Like most other Caribbean nations, Belize has been afflicted with Yellow Leaf (YL) palm disease (also called Lethal Yellowing Disease) for the past 12 years. The disease is caused by an organism that attacks the head of the palm tree where its growth is concentrated, and causes the tree to die when this part of the tree rots away. The organism is spread from tree to tree through the leaf hopper insect, which feeds on the leaves.
First seen in southern Florida in the 1970’s, YL disease is 95% fatal to most palm trees, in particular the Jamaican Tall variety which is the most common coconut palm found throughout the Caribbean. The Jamaican Tall palm is most favored for producing commercial grade coconuts, and is the primary palm tree used in coconut plantations. It spreads prolifically, and is found almost everywhere in the tropical latitudes of our hemisphere.
Once the disease takes hold of a tree, the coconuts are shed from the tree, and it ceases to flower. Then the leaves turn yellow and as they die their stems break, leaving a characteristic signature of broken, hanging dead leaves. Eventually the crown rots and falls off the tree, leaving a dead trunk that can stand for years (this photo was taken on a nearby island that is not treating their trees as often as they should).
Horticulturalists in Florida studied the disease and developed a system to vaccinate the trees which prevents infection. This is an arboreal based tetracycline drug, and it is administered 4 times a year to save palm trees in afflicted areas. At right are the equipment and supplies needed for our quarterly treatment.
On Long Caye, where YL disease was first seen in 1998, we currently treat about 500 trees. We spend about $3000 US/year treating our 4-500 trees that are infected with the disease. All of the other trees on the island, estimated to be over 1000 palms, died of the disease within two years of infection since they either were not treated, or were vaccinated too late. The tetracycline is mixed from a powder, then injected into a bullet case in which the firing cap has been replaced by silicone, which is drilled into the trunk. The size of the hole is carefully calculated to be slightly smaller than the volume of the injected liquid. This allows the mix to be pressurized so that it will flow into the tree’s sap. The shells do ‘bleed’ a bit and stain the trunks.
In addition, we have planted over 500 ‘hybrid’ palm trees that have been bred to be disease resistant. We bought these palm starts from the Belize government, which purchased the nuts from a facility in Jamaica. We have spent an additional $3200 US on these trees, not counting the labor to plant and maintain them. We don’t do any more plantings because there is no more room on the island for any trees! These trees have grown very fast and have replaced those that we lost, so the island is once again covered with a thick forest of palm trees.