Interspecific host discrimination and competition inApoanagyrus (Epidinocarsis) lopeziandA.(E.)diversicornis, parasitoids of the cassava mealybugPhenacoccus manihoti

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Abstract
Choice experiments on interspecific host discrimination inA.lopeziandA. diversicorniswere carried out on discs of cassava leaf containing four hosts (P.manihoti) that had been parasitized by the other species and four unparasitized hosts. A.lopeziaccepted both host types equally for oviposition, whereasA.diversicornisaccepted fewer hosts that had been parasitized byA.lopezithan unparasitized ones.A.diversicornisis therefore capable of interspecific host discrimination, but such a capability was not demonstrated forA.lopezi. Survival probability in singly parasitized hosts was 0.85 for both parasitoid species. When the time interval between ovipositions was 2 h or less, survival in multiparasitized hosts was 0.68 forA.lopeziand 0.17 forA.diversicornis, irrespective of priority. IncreasingA.lopezipriority to 24±2h did not increaseA.lopezisurvival.A.diversicornissurvival, however, increased to 0.43 whenA.diversicorniswas given 24 ± 2 h priority.A.diversicorniseggs took 19 h longer thanA.lopezieggs to hatch. This could explain the difference in competitive abilities in multiparasitized hosts. The observed difference in host selection behaviour betweenA.lopeziandA.diversicornisis in accordance with the different benefits of multiparasitism:A.lopezigains more thanA.diversicornisbecause of its superior within‐host competitive abilities. Neither species avoided multiparasitism completely. The low survival probability ofA.diversicornisin multiparasitized hosts may partly explain its failure to establish when introduced into Africa as part of a biological control programme ofP.manihoti.