Florida Citrus Canker & Greening — Florida

Citrus bacterial canker, caused by the bacterium Xanthomonas citri subsp. citri, and citrus greening — formally Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas) — are the two bacterial diseases that together dismantled what was once the dominant citrus industry in the United States. Florida had, at its peak, been the third-largest orange producer in the world behind Brazil and China, with approximately 95 percent of its oranges processed for juice, according to UF/IFAS EDIS FE983. Canker first entered Florida from Japan in 1910, was declared eradicated in 1933, and re-emerged repeatedly — culminating in a costly joint FDACS–USDA-APHIS eradication program that ended in 2006 after nearly $1 billion had been spent. HLB, vectored by the Asian citrus psyllid (Diaphorina citri), was detected in Florida in August 2005 near Homestead and Florida City and had spread to every county with commercial citrus by February 2010. The USDA Economic Research Service documents that Florida orange production declined approximately 92 percent from the 2003–04 peak through 2024 — a contraction described as the largest in the state's agricultural history.

The first documented introduction of citrus bacterial canker into Florida occurred in 1910, when trifoliate rootstock infected with the Asian 'A' strain arrived from Japan. The response was immediate and extensive: the eradication campaign destroyed more than three million nursery plants and more than 250,000 field trees, and eradication was declared successful in 1933, according to the National Academies Press strategic planning report on the Florida citrus industry. A second outbreak was detected in 1984, and a third, larger outbreak emerged in south Florida in 1995, triggering the modern Citrus Canker Eradication Program (CCEP), operated jointly by the Florida Department of Agriculture and Consumer Services Division of Plant Industry (FDACS-DPI) and USDA-APHIS.

The 1995 protocol required the removal of all citrus trees within 125 feet of any infected tree. In 2000, that radius was extended to 1,900 feet — a change that dramatically amplified the program's reach and cost. Program expenditures escalated from $10 million in 1996 to $50 million in 1999, with a federal appropriation of $36 million annually at its height. Regulated counties identified in the USDA-APHIS environmental assessment included Dade, Broward, Collier, Manatee, and Hendry. The four hurricanes of 2004–05 dispersed the canker pathogen across the state; by the 2004 season, 80,000 acres of commercial citrus had been identified as affected. The CCEP was terminated in 2006 after close to $1 billion had been spent without achieving eradication, leaving growers deeply skeptical of eradication-based strategies — a legacy documented by researchers at UF/IFAS and published in the Journal of Integrated Pest Management.

The failure of the canker program had direct regulatory consequences for HLB. When greening emerged just before the canker program ended, Florida chose not to implement mandatory tree removal for HLB-infected trees; the only mandatory HLB regulation required nursery trees to be grown in protected structures to supply disease-free stock. The UF/IFAS analysis of disease management program evolution documents that spray applications for processed-juice oranges increased from 2 per year before 2004 to 3–4 after the canker program ended, and to 8–9 after HLB and citrus black spot — detected in Florida in 2010 — were added to management requirements. For Indian River fresh-market grapefruit, the comparable progression was from 6 to 10 to 14 sprays per year.

Huanglongbing — the name translates from Chinese as 'yellow shoot disease' — is caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas). The Asian citrus psyllid (Diaphorina citri Kuwayama), the insect vector, was first confirmed in Florida in 1998 and spread throughout the state wherever citrus is grown. The psyllid feeds on new citrus flush, acquires CLas from infected trees, and transmits the pathogen to healthy trees as infected nymphs and adults. HLB infects the phloem, disrupting nutrient uptake throughout the tree. The 2025–2026 Florida Citrus Production Guide published by UF/IFAS confirms that the Asian species of CLas, which prevails in warm, low-altitude environments, is the pathogen responsible for HLB in Florida, and that no citrus cultivar is immune.

Characteristic symptoms include asymmetrical leaf chlorosis known as 'blotchy mottle,' premature fruit drop, small and misshapen fruit, and progressive tree decline leading to mortality. HLB was first observed in non-commercial citrus near Homestead and Florida City in August 2005, as documented by the UF/IFAS Citrus Research and Education Center (CREC). By February 2010, the disease had spread to all three of Florida's traditional citrus-growing regions: Central Florida, Southwest Florida, and the Indian River district, according to Southern Ag Today. The same source documents subsequent detection in Louisiana in 2008, Georgia and South Carolina in 2009, and Texas and California in 2012, establishing HLB as a federally recognized biosecurity matter extending well beyond Florida.

The combined impact of citrus canker, HLB, and associated storms produced a contraction across every measurable dimension of Florida's citrus economy. The IR-4 Project documented cumulative losses through 2024 at $20 billion in lost revenue, 33,000 jobs lost, and 50 million trees lost, while noting that hurricanes, declining orange juice consumption, and land conversion to residential and solar development also contributed alongside HLB. Production fell from approximately 300 million boxes in 2004 to roughly 20 million boxes in 2024.

The institutional contraction is equally stark. The number of citrus growers in Florida fell from 7,389 in 2002 to 2,775 in 2017, according to USDA Census data cited in the Journal of Integrated Pest Management. A Choices magazine analysis drawing on USDA Census data calculated a 69 percent decrease in growers from 2002 to 2022, with juice processors falling 83 percent and packinghouses 78 percent from 2005 levels. The USDA NASS Florida Citrus Statistics 2022–23 recorded an on-tree crop value of $194 million for the 2022–23 season — 61 percent below the $501 million recorded the prior season — and Florida's share of U.S. citrus production had fallen to 17 percent. According to Choices magazine, U.S. orange juice imports surpassed domestic production during at least the four seasons preceding 2024, with imports rising roughly 50 percent since HLB was first detected.

Florida's commercial citrus production has historically concentrated in a band of central and southern peninsula counties. As of the 2022–23 USDA NASS annual inventory, DeSoto County led the state with 60,845 acres of citrus, while Hendry County recorded the largest single-season acreage loss at 11,073 acres. Other major producing counties include Polk, Hardee, Highlands, Indian River, St. Lucie, Collier, Charlotte, Hillsborough, and Manatee. The Indian River district along the Atlantic coast has historically been associated with premium fresh-market grapefruit, while Highlands County's Lake Placid–Sebring corridor and southwest Florida counties such as Collier and Lee represent the southern extent of grove concentration.

The USDA NASS Florida Citrus and Avocado Annual Statistical Bulletin 2024 recorded total citrus acreage statewide at 332,256 acres, down 11 percent from the prior survey, representing a net loss of 43,046 acres. All 24 published counties showed acreage decreases; new plantings totaled 6,203 acres, and total citrus trees statewide stood at 50.3 million, down 10 percent. Bearing acreage has declined an average of 3 percent per year since 2003–04, according to the USDA Economic Research Service. The Choices magazine analysis calculated that citrus-bearing acreage statewide has decreased by approximately 50 percent since HLB was first detected, with counties farther from the historical Polk–DeSoto production center having largely exited commercial production. Land formerly in citrus has been converted to residential subdivisions and utility-scale solar farms under multi-year lease contracts, further limiting the physical base for any future reconstitution of the industry.

The UF/IFAS Citrus Research and Education Center (CREC) maintains more than 100 ongoing HLB research projects, with psyllid management strategies and disease-tolerant breeding forming two principal tracks. In April 2025, UF/IFAS breeders announced the release of six new HLB-tolerant citrus varieties for Florida growers — the product of multi-year breeding programs aimed at providing commercially viable cultivars that can withstand HLB pressure in grove conditions.

In January 2025, University of Florida scientists led by researcher Lukasz Stelinski published research on a genetically modified citrus tree engineered to kill all juvenile Asian citrus psyllids that feed on it. The University of Florida reported that Stelinski described the approach as one that 'could curtail the ability of an otherwise very effective vector from spreading the pathogen,' with USDA funding cited for the work. Two additional biotechnology approaches are at regulatory review stages. Texas A&M University and the company Silvec Biologics are pursuing EPA approval for a biological treatment using spinach defensins that demonstrated up to 50 percent yield increases in treated trees compared to untreated controls over multi-year trials, with the IR-4 Project facilitating regulatory submissions. A CRISPR-based approach developed by the company Soilcea — which edits HLB-susceptibility genes and showed a nearly 17,000-fold reduction in CLas in trials — has been submitted for EPA approval and received USDA HLB Multi-Agency Coordinating Group funding, as documented by the IR-4 Project. Analysts at Choices magazine note, however, that even a scientific breakthrough would face severe infrastructure constraints to industry recovery, given that packinghouses are down 78 percent and juice processors down 83 percent from pre-HLB levels.

Citrus canker and HLB connect to Florida's broader agricultural geography in ways that extend beyond the grove. The traditional citrus belt of central Florida's ridge counties — Polk, Highlands, Hardee, and DeSoto — overlaps with cattle ranching and vegetable production zones, and HLB-driven grove abandonment has accelerated land conversion to residential subdivisions and utility-scale solar farms, intersecting directly with Florida's rapid population growth dynamics, as documented in the Choices magazine analysis.

Citrus groves historically blanketed watersheds feeding Lake Okeechobee and the Northern Everglades, and grove abandonment has altered hydrology and nutrient loading patterns studied by the South Florida Water Management District (SFWMD) and UF/IFAS researchers. At the national policy level, HLB's documented spread to Louisiana (2008), Georgia and South Carolina (2009), and Texas and California (2012) — recorded by Southern Ag Today — reinforces that Florida's disease crisis is a federally recognized biosecurity matter governed by USDA-APHIS regulatory frameworks and the Federal Plant Pest Act. The USDA NASS May 2025 Florida citrus forecast, which placed total 2024–25 all-orange production at 11.6 million boxes — 36 percent below the prior season — cited Hurricane Milton in October 2024 as a contributing factor alongside ongoing HLB pressure, illustrating how disease vulnerability compounds storm exposure in a way that no single-cause analysis can capture.