Enhancing Biological Control of Turf-Infesting Scarabaeid Grubs by Native and Exotic Tiphiid Wasps

Conservation and enhancement of natural enemies is necessary to reduce reliance on pesticide usage in urban landscapes, especially turfgrass. Wasps in the genus Tiphia (Hymenoptera: Tiphiidae) are the dominant parasitoids attacking scarabaeid white grubs, the most widespread and destructive insect pests of lawns, golf courses, parks, sports fields, and other turf sites. Tiphia vernalis Rohwer, an exotic species that was introduced for control of the Japanese beetle, is now established over much of the eastern United States. Its utility, however, is limited by lack of knowledge of the wasps' behavior and requirements for adaptation to suburban environments. Tiphia pygidialis Allen, a native species that parasitizes masked chafers (Cyclocephala spp.), our most injurious endemic grubs, is widespread and locally abundant, but its biology has never been studied. This proposal is for the first in-depth study of the biology and host relationships of both Tiphia species. We will investigate ovipositional behavior, cues used to locate grubs in the soil, and effects of the parasitoids on behavior and physiology of their hosts. Feasibility of enhancing Tiphia populations through augmentation of wild flowers or other carbohydrate resources also will be examined. Finally, compatibility of Tiphia with other pest control tactics, including use of preventive insecticides, entomopathogens, and endophytic grasses, will be determined. This study will clarify the role of Tiphia in regulating grub populations and identify factors that may increase their impact in urban landscapes. Information it provides will expedite conservation biological control and also may enhance the success of Tiphia introductions being made by regulatory agencies into areas where the Japanese beetle and other invasive grub species recently have spread.