Evaluation of ornamental plants as nectar sources for Tiphia parasitoids

Tiphia vernalis Rohwer and Tiphia popilliavora Rohwer. (Hymenoptera: Tiphiidae) were imported from Asia for Japanese beetle control. T. vernalis adults emerge in the spring and they have been observed feeding on honeydew deposits from soft scales or aphids and on nectar. T. popilliavora is said to feed on nectar from wild carrot Daucus carota. One approach in conservation biological control is to provide food resources to natural enemies either through food sprays or by incorporating flowering plant habitats that could provide food resources over a period of time. Thus, the objective of this study was to identify ornamental plants that can serve as a source of nectar for Tiphia wasps in Connecticut.

For T. vernalis, ornamental plants were selected based on their production of extrafloral nectar. It was hypothesized that this characteristic will be the best suited to the nectar feeding habits of this wasp given the timing of its occurrence. Plants selected included three cultivars of Paeonia lactiflora, Viburnum dentatum and Sambucus canadensis. For T. popilliavora, plants were selected based on their flower arrangement, flowering phenology and ornamental use. The plants selected included wild carrot D. carota, Achillea filipendulina, three cultivars of A. millefolium , and ornamental goldenrod Solidago cutleri.

T. vernalis wasps were observed feeding off the extrafloral nectar on all the plants selected. However, T. vernalis were observed feeding extensively from the extrafloral nectar of peonies. Of the plants selected for summer Tiphia only the wild carrot attracted a significant number of Tiphia wasps.