Facultative hyperparasitism in Brachymeria pomonae (Hymenoptera : Chalcididae)
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This report summarizes a study designed to uncover any tendency towards hyperparasitic behavior in Brachymeria pomonae (Cameron), a parasitoid of pink bollworm (PBW) (Pectinophora gossypiella Saunders) imported from Australia to California for biological control of the latter pest species. Brachymeria pomonae hyperparasitized both Apanteles oenone Nixon (ca. 10% of pupae exposed) and Cardiochiles nigriceps Viereck (ca. 23% of pupae exposed), and all hyperparasitic offspring of B. pomonae were males. However, B. pomonae's aggressive primary parasitism of several lepidopterous hosts, together with the low hyperparasitism rates and the failure to produce hyperparasitic female offspring suggested that hyperparasitism is a facultative behavior in this parasitoid. Brachymeria pomonae caused substantial mortality in A. oenone and C. nigriceps as a result of ovipositional probing. Finally, it did not attack PBW nor A. oenone pupae if they were not enclosed in a PBW cocoon, but aggressively attacked the pupae of both when enclosed in PBW cocoons. The results are of significance because B. pomonae was a candidate for release against PBW in California. Because of its facultative hyperparasitic habit, no effort was made to release it from quarantine. The basis for this decision, including the uncertain impact that hyperparasitoids may have on biological control programs, is discussed.