Citrus canker
Encyclopedia
Citrus canker is a disease affecting citrus
species that is caused by the bacterium Xanthomonas axonopodis. Infection causes lesions on the leaves, stems, and fruit
of citrus trees, including lime, oranges, and grapefruit. While not harmful to humans, canker significantly affects the vitality of citrus trees, causing leaves and fruit to drop prematurely; a fruit infected with canker is safe to eat but too unsightly to be sold.
The disease, which is believed to have originated in South East Asia, is extremely persistent when it becomes established in an area. Citrus groves have been destroyed in attempts to eradicate the disease. Brazil
and the United States
are currently suffering from canker outbreaks.
length approximately 5 Mbp
. There are a number of types of citrus canker disease caused by different pathovar
s and variants of the bacterium:
Plants infected with citrus canker have characteristic lesions on leaves, stems, and fruit with raised, brown, water-soaked margins, usually with a yellow halo
or ring effect around the lesion. Older lesions have a corky appearance, still in many cases retaining the halo effect. The bacterium propagates in lesions in leaves, stems, and fruit. The lesions ooze bacterial cells that, when dispersed by windblown rain, can spread to other plants in the area. Infection may spread further by hurricanes. The disease can also be spread by from contaminated equipment, and by transport of infected or apparently healthy plants. Due to latency of the disease, a plant may appear to be healthy, but actually be infected.
Citrus canker bacteria can enter through a plant's stomata or through wounds on leaves or other green parts. In most cases, younger leaves are considered to be the most susceptible. Also, damage caused by Citrus Leaf Miner larvae (Phyllocnistis citrella) can be sites for infection to occur. Within a controlled laboratory setting, symptoms can appear in 14 days following inoculation into a susceptible host. In the field environment, the time for symptoms to appear and be clearly discernible from other foliar diseases varies; it may be on the order of several months after infection. Lower temperature increases the latency of the disease. Citrus canker bacteria can stay viable in old lesions and other plant surfaces for several months.
(PCR) can be conducted to confirm diagnosis and may help to identify the particular canker strain.
-based bactericides, and destroying infected trees and all surrounding trees within an appropriate radius.
, South
and Central Africa
, the Middle East
, Bangladesh
, the Pacific Islands
, some countries in South America, and Florida
. Some areas of the world have eradicated citrus canker and others have ongoing eradication programs, but the disease remains endemic in most areas where it has appeared. Because of its rapid spread, high potential for damage, and impact on export sales and domestic trade, citrus canker is a significant threat to all citrus-growing regions.
and was eradicated each time. In 2004 an unexplained outbreak occurred in Central Queensland
. The state and federal governments ordered that all commercial groves, all non-commercial citrus trees, and all native lime trees (C. glauca) in the vicinity of Emerald
be destroyed rather than trying to isolate infected trees. Eradication was successful with permission to replant being granted to farmers by the biosecurity unit of the Queensland Department of Primary Industries in early 2009.
. Citrus agriculture is the second most important agricultural activity in the Brazil
ian state of São Paulo
, the largest sweet orange production area in the world. There are over 100,000 groves in São Paulo, and the area planted with citrus is increasing. Of the ~2 million trees, greater than 80% of the trees are a single variety of orange, and the remainder is made up of tangerine and lemon trees. Because of the uniformity in citrus variety the state has been adversely affected by canker, causing crop and monetary losses. In Brazil rather than destroying entire groves to eradicate the disease, contaminated trees and trees within a 30 m radius are destroyed, up to 1998 over half a million trees had been destroyed.
in 1910 not far from the Georgia
– Florida border. Subsequently, canker was discovered in 1912 in Dade County
, more than 400 miles (643.7 km) away. Beyond Florida, the disease was discovered in the Gulf States and reached as far north as South Carolina
. It took more than 20 years to eradicate that outbreak of citrus canker, from 1914 through 1931, $2.5 million in state and private funds were spent to control it—a sum equivalent to $28 million in 2000 dollars. In 26 counties, some 257,745 grove trees and 3,093,110 nursery trees were destroyed by burning. Citrus Canker was detected again on the Gulf Coast of Florida in 1986 and declared eradicated in 1994.
The most recent outbreak of citrus canker was discovered in Miami Dade County Florida on Sept. 28, 1995 , by Louis Willio Francillon, a Florida Department of Agriculture Agronomist . Despite eradication attempts, by late 2005 the disease had been detected in many places distant from the original discovery, for example, in Orange Park, FL, 315 miles (500 km) away. In January 2000, the Florida Department of Agriculture adopted a policy of removing all infected trees and all citrus trees within a 1900 ft radius of an infected tree in both residential areas and commercial groves. Previous to this eradication policy, the department eradicated all citrus trees within 125 ft of an infected one. The program ended in January 2006 following a statement from the USDA that eradication was infeasible.
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
species that is caused by the bacterium Xanthomonas axonopodis. Infection causes lesions on the leaves, stems, and fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
of citrus trees, including lime, oranges, and grapefruit. While not harmful to humans, canker significantly affects the vitality of citrus trees, causing leaves and fruit to drop prematurely; a fruit infected with canker is safe to eat but too unsightly to be sold.
The disease, which is believed to have originated in South East Asia, is extremely persistent when it becomes established in an area. Citrus groves have been destroyed in attempts to eradicate the disease. Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
are currently suffering from canker outbreaks.
Biology
Xanthomonas axonopodis is a rod shaped gram negative bacterium with polar flagella. The bacterium has a genomeGenome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
length approximately 5 Mbp
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
. There are a number of types of citrus canker disease caused by different pathovar
Pathovar
A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one or more plant hosts.Pathovars are named as a ternary or...
s and variants of the bacterium:
- The Asiatic type of canker (Canker A), X. axonopodis pv. citri, caused by a group of strains originally found in Asia, is the most widespread and severe form of the disease.
- Cancrosis B, caused by a group of X. axonopodis pv. aurantifolii strains originally found in South America is a disease of lemons, key limeKey limeThe Key lime is a citrus species with a globose fruit, 2.5–5 cm in diameter , that is yellow when ripe but usually picked green commercially. It is smaller, seedier, has a higher acidity, a stronger aroma, and a thinner rind than that of the Persian lime...
, bitter orangeBitter orangeThe name "bitter orange", also known as Seville orange, sour orange, bigarade orange, and marmalade orange, refers to a citrus tree and its fruit. Many varieties of bitter orange are used for their essential oil, which is used in perfume and as a flavoring...
, and pomeloPomeloThe pomelo is a citrus fruit native to Southeast Asia. It is usually pale green to yellow when ripe, with sweet white flesh and very thick albedo . It is the largest citrus fruit, 15–25 cm in diameter, and usually weighing 1–2 kg...
. - Cancrosis C, also caused by strains within X. axonopodis pv. aurantifolii, only infects key lime and bitter orange.
- A* strains, discovered in OmanOmanOman , officially called the Sultanate of Oman , is an Arab state in southwest Asia on the southeast coast of the Arabian Peninsula. It is bordered by the United Arab Emirates to the northwest, Saudi Arabia to the west, and Yemen to the southwest. The coast is formed by the Arabian Sea on the...
, Saudi ArabiaSaudi ArabiaThe Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
, IranIranIran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
, and IndiaIndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, only infects key lime.
Pathology
Halo (optical phenomenon)
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
or ring effect around the lesion. Older lesions have a corky appearance, still in many cases retaining the halo effect. The bacterium propagates in lesions in leaves, stems, and fruit. The lesions ooze bacterial cells that, when dispersed by windblown rain, can spread to other plants in the area. Infection may spread further by hurricanes. The disease can also be spread by from contaminated equipment, and by transport of infected or apparently healthy plants. Due to latency of the disease, a plant may appear to be healthy, but actually be infected.
Citrus canker bacteria can enter through a plant's stomata or through wounds on leaves or other green parts. In most cases, younger leaves are considered to be the most susceptible. Also, damage caused by Citrus Leaf Miner larvae (Phyllocnistis citrella) can be sites for infection to occur. Within a controlled laboratory setting, symptoms can appear in 14 days following inoculation into a susceptible host. In the field environment, the time for symptoms to appear and be clearly discernible from other foliar diseases varies; it may be on the order of several months after infection. Lower temperature increases the latency of the disease. Citrus canker bacteria can stay viable in old lesions and other plant surfaces for several months.
Detection
The disease can be detected in groves and on fruit by the appearance of lesions. Early detection is critical in quarantine situations. Bacteria can be tested for pathogenicity by inoculating multiple citrus species with the bacterium. Additional diagnostic tests (antibody detection, fatty-acid profiling, and genetic procedures using polymerase chain reactionPolymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
(PCR) can be conducted to confirm diagnosis and may help to identify the particular canker strain.
Susceptibility
All species and varieties of citrus have not been tested for citrus canker. Most of the common species and varieties of citrus are susceptible to citrus canker. Some species are more susceptible than others, while a few species are resistant to infection.| Susceptibility | Variety |
|---|---|
| Highly susceptible | Grapefruit Grapefruit The grapefruit , is a subtropical citrus tree known for its sour fruit, an 18th-century hybrid first bred in Barbados. When found, it was named the "forbidden fruit"; it has also been misidentified with the pomelo or shaddock , one of the parents of this hybrid, the other being sweet orange The... (Citrus x paradisi), Key lime Key lime The Key lime is a citrus species with a globose fruit, 2.5–5 cm in diameter , that is yellow when ripe but usually picked green commercially. It is smaller, seedier, has a higher acidity, a stronger aroma, and a thinner rind than that of the Persian lime... (C. aurantiifolia), Pointed leaf Hystrix (C. hystrix), lemon Lemon The lemon is both a small evergreen tree native to Asia, and the tree's ellipsoidal yellow fruit. The fruit is used for culinary and non-culinary purposes throughout the world – primarily for its juice, though the pulp and rind are also used, mainly in cooking and baking... (C. limon) |
| Susceptible | Limes (C. latifolia) including Tahiti lime, Palestine sweet lime; Trifoliate orange Trifoliate orange Trifoliate Orange, Poncirus trifoliata , is a member of the family Rutaceae, closely related to Citrus, and sometimes included in that genus, being sufficiently closely related to allow it to be used as a rootstock for Citrus... (Poncirus trifoliata); Citranges/Citrumelos (P. trifoliata hybrids); Tangerine Tangerine __notoc__The tangerine is an orange-colored citrus fruit which is closely related to the Mandarin orange . Taxonomically, it should probably be formally named as a subspecies or variety of Citrus reticulata; further work seems to be required to ascertain its correct scientific name... s, Tangor Tangor The tangor is a citrus fruit hybrid of the mandarin orange and the sweet orange... s, Tangelo Tangelo The tangelo , Citrus × tangelo, is also widely known as the honeybell. Tangelo is a citrus fruit that is a hybrid of a tangerine and either a pomelo or a grapefruit. The fruits are the size of an adult fist and have a tangerine taste, but are very juicy, to the point of not providing much flesh... s (C. reticulata hybrids); Sweet oranges (C. sinensis); Bitter oranges (C. aurantium) |
| Resistant | Citron Citron Not to be confused with Cintron.The citron is a fragrant citrus fruit, botanically classified as Citrus medica by both the Swingle and Tanaka systems... (C. medica), Mandarin Mandarin orange The orange, also known as the ' or mandarine , is a small citrus tree with fruit resembling other oranges. Mandarin oranges are usually eaten plain or in fruit salads... s (C. reticulata) |
| Highly resistant | Calamondin Calamondin × Citrofortunella microcarpa, the Calamondin or Calamansi, is a fruit tree in the family Rutaceae, commonly called the calamondin, golden lime, panama orange, chinese orange, acid orange, calamonding, or calamandarin in English. It is believed to originate from China and has spread throughout... (X Citrofortunella), Kumquat Kumquat Cumquats or kumquats are a group of small fruit-bearing trees in the flowering plant family Rutaceae, either forming the genus Fortunella, or placed within Citrus sensu lato... (Fortunella spp.) |
| Modified from: Gottwald, T.R. et al. (2002). Citrus canker: The pathogen and its impact. Online. Plant Health Progress | |
Management
Citrus canker outbreaks are prevented and managed in a number of ways. In countries that do not have canker, the disease is prevented from entering the country by quarantine measures. In countries with new outbreaks, eradication programs that are started soon after the disease has been discovered have been successful; such programs rely on destruction of affected groves. When eradication has been unsuccessful and the disease has become established, management options include replacing susceptible citrus cultivars with resistant cultivars, applying preventive sprays of copperCopper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
-based bactericides, and destroying infected trees and all surrounding trees within an appropriate radius.
Distribution and economic impact
Citrus canker is thought to originate in the area of Southeast Asia-India. It is now also present in JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, South
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
and Central Africa
Central Africa
Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....
, the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
, Bangladesh
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
, the Pacific Islands
Pacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
, some countries in South America, and Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
. Some areas of the world have eradicated citrus canker and others have ongoing eradication programs, but the disease remains endemic in most areas where it has appeared. Because of its rapid spread, high potential for damage, and impact on export sales and domestic trade, citrus canker is a significant threat to all citrus-growing regions.
Australia
The citrus industry is the largest fresh-fruit exporting industry in Australia. Australia has had three outbreaks of citrus canker, all of which have been successfully eradicated. The disease was found twice during the 1900s in the Northern TerritoryNorthern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
and was eradicated each time. In 2004 an unexplained outbreak occurred in Central Queensland
Central Queensland
Central Queensland is an ambiguous geographical division of Queensland that centres on the eastern coast, around the Tropic of Capricorn. Its major regional centre is Rockhampton and the Capricorn Coast and the area extends west to the Central Highlands at Emerald, north to the Mackay Regional...
. The state and federal governments ordered that all commercial groves, all non-commercial citrus trees, and all native lime trees (C. glauca) in the vicinity of Emerald
Emerald, Queensland
Emerald is a town located in the Central Highlands district of Central Queensland, Australia. At the 2006 census, Emerald had a population of 10,999. The town is the business centre for the Central Highlands Regional Council....
be destroyed rather than trying to isolate infected trees. Eradication was successful with permission to replant being granted to farmers by the biosecurity unit of the Queensland Department of Primary Industries in early 2009.
Brazil
Citrus is an important domestic and export crop for BrazilBrazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. Citrus agriculture is the second most important agricultural activity in the Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
ian state of São Paulo
São Paulo (state)
São Paulo is a state in Brazil. It is the major industrial and economic powerhouse of the Brazilian economy. Named after Saint Paul, São Paulo has the largest population, industrial complex, and economic production in the country. It is the richest state in Brazil...
, the largest sweet orange production area in the world. There are over 100,000 groves in São Paulo, and the area planted with citrus is increasing. Of the ~2 million trees, greater than 80% of the trees are a single variety of orange, and the remainder is made up of tangerine and lemon trees. Because of the uniformity in citrus variety the state has been adversely affected by canker, causing crop and monetary losses. In Brazil rather than destroying entire groves to eradicate the disease, contaminated trees and trees within a 30 m radius are destroyed, up to 1998 over half a million trees had been destroyed.
United States
Citrus canker was first found in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in 1910 not far from the Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
– Florida border. Subsequently, canker was discovered in 1912 in Dade County
Miami-Dade County, Florida
Miami-Dade County is a county located in the southeastern part of the state of Florida. As of 2010 U.S. Census, the county had a population of 2,496,435, making it the most populous county in Florida and the eighth-most populous county in the United States...
, more than 400 miles (643.7 km) away. Beyond Florida, the disease was discovered in the Gulf States and reached as far north as South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
. It took more than 20 years to eradicate that outbreak of citrus canker, from 1914 through 1931, $2.5 million in state and private funds were spent to control it—a sum equivalent to $28 million in 2000 dollars. In 26 counties, some 257,745 grove trees and 3,093,110 nursery trees were destroyed by burning. Citrus Canker was detected again on the Gulf Coast of Florida in 1986 and declared eradicated in 1994.
The most recent outbreak of citrus canker was discovered in Miami Dade County Florida on Sept. 28, 1995 , by Louis Willio Francillon, a Florida Department of Agriculture Agronomist . Despite eradication attempts, by late 2005 the disease had been detected in many places distant from the original discovery, for example, in Orange Park, FL, 315 miles (500 km) away. In January 2000, the Florida Department of Agriculture adopted a policy of removing all infected trees and all citrus trees within a 1900 ft radius of an infected tree in both residential areas and commercial groves. Previous to this eradication policy, the department eradicated all citrus trees within 125 ft of an infected one. The program ended in January 2006 following a statement from the USDA that eradication was infeasible.
External links
- Species Profile- Citrus Canker (Xanthomonas axonopodis), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
. Lists general information and resources for Citrus Canker. - Should Florida Learn to Live with Canker - Redorbit
- http://www.highbeam.com/doc/1G1-77877735.html