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The not-so-mellow lethal yellow

The "Nafaluma" National Coconut Network has replanted over 15% of the affected area with resistant varieties.  Credit: Dr. Maria Mercedes Roca de Doyle, Pan American College of Agriculture, Zamorano, Honduras

By RORY O’CONNOR
Special to HTW

Border disputes and protectionist policies may keep economic enterprises from freely crossing international boundaries in some regions of the Caribbean, but such is not the case with environmental phenomena. Lethal Yellowing (LY) disease is one such example, moving across the region with an ease that would be the envy of modern day globalization proponents.

LY is a fast spreading illness affecting coconut and other palm tree species. Caused by a phytoplasm, which is similar to a bacteria (though with no cell wall), the disease is spread by a small plant-hopper whose scientific name is myndus crudus. The sap-sucking creature transmits the illness by ingesting the phytoplasm from infected trees and then injecting it into healthy trees through the course of its activities.

Symptoms of the disease include the premature fall of fruit, a blackening of a tree’s flowers, and a yellowing of the leaves (hence the name). A mature tree will die within five to eight months of infection, leaving nothing more than a bare trunk resembling a telephone pole.

The disease was first identified on the island of Jamaica in the 1800’s and since then has become endemic in many Caribbean nations as well as in Africa and Asia. During the period covering the 1960’s to the 1980’s, the disease threatened to wipe out Jamaica’s coconut-palm industry completely, while it also spread to the southern United States (Florida) and Mexico. Most recently LY has been detected in Belize and Guatemala.

In Honduras, LY was originally detected on the island of Roatán in 1995 and soon thereafter appeared on the mainland. Hurricane Mitch in 1998 helped to rapidly disperse the vector. It is estimated that the disease has wiped out as much as 90% of the Atlantic Tall variety of coconut trees, native to the Northern Coast. While the loss of coconut palm trees has adversely affected the tourist industry, it has more significantly changed the way of life of Honduras’ coastal peoples, especially the Garifuna or Garinagu, an Afro-Caribbean ethnic group.

The Garifuna people rely on the coconut palms as a fundamental source of food (almost every traditional Garifuna dish involves the use of coconut meat, milk, or oil in one form or another). In addition, the trees serve to provide shade, shelter for housing, feed for animals, a fuel source, medicinal creams, and refreshing, nutritious drinks. Therefore, the loss of the Atlantic Tall in Honduras has dealt a devastating blow to the traditional Garifuna way of life.

The key to fighting LY, which currently has no known cure, lies within a combination of scientific research and community collaboration. Dr. Maria Mercedes Roca de Doyle, a plant pathologist and professor at the prestigious Pan American College of Agriculture (Zamorano), is a leading expert in the field. Together with the National Network to Save the Coconut or WAFALUMA (which means “Our Coconut” in the Garifuna language), Dr. Doyle is focusing on the following priorities to combat LY: research, reforestation, production in local nurseries, training, and the prospecting of resistant seed material in the region.

“The Jamaican researchers continue to focus heavily on the technical side of the disease, but we [Honduras] have to evaluate material”, states the British-educated, Bolivian national. Evidence of new outbreaks of LY in Jamaica amongst coconut species that were formerly thought to be resistant has made the need for empirical testing in Honduras all the more urgent.

LY can be treated with the antibiotic oxytetracyclene, but Dr. Doyle points out that it is not a permanent solution and apart from logistical difficulties involved in its application, has prohibitive costs. “Oxytetracycline could be used to suppress symptoms, but single palm applications are expensive and not suitable for large-scale use,” she says.

“The only viable solution lies in replanting affected areas with resistant varieties”, she notes. A lack of funding and most recently, the outbreak of the possible new strain in Jamaica have limited the research and reforestation efforts. Traditionally, the more tolerant coconut species have been Malayan Dwarfs (Red, Yellow, and Green) and hybrid Maypan and Mapan varieties, formed by the cross-pollination of Malayan Dwarfs and a Panama or Pacific Tall.

Unfortunately, the Malayan Dwarfs, while having shown the highest level of tolerance to LY to date, do not offer the same quality of meat, milk, and oil as compared to the traditional Atlantic Tall, which has hampered the species acceptance in Garifuna communities. Aesthetically speaking, the Malayan Dwarfs substitute adequately, making them an effective backdrop for the tourist industry.

The Pacific Tall variety appears to be the best substitute for its Atlantic counterpart and will likely become a significant part of future replanting efforts.

A recent program funded by Catholic Relief Services, a U.S. non-governmental organization, through CARITAS, the charitable arm of the Catholic Church in Honduras, managed to replant coconut palms in 26 Garifuna communities. The program’s term finished earlier this year and the search continues for financial backing to build upon the progress made. CAUSE Canada, a Canadian non-governmental organization, will soon begin work on a pilot coconut reforestation program in three Garifuna communities with the generous support of the Canadian International Development Association (CIDA).

The critical component of future efforts will be balancing the scientific and technical realities of LY with the nutritional needs of the Garifuna people. Just as coconut growth is slow but sustained, so to must be the process of combating Lethal Yellowing. The author wishes to express his gratitude to Dr. Doyle at the Pan American College of Agriculture for her generosity in sharing her knowledge of LY as well as a wealth of informative resources.