Native Polistes wasps (Hymenoptera: Vespidae) hold potential as biocontrol agents for lepidopteran pests of Brassica.

Abstract

Social paper wasps regularly prey upon lepidopteran larvae, some of which are economically impactful agricultural pest species. We examined the potential of native North American Polistes metricus Say (Hymenoptera: Vespidae) and Polistes fuscatus (Fabricius) for biocontrol of Brassica L. pests in an experimental setting. First, we translocated P. metricus to one-half of a divided screened hoop house and placed a mix of 4th-5th instar lepidopteran larvae (Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), Pieris spp. Schrank (Lepidoptera: Pieridae), and Plutella xylostella (L.) (Lepidoptera: Plutellidae)) on half of the broccoli plants on both sides of the hoop house. We recorded and replaced missing caterpillars daily, and assessed leaf damage after 1wk. P. metricus was 100% effective at removing all caterpillars from the wasp side of the hoop house, and plant damage by caterpillars was significantly reduced in the presence of wasps. We then replicated the study using a different combination of Polistes (fuscatus) and Brassica crop (kale) with a 2 × 2 experimental design in which plants had either T. ni larvae added or absent (factor 1), and were either covered with insect mesh or left exposed (factor 2). By the second day of exposure to these pest species, wasps removed over 80% of the larvae within 3h of placing them on the plants. We discuss implications of this study for the potential use of native Polistes wasps as an integrated pest management strategy.