RONCES DISEASE OF WAX PALM THREATENS THE NATIONAL TREE OF COLOMBIA
ER BOA1 and C RODRIGUEZ2
1CABI Bioscience, Egham, Surrey TW20 9TY, UK; 2Univ. de Quindio, A.A. 460, Armenia, Colombia
Background and objectives
Ceroxylon quindiuense is the tallest known palm. Once a valuable source of wax, today it has a vital ecological role protecting slopes and watersheds. It is also used for construction. There are wide concerns that populations are declining, both in terms of numbers and health . It became the national tree of Colombia in 1985 and is protected by law. In the early 1990s a new disease was reported from Toliina. Early studies were limited to general surveys and minor sampling of diseased palms. A collaborative project between the authors began in 1997 with the objectives of measuring disease losses, describing symptom development and investigating the cause. Preliminary results are presented here.
Materials and methods
Disease impact was measured by sampling groups of 50 to 130 trees and grading them according to symptom development. A five point disease scale was adapted from that used by the Fundacion Herencia Verde (unpublished report). Binocular surveys were carried out in November 1997. Observation plots of up to 10 trees were established to monitor symptom development.
Results and Conclusions
Symptom development is still unclear. In the early stages of the disease it is difficult to differentiate between palms which are stressed and those which have Ronces disease. Wilting of crowns appears to be an early symptom, prior to the death of the oldest leaves. In the latter, more distinct stages, the outer, older leaves of the crown become brown and collapse. The central spear of leaves is the last part of the crown to die. Some trees show a marked narrowing of the trunk region below the crown, indicating a disruption to growth. There is no obvious comparison between Ronces disease and lethal yellowing of palms. The disease appears to start at the base of the tree and not in the crown.
Some palms show extensive internal staining and rot at the latter stages of symptom development. Sai-npling of palms for pathogenic organisms has been very limited, but there is no evidence to support early theories that the disease was caused by Ceratocystis. This appears to have been based on the confirmed discovery of a scolytid beetle, Phloeotribus sp. This can be found feeding at the base of disease palms but is not always associated with palms at an early stage of symptom development.
The disease is most prominent in Roncesvalles, southwest of lbagu. Surveys showed that up to 55% of wax palms were killed. Diseased trees have also been observed at Anaime, close to Cajamarca and Tenerife close to Cali. There is no conclusive evidence that Ronces disease is present in the Toche region. It was originally suggested that forest clearance and human interference were linked to the appearance of the disease, but disease can be found in forest areas as well as pasture lands. Studies are at an early stage and the conclusions presented here are tentative. Long term research is required to answer pressing questions about its cause, origin and future threat to the wax palm.
1. Madrinan, S. and Schultes, R.E. (1995) Elaesis 7, 35-56.