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On the coexistence of the cassava mealybug parasitoids Apoanagyrus diversicornis and A. lopezi (Hymenoptera: Encyrtidae) in their native South America
Published online by Cambridge University Press: 10 July 2009
Abstract
The encyrtid parasitoid Apoanagyrus diversicornis (Howard) (formerly known as Epidinocarsis diversicornis) failed to establish itself in Africa where it was introduced, in addition to A. lopezi De Santis for the biological control of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. Apoanagyrus lopezi is a better competitor and available evidence suggests that competition prevents the coexistence. Yet, both parasitoid species were reared from P. manihoti in the same locality in their native South America. Competition should prevent coexistence on P. manihoti in South America as well as in Africa. We investigated how A. diversicornis persists in South America. The use of alternative hosts could explain its persistence. We aimed at finding possible alternative hosts for A. diversicornis that can serve as a refuge from competition with A. lopezi. The existing information on the distribution of A. lopezi and A. diversicornis and their known hosts in South America is reviewed. Candidate alternative hosts for A. diversicornis were selected and tested. Alternative hosts should at least be suitable for development of A. diversicornis and unsuitable for development of A. lopezi. Only Phenacoccus herreni Cox & Williams met these requirements. Phenacoccus madeirensis Green, P. solani Ferris and Ferrisia virgata (Cockerell) were unsuitable hosts for both species. In cages with continuous parasitoid populations under strong interspecific competition, A. diversicornis did significantly better if half the population of P. manihoti was replaced by P. herreni. This supports the hypothesis that P. herreni can serve as an alternative host for A. diversicornis in South America and that its presence enhances coexistence of A. diversicornis and A. lopezi. Phenacoccus herreni is absent in Africa.
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- Copyright © Cambridge University Press 1996
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