Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae) as a Potential Natural Enemy of Maize-Infesting Ulidiidae

Euxesta annonae Fabricius, E. eluta Loew, E. stigmatias Loew, and Chaetopsis massyla Walker (Diptera: Ulidiidae) are primary sweet corn pests in Florida. Few natural enemies of these flies are known. The pupal parasitoid Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae) was discovered in a laboratory colony of E. eluta and E. stigmatias, and its potential as a biological control agent was studied. Development times in fresh, chilled, and frozen E. eluta pupae were recorded. Fly larvae were allowed to dig into soil to pupate, and pupae covered by 2.5 cm of soil were presented to wasps to determine if Pachycrepoideus vindemmiae could locate them. Finally, to evaluate susceptibility to insecticides commercially used in ear-stage sweet corn, adult parasitoids were caged on maize leaves treated with chlorpyrifos, methomyl, or zeta cypermethrin for 24 h. Pachycrepoideus vindemmiae completed development in normal, chilled, and frozen fly pupae in 15-17 days. None of the fly pupae covered by soil were parasitized. Chlorpyrifos and methomyl residues killed >95% of Pachycrepoideus vindemmiae within 24 h. Zeta cypermethrin was slower acting, but resulted in 50% mortality after 24 h. Therefore, Pachycrepoideus vindemmiae does not appear to be well suited as an effective biological control agent of maize-infesting Ulidiidae in sweet corn fields. This is the first known account of this cosmopolitan parasitoid attacking maize-infesting ulidiids.