AbstractPhloem Necrosis of the trunk of the rubber tree in Ivory Coast. 2. Etiology of the disease. Numerous experiments were performed in order to identify the causal pathogen of rubber tree Phloem Necrosis. Trials of control by fungicides and bactencides, of identification of the microorganisms isolated from decayed tissues, of transmission from diseased to healthy trees and also, microscopic observations of necrotic phloem samples, all failed in practice. However, symptomatology and epidemic spread in plantation suggest a pathological cause of this disease.