Distribution, host plants and abundance of the invasive mango mealybug, Rastrococcus iceryoides and its associated natural enemies in Africa

Rastrococcus iceryoides (Green) (Hemiptera: Pseudococcidae) is an alien invasive pest reported from Tanzania, Kenya and Malawi attacking several important horticultural crops. A survey of cultivated and wild host plants was conducted in major horticultural production areas of Kenya and Tanzania to ascertain its distribution, host range and associated natural enemies. Our survey revealed that R. iceryoides has a broad hosts range that included 30 cultivated and wild host plant species from 16 different families. The following were the most heavily infested host plants in order of abundance, Mangifera indica, Parkinsonia aculeata, Cajanus cajan and Caesalpinia sepiaria with infestation levels ranging from 26.0 ± 3.1 to 541.0 ± 127.9 mealybugs/30 cm twig. A total of 21 indigenous parasitoid species were recorded from R. iceryoides. Anagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae) was found to be the most widely distributed and abundant with percentage parasitization of 3-20%. However, this parasitoid was subjected to high levels of hyperparasitism, which markedly impacted on its efficacy in suppressing R. iceryoides. Thirty-eight species of predators belonging to seven families were also recorded attacking the mealybug during the survey. Despite the diversity of these natural enemies, R. iceryoides has remained one of the most damaging pest of its preferred host (mango) in Tanzania and this is probably attributed to the lack of efficient co-evolved natural enemies. There is the need for exploration and introduction of efficient natural enemies from its aboriginal home of India to minimize the impact of R. iceryoides on horticulture in Africa. This activity is underway.

Key-words: Rastrococcus iceryoides, Distribution, Host plants; Indigenous natural enemies; Biological control.