ON THE COEXISTENCE OF THE CASSAVA MEALYBUG PARASITOIDS APOANAGYRUS-DIVERSICORNIS AND APOANAGYRUS-LOPEZI (HYMENOPTERA, ENCYRTIDAE) IN THEIR NATIVE SOUTH-AMERICA
Jwam. Pijls et Jm. Vanalphen, ON THE COEXISTENCE OF THE CASSAVA MEALYBUG PARASITOIDS APOANAGYRUS-DIVERSICORNIS AND APOANAGYRUS-LOPEZI (HYMENOPTERA, ENCYRTIDAE) IN THEIR NATIVE SOUTH-AMERICA, Bulletin of entomological research, 86(1), 1996, pp. 51-59
The encyrtid parasitoid Apoanagyrus diversicornis (Howard) (formerly k
nown as Epidinocarsis divevsicornis) failed to establish itself in Afr
ica where it was introduced, in addition to A. lopezi De Santis for th
e biological control of the cassava mealybug, Phenacoccus manihoti Mat
ile-Ferrero. Apoanagyrus lopezi is a better competitor and available e
vidence suggests that competition prevents the coexistence. Yet, both
parasitoid species were reared from P. manihoti in the same locality i
n their native South America. Competition should prevent coexistence o
n P. manihoti in South America as well as in Africa. We investigated h
ow A. diversicornis persists in South America. The use of alternative
hosts could explain its persistence. We aimed at finding possible alte
rnative hosts for A. diversicornis that can serve as a refuge from com
petition with A. lopezi. The existing information on the distribution
of A. lopezi and A. diversicornis and their known hosts in South Ameri
ca 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 con
tinuous 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 th
at P. herreni can serve as an alternative host for A. diversicornis in
South America and that its presence enhances coexistence of A. divers
icornis and A. lopezi. Phenacoccus herreni is absent in Africa.