New Technologies for Rearing Epidinocarsis lopezi (Hym., Encyrtidae), a Biological Control Agent Against the Cassava Mealybug, Phenacoccus manihoti (Hom., Pseudococcidae)

Abstract

The cassava mealybug (CM) Phenacoccus manihoti Matile-Ferrero (Hom., Pseudococcidae) was accidentally introduced into Africa in the early 1970s, and it subsequently spread over most of the continent. Through its feeding damage and stunting of the tips, it dramatically reduced tuber yields, thereby becoming the most important pest of cassava (Neuenschwander & Herren 1988). To combat this new pest in collaboration with numerous national and international agencies, the Biological Control Program of the International Institute of Tropical Agriculture (IITA) was established (Herren 1987). Following extended exploration in South America (Yaseen 1986, Lohr et al. 1990) and quarantine at the International Institute of Biological Control (IIBC) in the United Kingdom, the solitary and host-specific wasp Epidinocarsis lopezi (De Santis) (Hym., Encyrtidae) was imported into Africa, reared, and first released in Nigeria in 1981 (Herren & Lema 1982). By 1988, it had been successfully established in 21 African countries and had spread over an area of over 1.5 million km2 (Herren etal. 1987, Neuenschwander & Herren 1988). CM populations declined after the release and have remained low since (Hammond et al. 1987, Neuenschwander & Hammond 1988, Hammond & Neuenschwander 1990). Surveys of subsistence farms (Neuenschwander et al. 1989a), exclusion experiments (Neuenschwander et al. 1986), and a computer simulation model 354(Gutierrez et at. 1988a, b) have all documented the efficiency of E. lopezi in preventing CM outbreaks. Overall, the project is considered an economic success (Norgaard 1988), though criticism from some countries like the Congo persists (Nenon & Fabres 1988, Le Ru et al, in press). In Nigeria, ecological conditions where CM damage persisted (less than 5 % of all fields) have now been characterized (Neuenschwander et al. 1990); similar conditions might prevail in the Congo.