Potential for sugar sprays and flowering plants to increase parasitism of white grubs (Coleoptera: Scarabaeidae) by tiphiid wasps (Hymenoptera: Tiphiidae)

Abstract

We examined the effects of supplemental food sources on parasitism of turf-infesting white grubs (Coleoptera: Scarabaeidae) by tiphiid wasps (Hymenoptera: Tiphiidae). Survival of spring active Tiphia vernalis Rohwer and late summer active Tiphia pygidialis Allen, parasitoids of Japanese beetle, Popillia japonica Newman, and masked chafer, Cyclocephala spp., grubs, respectively, was significantly increased when wasps were provided with 10% sugar water in the laboratory. Presence of a grub for host feeding did not affect wasp longevity. Sugar sprays applied directly to turf were examined as a method for increasing grub parasitism rates. Large numbers of T. pygidialis visited turf sprayed with sugar water to feed. Parasitism of Cyclocephala spp. grubs by T. pygidialis was reduced in sugar-sprayed turf, but higher in turf plots located near sugar-sprayed turf. T. vernalis, which feeds on homopteran honeydew secretions, was never observed feeding on sugar-sprayed turf, nor did such treatments affect its parasitism of P. japonica in or near sugar-sprayed turf. Gardens of spring- or fall-blooming flowering plants were established and monitored to determine whether particular species might attract Tiphia spp. No T. pygidialis were observed feeding on flowers in fall-blooming gardens. Large numbers of T. vernalis were observed feeding on nectar from peony, Peonia lactiflora Pallas, in the spring-blooming garden. When replicated plantings of P. lactiflora were established in a stand of turf, parasitism of P. japonica was significantly higher near the peonies. Incorporating such nectar-producing flowers into a landscape may increase parasitism of P. japonica by T. vernalis.