May is the time for Spring Tiphia
By Ana Legrand, University of Connecticut
|Fig 1. Adult Spring Tiphia wasps|
As spring is upon us, we set out to monitor for pests and prepare our management actions. If you have dealt with the Japanese and oriental beetle grubs you might have wondered what natural enemies might be out there that give these pests some trouble. One of them is the Spring Tiphia parasitic wasp (Fig. 1). These shiny black wasps are solitary. They do not live in nests or swarms and they only have one generation per year. Male wasps emerge first and 3 to 4 days later females emerge. In Connecticut, Spring Tiphia are active from the first week of May to the beginning of June with a peak in numbers observed around the last week of May. After mating, female wasps discretely burrow into the soil and search for grubs. When a host is found, the wasp stings it and paralyzes it momentarily while the wasp attaches one egg on the ventral groove between the third thoracic and first abdominal segments.
|Fig. 2: Spring Tiphia larva feeding on Japanese beetle grub|
The egg stage lasts for 9-10 days and the larval stage lasts about 20 days. The parasitic larva after hatching is found outside the host, securely attached and feeding on it until the host dies (Fig. 2). The parasitic larva grows rapidly and the full-grown larva spins a papery, water resistant, silken cocoon (Fig.3). It completes its development within the cocoon and transforms into an adult wasp. It passes the winter in this stage within the cocoon until the next spring when adults emerge to start the cycle all over again. Spring 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 or oriental beetle grubs in the period of time when the grubs are feeding before pupation. We have conducted surveys that find the Spring Tiphia present in every Connecticut county. In one survey we found a range of 61 to 100% parasitism on the Japanese beetle grubs. In addition, the Spring Tiphia is also inflicting some mortality on oriental beetle populations with a parasitism rate ranging from 7% to 33% in low-density oriental beetle populations.
|Fig. 3: Spring Tiphia cocoon|
One important question to ask is how to conserve these naturally occurring wasps in order to benefit the most from them. The Spring Tiphia uses nectar and insect honeydew to supplement their diet. Often these wasps are observed on maple, cherry and Tulip tree foliage looking for aphids as a source of honeydew. However, it would be best to provide them with more dependable sources of a sugary substance. By providing nectar resources to the wasp we can enhance their survival. In our studies we have documented that peonies are a good source of nectar for these wasps because they feed on the extrafloral nectar secreted by the unopened peony flower bud. In fact, if you have peonies you might find the wasps there before the flower fully opens. Thus, planting peonies such as ‘Big Ben’, ‘Festiva’, ‘Bowl of Beauty’ or ‘Sarah Bernhardt’ will provide essential nutritional resources to the wasps and help in their conservation.
Ana Legrand is an entomologist who works on biocontrol of white grubs at the University of Connecticut. Photos by Ana Legrand