Pseudocercospora Fruit and Leaf Spot

Pseudocercospora Fruit and Leaf Spot


 

History of Pseudocercospora Fruit and Leaf Spot (PFLS)

Pseudocercospora Fruit and Leaf Spot (PFLS), formerly known as Phaeoramularia Fruit and Leaf Spot, is a fungal disease caused by Pseudocercospora angolensis. This disease is currently found in Sub-Saharan Africa, the Comoros Islands, and Yemen, but not in South Africa, a major citrus producing country. PFLS was first found in 1952 in Angola and Mozambique and has since become a serious disease in Sub-Saharan Africa. The fungus thrives in warm humid environments which increases the potential of a disease establishment in Florida. This disease causes extensive damage, not only to the fruit, but also to the tree canopy. Without the use of fungicides, crop losses have been known to reach 50-100%. This disease affects all varieties of citrus, but grapefruit, oranges, pummelos, and mandarins are highly susceptible. Lemons are less susceptible than other types of citrus, followed by limes which are the least susceptible. At this time no alternate hosts of PFLS are known.   

How to Report a Suspected Find

If you suspect you may have Pseudocercospora Fruit and Leaf Spot, 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.

Fruit Symptoms

Lesions on young green fruit begin as small, individual, protruding swellings with yellow halos. Mature fruit lesions are dark brown to black and are generally ½ inch (10mm) in diameter. They are flat or sunken with a yellow halo and eventually develop necrotic centers. Their shape can be circular or irregular and the lesions can coalesce. Premature fruit drop can occur, but fruit may also remain on the tree and become dried up and mummified, leading to yield and profit loss. The infected fruit has poor juice quality and therefore cannot be used for processing or sold for the fresh market.

Leaf and Stem Symptoms

Leaf lesions of PFLS are circular to irregularly shaped. They can either be individual or coalescent with a brown or grayish center surrounded by a yellow halo. Young flush may look bleached in color and can be killed resulting in leaf drop. Leaves are the main source of inoculum. The lesions are brown to gray when the fungus is dormant, and when sporulating the lesions become black in color. The leaf lesions of PFLS can be mistaken for citrus canker, but unlike canker lesions which are raised, PFLS lesions are flat or sunken.

Stem symptoms of PFLS are rare and are usually the result of leaf lesions extending past the petiole. These lesions can become corky and crack. A collection of lesions in an area can cause stem dieback and results in secondary shoots growing at that point.

Spread

The causal agent of PFLS is the fungus Pseudocercospora angolensis and leaves are the main source of inoculum. The asexual spores (conidia) multiply on leaf lesions, become airborne, and are dispersed long distances by windblown rain. Conidia can also be dispersed short distances by rain splash. Humans can be another means of long distance spread when infected plant material and fruit are moved from area to area. Although the conditions in Florida are favorable for PFLS, more information is needed to determine the extent to which this disease could become established and spread in the state. There is no known sexual stage of this fungus.

Regulations and Management

There are no specific regulations for this exotic disease. However, it is always important when replanting in the field, to use only 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 about this disease. In countries affected by PFLS, fungicide sprays (copper hydroxide, chlorothalonil, and flusilazole) are used to manage this disease. Sprays are applied every 10-14 days and are required to form a protective coating on the fruit until several months after bloom when the fruit is most susceptible.

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Links

Resources

If you would like to obtain laminated identification sheets or copies of the other various educational materials, please contact Jamie Burrow, 863-956-8648 or jdyates@ufl.edu

Contacts

Megan Dewdney, Ph.D. Plant Pathologist 863.956.1151  mmdewdney@ufl.edu
Ozgur Batuman, Ph.D. Plant Pathologist 239.658.3400  obatuman@ufl.edu
Jamie Burrow Extension Program Coordinator 863.956.8648  jdyates@ufl.edu
Amit Levy, Ph.D. Plant Pathologist 863.956.1151  amitlevy@ufl.edu

Florida Multi-County Citrus Extension Agents