Introducing the Vector: How Coconut Lethal Yellowing Disease may have reached the Caribbean

Abstract

Recent reports from Jamaica tell of an increase in the incidence of coconut lethal yellowing disease and raise the spectre of the epidemic of forty years ago. Is this just another coincidence in a series that seem to link the disease with Jamaica? The future threat is to susceptible coconut varieties in Caribbean islands from Puerto Rico to Trinidad and Latin American countries from Nicaragua to Brazil. Will the disease progress in domino fashion from country to country or will it jump some countries to reach others? To answer this, consider the possibility that the disease originated outside the Caribbean and if it did, how did it first reach Jamaica? Coconut lethal yellowing is a phytoplasma disease and, in the absence of any contrary evidence, plant pathologists believe that phytoplasma diseases are NOT carried from place to place by seeds. Rather, they ARE transmitted from plant to plant by insect vectors. So the first coconuts, taken to Jamaica in the 16th century would not have carried the disease. Since the palms became widespread through the island over the following three centuries (Harries 1980), it is unlikely that the disease was already present during that time. The same can be said everywhere else in Latin American and the Caribbean where all coconuts share a similar history of introduction and healthy establishment (Harries 2001). So it is unfortunate that some popular and scientific accounts of coconut lethal yellowing disease imply that “it originated in Jamaica” or that “it reached continental USA and Mexico from Jamaica”. The same disease occurs in Hispaniola (Haiti & Dominican Republic), the Bahamas (reputedly) and the Cayman Islands, as well as in Cuba. Cuba, by its greater size and proximity to the continent, might seem a more likely focus for the disease. What these accounts are indirectly acknowledging is that it was the publicity generated by a successful Research and Development program during the 1960s and 70s (Gowdie & Romney 1976) that has held Jamaica in the lethal yellowing spotlight. The disease has spread throughout Jamaica and Cuba, to a lesser extent in Haiti (but, exceptionally, not at all in Dominican Republic (Harries et al. 2001)), the Gulf Coast states of USA and Mexico and the Caribbean coast from Mexico to Honduras (Harries 2001). Before the disease inexorably moves to other Latin American countries, from Nicaragua to Brazil, and Caribbean islands, from Puerto Rico to Trinidad and Tobago, there may be more to be learned from Jamaica where, even now, disease activity seems to be reintensifying.