Rastrococcus invadensWilliams has been the most important polyphagous pest of horticultural crops since 1982 in some West African countries. It originated in South-East Asia and was probably introduced on infested plant material. The pest has been reported up to 150 km north of the coast of Benin and 500 km north from the coast in Togo. Although the species is polyphagous, mango, citrus, breadfruit, banana, frangipani (Plumeria alba) and species of Ficus are among the most attacked hosts. Several indigenous natural enemies were identified, but their ability to regulate the populations of R. invadens is very low. The most important among the predators were the coccinellids Chilocorus nigrita (F.), Exochomus promtus Weise and E. troberti Mulsant and the lycaenids Spalgis spp. In Togo, an indigenous parasitoid, Anagyrus sp. ?nr aurantifrons Compere, has become adapted to the pest.

Rastrococcus invadens Williams was first noticed in Togo in 1981 and has since become a serious pest on many plants, especially mango and citrus. In June 1986, a programme for its biological control was begun, resulting in the introduction into Togo in October 1987 of an encyrtid parasitoid, Gyranusoidea tebygi Noyes. The parasitoid was reared under a simple system and releases were made from November 1987. The parasitoid established readily under a range of ecological conditions and produced significant control within the first year up to 100 km from each release point.

In 1988/89 the nature and degree of hyperparasitism in two newly introduced parasitoids of exotic mealybug plant pests were examined in Togo. Associated with Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) (cassava mealybug) five indigenous hymenopterous hyperparasitoids were found adapted to the primary parasitoid Epidinocarsis lopezi (De Santis): Chartocerus sp. A (Signiphoridae), Prochiloneurus insolitus (Alam), P. aegyptiacus (Mercet) (Encyrtidae), Tetrastichus sp. (Eulophidae), and Marietta leopardina Motschulsky (Aphelinidae). The rate of hyperparasitism varied considerably (20–90%). At one sampling site Chartocerus sp. A was most frequent (52%), at the other site P. insolitus was found to dominate (55%). The same hyperparasitoids were associated with Rastrococcus invadens Williams (Hemiptera: Pseudococcidae), but with an additional Chartocerus (sp. B). Hyperparasitism ranged from 56 to 86%, with Chartocerus sp. A being the most important species. Multiple parasitism was observed on several occasions. In spite of generally high hyperparasitism, no detrimental effect on the control efficiency of either primary parasitoid was noticed.