History of Erythroxylum and Notes on Diseases and Pests at Kauai Field Site

Lee Darlington, Weed Science Laboratory, Beltsville Agricultural Research Center

Beltsville, MD 20705

Prior to ARS developing its tropical research site on Kauai in 1987, a major soft drink manufacturer had already started a research project (Alakea project) to cultivate coca at that location from 1964 until 1984. In the first year of the Alakea project, coca plants were first obtained from Lyon Arboretum, Honolulu, (3 plants); Foster Gardens, Honolulu (3 plants) and Marks Estates (5 plants).

The following year, 8,000 seed from Trujillo, Peru were obtained, but only about 20% germinated. A damping off disease occurred who symptoms are chlorosis, sometimes followed by abscission of all or most of the leaves although they appeared healthy, and wilting followed by death of the seedling. The roots appeared water soaked. The problem was thought to be due to the potting mixture or water supply. Another 8,000 seeds were received from Cuzco, Peru. No information was available on percent germination or damping off disease from these seeds. Diseases of coca during the first years included damping off, root rots, crown rot, leaf drop, drooping, and sooty mold. Other pests included cutworms, leaf rollers and mites.

In 1975, three separate field nurseries were set up. As plants died, they were replaced with healthy seedlings. Disease symptoms included leaf defoliation, wilting of young leaves, drying of twigs, and finally death of the plant. Upon dissection of the branches, brown discoloration of the vascular bundles and the cambium layer was observed. It was common to see one half of a tree healthy and the other half wilting and dying. Later, the whole tree died.

In 1976 infect pests included a twig borer, Xylosandrus compactus and a Kauai moth, Melipotis indomita- the caterpillars ate the leaves. Disease was becoming a bigger problem. Symptoms included wilting of new shoots, followed by leaf defoliation and finally death of the plant.  This disease attacks both seedling and mature plants. The disease was suspected to be caused by a fungus, Fusarium sp. or bacteria which clogged the vascular system.

No written information from the 80's was available but people who worked on the project stated that the major disease disease was commonly known as "fruiting to death" disease. Fields 5 years or older suffered losses of at least 80%. Fusarium oxysporum was identified as the wilt organism and was the major cause of terminating the project.

The USDA/ARS project started in November of 1987 when 1300 Beltsville, MD greenhouse grown plants (seed from Tingo Maria, Peru (E. Coca) and from Venezuela ( E. novogranatense) were transplanted into the present secure site area at Kauai. Another 1100 plants from the same two sources via Beltsville were planted, in March, 1988. From the original planting, only 1 out of 370 E. novogranatense plants died, but 153 out of 852 E. coca plants died within three months. It was at this time (March, 1988) that Fusarium oxysporum was identified as the problem and several isolates were obtained and field tests were conducted. This began the active pursuit of a mycoherbicide for controlling coca.