Guignardia citricarpa (citrus black spot)
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Guignardia citricarpa Kiely
Preferred Common Name
- citrus black spot
Other Scientific Names
- Phoma citricarpa McAlpine
- Phoma citricarpa var. mikan Hara
- Phyllosticta citricarpa (McAlpine) Aa
- Phyllostictina citricarpa (McAlpine) Petr.
International Common Names
- Spanish: mancha negra de las frutas de cítricos; manchas negras de los agrios
- French: maladie des taches noires des agrumes; taches noires des fruits des agrumes
- Portuguese: pinta preta dos citros
Local Common Names
- Germany: Fruchtfleckigkeit: Zitrus; Schwarzfleckigkeit: Zitrus
- GUIGCI (Guignardia citricarpa)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Fungi
- Phylum: Ascomycota
- Subphylum: Pezizomycotina
- Class: Dothideomycetes
- Order: Botryosphaeriales
- Family: Botryosphaeriaceae
- Genus: Guignardia
- Species: Guignardia citricarpa
Notes on Taxonomy and NomenclatureTop of page The position of the black spot fungus within the Ascomycetes has been unclear. Barr (1972) proposed that the genus Guignardia Viola & Ravaz be considered synonymous with Botryosphaeria Ces. & De Not., but the genera currently remain separated. Guignardia differs from Botryosphaeria in having unilocular ascomata, smaller ascospores and different anamorphs. Punithalingam (1974) limited the genus Guignardia to species with Phyllosticta anamorphs and assigned species with other anamorphs to the genus Discosphaerina Höhn. Bissett (1986) proposed that the species of Guignardia with Phyllosticta anamorphs be placed in the genus Discochora Höhn. Currently the anamorph is Phyllosticta citricarpa with a Leptodothiorella spermatial state (van der Aa, 1973).
The anamorph of the black spot fungus was first described by McAlpine (1899) and designated Phoma citricarpa McAlpine. The telemorph was described in 1948 and designated Guignardia citricarpa Kiely (Kiely, 1948). Van der Aa (1973) reclassified the anamorph as Phyllosticta citricarpa (McAlpine) van der Aa.
Two strains of Guignardia citricarpa have long been recognized, one pathogenic to citrus and the other non-pathogenic to citrus and widespread on other hosts (Kiely, 1948; Chiu, 1955; Lee, 1969; Kotzé, 1981). The non-pathogen can be distinguished by its faster growth, colony type, and production of pycnidia in ascocarps in culture. Its geographic distribution is much wider than the type that is pathogenic to citrus. Meyer et al. (2001) considered that the two types represented different species. Baayen et al. (2002) used many of the above characteristics, as well as the presence or absence of a mucoid sheath on conidia, the sequences of the ITS region and amplified fragment length polymorphisms to distinguish the types as species. The widespread non-pathogenic strain is now designated Guignardia mangiferae and the citrus black spot pathogen as Guignardia citricarpa.
DescriptionTop of page Ascomata of G. citricarpa are formed on fallen, decomposing leaves. Perithecia are aggregated, globose, non-papillate, and about 100-175 µm in diameter (Kotzé, 2000). Asci are cylindrical, clavate, and each contain eight spores. Ascospores are 4.5 x 6.5 µm wide by 12.5-16 µm long, hyaline, nonseptate, multi-guttulate and swollen in the centre. A colourless appendage occurs at each end.
Pycnidia are found in abundance on dead fallen leaves, and are also produced on fruit and peduncles. They are dark brown to black and 115-190 µm in diameter. Conidia are obovate to elliptical, hyaline, nonseptate, multiguttulate with a colourless appendage and are 5.5-7.0 µm wide by 8.0-10.5 µm long.
In culture, colonies of G. citricarpa are dark brown to black and the mycelium is thick and prostrate. On cherry decoction agar, colonies are dark with a wide translucent zone and lobate margins (Baayen et al., 2002). Pycnidia are produced in culture, but if perithecia form they are usually infertile. However, in vitro production of ascospores by G. citricarpa has been reported (Moran Lemir et al., 2000).
DistributionTop of page
Previous records of Guignardia on citrus in some countries may involve the non-pathogenic species Guignardia mangiferae. The countries, states and provinces listed are locations where G. citricarpa is known to be present or where substantial evidence exists that black spot occurs.
G. citricarpa has additionally been reported from Mexico and Japan (Stringari et al., 2009) and but an established presence is not confirmed by other publications.
Records in CMI (1990) for Burma, India, Iran, Israel, Korea Republic, Lebanon, Malaysia, Pakistan, Singapore, Sri Lanka, Thailand, Vietnam, Egypt, Tanzania, Cook Islands, Niue, Tonga, W. Samoa, Fiji, Hawaii (USA), Papua New Guinea, Georgia, Belize, Honduras, Jamaica, Trinidad, Peru, Vanuatu and Venezuela may also be misidentifications.
The situation in Hong Kong, Swaziland and Nigeria is still unclear.
See also CABI/EPPO (1998, No. 204).
Distribution TableTop of page
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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Afghanistan||Absent, confirmed by survey||EPPO, 2014|
|Azerbaijan||Absent, confirmed by survey||EPPO, 2014|
|Bahrain||Absent, confirmed by survey||EPPO, 2014|
|Bangladesh||Absent, unreliable record||EPPO, 2014|
|Brunei Darussalam||Absent, confirmed by survey||EPPO, 2014|
|Cambodia||Absent, confirmed by survey||EPPO, 2014|
|China||Restricted distribution||Zheng, 1983; CABI/EPPO, 2012; EPPO, 2014|
|-Fujian||Present||CABI/EPPO, 2012; EPPO, 2014|
|-Guangdong||Present||CABI/EPPO, 2012; EPPO, 2014|
|-Hong Kong||Present||Grasso, 1970a; Grasso, 1970b; CABI/EPPO, 2012; EPPO, 2014|
|-Sichuan||Present||CABI/EPPO, 2012; EPPO, 2014|
|-Yunnan||Present||CABI/EPPO, 2012; EPPO, 2014|
|-Zhejiang||Present||CABI/EPPO, 2012; EPPO, 2014|
|Georgia (Republic of)||Absent, confirmed by survey||EPPO, 2014|
|India||Restricted distribution||EPPO, 2014; Das et al., 2018|
|-Assam||Absent, confirmed by survey||EPPO, 2014|
|-Maharashtra||Present||Das et al., 2018|
|Indonesia||Present||CABI/EPPO, 2012; EPPO, 2014|
|-Java||Present||CABI/EPPO, 2012; EPPO, 2014|
|Iran||Absent, confirmed by survey||EPPO, 2014|
|Iraq||Absent, confirmed by survey||EPPO, 2014|
|Israel||Absent, confirmed by survey||EPPO, 2014|
|Japan||Absent, reported but not confirmed||CABI/EPPO, 2012; EPPO, 2014|
|-Honshu||Absent, confirmed by survey||EPPO, 2014|
|-Ryukyu Archipelago||Absent, confirmed by survey||EPPO, 2014|
|Jordan||Absent, confirmed by survey||EPPO, 2014|
|Korea, Republic of||Absent, unreliable record||CABI/EPPO, 2012; EPPO, 2014|
|Kuwait||Absent, confirmed by survey||EPPO, 2014|
|Lebanon||Absent, confirmed by survey||EPPO, 2014|
|Malaysia||Absent, confirmed by survey||EPPO, 2014|
|-Peninsular Malaysia||Absent, confirmed by survey||EPPO, 2014|
|-Sabah||Absent, confirmed by survey||EPPO, 2014|
|-Sarawak||Absent, confirmed by survey||EPPO, 2014|
|Myanmar||Absent, confirmed by survey||EPPO, 2014|
|Oman||Absent, confirmed by survey||EPPO, 2014|
|Pakistan||Absent, confirmed by survey||EPPO, 2014|
|Philippines||Present||Grasso, 1970a; Grasso, 1970b; CABI/EPPO, 2012; EPPO, 2014|
|Qatar||Absent, confirmed by survey||EPPO, 2014|
|Saudi Arabia||Absent, confirmed by survey||EPPO, 2014|
|Sri Lanka||Absent, confirmed by survey||EPPO, 2014|
|Taiwan||Present||Grasso, 1970a; Grasso, 1970b; Chiu, 1955; Huang and Chang, 1972; CABI/EPPO, 2012; EPPO, 2014|
|Thailand||Absent, reported but not confirmed||CABI/EPPO, 2012; EPPO, 2014|
|Turkey||Absent, confirmed by survey||EPPO, 2014|
|Uzbekistan||Absent, confirmed by survey||EPPO, 2014|
|Vietnam||Absent, confirmed by survey||EPPO, 2014|
|Yemen||Absent, confirmed by survey||EPPO, 2014|
|Algeria||Absent, confirmed by survey||EPPO, 2014|
|Angola||Present||EPPO, 2014; Bassimba et al., 2018|
|Benin||Absent, unreliable record||EPPO, 2014|
|Botswana||Absent, confirmed by survey||EPPO, 2014|
|Burkina Faso||Absent, confirmed by survey||EPPO, 2014|
|Cameroon||Absent, confirmed by survey||EPPO, 2014|
|Central African Republic||Absent, confirmed by survey||EPPO, 2014|
|Congo||Absent, confirmed by survey||EPPO, 2014|
|Congo Democratic Republic||Absent, confirmed by survey||EPPO, 2014|
|Côte d'Ivoire||Absent, confirmed by survey||EPPO, 2014|
|Egypt||Absent, confirmed by survey||EPPO, 2014|
|Ethiopia||Absent, confirmed by survey||EPPO, 2014|
|Gabon||Absent, confirmed by survey||EPPO, 2014|
|Ghana||Present||Brentu et al., 2012; CABI/EPPO, 2012; EPPO, 2014|
|Guinea||Absent, unreliable record||EPPO, 2014|
|Guinea-Bissau||Absent, confirmed by survey||EPPO, 2014|
|Kenya||Present||CABI/EPPO, 2012; EPPO, 2014|
|Liberia||Absent, confirmed by survey||EPPO, 2014|
|Libya||Absent, confirmed by survey||EPPO, 2014|
|Madagascar||Absent, confirmed by survey||EPPO, 2014|
|Malawi||Absent, confirmed by survey||EPPO, 2014|
|Mauritius||Absent, confirmed by survey||EPPO, 2014|
|Morocco||Absent, confirmed by survey||EPPO, 2014|
|Mozambique||Restricted distribution||Carvalho, 1974; CABI/EPPO, 2012; EPPO, 2014|
|Namibia||Present, few occurrences||CABI/EPPO, 2012|
|Nigeria||Present||CABI/EPPO, 2012; EPPO, 2014|
|Senegal||Absent, confirmed by survey||EPPO, 2014|
|Seychelles||Absent, confirmed by survey||EPPO, 2014|
|Sierra Leone||Absent, confirmed by survey||EPPO, 2014|
|Somalia||Absent, confirmed by survey||EPPO, 2014|
|South Africa||Restricted distribution||McOnie, 1964; Whiteside, 1965; CABI/EPPO, 2012; EPPO, 2014|
|Sudan||Absent, confirmed by survey||EPPO, 2014|
|Swaziland||Restricted distribution||CABI/EPPO, 2012; EPPO, 2014|
|Tanzania||Absent, confirmed by survey||EPPO, 2014|
|Togo||Absent, confirmed by survey||EPPO, 2014|
|Tunisia||Absent, confirmed by survey||EPPO, 2014|
|Uganda||Present||Reeder et al., 2009; CABI/EPPO, 2012; EPPO, 2014|
|Zambia||Present||CABI/EPPO, 2012; EPPO, 2014|
|Zimbabwe||Present||Whiteside, 1965; CABI/EPPO, 2012; EPPO, 2014|
|Mexico||Absent, reported but not confirmed||CABI/EPPO, 2012; EPPO, 2014|
|USA||Restricted distribution||NAPPO, 2010; CABI/EPPO, 2012; EPPO, 2014|
|-Florida||Present, few occurrences||NAPPO, 2010; CABI/EPPO, 2012; Schubert et al., 2012; EPPO, 2014|
|-Hawaii||Absent, confirmed by survey||EPPO, 2014|
Central America and Caribbean
|Antigua and Barbuda||Absent, confirmed by survey||EPPO, 2014|
|Bahamas||Absent, confirmed by survey||EPPO, 2014|
|Belize||Absent, confirmed by survey||EPPO, 2014|
|Cayman Islands||Absent, confirmed by survey||EPPO, 2014|
|Costa Rica||Absent, confirmed by survey||EPPO, 2014|
|Cuba||Present||CABI/EPPO, 2012; EPPO, 2014|
|Dominica||Absent, confirmed by survey||EPPO, 2014|
|Dominican Republic||Absent, confirmed by survey||EPPO, 2014|
|El Salvador||Absent, confirmed by survey||EPPO, 2014|
|Grenada||Absent, confirmed by survey||EPPO, 2014|
|Guatemala||Absent, confirmed by survey||EPPO, 2014|
|Haiti||Absent, confirmed by survey||EPPO, 2014|
|Honduras||Absent, confirmed by survey||EPPO, 2014|
|Jamaica||Absent, confirmed by survey||EPPO, 2014|
|Montserrat||Absent, confirmed by survey||EPPO, 2014|
|Nicaragua||Absent, confirmed by survey||EPPO, 2014|
|Panama||Absent, confirmed by survey||EPPO, 2014|
|Puerto Rico||Absent, confirmed by survey||EPPO, 2014|
|Saint Lucia||Absent, confirmed by survey||EPPO, 2014|
|Saint Vincent and the Grenadines||Absent, confirmed by survey||EPPO, 2014|
|Trinidad and Tobago||Absent, confirmed by survey||EPPO, 2014|
|Argentina||Restricted distribution||Rodriguez and Mazza Gaiad, 1996; Foguet et al., 1985; Garran, 1996; CABI/EPPO, 2012; EPPO, 2014|
|Bolivia||Absent, confirmed by survey||EPPO, 2014|
|Brazil||Restricted distribution||CABI/EPPO, 2012; EPPO, 2014|
|-Espirito Santo||Present||CABI/EPPO, 2012|
|-Minas Gerais||Present||CABI/EPPO, 2012|
|-Rio de Janeiro||Present||Robbs et al., 1980; CABI/EPPO, 2012; EPPO, 2014|
|-Rio Grande do Sul||Present||Robbs et al., 1980; Robbs and Bittencourt, 1995; CABI/EPPO, 2012; EPPO, 2014|
|-Santa Catarina||Present||CABI/EPPO, 2012|
|-Sao Paulo||Present||Goes and Feichtenberger, 1993; Goes at al., 2000; CABI/EPPO, 2012; EPPO, 2014|
|Chile||Absent, confirmed by survey||EPPO, 2014|
|Colombia||Absent, confirmed by survey||EPPO, 2014|
|Guyana||Absent, confirmed by survey||EPPO, 2014|
|Paraguay||Absent, confirmed by survey||EPPO, 2014|
|Peru||Absent, confirmed by survey||EPPO, 2014|
|Suriname||Absent, confirmed by survey||EPPO, 2014|
|Uruguay||Absent, unreliable record||EPPO, 2014|
|Venezuela||Absent, confirmed by survey||EPPO, 2014|
|Albania||Absent, confirmed by survey||EPPO, 2014|
|Bosnia-Hercegovina||Absent, confirmed by survey||EPPO, 2014|
|Croatia||Absent, confirmed by survey||EPPO, 2014|
|Cyprus||Absent, confirmed by survey||EPPO, 2014|
|France||Absent, confirmed by survey||EPPO, 2014|
|Greece||Absent, confirmed by survey||EPPO, 2014|
|Italy||Absent, intercepted only||CABI/EPPO, 2012; EPPO, 2014|
|-Sicily||Absent, confirmed by survey||EPPO, 2014|
|Malta||Absent, confirmed by survey||EPPO, 2014|
|Montenegro||Absent, confirmed by survey||EPPO, 2014|
|Netherlands||Absent, intercepted only||NPPO of the Netherlands, 2013; EPPO, 2014|
|Portugal||Absent, confirmed by survey||EPPO, 2014|
|Russian Federation||Present||Present based on regional distribution.|
|-Russian Far East||Present||CMI, 1990|
|Spain||Absent, intercepted only||CABI/EPPO, 2012; EPPO, 2014|
|-Spain (mainland)||Absent, intercepted only||CABI/EPPO, 2012|
|American Samoa||Absent, confirmed by survey||EPPO, 2014|
|Australia||Restricted distribution||CABI/EPPO, 2012; EPPO, 2014|
|-New South Wales||Present||CABI/EPPO, 2012; EPPO, 2014|
|-Queensland||Present||CABI/EPPO, 2012; EPPO, 2014|
|Cook Islands||Absent, invalid record||CABI/EPPO, 2012; EPPO, 2014|
|Fiji||Absent, invalid record||CABI/EPPO, 2012; EPPO, 2014|
|French Polynesia||Absent, confirmed by survey||EPPO, 2014|
|Guam||Absent, confirmed by survey||EPPO, 2014|
|New Zealand||Absent, invalid record||CABI/EPPO, 2012; EPPO, 2014|
|Niue||Absent, invalid record||CABI/EPPO, 2012; EPPO, 2014|
|Papua New Guinea||Absent, unreliable record||EPPO, 2014|
|Samoa||Absent, invalid record||CABI/EPPO, 2012; EPPO, 2014|
|Tonga||Absent, invalid record||CABI/EPPO, 2012; EPPO, 2014|
|Vanuatu||Absent, reported but not confirmed||CABI/EPPO, 2012; EPPO, 2014|
|Wallis and Futuna Islands||Absent, confirmed by survey||EPPO, 2014|
Growth StagesTop of page Fruiting stage, Post-harvest, Vegetative growing stage
SymptomsTop of page Several different types of symptoms occur on citrus, generally referred to as hard or shot hole spot, false melanose, freckle spot and virulent spot. The lesions of hard spot generally occur on mature fruit and are several millimeters in diameter. These spots are crater-like with a light centre, a dark-brown to black rim, and often have a green halo on mature orange fruit. Pycnidia are often apparent in these lesions. False melanose usually appears on green fruit and consists of raised dark-brown to black specks that may coalesce. No pycnidia form on these lesions and the pathogen is difficult to isolate. Freckle spots are orange to red, slightly depressed, 1-3 mm in diameter and occur late in the season. The spots turn brown with age. Virulent spots are large, slightly sunken and spread irregularly over large areas of the mature fruit. The pathogen is most readily isolated from these types of lesions and pycnidia may eventually form.
Leaf lesions are uncommon on most citrus but may be more frequent on lemons. Lesions are small, sunken necrotic spots with light centre and a dark rim and may have a chlorotic halo.
List of Symptoms/SignsTop of page
|Fruit / extensive mould|
|Fruit / lesions: black or brown|
|Fruit / lesions: scab or pitting|
|Leaves / abnormal colours|
|Leaves / abnormal leaf fall|
|Stems / discoloration of bark|
Biology and EcologyTop of page Biotypes
Initially two strains were recognized, the pathogenic and the non-pathogenic. These have now been separated in to two species, Guignardia citricarpa and G. mangiferae. However, both species occur on citrus fruit (Sutton and Waterston, 1966). G. citricarpa causes black spot and can be readily isolated from certain lesion types. G. mangiferae is most commonly recovered from wounds on fruit produced by mechanical injury, spray burns or other damage.
The cultural characteristics and morphology of Phoma citricarpa and P. citricarpa var. mikan and their teleomorphs were compared (Wang and Tsai, 1974). No differences were found between the two taxa in morphology, sporulation or other characteristics when grown on several types of media at varying temperatures. Studies of the formation of conidiomata, conidia and spore ooze showed that the size of conidia varied with media type, temperature and light conditions. The teleomorph of the two taxa produce ascospores of the same size and shape when grown on potato dextrose agar with plant tissue. The authors concluded that there was insufficient information to separate the two taxa on the basis of morphological criteria (Wang and Tsai, 1974).
Ascospores from infected, fallen leaves are the major source of inoculum (McOnie, 1967; Timmer, 1999; Kotze, 2000). Pseudothecial development in decomposing leaves occurs from 40 to 180 days after leaf fall, depending on the frequency of wetting and drying. The optimum temperature for ascomata formation is 21-28°C and no pseudothecia are formed below 7°C or above 35°C (Lee and Huang, 1973). Prolonged periods of wetness prevent pseudothecia formation since the leaves are rapidly colonized by competing saprobes. Once ascospores are mature, rainfall or irrigation may trigger their release. Ascospores are carried by wind throughout the canopy and long distances beyond (Huang and Chang, 1972).
When ascospores are deposited on fruit or vegetative tissues under moist conditions, they germinate to form an appressorium (Timmer, 1999; Kotzé, 2000). An infection peg penetrates the cuticle and epidermis to form quiescent infections on leaves or fruit. Quiescent infections on fruit develop to produce the typical black spot symptom after the fruit attains full size or becomes mature. Such infection on leaves seldom develops. However, the fungus colonizes the leaf as a saprophyte after the leaf dies and eventually forms pycnidia or pseudothecia.
The anamorph probably plays only a minor role in the disease cycle (Timmer, 1999; Kotze, 2000). Conidia produced on the leaves and fruit in the canopy are capable of infecting the leaves and fruit. However, conidia produced on dead leaves can only reach susceptible fruit and leaves by splash dispersal into the canopy. Conidia produced on fruit can be washed down through the canopy and infect leaves and younger fruit that are still at the susceptible stage.
In most subtropical citrus areas, leaf fall occurs just before or about the time of bloom. Fruit are susceptible for at least 4-5 months after petal fall. Ascospores are released whenever conditions are favorable during that time and produce the quiescent infections. Thus infections probably occur throughout spring until at least mid-summer whenever conditions are favorable. Fruit must be protected during that entire time to achieve a high degree of control.
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Flowers/Inflorescences/Cones/Calyx||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Fruits (inc. pods)||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Leaves||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Stems (above ground)/Shoots/Trunks/Branches||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Plant parts not known to carry the pest in trade/transport|
|Growing medium accompanying plants|
ImpactTop of page Black spot has been present in Australia, South Africa and parts of Asia for many years (Kotze, 2000). Most of the losses in Australia and South Africa have been due to the external blemishes which make fruit unsuitable for the fresh market. Some losses to fruit drop occurred in years favourable for disease development and when fruit was held on the trees past peak maturity. However, now that black spot is well established in areas of southern South America, fruit losses may periodically be severe. Internal quality of fruit may also be affected. Total soluble solids were unaffected in black spot affected fruit, but acid was lower (Anon., 1988).
Latent infections are common on leaves and occasionally symptoms appear. No harmful effects from leaf infection have been reported.
DiagnosisTop of page
A method for detection of G. citricarpa using loop-mediated isothermal amplification (LAMP) has been developed which can be used to confirm the presence of G. citricarpa in black spot lesions, including those lacking pycnidia (Tomlinson et al., 2013). The LAMP assay can be used to test crude extracts prepared directly from lesions on fruit, and the entire test is faster than previously described PCR-based methods for detection of G. citricarpa. The method is sufficiently simple to allow deployment of the test in the field, for example, in the course of import inspections.
Detection and InspectionTop of page
Often black spot can be identified with considerable certainty if hard spot lesions with pycnidia are present. However, freckle spot, false melanose and virulent spot can be confused with many other diseases and injuries (Kotze, 2000). G. citricarpa is isolated relatively easily from virulent spot or hard spot lesions, but may be difficult or impossible to isolate from the other symptom types.
Once a species of Guignardia has been isolated from symptomatic tissue, the species involved must be determined. G. citricarpa grows more slowly on cherry decoction agar than G. mangiferae, produces lighter colonies which are more lobate, with a wider translucent zone than G. mangiferae (Baayen et al., 2001). G. citricarpa produces a yellow pigment on oatmeal agar not produced by G. mangiferae. G. mangiferae usually produces fertile perithecia in culture whereas G. citricarpa does not. Conidia of G. citricarpa lack the visible mucoid sheath present on those of G. mangiferae.
The two species can also be distinguished by Amplified Fragment Length Polymorphism (AFLP) analysis or sequencing of the ITS spacer region (Baayen et al., 2000).
Identification of species of Guignardia from citrus requires isolation of the slow-growing fungus and comparison of several of the above-listed traits to verify the identity. Proof of pathogenicity requires inoculation of fruit or leaves and an incubation period of weeks or months before symptoms appear (Kotze, 2000). Thus, detection and identification is currently difficult and time-consuming. However, species-specific primers from the ITS region and other regions of the genome have been developed (Sanders et al., 2003). These primers are quite reliable for differentiation of the two species when used with pure cultures of the fungus. If they prove successful for detection and identification of species using colonized plant material they should greatly speed diagnosis of black spot.
Polymerase chain reaction (PCR) can be used to diagnose G. citricarpa. Bonants et al. (2003) recorded the efficiency of PCR-based detection methods as 60-70% for lesions without pycnidia and 90% for lesions with pycnidia, and a reliability of 99% by analysing multiple lesions per sample. Gent-Pelzer et al. (2007) developed a TaqMan PCR method for the diagnosis of G. citricarpa on citrus fruit which was more sensitive than conventional PCR. Their specific primer/TaqMan probe was able to discriminate between G. citricarpa and G. mangiferae. Stringari et al. (2009) used random amplified polymorphic DNA (RAPD) markers to develop specific primers for the identification of G. citricarpa with PCR.
Detection based on host plant symptoms and identification by morphological and molecular methods are detailed in OEPP/EPPO (2003; 2009).
Prevention and ControlTop of page
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.Exclusion
Efforts have been made to exclude black spot from areas where it is not currently present. Clearly, living or dead vegetative tissues represent a high risk for introduction since airborne ascospores can be produced on these tissues under favourable conditions. Living trees or even budwood could carry quiescent infections. The importance of dispersal by fruit has been questioned since the fungus produces only water-dispersed conidia on symptomatic fruit (Kotze, 2000).
The removal of infected, off-season fruit may be useful to reduce conidial inoculum in some situations (Kotze, 1981). Mechanical removal of leaf litter from the orchard floor reduces disease pressure and facilitates control, but is costly.
Sour orange (Citrus aurantium) is one of the few species of citrus that is resistant to black spot. Grapefruit (C. paradisi) and lemons (C. limon) are the most susceptible, whereas some mandarins (C. reticulata) are more tolerant (Kotze, 2000). Some attempts have been made to produce tolerant hybrids using sour orange as a source of resistance (Anon., 1974). It is unlikely that conventional breeding will produce commercially useful, tolerant cultivars in the foreseeable future. Genetic modification holds more promise for developing resistant cultivars, but progress is likely to be slow using these methods.
A number of fungicides such as copper products, dithiocarbamates, benzimidazoles and strobilurins are effective against black spot. However, resistance has developed to benzimidazoles in many areas (Kotze, 2000; Goes et al., 2000; Goes, 2002) and there is a potential problem with strobilurins. Fungicides must be chosen carefully to minimize the possible development of resistance.
For many years, protective products such as the coppers and dithiocarbamates were the basis for the control program ( Bertus, 1981; Kiely, 1950,1976; Kotzé, 1981; Tsai, 1981). Subsequently mid-summer postinfectional applications of benzimidazoles were sufficient for control in many areas (Kellerman and Kotzé, 1973, 1979). However, with the development of resistance (Herbert and Grech, 1985) many growers have returned to the use of protectant sprays or combinations of systemic and protectant products (Goes et al., 2000; Goes, 2002).
Spore trapping and rainfall and dew measurements have been helpful in determining the timing of ascospore release and the need for fungicide applications in South Africa (Kotze, 2000). In Brazil, infections seem to occur to varying degrees throughout the susceptible period and fruit must be protected from petal fall to mid-summer (Reis, 2002).
Fruit from black spot-infested groves often bear quiescent infections that may later develop into black spot lesions in transport or at the final destination (Hall, 1973). Fruit produced for the fresh market should be refrigerated and kept as cold as possible to slow development of the lesions. On the other hand, if it is desirable that black spot symptoms are expressed as soon as possible for detection of the disease, then fruit should be held at 27°C under continuous light.
Preharvest sprays of benzimidazole fungicides are effective in preventing or delaying symptom expression during transport or storage (Nam et al., 1993). Postharvest applications of fungicides are generally less effective in preventing symptom development (Andrade et al., 2001a, b). However, treatment with guazatine or imazalil, hot water or waxing decreased the viability of the pathogen in black spot lesions (Korf et al., 2001). Postharvest waxing also decreased the manifestation of symptoms following postharvest storage (Wild, 1981).
ReferencesTop of page
AVA, 2001. Diagnostic records of the Plant Health Diagnostic Services, Plant Health Centre, Agri-food & Veterinary Authority, Singapore
Baayen RP, Bonants PJM, Verkley G, Carroll GC, Aa HAvan der, Weerdt Mde, Brouwershaven IRvan, Schutte GC, Maccheroni WJr, Blanco CGde, Azevedo JL, 2002. Nonpathogenic isolates of the citrus black spot fungus, Guignardia citricarpa, identified as a cosmopolitan endophyte of woody plants, G. mangiferae (Phyllosticta capitalensis). Phytopathology, 92(5):464-477; 43 ref
Barr ME, 1972. Preliminary studies on the Dothideales in temperate North America. Contrib. Univ. Mich. Herb., 9:523-638
Bassimba, D. D. M., Nzambi, N., Paixão, M. I. S., Katula, I. G., Vicent, A., 2018. First report of citrus black spot caused by Phyllosticta citricarpa in Angola. Plant Disease, 102(3), 683. http://apsjournals.apsnet.org/loi/pdis doi: 10.1094/pdis-09-17-1374-pdn
Bissett J, 1986. A note on the typification of Guignardia. Mycotaxon, 25:519-522
Bonants PJM, Carroll GC, Weerdt Mde, Brouwershaven IRvan, Baayen RP, 2003. Development and validation of a fast PCR-based detection method for pathogenic isolates of the citrus black spot fungus, Guignardia citricarpa. European Journal of Plant Pathology, 109(5):503-513
Brentu FC, Oduro KA, Offei SK, Odamtten GT, Vicent A, Peres NA, Timmer LW, 2012. Crop loss, aetiology, and epidemiology of citrus black spot in Ghana. European Journal of Plant Pathology, 133(3):657-670. http://springerlink.metapress.com/link.asp?id=100265
Chiu RJ, 1955. Studies on black spot of citrus. J. Agric. For., 9:1-8
Cobb NA, 1897. Letters on the diseases of plants: black-spot of the orange. Agr. Gazette New South Wales, 8:229-31
Das, A. K., Nerkar, S., Kumar, A., 2018. First report of Phyllosticta citricarpa causing citrus black spot on Citrus sinensis and C. reticulata in India. Plant Disease, 102(8), 1661-1662. http://apsjournals.apsnet.org/loi/pdis doi: 10.1094/PDIS-08-17-1248-PDN
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Foguet JL, Deramallo NV, Leal GT, 1985. Presencia de mancha negra de los citros en Tucumßn. Avance Agroindustrial, 6:9-10
Garran SM, 1996. Citrus black spot in the Northeast of Entre Rios: etiology, epidemiology and control. Proceedings of the International Society of Citriculture, 466-470
Gent-Pelzer MPEvan, Brouwershaven IRvan, Kox LFF, Bonants PJM, 2007. A TaqMan PCR method for routine diagnosis of the quarantine fungus Guignardia citricarpa on citrus fruit. Journal of Phytopathology, 155(6):357-363. http://www.blackwell-synergy.com/loi/jph
Goes A de, 2002. Efeito da combinatpo de fungicidas sistOmicos e protetores no controle da mancha preta dos frutos citricos causada por Guignardia citricarpa. Summa Phytopathologia, 28:9-13
Goes A de, Andrade AG, Moretto KCK, 2000. Efeito de diferentes tipos de =leos na mistura de benomyl + mancozeb no controle de Guignardia citricarpa, agente causal da mancha preta dos frutos cftricos. Summa Phytopathologica, 26:233-236
Goes A de, Feitchtenberger E, 1993. OcorrOncia da mancha preta causada por Phyllosticta citricarpa (McAlp.) Van der Aa (Guignardia citricarpa Kiely) em pomares cftricos do Estado de Spo Paulo. Fitopatologia Brasileira, 18:138
Grasso S, 1970. Notes on the principal cryptogamic diseases of citrus in several countries of eastern Asia (Japan, Formosa, Hong Kong and the Philippines). Universita di Catania, Italy. Tecnica Agricola, 22:577-591
Hall EG, 1973. Storage and market diseases of [citrus] fruit. XVI. CSIRO Food Research Quarterly, 33:3, Supplement
Huang CS, Chang SL, 1972. Leaf infection with citrus black spot and perithecial development in relation to ascospore discharge of Guignardia citricarpa Kiely. Journal of Taiwan Agricultural Research, 21(4):256-263
Kiely TB, 1948. Preliminary studies on Guignardia citricarpa n. sp., the acigerous stage of Phoma citricarpa McAlp., and its relation to blackspot of citrus. Proceedings of the Linnaean Society of New South Wales, 73:249-92
Kiely TB, 1950. Control and epiphytology of black spot of citrus. New South Wales Department of Agriculture Science Bulletin, 71:1-66
Korf HJG, Schutte GC, KotzT JM, 2001. Effect of packhouse procedures on the viability of Phyllosticta citricarpa, anamorph of the citrus black spot pathogen. African Plant Protection, 7(2):103-109; 15 ref
KotzT JM, 2000. Black spot. In Compendium of Citrus Diseases, LW Timmer SM Garnsey, JH Graham, eds. St Paul, Minnesota, USA: APS Press, 23-25
Lee YS, 1969. Pathogenicity of different isolates of Guignardia citricarpa Kiely from various sources of Ponkan fruits, Journal of Taiwan Agriculture Research Agriculture Research, 18:45-50
Lee YS, Huang CS, 1973. Effect of climatic factors on the development and discharge of ascospores of the citrus black spot fungus. Journal of Taiwan Agricultural Research, 22:135-144
McAlpine D, 1899. Fungus diseases of citrus trees in Australia and their treatment. Melbourne, Australia: Brain
McOnie KC, 1964. The latent occurence in citrus and other hosts of a Guignardia easily confused with G. citricarpa, the citrus black spot pathogen. Phytopathology, 54:40-43
McOnie KC, 1967. Germination and infection of citrus by ascospores of Guignardia citricarpa in relation to control of black spot. Phytopathology, 57:743-746
Miles AK, Tan YP, Tan MK, Donovan NJ, Ghalayini A, Drenth A, 2013. Phyllosticta spp. on cultivated Citrus in Australia. Australasian Plant Pathology, 42(4):461-467. http://rd.springer.com/article/10.1007/s13313-013-0208-0
Moran Lemir AH, Stadnik MJ, Buchenauer H, Canton NV, 2000. In vitro production of ascospores and pathogenicity of Guignardia citricarpa, causal agent of citrus black spot. Summa Phytopathologica, 26(3):374-376; 13 ref
Nam KW, Kweon HM, Song NH, 1993. Storage of satsuma mandarin. I. Storability of satsuma mandarin influenced by thiophanate-methyl treatment and mechanical injuries. Journal of the Korean Society for Horticultural Science, 34(4):279-284
Punithalingam E, 1974. Studies on Sphaeropsidales in culture. II. Mycological Papers, 136:1-63
Reeder R, Kelly PL, Harling R, 2009. First confirmed report of citrus black spot caused by Guignardia citricarpa on sweet oranges (Citrus sinensis) in Uganda. Plant Pathology, 58(2):399. http://www.blackwell-synergy.com/loi/ppa
Reis RR, 2002. InfluOncia de controle e de fatores climßticos na produtpo e liberatpo de asc=sporos de Guignardia citricarpa, em pomares de laranjeiras 'Natal e 'ValOncia'. Jaboticabal: [s.n.], 2002. vi, 87 f.. Dissertatpo (mestrado) - Universidade Estadual Paulista, Faculdade de CiOncias Agrßrias e Veterinßrias
Robbs CF, Bittencourt AM, 1995. A mancha preta dos frutos um dos fatores limitantes a produtpo citrfcola do estado do Rio de Janeiro. Comunicado TTcnico, EMBRAPA, CTAAA, 19: 1-5
Robbs CF, Pimentel JP, Ribeiro RLD, 1980. A mancha preta dos frutos cftricos causada por Phoma citricarpa. Fitopatologia Brasileira, 5:445
Rodriguez VA, Mazza Gaiad SM, 1996. The effects of fungicides and fertilization on the control of black spot of citrus (Guignardia citricarpa). Proceedings of the International Society of Citriculture, 5:482-484
Sanders GM, Meyer L, Kosten L, 2003. Application of species-specific primers in the South African citrus industry. Proceedings of the International Congress Plant Pathology, Christchurch, New Zealand, 82
Santos PJCdos, Savi DC, Gomes RR, Goulin EH, Senkiv Cda C, Tanaka FAO, Almeida ÁMR, Galli-Terasawa L, Kava V, Glienke C, 2016. Diaporthe endophytica and D. terebinthifolii from medicinal plants for biological control of Phyllosticta citricarpa. Microbiological Research, 186/187:153-160. http://www.sciencedirect.com/science/journal/09445013
Schubert TS, Dewdney MM, Peres NA, Palm ME, Jeyaprakash A, Sutton B, Mondal SN, Wang NY, Rascoe J, Picton DD, 2012. First report of Guignardia citricarpa associated with citrus black spot on sweet orange (Citrus sinensis) in North America. Plant Disease, 96(8):1225. http://apsjournals.apsnet.org/loi/pdis
Stringari D, Glienke C, Christo Dde, Maccheroni Júnior W, Azevedo JLde, 2009. High molecular diversity of the fungus Guignardia citricarpa and Guignardia mangiferae and new primers for the diagnosis of the Citrus Black Spot. Brazilian Archives of Biology and Technology, 52(5):1063-1073. http://www.tecpar.br
Timmer LW, 1999. Diseases of fruit and foliage. In: Timmer LW, Duncan LW, eds. Citrus Health Management. St. Paul, Minnesota, USA: APS Press, 107-115
Tomlinson JA, Ostoja-Starzewska S, Webb K, Cole J, Barnes A, Dickinson M, Boonham N, 2013. A loop-mediated isothermal amplification-based method for confirmation of Guignardia citricarpa in citrus black spot lesions. European Journal of Plant Pathology, 136(2):217-224. http://rd.springer.com/journal/10658
Tsai YP, 1981. Citrus black spot control in Taiwan. Proceedings of the International Society of Citriculture, 1981. Volume I, 344-346, 20
Van der Aa HY, 1973. Studies in Phylloticta. Studies in Mycologia, 5:1-110
Whiteside JO, 1965. Blackspot disease in Rhodesia. Rhodesia Agricultural Journal, 64:87-91
Wild BL, 1981. The effects of waxing citrus fruit. Rural Newsletter, 79:14-19
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