Root-rot diseases of the rubber tree in the Ivory Coast. 1. Severity, dynamics, and characterization of epidemics

Abstract

An epidemiological survey was carried out in a rubber tree (Heveabrasiliensis Willd. ex A. Juss) plantation to study and describe the epidemics of the root-rotting fungi Rigidoporuslignosus (Klotzsch) Imazeki and Phellinusnoxius (Corner) G. Cunn. Infection and mortality of the trees were systematically recorded half-yearly for 6 years. During the first year, the outbreak resulted in a considerable enlargement of the initial disease centers and the appearance of new ones. Pathogen activity was found to decrease 6 years after planting. This was attributed to the increase in defense reactions with the age of the tree and to disruption of trophic connections between forest inocula and decaying taproots of rubber trees. The type of root disease is discussed, mainly in terms of the kinetics of the creation of disease centers.