Lethal yellowing is a devastating disease that affects palms including coconuts. It is caused by a phytoplasma, specialized bacteria that are transmitted between plants by insect vectors.
Symptoms and Infestation
Lethal yellowing (LY) gets its name from the yellowing and drooping of palm fronds beginning with the lower fronds and advancing up through the crown. The disease characteristically has the following progression:
Premature dropping of mature and immature coconuts (fruits on other varieties) in a process called ‘shelling’. Most of the fallen nuts will have a brown or black water-soaked area immediately under the calyx.
Flower stalks (inflorescences) begin to blacken. Most male flowers will be dead on the blackened inflorescences and no fruits will set.
Palm fronds start to yellow (or, in the case of some species, turn greyish-brown), beginning with the older, lower fronds and advancing upward through the crown. Fronds that have yellowed will die, turn brown and hang down.
The spear leaf collapses and the bud dies. By the time that this happens, the tree is already dead.
The entire crown falls from the tree leaving a forlorn ‘telephone pole’ stalk.
Current location of the pathogen includes:
Caribbean: Cayman Islands, Bahamas, Belize, Cuba, Dominican Republic, Haiti, Jamaica, Netherlands Antilles, St. Kitts and Nevis
Central America: Honduras, Guatamala
North America: Mexico – Yucatan Peninsula; USA – Florida, Texas
The most practical long term solution to controlling lethal yellowing is the use of resistant cultivars. Coconut cultivars, such as the ‘Malayan Dwarf’ or hybrid ‘Maypan’ (Malayan Dwarf x Panama Tall), have exhibited acceptable levels of resistance in most areas.
Chemical control is achieved by application of the antibiotic oxytetracycline HCl (often referred to as OTC) administered to palms by liquid injection into the trunk. The antibiotic can also be used preventively to protect palms when lethal yellowing is known to occur in the area
What Can We Do?
Do NOT bring into your country any palms, seedlings or vegetative material of palms without the required Plant Quarantine Import Permits/Approval
When you travel declare all agricultural items.
If you suspect that a particular palm had LY disease, report this immediately to your Ministry or department of Agriculture.