Influence of the host plant of the cassava mealybugPhenacoccus manihoti(Hemiptera: Pseudococcidae) on biological characteristics of its parasitoidApoanagyrus lopezi(Hymenoptera: Encyrtidae)

Abstract

AbstractThe influence of the host plant of the cassava mealybug,Phenacoccus manihotiMatile Ferrero on the encyrtid parasitoidApoanagyrus lopeziDe Santis was studied in the laboratory. Four different host plants were used: two cultivars of cassava,Manihot esculenta(Euphorbiaceae), cv. Incoza and cv. MM79; Faux caoutchouc, a hybrid ofM. esculenta × M glaziovii;and talinumTalinum triangularae(Portulacaceae), a common weed in cassava fields. Plants were selected for different levels of antibiotic resistance toP. manihoti. Mealybug mortality due to host feeding by the adult parasitoid and the percentage of mealybugs parasitized were significantly lower when mealybugs were reared on theManihotcultivars and hybrid than when reared on talinum. However, the encapsulation rate was significantly lower inP. manihotireared on talinum. The highest percentage parasitism and the lowest rate of emergence were recorded on cv. Incoza, the most resistantManihotcultivar. The sex ratio did not vary significantly with the host plant used. The total developmental time and size of male and female progeny ofA. lopezidiffered significantly betweenP. manihotireared on different host plants. AmongManihotplants, parasitoid size was positively correlated with development time and negatively with plant resistance. Results suggest that the parasitoid,A. lopezi, might perform better if cassava cultivars were selected for their strong antixenosis but low antibiotic characteristics.