Laurel wilt in Florida: identifying and managing a fast-moving avocado and bay killer.

Laurel wilt is the most aggressive tree disease currently active in Florida, and the average homeowner has never heard of it. It moved into the state through Jacksonville around 2005, reached South Florida's commercial avocado groves by 2012, and has now been documented in every county on the peninsula. Trees in the Lauraceae family — avocado, redbay, swamp bay, silk bay, sassafras, camphor — die in weeks once infected, not seasons. There is currently no cure on a tree once symptoms appear in more than 10% of the canopy.

What homeowners can do is recognize the disease early, protect uninfected trees with preventive injection where it is justified, and — critically — dispose of infected wood in a way that does not spread the beetle to the next yard.

How the disease works

Laurel wilt is caused by a fungus, Raffaelea lauricola, vectored by the redbay ambrosia beetle (Xyleborus glabratus). The beetle, originally from Asia, was introduced through wood packaging in Georgia in the early 2000s. Female beetles bore tiny galleries into the sapwood of host trees and carry the fungus with them. The fungus blocks the tree's vascular tissue from the inside, and the tree wilts — not from lack of water in the soil, but from inability to move water within itself.

The result is the disease's most distinctive feature: a tree with green leaves that suddenly turn red-brown and stay attached to the branches for months. A drought-stressed or freeze-killed tree drops its leaves. A laurel-wilt-killed tree keeps them, like dried flowers on the canopy. Once you have seen it, you do not mistake it for anything else.

Identifying the disease on your property

The species at risk

• Avocado (Persea americana) — the biggest economic concern; commercial groves in Miami-Dade have lost tens of thousands of trees.
• Redbay (Persea borbonia) — a common native that has been functionally eliminated from much of north Florida.
• Swamp bay (Persea palustris) — wetland edges and hammocks.
• Silk bay (Persea humilis) — sandhills and scrub.
• Sassafras (Sassafras albidum) — north Florida only.
• Camphor tree (Cinnamomum camphora) — susceptible but more resistant than the natives.

The symptom timeline

1. Week 1–2: A single branch or section of the canopy wilts. Leaves droop, then go from green to a dull red-brown over a few days.
2. Week 2–4: Wilt spreads to adjacent branches. The dead leaves remain attached.
3. Week 4–12: Most of the canopy is brown but still leafy. Tiny entry holes (the size of a pencil tip or smaller) appear on the trunk and major limbs, often with fine sawdust "toothpicks" protruding.
4. Month 3–6: Tree is dead. Wood remains a viable beetle nursery for one to two more years if not chipped or burned.

What to do with an infected tree

Once a tree is symptomatic on more than 10% of the canopy, treatment is no longer effective and the tree is now a beetle factory threatening every other Lauraceae host in flight range — typically a few hundred yards. The protocol matters:

1. Remove the tree promptly. Do not delay through a season hoping it recovers; it will not.
2. Chip all wood, including branches over 1 inch in diameter, to chip size under 1 inch. The beetle cannot reproduce in chips that small.
3. Do not move the wood. Florida prohibits transporting unprocessed wood of laurel family hosts off the property under the state's quarantine guidance. Hauling "firewood from the dead tree" to a friend's cabin is exactly how this disease spread up the east coast.
4. Do not burn unchipped logs unless local burn permits allow it; if you do burn, do it on site.
5. Keep the chips on the property as mulch (away from other Lauraceae). Sun and decomposition kill the fungus and beetles within months.

Protecting a healthy tree

There is one preventive treatment with good field evidence: trunk injection with propiconazole (commonly sold as Alamo or Quali-Pro Propiconazole 14.3) before the tree becomes infected. It must be done by a licensed applicator using proper macro-injection equipment, and it works only as prophylaxis — not as a cure on an already-symptomatic tree. A treatment lasts 12–24 months and runs $300–$800 per mature tree depending on diameter and access.

Whether that math is worth it depends on the tree. A specimen 40-year-old Hass avocado that is a centerpiece of the property: yes, almost certainly. A scrubby self-seeded redbay in a back corner: no. Most homeowners with one or two valued avocado trees in laurel-wilt-active counties are now on a 12-month injection cycle.

What does not work

• Soil-applied systemic insecticides. The redbay ambrosia beetle does not feed on the wood the way a typical pest does — it inoculates the wood with the fungus and lets the fungus do the killing. Insecticide that targets feeding insects does not reach the beetle.
• Sprayed fungicides. The disease is inside the vascular tissue; surface sprays cannot reach it.
• Waiting it out. Resistance does not appear to be developing in native redbay populations on any usable timeline, and the beetle vector is now widely established.
• Hauling the infected tree to the dump. Most municipal yard-waste streams in Florida grind and reuse material; unchipped infected logs in the wrong stream are exactly the spread mechanism.

The bigger picture for Florida

Redbay was the dominant understory tree of Florida's coastal hammocks for thousands of years. Functionally, it is now ecologically extinct across most of the state, a loss comparable in scale to the American chestnut a century earlier. The commercial avocado industry in South Florida has spent the last decade managing the disease at enormous expense and is largely succeeding through aggressive injection programs, scouting, and rapid removal protocols. Homeowner trees, scattered and unmanaged, are the gap. The most valuable thing the average homeowner can do is identify the disease quickly when it shows up and dispose of infected wood correctly, so the beetle does not leave the property.