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

Laura Ogle, Hugh Harries

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.

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