FACULTATIVE HYPERPARASITISM IN BRACHYMERIA-POMONAE (HYMENOPTERA, CHALCIDIDAE)

This report summarizes a study designed to uncover any tendency toward s hyperparasitic behavior in Brachymeria pomonae (Cameron), a parasito id of pink bollworm (PBW) (Pectinophora gossypiella Saunders) imported from Australia to California for biological control of the latter pes t species. Brachymeria pomonae hyperparasitized both Apanteles oenone Nixon (ca. 10% of pupae exposed) and Cardiochiles nigriceps Viereck (c a. 23% of pupae exposed), and all hyperparasitic offspring of B. pomon ae were males. However, B. pomonae's aggressive primary parasitism of several lepidopterous hosts, together with the low hyperparasitism rat es and the failure to produce hyperparasitic female offspring suggeste d that hyperparasitism is a facultative behavior in this parasitoid. B rachymeria pomonae caused substantial mortality in A. oenone and C. ni griceps as a result of ovipositional probing. Finally, it did not atta ck 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 cocoo ns. The results are of significance because B. pomonae was a candidate for release against PBW in California. Because of its facultative hyp erparasitic habit, no effort was made to release it from quarantine. T he basis for this decision, including the uncertain impact that hyperp arasitoids may have on biological control programs, is discussed.