Parasitism and predation in Planococcoides njalensis (Laing) (Homoptera: Pseudococcidae) on cacao in Ghana.
From 1988 to 1992, 1870 colonies of Planococcoides njalensis (Laing) were sampled from 188 randomly distributed cacao farms in Ghana. Natural enemies obtained from these colonies included two predatory beetles, Hyperaspis egregia Mader and Scymnus (Pullus) sp., and a predatory Diptera, Coccodiplosis coffeae Barnes (Cecidomyiidae). Six hymenopterous parasitoids, Aenasius abengouroui (Risbec), Anagyrus beneficians Compere, A. amoenus Compere, Leptomastix dactylopii Howard, Tropidophryne melvillei Compere, and Chryptochetum (Lestophonus) sp. were observed. A hymenopterous hyperparasitoid, Cheiloneurus carinatus Compere and a parasitoid of C. coffeae, i.e., Xyphigaster pseudococci Risbec, were also observed, as were unidentified Lepidoptera whose exact role was uncertain. Coccodiplosis coffeae was the most common natural enemy, followed by A. abengouroui, Hyperaspis-Scymnus, A. beneficians, L. dactylopii, and C. carinatus. The rates of parasitism were low for the individual species with the highest (0.8 to 6%) by A. abengouroui. Simultaneous parasitism by more than one species was common in infested colonies. This gave rise to monthly parasitism levels ranging from 0.9 to 11.6%. The observations of A. abengouroui, A. amoenus, and H. egregia appear to be the first indication of their presence on Ghanaian cacao. The recovery of L. dactylopii suggests its establishment in Ghana after it was introduced here in 1949. The frequencies of occurrence of the beneficial insects and their proportional representations in the mealybug's colonies are discussed.