Spring Tiphia (Tiphia vernalis)

The spring Tiphia: a natural enemy of the Japanese beetle

Tiphia vernalis Rohwer 
(Hymenoptera Tiphiidae)

During the 1920s and early 1930s USDA entomologists imported Tiphia vernalis Rohwer (Hymenoptera: Tiphiidae) from Korea for Japanese beetle biocontrol and several releases were made throughout the northeastern United States. T. vernalis, known as spring Tiphia, also parasitize oriental beetles and do not parasitize any native scarab beetle species (Ladd and McCabe 1966). Spring Tiphia attack on average 60% of Japanese beetle larvae (King and Parker 1950). The rate of parasitization on oriental beetle larvae is 33% from Connecticut turf surveys (Legrand 2009a) and 13-30% from surveys in Ohio nurseries (Reding and Klein 2001). Spring Tiphia females are about half an inch long and the males are about three-eighths of an inch long. These shiny black wasps are solitary, do not live in nests or swarms and they have only one generation per year. Male wasps emerge first and 3 to 4 days later females emerge. A survey by Ramoutar and Legrand (2007) indicated that T. vernalis adults in Connecticut are active from the first week of May to the beginning of June with a peak in numbers observed in the last week of May. After mating, female wasps burrow into the soil in search of third instar larvae. When a grub is found, the female Tiphia stings it to paralyze it while she attaches one egg on the ventral groove between the third thoracic and first abdominal segments. T. vernalis are ectoparasitoids. The full-grown Tiphia larva spins a water-resistant silken cocoon. It transforms into an adult wasp and passes the winter in this stage within the cocoon until the next spring when adults emerge to start the cycle again. Tiphia females live for about a month and may lay 40-50 eggs on as many different grub hosts. The female wasps seek out the fully-grown Japanese beetle grubs in the period of time when the grubs are feeding before pupation. 

T. vernalis adults feed on honeydew deposits from soft scales or aphids and on nectar (Balock 1934, King and Parker 1950). The use of plants that harbor aphids for honeydew or that produce nectar has been suggested for the benefit of this parasitoid. Extrafloral nectar from peonies significantly attracts T. vernalis resulting in grub parasitism increases near the peonies (Rogers and Potter 2004, Legrand 2009b, Legrand 2015). Nectar resources are important for these insects given that provision of sugar water in the laboratory increased their longevity from an average of 6 to 30 days (Rogers and Potter 2004). 

Spring Tiphia exhibit an array of complex host-finding behaviors and plant volatiles play a role in host-finding. These parasitoids were highly attracted to volatiles emitted by grub-infested tall fescue and Kentucky bluegrass over un-infested grasses. In contrast, wasps did not exhibit a significant preference for grub-infested perennial ryegrass as compared to the control plants (Obeysekara et al. 2014). Levels of key terpene compounds emitted by grub-infested Kentucky bluegrass and tall fescue were greater than that of control plants. Low levels of terpenes were observed for both test and control perennial ryegrass. Terpene levels produced by perennial ryegrass were so low that individual terpene compounds could not be identified.  The elevated levels of terpenes emitted by grub-infested Kentucky bluegrass and tall fescue coincided with the attractiveness to the Tiphiid wasps (Obeysekara et al. 2014).