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The acitivty and spatial distribution of eight enzymes in adult tap root tissues colonized by R. lignosus and P. noxius are investigated. Their physiological significance in the pathogenic process is discussed.

Some reactions differentiated by rubber trees to root rot diseases are described at molecular, cellular and histological levels.

In spite of numerous aeroplane flights and different interpretations of the infrared colour photographs obtained, the remote sensing of root rotting fungi of rubber tree has failed in practice in the Ivory Coast. The reasons for this failure and conclusions on the efficiency of this method are discussed.

New method of direct control of Rigidoporus lignosus, causing agent of white root rot of Hevea. A new method of direct control of Hevea whith root disease caused by Rigidoporus lignosts (Kl.) Imaz is being used in many countries in Africa; after detection and marking diseased trees and trees in direct contact, the treatment consists of pouring 21 of 0.5% calixin cmulsion into the cuvette 2 times every 6 months. This method which has been used in field trials for 3 years, seems to give encouraging results. and has confirmed the efficiency of Calisin for direct control of the white root disease.

Pathogenicity and physiological characteristics were studied for the two populations of isolates. Exidence of variations has been demonstratcd for each fungus but no correlations could be established between the in vivo and in vitro parameters.

Pathogenicity of isolates of the root rotting fungi Rigidoporus lignosws and Phellinus noxius was tested on rubber seedlings (Hevea brasiliensis) by artificial inoculation under controlled conditions. Variation in virulence within the isolates tested was demonstrated and discussed.