Florida Citrus Canker and Citrus Greening

Citrus canker and citrus greening (huanglongbing, or HLB) are two bacterial diseases of Florida citrus: canker causes lesions on leaves, stems and fruit, while greening attacks the tree's vascular system and cannot be cured once a tree is infected (FDACS Citrus Canker FAQ; FDACS).

Citrus canker produces brown, raised lesions with an oily, water-soaked margin and a yellow halo on Florida citrus leaves, stems and fruit, and it causes premature leaf and fruit drop until a tree becomes unproductive (FDACS Citrus Canker FAQ). Old leaf lesions can fall out and leave a shot-hole look. Infected fruit is safe to eat but too unsightly to be sold.

Citrus greening is caused by the bacterium Candidatus Liberibacter asiaticus, and the Chinese name huanglongbing means yellow shoot disease, after the bright yellow shoot symptom that commonly occurs on a sector of an infected tree (UF/IFAS CG086). It affects every citrus cultivar regardless of rootstock; symptoms are severe on sweet orange, mandarins and mandarin hybrids and moderate on lemon and sour orange. The bacterium found in Florida has not been cultured, and formal diagnosis is done by PCR.

The two diseases do not travel the same way through Florida groves. FDACS says greening moves mainly through citrus psyllids and also through grafting and the movement of infected plant material, but not through casual contact with tools or through wind and rain (FDACS). Canker is the opposite: it spreads rapidly by wind and rain, landscaping equipment, hands, clothing and moved plants (FDACS). Both sit on the USDA list of five exotic citrus pests and diseases established in the United States (USDA APHIS).

Florida fought the 1995 canker outbreak with a joint FDACS and USDA eradication program that cut infected and nearby citrus trees until 2006, when, after the 2004 and 2005 hurricanes spread it through the main citrus regions, canker was classified as endemic (UF/IFAS FE915).

Canker has been a serious concern in commercial Florida citrus groves since an outbreak was detected in south Florida in 1995 (UF/IFAS). The FDACS Division of Plant Industry and USDA program first removed diseased trees and every other citrus tree within 125 feet. In 2000 the eradication radius was extended to 1,900 feet. Homeowners in certain Florida counties challenged the rule and its constitutionality, which temporarily halted eradication and let the disease spread.

During 2004 and 2005, four hurricanes and one tropical storm crossed Florida and carried canker through the state's main citrus production regions (UF/IFAS FE915). In 2006 the eradication program was terminated and canker was classified as endemic. Growers switched to extra copper sprays, and fresh market growers had to certify that groves and fruit packed in cartons were free of canker to meet USDA and foreign market rules, particularly those of Europe.

FDACS now says the individual canker quarantines have been eliminated, but a USDA statewide quarantine remains and restricts shipping or taking citrus fruit out of Florida (FDACS). Voluntary removal of a backyard citrus tree is allowed.

Citrus greening was found for the first time in the United States in August 2005 in south Miami-Dade County, seven years after its insect carrier, the Asian citrus psyllid, was discovered in Florida in 1998 (FDACS; UF/IFAS).

The Asian citrus psyllid is now found throughout Florida wherever citrus is grown, and it is present year round, with peak activity and movement in spring and summer when trees push new flush (UF/IFAS CG086). Because HLB is so common in Florida citrus, a moving psyllid is likely to carry the bacterium from tree to tree, adding disease pressure to infected trees and establishing it in young plantings. UF/IFAS notes that young trees can die within one to two years of planting and that HLB also travels in infected budwood.

Blotchy mottle, an asymmetrical yellowing of the leaf, is among the early leaf symptoms, and UF/IFAS calls it the most diagnostic symptom of greening, especially on sweet orange (UF/IFAS CG086). It can be confused with severe citrus tristeza virus, Phytophthora root rot, waterlogging, citrus blight and some nutrient deficiencies, and UF/IFAS notes that diagnosis by symptoms alone may be difficult.

Some ornamental plants also host greening. FDACS lists Chinese box orange and curry leaf among greening hosts (FDACS), and UF/IFAS says orange jessamine and box orange host both the psyllid and the bacterium, so their movement is restricted under state compliance agreements (UF/IFAS).

Florida had 165,359 acres of commercial citrus in the 2026 Commercial Citrus Inventory, down 21 percent from the last annual survey and down from 797,303 acres in the 2002 survey (USDA NASS).

Every one of the 23 Florida counties NASS publishes lost citrus acreage in the 2026 survey (USDA NASS). Polk County lost the most, 10,944 acres, yet still leads with 37,529 acres, followed by Highlands County with 34,671 acres. New plantings fell to 5,200 acres. Orange groves cover 143,650 acres, and Valencia accounts for 67 percent of that orange acreage.

All orange production in Florida increased 5 percent to 13.0 million boxes in the 2025-2026 season, and Valencia oranges reached 8.18 million boxes (USDA NASS Citrus Summary). A reader comparing sources should know that the FDACS agriculture overview page still reports the 2023-2024 season, when Florida orange production was 18.0 million boxes (FDACS); the NASS summary of August 27, 2026 is the newer figure.

UF/IFAS guidance manages greening with psyllid control, nutrition and irrigation, and oxytetracycline trunk injection was widely adopted in Florida in 2023, though UF/IFAS makes no formal recommendation on injection (UF/IFAS CG086).

By 2006 Florida growers began using an HLB management program advocated by growers in Sao Paulo, Brazil, which combined psyllid sprays, scouting every tree at least four times a year and removing symptomatic trees (UF/IFAS FE915). By 2010 most Florida growers had stopped removing trees and focused on psyllid control. Citrus Health Management Areas, where neighbors coordinate sprays, began in 2010; Florida had 35 by 2012 and 55 by the end of 2015, though only 19 were estimated to be active.

The cost shows in the spray counts. In a UF/IFAS cost study of southwest Florida juice oranges and Indian River fresh grapefruit, average annual pest control before 2004 consisted of two sprays for processed juice fruit and six for fresh market grapefruit (UF/IFAS FE915). After the hurricanes and the end of canker eradication that rose to 3 or 4 and 10, and after HLB and the 2010 discovery of citrus black spot in a southwest Florida grove it reached 8 to 9 and 14. With aerial and ultra low volume psyllid sprays added, processed oranges reached 11 sprays a year.

Oxytetracycline trunk injection was widely adopted in Florida in 2023 after two injectable formulations were registered (UF/IFAS CG086). UF/IFAS reports promising results in some locations but not everywhere and says it will review the data each year. The same 2026 to 2029 guide stresses certified disease-free trees, windbreaks against psyllid migration, frequent irrigation and complete fertilizer programs, and notes insecticide resistance in several Florida counties.

A Florida homeowner may plant citrus only from state-registered nurseries that sell certified trees, may remove a tree voluntarily, and faces USDA statewide quarantine restrictions on shipping or taking citrus fruit out of Florida (FDACS).

FDACS asks residents who suspect canker not to mail or bring samples to the county Extension office; instead, the Extension office is asked to send an agent to examine the tree (FDACS). UF/IFAS Extension has offices in all 67 Florida counties (UF/IFAS Extension). Because of citrus canker and citrus greening, FDACS strongly recommends that residents find alternatives to planting citrus.

Nurseries carry the heavier rules. Citrus greening host plants must be produced in an approved structure designed to exclude the Asian citrus psyllid, and the state rules are 5B-62, Florida Administrative Code, for the Citrus Nursery Stock Certification Program and 5B-63 for the Citrus Health Response Program (FDACS Citrus Health Response Program). The FDACS Citrus Health Response Program also runs the citrus budwood registration program and an abandoned grove initiative, since abandoned Florida groves can harbor pests and diseases. The program's listed contact is at 3027 Lake Alfred Rd., Winter Haven, FL 33881-1438, phone (863) 298-3000.

At the federal level, the USDA APHIS Citrus Health Response Program, run with state agriculture departments, surveys commercial and residential citrus areas and keeps quarantine boundaries matched to where pests are found (USDA APHIS). Last verified: October 15, 2026, on the FDACS website.