STUDY OF PEST INCIDENCE ON FEMALE OIL PALM INFLORESCENCES IN WEST-AFRICA

Female inflorescences may be attacked by three pests: Prosoestus minor Mshl and Prosoestus sculptilis Faust (Curculionidae) and Elaeidiphilos adustalis Hampson (Pyralidae). The biological cycle of these insects was studied. They destroy the stigmata ol mine a gallery in the gynaecium of female flowers. In general, female inflorescences are attacked by at least two pest species, of which P. minor is the most frequent and most numerous. This species is accompanied by P. sculptilis or E. adustalis, or sometimes both species at the same time. Attack incidence was studied theoretically by insect introduction, then under natural conditions, using a visual observation scale. Damage caused by these insects invariably leads to very significant falls in the fruit weight:bunch weight ratio. The mesocarp/fruit weight is not affected, but the oil/fresh mesocarp rate can be in the event of severe P. sculptilis attacks. As a result, there cart be a considerable reduction in oil extraction rates at the mill. Trials of chemical treatments show that it is possible to provide female inflorescences with effective protection against attack by such insects by spraying all the female inflorescences regularly with Evisect S.