Résumé
The existence of a high lignified star-shaped cavity at the base of the bole, or more precisely at the root - bole interface, has been clearly identified for the first time. This cavity appears to be a perfect culture chamber for Ganoderma development. Random observations of the initial stage of Basal Stem Rot infection in young palms showed the development of infectious stroma-like structures inside the cavity prior to colonisation of the bole. The existence of a lignified scar in 8-month-old seedlings was revealed by initial observation. The scar then developed further inside the star-shaped cavity (Breton et al, 2009a; Breton et al, 2009b). Specific observation during early growth stages in the nursery revealed the appearance of a very tiny scar after 5 months on a few seedlings. The number of affected seedlings increased rapidly to reach nearly 100% after 9 months. The scar grew quickly in all directions and the resulting cavity could reach 50% of bole diameter, 13 mm wide and 8 mm deep at this stage. The star-shaped cavities have 2 to 5 branches. After 6 to 7 months in the nursery, once the star-shaped cavity was extended enough, the development of mycelium (not identified) and / or presence of tiny arthropods such as aphids, Chilopodae larva and small ants ware frequently observed. These results demonstrate the role of this star-shaped cavity as a perfect culture chamber for fungus and a possible refuge for pests, predators or disease vectors at very early stages of oil palm development. This star-shaped cavity definitely appears to be an interesting target for preventive action against Basal Stem Rot, i.e. Biocontrol by antagonistic, long-lasting fungicide, etc. (Résumé d'auteur)