its control. Camellia Journal, 38(3):33-34

Holcomb GE, 1990. Camellia flower blight: a summary of nine years of tests with flower protectant fungicides. American Camellia Yearbook, No. 45:169-173

Holcomb GE, 1991. A brief history and progress on camellia flower blight control in the United States. International Camellia Journal, 23:72-73

Holcomb GE, 1994. Long-term storage of the camellia flower blight fungus Ciborinia camelliae. American Camellia Yearbook, No. 49:78-79; 4 ref.

Holcomb GE, 1997. Louisiana flower blight tests in 1997. American Camellia Yearbook, 1997:32-33.

IPPC, 2006. IPP Report No. NL-3/2. Rome, Italy: FAO.

Iriyama K, 1980. Camellia petal blight research in Japan. American Camellia Yearbook, 1980:95-101.

Ito K, 1973. Pathology of Forest Trees, Part 2. Tokyo, Japan: Norin Shuppan Co., Ltd.

Kohn LM, 1979. A monographic revision of the genus Sclerotinia. Mycotaxon, 9(2):365-444

Kohn LM; Nagasawa E, 1984. A taxonomic reassessment of Sclerotinia camellip Hara (= Ciborinia camellip Kohn), with observations on flower blight of camellia in Japan. Transactions of the Mycological Society of Japan, 25(2):149-161

Mansilla JP; Pintos C; Salinero MC, 1999. Ciborinia camelliae Kohn: Marchitamiento de la flor de camelia. Leaflet. Pontevedra, Spain: Estaci=n de Fitopatologia "Do Areeiro", Servicio Agrario.

Mansilla JP; Pintos C; Salinero MC, 1999. Detecci=n en Espa±a de Ciborinia camelliae Kohn. Phytoma, 109:24-27.

Peper K, 1999. Die BraunfSulen der Kamelienblnte: Ciborinia camelliae Kohn. Die Kamelie Nr. 1, November 1999.

Plakidas AG, 1950. Camellia flower blight in Louisiana. Plant Disease Reporter, 34:188.

Plakidas AG, 1957. Camellia petal blight found in Texas. Plant Disease Reporter, 41:547.

Plakidas AG, 1961. Present status of control of camellia petal blight. Camellian, 12(3):4-6.

Raabe RD; McCain AH; Paulus AO, 1978. Diseases and pests. In: Feathers DL, Brown MH, eds. The camellia. Its History, Culture, Genetics and a look into its Future Development. Columbia, South Carolina, USA: Southern Californian Camellia Society, Inc., 279-285.

Rayner RW, 1970. A Mycological Colour Chart. Wallingford, UK: CAB International.

Richmond RG, 1949. Camellia flower spot in Oregon. Plant Disease Reporter, 33:404.

Scott M, 1999. Camellia flower blight - Ciborinia camelliae. Horticultural Development Corp. News, 57:18.

Stewart TM; Neilson H, 1993. Flower blight, a new disease of camellias in New Zealand. New Zealand Camellia Bulletin, 116:29-33.

Taylor CH; Long PG, 2000. Review of literature on camellia flower blight caused by Ciborinia camelliae. New Zealand Journal of Crop and Horticultural Science, 28(2):123-138; 5 pp. of ref.

Thomas HE; Hansen HN, 1946. Camellia flower blight. Phytopathology, 36:380-381.

Wilby RB, 1954. The camellia blight and me. Camellian, 5(1):12.

Winstead NN; Nelson EC; Haasis FA, 1954. Distribution of Sclerotinia camelliae in North Carolina. Plant Disease Reporter, 38:670-672.

Yoshimi S, 1979. Tsubaki-no-chawan-take (Sclerotinia camelliae Hara forma macrospora). In: Aoki M, Yoshimi S, eds. Illustrations of Japanese Mushrooms Vol. 5, No. 1027. Japan, Tokorozawa-shi and Kyoto: The Amateur Mushroom Association for Mushroom Research.

Young RA; Milbrath JA, 1950. Camellia flower blight. Oregon Agricultural Experiment Station Bulletin, 474:1-4.

Zummo N; Plakidas AG, 1960. Distances of spread of petal blight by wind blown spores. American Camellia Yearbook, 1960:40-43.

Distribution Maps

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