History of Citrus Leprosis
Citrus Leprosis is a non-systemic viral disease that is currently found in Mexico, Brazil and other countries in South and Central America. The virus is spreading northward towards the United States. The causal agent is the Citrus leprosis virus which is transmitted by the Tenuipalpidae family of false spider mites, genus Brevipalpus, also known as flat mites. These mites are currently found in Florida. This disease will only spread when both the virus and the vector (mites) are present.
There are two main types of Leprosis: C-type and N-type. The names refer to where in the cell the virus is located. The virus in the C-type Leprosis is located in the cytoplasm of the cell and the virus in the N-type Leprosis is located in the nucleus. The C-type Leprosis is more aggressive than the N-type. The symptoms of each type differ somewhat on the leaves and fruit, but not on the stem.
In the 1860’s, Leprosis was found in Florida and resulted in reduced citrus production. By 1926, there was a decline in the incidence of Leprosis, and by the 1950’s it was reported only on the east coast in small isolated areas. It is unclear why Leprosis disappeared from Florida, but it is thought that the increased use of miticides and cold winter temperatures contributed to the severe decline in mite populations, resulting in reduced inoculum and transmission. Leprosis has not been reported in Florida since 1968.
How to Report a Suspected Find
If you suspect you may have Leprosis, please contact your local Florida Department of Agriculture and Consumer Service's CHRP office for further diagnostic testing. Do not move infected plant material out of the area.
Sweet orange and mandarin varieties are most susceptible to Leprosis, but it can also affect Sour Orange. The rind of the fruit is affected by lesions produced at every feeding spot of the mites. As the fruit matures, the lesions become more pronounced and can be circular or irregularly shaped. The lesions can be either single or become coalescent. The centers of the lesions may crack with high temperatures. If the infection occurs when the fruit is close to harvest, the internal quality of the fruit is not compromised. Fruit infected with Leprosis can change color early and also become susceptible to rot. Premature fruit drop can occur from multiple lesions being present on the fruit, resulting in yield loss. Flowering is unaffected by Leprosis.
Leaf and Stem Symptoms
Each lesion represents a feeding spot from a mite. The symptoms typically take 1-2 months to appear after inoculation. Leaf symptoms of Leprosis start as yellow chlorotic spots and become brown in color. The lesions may also develop necrotic centers as they age. Leaf lesions are smooth to the touch. With severe infection, premature defoliation of the canopy can occur, which affects the health of the tree and impacts fruit production.
Stem and twig symptoms begin as chlorotic, shallow lesions that become dark brown to reddish in color. As the lesions age, they become corky and develop into scaling of the bark. The lesions can also cause girdling of the stem when they coalesce, resulting in stem and twig dieback .
Citrus Leprosis is spread by the Brevipalpus flat mite. As the mite feeds on the leaf, stem, or fruit, the plant tissue is infected with the virus. The mite can transmit the virus in any active stage of its life, but the virus is not thought to be transovarial, which means transmitted from the female to her offspring. For a mite to be infected with the virus, it must feed on infected plant material. The virus then multiplies within the mite, causing it to be a vector of the virus for the rest of its life.
Regulations and Management
Leprosis is not currently found in Florida. The USDA has developed a recovery plan if the disease should enter the United States. This recovery plan can be found below in the links section. The Brevipalpus mite is present in Florida, which increases the potential of a Leprosis outbreak, should the virus enter Florida. When replanting in the field, only use clean nursery stock from registered nurseries. Monitoring of groves and early detection are essential to reduce the spread of the disease and aid in eradication efforts, should this disease enter Florida. Educational resources and identification tools should be utilized by grove workers, managers, and other industry professionals to increase awareness and knowledge of this disease. In countries where the disease is present, growers prune out diseased wood to reduce the amount of inoculum present and chemical control of mites is recommended to reduce populations.
- Citrus Leprosis Research Update. R. Brlansky, W. Schneider, J. Hartung & A. Roy (August 2015)
- Citrus Leprosis: Understanding a Re-emerging Threat to Citrus Production. R. Brlansky & A. Roy (July 2014)
- Review of Exotic Citrus Diseases. M. Dewdney & R. Brlansky (November 2014)
If you would like to obtain laminated identification sheets or copies of the other various educational materials, please contact Jamie Burrow, 863-956-1151 ext. 1302 or firstname.lastname@example.org
|Ozgur Batuman, Ph.D.||Plant Pathologist||239.658.3400 email@example.com|
|Ron Brlansky, Ph.D.||Professor Emeritus, Plant Pathology||863.956.1151 firstname.lastname@example.org|
|Jamie Burrow||Extension Program Coordinator||863.956.8648 email@example.com|
|Megan Dewdney, Ph.D.||Plant Pathologist||863.956.1151 firstname.lastname@example.org|
|Amit Levy, Ph.D.||Plant Pathologist||863.956.1151 email@example.com|
|Jawwad Qureshi, Ph.D.||Entomologist||772.468.3922 firstname.lastname@example.org|
|Phil Stansly, Ph.D.||Entomologist||239.658.3400 email@example.com|
|Lukasz Stelinski, Ph.D||Entomologist||863.956.1151 firstname.lastname@example.org|
Florida Multi-County Citrus Extension Agents