Managing Laurel Wilt Disease (LBD) in Your South Florida Growing Stock
Managing Laurel Wilt Disease (LBD) in Your South Florida Growing Stock
Laurel Wilt Disease has permanently altered South Florida's nursery market. Since Raffaelea lauricola — the pathogenic fungus vectored by the redbay ambrosia beetle (Xyleborus glabratus) — arrived in Florida in 2005, it has killed an estimated 300 million trees in the southeast United States and devastated Miami-Dade's commercial avocado industry, which once represented the largest avocado production region in the continental US.
For nursery growers, the critical concern is protecting growing stock and ensuring propagation material is clean. An infected plant that ships to a landscape contractor creates liability, damages reputation, and spreads the disease to new sites.
How Laurel Wilt Disease Works
The disease involves two organisms working together:
The vector: The redbay ambrosia beetle (Xyleborus glabratus) is a tiny (1–2mm) bark beetle that bores into woody stems of susceptible host plants in the family Lauraceae. The beetle is native to Asia and was accidentally introduced to Georgia through infested packing material.
The pathogen: Raffaelea lauricola is a fungus carried by the beetle that it inoculates into the host's vascular system as it bores. The fungus colonizes the xylem, physically blocking water transport from roots to canopy. The tree cannot move water and wilts rapidly — often in 2–4 weeks from first symptom.
Why it kills so fast: Unlike many fungal wilts that progress slowly over a growing season, R. lauricola colonizes the xylem so aggressively that by the time wilt symptoms appear in the canopy, the infection has already moved through most of the vascular system. There is no effective cure once symptoms appear.
Which Species Are at Risk
All species in the family Lauraceae are potentially susceptible. In South Florida nurseries, the highest-risk genera are:
Lauraceae Species — Laurel Wilt Disease Risk Reference for South Florida Nurseries 2025
| Species | Common Name | LBD Risk | Commercial Importance |
|---|---|---|---|
| Persea americana | Avocado | Extremely High | Commercial crop; nursery stock |
| Persea palustris | Swamp bay | Extremely High | Native; landscape use |
| Persea borbonia | Redbay | Extremely High | Native; rarely in nursery trade |
| Cinnamomum camphora | Camphor tree | Moderate | Street tree; widely planted |
| Litsea spp. | Various | Moderate | Occasional in specialty trade |
| Ocotea coriacea | Lancewood / Florida licaria | Low–Moderate | Native; specialty landscape |
| All non-Lauraceae species | — | Not susceptible | No LBD risk |
Risk ratings current as of 2025. LBD host range may expand as the disease spreads. If you grow any Lauraceae species, treat all material as high-risk. Source: UF/IFAS; USDA Forest Service Southern Research Station; FloridaLandscapeIQ, 2025.
Detection: What to Look For
Early signs in the field:
- Wilting of individual branches or the entire crown, often appearing suddenly (days to 2 weeks)
- Leaves that wilt but remain attached — unlike drought stress where leaves drop, LBD-affected leaves remain brown and curled on the plant
- Small entry holes (1–2mm diameter) in bark at the base or main trunk, often accompanied by white powdery frass or fine sawdust
- Blue-gray to dark streaking in the sapwood when the bark is removed — the vascular discoloration is diagnostic
Lab confirmation: Visual diagnosis is strongly presumptive but not definitive. For disease confirmation, submit a sample of symptomatic wood (including the vascular discoloration) to the UF/IFAS Plant Diagnostic Center or FDACS Division of Plant Industry. Molecular testing (PCR) can confirm R. lauricola within 3–5 business days.
Nursery Protocol for LBD Management
Incoming material inspection: All incoming Lauraceae propagation material should be inspected for beetle entry holes and vascular discoloration before entering growing blocks. Source from growers who can attest to clean propagation history.
Quarantine block: Maintain a separate quarantine area for newly received Lauraceae material. Hold for 30 days under observation before integrating with established production.
Affected plant protocol: At the first sign of suspicious wilt in Lauraceae stock:
- Isolate the affected plant immediately
- Do not chip or mulch infected wood on-site — the beetle can emerge from recently-killed wood and infect nearby plants
- Double-bag and landfill or chip off-site in accordance with FDACS guidance
- Notify FDACS Division of Plant Industry if commercial avocado is affected
Beetle trapping: Redbay ambrosia beetle populations can be monitored with ethanol-baited traps (available commercially). High trap counts indicate elevated local beetle pressure and should trigger heightened inspections of all Lauraceae stock.
Propiconazole trunk injection: Research from UF/IFAS has shown that trunk injection of propiconazole (Alamo) can slow LBD progression and in some cases protect high-value trees. This is not a nursery production tool — it is most appropriate for valuable specimen avocados or landscape trees.
Sourcing Clean Material
The safest approach for growers who want to continue producing Persea americana (avocado) is to source material from growers outside LBD-endemic areas or from nurseries with documented clean propagation records. The FDACS Division of Plant Industry maintains information on current disease distribution.
Contact the FloridaLandscapeIQ Contractor Directory to find licensed nursery growers and landscape contractors familiar with LBD management in South Florida.
Source: UF/IFAS Laurel Wilt Information; USDA Forest Service Southern Research Station; FDACS Division of Plant Industry; FloridaLandscapeIQ Staff, April 2025.