The Influence of the Host Plant of the Cassava MealybugPhenacoccus manihotion the Plant and Host Preferences of Its ParasitoidApoanagyrus lopezi

Abstract

Abstract Olfactory responses of the parasitoid Apoanagyrus lopezi De Santis to odors emitted by four plant species or cultivars, characterized by different levels of antixenotic and antibiotic resistance to the cassava mealybug, Phenacoccus manihoti Matile-Ferroro, were studied in a Y-tube olfactometer. Three of the host plants used belong to the Euphorbiaceae: two cassava varieties (Incoza and Zanaga, Manihot esculenta Crantz) and the Faux-caoutchouc (FC) (a hybrid of M. esculenta and M. glaziovii Muel. Arg.). The fourth plant was Talinum ( Talinum triangularae Jack., Portulacaceae). In dual-choice tests, females of A. lopezi preferred the mealybug-infested plants to the uninfested plants or mealybugs alone. Female parasitoids discriminated between the different uninfested or infested-mealybug plant species and varieties. They preferred uninfested cassava M. esculenta to uninfested Talinum. Within the species M. esculenta, the parasitoid did not discriminate between uninfested plants of the varieties Incoza and Zanaga, but Zanaga was more attractive than the hybrid FC. When infested, Incoza and Zanaga were more attractive than Talinum or FC. The response of A. lopezi females to odors emanating from mealybugs reared on the four different host plants was also investigated. Females did not discriminate among mealybugs reared on plants of the Manihot genus. However, they showed a marked preference for the odor of mealybugs reared on Incoza and Zanaga rather than those reared on Talinum. The response of A. lopezi to chemicals emanating from different host plants is discussed in a tritrophic context and related to their antixenotic resistance.