# Citrus tristeza virus
**Citrus tristeza virus** (CTV, Citrus tristeza closterovirus) is a viral species of the genus *Closterovirus* that causes the most economically damaging disease of citrus. The species is ICTV-accepted and was formerly called Citrus tristeza closterovirus.[5](https://ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=12162) Reviews of a century of epidemics attribute more than 100 million dead citrus trees to the virus, and it continues to threaten citrus industries today.[1](https://par.nsf.gov/servlets/purl/10613158) • [3](https://doi.org/10.33545/26174693.2025.v9.i3sc.3938)
| Key facts | |
|---|---|
| Agent | Citrus tristeza virus, genus *Closterovirus*[5](https://ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=12162) |
| Virion | Flexuous rod, about 2000 nm long and 11–12 nm in diameter[1](https://par.nsf.gov/servlets/purl/10613158) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/) |
| Genome | Single-stranded (+)-sense RNA, about 19.3 kb; 12 open reading frames[1](https://par.nsf.gov/servlets/purl/10613158) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/) |
| Vectors | Aphids, most efficiently the brown citrus aphid (*Toxoptera citricida*); also infected budwood[1](https://par.nsf.gov/servlets/purl/10613158) |
| Main syndromes | Quick decline, stem pitting, seedling yellows, lime vein clearing[1](https://par.nsf.gov/servlets/purl/10613158) |
| Impact | More than 100 million trees killed worldwide[1](https://par.nsf.gov/servlets/purl/10613158) |
## The pathogen
CTV has a flexuous rod-shaped virion measuring 2000 nm in length and 12 nm in diameter; a biophysical characterization gives dimensions of about 2000 × 11 nm, with roughly 6% of the virion mass being RNA.[1](https://par.nsf.gov/servlets/purl/10613158) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/) It was the first closterovirus to be biophysically characterized.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/)
The genome is a single-stranded positive-sense RNA about 19.3 kilobases long, the largest nonsegmented genome known among plant RNA viruses.[1](https://par.nsf.gov/servlets/purl/10613158) It contains 12 open reading frames flanked by 5′ and 3′ untranslated regions (107 and 275 nucleotides in the T36 variant), which could encode at least 17 proteins.[1](https://par.nsf.gov/servlets/purl/10613158) Complete nucleotide sequences have been determined for at least nine distinct isolates.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/) The virion is bipolar: two coat proteins of 25 kDa (CP) and 27 kDa (CPm) encapsidate about 97% and 3% of the virion length, respectively.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/)
## Hosts and symptoms
CTV infects several species of the genus *Citrus*, including sour orange (*Citrus aurantium*) and any *Citrus* grafted onto sour orange rootstock, key lime and Seville orange, Hassaku orange and sweet orange, grapefruit, and mandarin. It also infects *Aeglopsis chevalieri*, *Afraegle paniculata*, and *Pamburus missionis* of the citrus subfamily Aurantioideae, as well as *Passiflora gracilis*, which belongs to an entirely different lineage of rosid plants. The virus is distributed worldwide wherever citrus trees grow.[6](https://www.annualreviews.org/content/journals/10.1146/annurev-virology-100520-114412)
Symptoms vary with host, strain virulence, and environmental conditions. A review distinguishes four main syndromes: quick decline and stem pitting, which are serious diseases of commercial citrus, and lime vein clearing and seedling yellows, which are mainly observed under laboratory conditions.[1](https://par.nsf.gov/servlets/purl/10613158)
Decline appears in sweet orange, mandarin, or grapefruit grafted on infected sour orange rootstock.
## Diagnosis and transmission
CTV is classically diagnosed by graft-inoculating a Mexican lime with tissue from a diseased plant, which develops predictable symptoms: leaf veins that turn corky, followed by chlorosis, and leaf cupping. Aggregates of cross-banded inclusion bodies in the phloem also indicate infection.
The virus replicates in the phloem cells of its hosts and is limited to phloem tissue. It is transmitted semi-persistently by aphids that penetrate the phloem to feed, and also in infected planting material used for grafting.[1](https://par.nsf.gov/servlets/purl/10613158) • [3](https://doi.org/10.33545/26174693.2025.v9.i3sc.3938) The brown citrus aphid (*Toxoptera citricida*) is considerably more efficient than other citrus aphids; in Florida it was shown to be six to twenty-five times as efficient as *Aphis gossypii*, the state's most efficient vector before the brown citrus aphid's arrival prior to 1995.
## Management
Quarantine works only where few trees are infected; where the brown citrus aphid is established, trees whose budwood is not free of CTV are destroyed because of how quickly the vector spreads the virus. Grafting on tristeza-tolerant rootstock instead of sour orange is the main cultural safeguard: Asian growers have long used [trifoliate orange](https://www.edgepedia.org/trifoliate-orange), Sunki, and Shiikuwasha rootstock, and hybrids such as Troyer citrange and Swingle citromelo show promise. Virus-free trees are produced by shoot-tip grafting or heat treatment. Where a virus-free field is impractical, preinoculation with a mild CTV strain protects trees against severe strains, provided bud-stock trees are inoculated at least four to six months before propagation and kept aphid-free.
## Impact
Epidemics in the first half of the twentieth century killed over 100 million trees, and the spread of *T. citricida* has increased the severity of the disease in [Central America](https://www.edgepedia.org/central-america) and the United States.[1](https://par.nsf.gov/servlets/purl/10613158)
## References
1. Citrus tristeza virus: A century-long challenge for the world's citrus industries. https://par.nsf.gov/servlets/purl/10613158
2. Citrus tristeza virus: a pathogen that changed the course of the citrus industry. https://pmc.ncbi.nlm.nih.gov/articles/PMC6640355/
3. The complex world of Citrus tristeza virus: A review on its impact on Citrus production and management approaches. https://doi.org/10.33545/26174693.2025.v9.i3sc.3938
4. Citrus tristeza virus: A large RNA virus with complex biology turned into a valuable tool for crop protection. PLOS Pathogens. https://journals.plos.org/plospathogens/article?id=10.1371%2Fjournal.ppat.1008416
5. Taxonomy browser: Citrus tristeza virus. NCBI. https://ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=12162
6. [Citrus Tristeza Virus: From Pathogen to Panacea, Annual Reviews](https://www.annualreviews.org/content/journals/10.1146/annurev-virology-100520-114412)
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*Topic: Encyclopedia › Life and health › Microorganisms and fungi › Viruses and acellular agents › Viruses of plants, fungi, protists, and other non-animal hosts › Crop and plant virus species › Citrus viruses*
*Initially written Sep 17, 2026 · Reviewed: Sep 19, 2026 · Edited: Sep 19, 2026; Oct 25, 2026 · Last review: Sep 19, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license