Figure 1.

Visual symptom level of RPW infestation in oil palm plantlings based on empirical observations in this greenhouse experiment. (A,B) Level 1 infestation observed between first to the third week: no symptoms visible especially at the sealed crown base. (C,D) Level 2 infestation observed between fourth to sixth week: dark oozes and smelly sap together with soft, creamy-coloured tissue appeared at the crown base; brown sawdust recorded between the plantling’s trunk and the base of the leaves. (E–G) Level 3 infestation observed between sixth to ninth week: host plant’s shoot started to lean to the ground; the leaves started to fall; loss of symmetry at palm upper crown. (H,I) Level 4 infestation observed at the ninth week: leaves collapsed and started to show skirting shape; shoot was dried out and fell off.