The population growth pattern of the cassava mealybugPhenacoccus manihotiMat‐Ferr was studied over two population cycles of the pest in Freetown, Sierra Leone. The numbers and rate of dispersal of the insect were higher and the damage it produced more severe in the dry season than in the rainy season. During the rainy season the mealybug population consisted mainly of adults. Even though rain is an important known abiotic natural control factor for the pest the decline in the insect's numbers started before the rainy season. This was attributed to reduction in the carrying capacity of the habitat. The indigenous natural enemies adopted the pest as a food source but did not control its population growth. The other mealybugs observed on the crop,P. madeirensis(Green) andFerrisia virgata(Cockerell) were economically insignificant.