History of Citrus Tristeza Virus – Stem Pitting
The Citrus tristeza virus (CTV) has been a problem for growers in Florida since the 1960’s. There are 3 main strains of CTV which cause varying symptoms: quick decline, stem pitting, and seedling yellows. The strain that is found in Florida causes quick decline. This strain of CTV caused a major change in horticultural practices. Sour Orange was once a widely used rootstock and now is no longer a primary rootstock in Florida, because of its high susceptibility to the disease. Trees planted on Sour Orange were being lost to this disease at an alarming rate. The stem pitting (SP) strain of CTV, which is not currently found in Florida, is more severe and is caused by different isolates. CTV-SP is found in Asia, Australia, South Africa, Brazil, and Columbia. Limes and grapefruit are the most susceptible varieties, but sweet orange and Rough Lemon exhibit strong stem pitting symptoms when infected. Mandarins can also show stem pitting symptoms, but are considered tolerant to the virus. Unlike CTV-quick decline, CTV-SP is not a disease of the bud union, but it attacks the scion varieties regardless of the rootstock variety.
How to Report a Suspected Find
If you suspect you may have Citrus Tristeza - Stem Pitting, 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
Tree vigor declines as the infection becomes more severe, resulting in off-season bloom and poor fruit production. Fruit infected with CTV-SP do not grow properly causing them to be small and misshapen.
Leaf and Stem Symptoms
The CTV-SP virus can be found in the phloem and the severity of symptoms can vary greatly between citrus varieties. The virus symptoms can be observed by removing the bark of the branches and trunk. Symptoms can range from mild: exhibiting pitting of the wood, to severe: which exhibits a ropy appearance to the wood. These symptoms cause depressions in the bark. If severe, the symptoms can be seen without removing the bark. This distortion of the wood causes a disruption in the cambium cells, inhibiting the vascular system and the proper movement of water and nutrients in the tree. Twigs are often brittle with thick bark. Leaves become chlorotic and dieback can occur in the canopy. Tree vigor and growth is greatly reduced.
Spread
CTV-SP is most effectively spread by the brown citrus aphid (Toxoptera citricida), but can also be spread by the melon aphid (Aphis gossypii) and the spirea aphid (Aphis spiraecola) less effectively. All of these aphids are found in Florida, which increases the potential of CTV-SP being spread around the state. This virus can also be transmitted through budding and grafting, making the use of clean budwood essential to reduce an infection.
Regulations and Management
Because of the potential for spread through budding and grafting, budwood certification is essential for reducing the spread of CTV-SP. Always use clean budwood and purchase clean nursery stock from a registered nursery. Control of the brown citrus aphid can also help to reduce inoculum. Replanting with tolerant varieties is recommended if CTV-SP has become endemic in the area. Educational resources and identification tools should be utilized by grove workers, managers, and other industry professionals to increase awareness and knowledge of this disease. If CTV-SP is suspected do not move plant material out of the infected area, and contact your local CHRP office.
Publications
- Stem Pitting Citrus Tristeza R. Brlansky (October 2006) PDF
- CTV Status in Florida S.J. Harper, S.J. Cowell, S.E. Halbert, R.H. Brlansky and W.O. Dawson (April 2015) PDF
Photo Gallery
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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
For questions, please email crec-web@ifas.ufl.edu
