POPULATION-DYNAMICS OF RASTROCOCCUS-INVADENS [HOM, PSEUDOCOCCIDAE] IN CONGO - INFLUENCE OF ACCIDENTAL INTRODUCTION OF THE ASIATIC PARASITOID GYRANUSOIDEA-TEBYGI [HYM, ENCYRTIDAE]

The study of fruit-trees mealybug Rastrococcus invadens Williams [Hom. : Pseudococcidae] population dynamics, before and after accidental introduction of the Indo-Pakistani primary parasitoid Gyranusoidea tebygi Noyes [Hym. : Encyrtidae], was investigated in Congo, on two of its host-plants, mango (Mangifera indica L., Anacardiaceae) and frangipani (Plumeria alba L., Apocynaceae). It shows that before introduction of the exotic parasitoid, the local entomophagous complex is little abundant and diversified. The population dynamics of the pest, very different on the two host-plants, seems more linked to the physiological and phenological characteristics of the plant than to climatic factors. On the two host-plants, the mealybug is able to develop 5 generations per year, each of 70-80 days. Three to four months after its introduction, G. tebygi developed 50 to 90 % of parasitism that significantly affects mealybug population dynamics. Eight to nine months later its establishment among low densities of the pest confirms its acclimatation. The 50 to 60 % of G. tebygi mortality attributable to the 8 species of the hyperparasitoid complex do not seem to prevent it from being an efficient parasitoid. The impact of R. invadens parasitoid complex was compared to the one of cassava mealybug.