AFPP-7 CONFERENCE INTERNATIONALE SUR LES RAVAGEURS EN AGRICULTURE Montpellier – 26 et 27 octobre 2005 ASSESSMENT OF ANTIXENOSIS AND TOLERANCE OF COCOA (THEOBROMA CACAO L.) TOWARDS MIRIDS SAHLBERGELLA

Field tests for antixenosis and tolerance of cocoa tree to damage by mirids were conducted on ten cocoa genotypes in an experimental plot on a research station in Cameroon. Sahlbergella singularis nymph was starved overnight and confined on a flush, in a nylon mesh sleeve cage and allowed to feed on the plant for 24 hours. Antixenosis was assessed by counting the number of feeding points on the flush after 24 hours. Assessment of tolerance was based on regular observations on the evolution of feeding damage and on sprouting of attacked twigs. Analyses of results revealed a highly significant effect of the genotype on the number of feeding points, on the ability of cocoa trees to contain extent of damage and on their ability to recover from it. Results also showed that these two last components must be considered as two distinct factors of the genetic resistance to mirid attack.