Host-plant relationships and natural enemies of the invasive mealybug, Rastrococcus iceryoides Green in Kenya and Tanzania

Abstract

The invasive mango mealybug, Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae) believed to be native to Southern Asia has rapidly invaded Kenya and Tanzania. A survey was carried out from February 2008–July 2009 to study its geographical distribution, host plant relationships and associated parasitoids in both countries. Our results infer that R. iceryoides is widely distributed across the coastal belts of both countries. Rastrococcus iceryoides was recorded from 29 cultivated and wild host plants from 16 families. Twenty-one of these host plants are new records. Among the cultivated host plants, M. indica (8153.6±19.2/20 twigs and 6054.3±29.2/80 leaves in Kibaha, and 2979.3±33.8/5 fruits in Kinondoni) and Cajanus cajan (L.) Millspaugh (1452.2±44.7/80 leaves and 4672.3±54.7/twig in Morogoro) recorded the highest levels of infestation. Parkinsonia aculeata (7892.3±25.1/20 twigs, 11.6±1.25/80 leaves and 42.2±5.1/5 fruits in Kinango), Caesalpinia sepiaria Roxb (266.3±6.3/80 leaves and 3116.1±17.5/20 twigs in Kinondoni) and Deinbollia borbonica Scheff., (215.7±10.3/80 leaves and 2253±22.9/20 twigs in Kibaha) were found to be the most heavily infested wild host plants. Six parasitoid species were recovered and are reported here for the first time to parasitize R. iceryoides. Anagyrus pseudococci Girault was the most dominant species accounting for 21% parasitism on M. indica and 20% parasitism on P. aculeata in Tanzania and Kenya, respectively. Despite this, the ability of the parasitoid to regulate the population of R. iceryoides was inadequate. Therefore, there is a need for foreign exploration and introduction of efficient coevolved natural enemies from its aboriginal home of Southern Asia to minimize its impact on horticulture in Africa.