Lethal Bronzing
Candidatus Phytoplasma aculeata
A fast, fatal disease of coconut and many other palms in the southeastern U.S., caused by a phytoplasma spread by a sap-feeding insect. Once symptoms begin a palm usually dies within a few months, and because the heart bud dies there is no recovery. First found in Florida in 2006, it was once called Texas Phoenix palm decline.
🔎 How to spot it
Symptoms appear in a set order. If fruit is present, the first sign is premature drop of the fruit, and emerging flower spikes blacken and die. Next the foliage discolors, beginning with the oldest, lowest leaves and advancing up the canopy to a dull bronze-brown as the fronds dry. The final stage is collapse of the spear (youngest, unopened) leaf, which means the bud has died. More than 20 palm species are hosts, including coconut, cabbage palm, Canary Island date palm, queen palm, and pygmy date palm.
🥀 Damage it causes
The disease is lethal and quick. The first symptoms show about four to five months after infection, and the palm then declines to a dead spear leaf in roughly two to three months. Once the bud dies the palm cannot recover and must be removed, and outbreaks can kill many palms across a neighborhood or planting.
🔬 What causes it
A phytoplasma, Candidatus Phytoplasma aculeata, a wall-less bacterium that lives in the palm phloem and cannot be grown in culture. It is carried palm to palm by sap-feeding planthoppers and leafhoppers as they feed; it cannot be spread mechanically on pruning tools or by root contact. It is genetically distinct from the lethal yellowing phytoplasma, though the two diseases look much alike.
🛡️ Prevent it
There is no cure, so the focus is protecting healthy palms and removing sources of infection. Remove and destroy symptomatic palms promptly to lower the amount of phytoplasma a planthopper can pick up, manage the insect vectors, and avoid planting highly susceptible species where the disease is active. Confirm the diagnosis with a lab test, since several palm problems look similar.
🧯 If it is already here
Valuable healthy palms near infected trees can be protected with trunk injections of the antibiotic oxytetracycline (OTC) repeated every three to four months for at least two years, but this only suppresses the disease and must be kept up. Once a palm shows symptoms the labeled OTC rate will not reverse them, so a symptomatic palm cannot be saved and should be taken out.
💡 Good to know
Premature fruit drop together with blackened new flower spikes is the early warning, well before the fronds bronze. Because the bud itself dies, a collapsed spear leaf means the palm is lost, so prompt removal and protecting nearby palms are the only useful responses. It closely resembles lethal yellowing and needs a lab test to tell them apart.
🌱 Plants it affects
3 plants in the library can be affected by this problem
For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.